diff --git a/dist/shell.c b/dist/shell.c
index 184c98f..8879b36 100644
--- a/dist/shell.c
+++ b/dist/shell.c
@@ -94,7 +94,7 @@
 
 /* Return the difference of two time_structs in seconds */
 static double timeDiff(struct timeval *pStart, struct timeval *pEnd){
-  return (pEnd->tv_usec - pStart->tv_usec)*0.000001 +
+  return (pEnd->tv_usec - pStart->tv_usec)*0.000001 + 
          (double)(pEnd->tv_sec - pStart->tv_sec);
 }
 
@@ -149,7 +149,7 @@
         if( NULL != getProcessTimesAddr ){
           return 1;
         }
-        FreeLibrary(hinstLib);
+        FreeLibrary(hinstLib); 
       }
     }
   }
@@ -191,7 +191,7 @@
 #define HAS_TIMER hasTimer()
 
 #else
-#define BEGIN_TIMER
+#define BEGIN_TIMER 
 #define END_TIMER
 #define HAS_TIMER 0
 #endif
@@ -201,868 +201,6 @@
 */
 #define UNUSED_PARAMETER(x) (void)(x)
 
-
-/**************************************************************************
-***************************************************************************
-** Begin genfkey logic.
-*/
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined SQLITE_OMIT_SUBQUERY
-
-#define GENFKEY_ERROR         1
-#define GENFKEY_DROPTRIGGER   2
-#define GENFKEY_CREATETRIGGER 3
-static int genfkey_create_triggers(sqlite3 *, const char *, void *,
-  int (*)(void *, int, const char *)
-);
-
-struct GenfkeyCb {
-  void *pCtx;
-  int eType;
-  int (*xData)(void *, int, const char *);
-};
-typedef struct GenfkeyCb GenfkeyCb;
-
-/* The code in this file defines a sqlite3 virtual-table module that
-** provides a read-only view of the current database schema. There is one
-** row in the schema table for each column in the database schema.
-*/
-#define SCHEMA \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "tablename,"         /* Name of table */                                   \
-  "cid,"               /* Column number (from left-to-right, 0 upward) */    \
-  "name,"              /* Column name */                                     \
-  "type,"              /* Specified type (i.e. VARCHAR(32)) */               \
-  "not_null,"          /* Boolean. True if NOT NULL was specified */         \
-  "dflt_value,"        /* Default value for this column */                   \
-  "pk"                 /* True if this column is part of the primary key */  \
-")"
-
-#define SCHEMA2 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "from_tbl,"          /* Name of table */                                   \
-  "fkid,"                                                                    \
-  "seq,"                                                                     \
-  "to_tbl,"                                                                  \
-  "from_col,"                                                                \
-  "to_col,"                                                                  \
-  "on_update,"                                                               \
-  "on_delete,"                                                               \
-  "match"                                                                    \
-")"
-
-#define SCHEMA3 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "tablename,"         /* Name of table */                                   \
-  "seq,"                                                                     \
-  "name,"                                                                    \
-  "isunique"                                                                 \
-")"
-
-#define SCHEMA4 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "indexname,"         /* Name of table */                                   \
-  "seqno,"                                                                   \
-  "cid,"                                                                     \
-  "name"                                                                     \
-")"
-
-#define SCHEMA5 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "triggername,"       /* Name of trigger */                                 \
-  "dummy"              /* Unused */                                          \
-")"
-
-typedef struct SchemaTable SchemaTable;
-static struct SchemaTable {
-  const char *zName;
-  const char *zObject;
-  const char *zPragma;
-  const char *zSchema;
-} aSchemaTable[] = {
-  { "table_info",       "table", "PRAGMA %Q.table_info(%Q)",       SCHEMA },
-  { "foreign_key_list", "table", "PRAGMA %Q.foreign_key_list(%Q)", SCHEMA2 },
-  { "index_list",       "table", "PRAGMA %Q.index_list(%Q)",       SCHEMA3 },
-  { "index_info",       "index", "PRAGMA %Q.index_info(%Q)",       SCHEMA4 },
-  { "trigger_list",     "trigger", "SELECT 1",                     SCHEMA5 },
-  { 0, 0, 0, 0 }
-};
-
-typedef struct schema_vtab schema_vtab;
-typedef struct schema_cursor schema_cursor;
-
-/* A schema table object */
-struct schema_vtab {
-  sqlite3_vtab base;
-  sqlite3 *db;
-  SchemaTable *pType;
-};
-
-/* A schema table cursor object */
-struct schema_cursor {
-  sqlite3_vtab_cursor base;
-  sqlite3_stmt *pDbList;
-  sqlite3_stmt *pTableList;
-  sqlite3_stmt *pColumnList;
-  int rowid;
-};
-
-/*
-** Table destructor for the schema module.
-*/
-static int schemaDestroy(sqlite3_vtab *pVtab){
-  sqlite3_free(pVtab);
-  return 0;
-}
-
-/*
-** Table constructor for the schema module.
-*/
-static int schemaCreate(
-  sqlite3 *db,
-  void *pAux,
-  int argc, const char *const*argv,
-  sqlite3_vtab **ppVtab,
-  char **pzErr
-){
-  int rc = SQLITE_NOMEM;
-  schema_vtab *pVtab;
-  SchemaTable *pType = &aSchemaTable[0];
-
-  UNUSED_PARAMETER(pzErr);
-  if( argc>3 ){
-    int i;
-    pType = 0;
-    for(i=0; aSchemaTable[i].zName; i++){
-      if( 0==strcmp(argv[3], aSchemaTable[i].zName) ){
-        pType = &aSchemaTable[i];
-      }
-    }
-    if( !pType ){
-      return SQLITE_ERROR;
-    }
-  }
-
-  pVtab = sqlite3_malloc(sizeof(schema_vtab));
-  if( pVtab ){
-    memset(pVtab, 0, sizeof(schema_vtab));
-    pVtab->db = (sqlite3 *)pAux;
-    pVtab->pType = pType;
-    rc = sqlite3_declare_vtab(db, pType->zSchema);
-  }
-  *ppVtab = (sqlite3_vtab *)pVtab;
-  return rc;
-}
-
-/*
-** Open a new cursor on the schema table.
-*/
-static int schemaOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
-  int rc = SQLITE_NOMEM;
-  schema_cursor *pCur;
-  UNUSED_PARAMETER(pVTab);
-  pCur = sqlite3_malloc(sizeof(schema_cursor));
-  if( pCur ){
-    memset(pCur, 0, sizeof(schema_cursor));
-    *ppCursor = (sqlite3_vtab_cursor *)pCur;
-    rc = SQLITE_OK;
-  }
-  return rc;
-}
-
-/*
-** Close a schema table cursor.
-*/
-static int schemaClose(sqlite3_vtab_cursor *cur){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  sqlite3_finalize(pCur->pDbList);
-  sqlite3_finalize(pCur->pTableList);
-  sqlite3_finalize(pCur->pColumnList);
-  sqlite3_free(pCur);
-  return SQLITE_OK;
-}
-
-static void columnToResult(sqlite3_context *ctx, sqlite3_stmt *pStmt, int iCol){
-  switch( sqlite3_column_type(pStmt, iCol) ){
-    case SQLITE_NULL:
-      sqlite3_result_null(ctx);
-      break;
-    case SQLITE_INTEGER:
-      sqlite3_result_int64(ctx, sqlite3_column_int64(pStmt, iCol));
-      break;
-    case SQLITE_FLOAT:
-      sqlite3_result_double(ctx, sqlite3_column_double(pStmt, iCol));
-      break;
-    case SQLITE_TEXT: {
-      const char *z = (const char *)sqlite3_column_text(pStmt, iCol);
-      sqlite3_result_text(ctx, z, -1, SQLITE_TRANSIENT);
-      break;
-    }
-  }
-}
-
-/*
-** Retrieve a column of data.
-*/
-static int schemaColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  switch( i ){
-    case 0:
-      columnToResult(ctx, pCur->pDbList, 1);
-      break;
-    case 1:
-      columnToResult(ctx, pCur->pTableList, 0);
-      break;
-    default:
-      columnToResult(ctx, pCur->pColumnList, i-2);
-      break;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Retrieve the current rowid.
-*/
-static int schemaRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  *pRowid = pCur->rowid;
-  return SQLITE_OK;
-}
-
-static int finalize(sqlite3_stmt **ppStmt){
-  int rc = sqlite3_finalize(*ppStmt);
-  *ppStmt = 0;
-  return rc;
-}
-
-static int schemaEof(sqlite3_vtab_cursor *cur){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  return (pCur->pDbList ? 0 : 1);
-}
-
-/*
-** Advance the cursor to the next row.
-*/
-static int schemaNext(sqlite3_vtab_cursor *cur){
-  int rc = SQLITE_OK;
-  schema_cursor *pCur = (schema_cursor *)cur;
-  schema_vtab *pVtab = (schema_vtab *)(cur->pVtab);
-  char *zSql = 0;
-
-  while( !pCur->pColumnList || SQLITE_ROW!=sqlite3_step(pCur->pColumnList) ){
-    if( SQLITE_OK!=(rc = finalize(&pCur->pColumnList)) ) goto next_exit;
-
-    while( !pCur->pTableList || SQLITE_ROW!=sqlite3_step(pCur->pTableList) ){
-      if( SQLITE_OK!=(rc = finalize(&pCur->pTableList)) ) goto next_exit;
-
-      assert(pCur->pDbList);
-      while( SQLITE_ROW!=sqlite3_step(pCur->pDbList) ){
-        rc = finalize(&pCur->pDbList);
-        goto next_exit;
-      }
-
-      /* Set zSql to the SQL to pull the list of tables from the
-      ** sqlite_master (or sqlite_temp_master) table of the database
-      ** identfied by the row pointed to by the SQL statement pCur->pDbList
-      ** (iterating through a "PRAGMA database_list;" statement).
-      */
-      if( sqlite3_column_int(pCur->pDbList, 0)==1 ){
-        zSql = sqlite3_mprintf(
-            "SELECT name FROM sqlite_temp_master WHERE type=%Q",
-            pVtab->pType->zObject
-        );
-      }else{
-        sqlite3_stmt *pDbList = pCur->pDbList;
-        zSql = sqlite3_mprintf(
-            "SELECT name FROM %Q.sqlite_master WHERE type=%Q",
-             sqlite3_column_text(pDbList, 1), pVtab->pType->zObject
-        );
-      }
-      if( !zSql ){
-        rc = SQLITE_NOMEM;
-        goto next_exit;
-      }
-
-      rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pTableList, 0);
-      sqlite3_free(zSql);
-      if( rc!=SQLITE_OK ) goto next_exit;
-    }
-
-    /* Set zSql to the SQL to the table_info pragma for the table currently
-    ** identified by the rows pointed to by statements pCur->pDbList and
-    ** pCur->pTableList.
-    */
-    zSql = sqlite3_mprintf(pVtab->pType->zPragma,
-        sqlite3_column_text(pCur->pDbList, 1),
-        sqlite3_column_text(pCur->pTableList, 0)
-    );
-
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-      goto next_exit;
-    }
-    rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pColumnList, 0);
-    sqlite3_free(zSql);
-    if( rc!=SQLITE_OK ) goto next_exit;
-  }
-  pCur->rowid++;
-
-next_exit:
-  /* TODO: Handle rc */
-  return rc;
-}
-
-/*
-** Reset a schema table cursor.
-*/
-static int schemaFilter(
-  sqlite3_vtab_cursor *pVtabCursor,
-  int idxNum, const char *idxStr,
-  int argc, sqlite3_value **argv
-){
-  int rc;
-  schema_vtab *pVtab = (schema_vtab *)(pVtabCursor->pVtab);
-  schema_cursor *pCur = (schema_cursor *)pVtabCursor;
-  UNUSED_PARAMETER(idxNum);
-  UNUSED_PARAMETER(idxStr);
-  UNUSED_PARAMETER(argc);
-  UNUSED_PARAMETER(argv);
-  pCur->rowid = 0;
-  finalize(&pCur->pTableList);
-  finalize(&pCur->pColumnList);
-  finalize(&pCur->pDbList);
-  rc = sqlite3_prepare(pVtab->db,"SELECT 0, 'main'", -1, &pCur->pDbList, 0);
-  return (rc==SQLITE_OK ? schemaNext(pVtabCursor) : rc);
-}
-
-/*
-** Analyse the WHERE condition.
-*/
-static int schemaBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
-  UNUSED_PARAMETER(tab);
-  UNUSED_PARAMETER(pIdxInfo);
-  return SQLITE_OK;
-}
-
-/*
-** A virtual table module that merely echos method calls into TCL
-** variables.
-*/
-static sqlite3_module schemaModule = {
-  0,                           /* iVersion */
-  schemaCreate,
-  schemaCreate,
-  schemaBestIndex,
-  schemaDestroy,
-  schemaDestroy,
-  schemaOpen,                  /* xOpen - open a cursor */
-  schemaClose,                 /* xClose - close a cursor */
-  schemaFilter,                /* xFilter - configure scan constraints */
-  schemaNext,                  /* xNext - advance a cursor */
-  schemaEof,                   /* xEof */
-  schemaColumn,                /* xColumn - read data */
-  schemaRowid,                 /* xRowid - read data */
-  0,                           /* xUpdate */
-  0,                           /* xBegin */
-  0,                           /* xSync */
-  0,                           /* xCommit */
-  0,                           /* xRollback */
-  0,                           /* xFindMethod */
-  0,                           /* xRename */
-};
-
-/*
-** Extension load function.
-*/
-static int installSchemaModule(sqlite3 *db, sqlite3 *sdb){
-  sqlite3_create_module(db, "schema", &schemaModule, (void *)sdb);
-  return 0;
-}
-
-/*
-**   sj(zValue, zJoin)
-**
-** The following block contains the implementation of an aggregate
-** function that returns a string. Each time the function is stepped,
-** it appends data to an internal buffer. When the aggregate is finalized,
-** the contents of the buffer are returned.
-**
-** The first time the aggregate is stepped the buffer is set to a copy
-** of the first argument. The second time and subsequent times it is
-** stepped a copy of the second argument is appended to the buffer, then
-** a copy of the first.
-**
-** Example:
-**
-**   INSERT INTO t1(a) VALUES('1');
-**   INSERT INTO t1(a) VALUES('2');
-**   INSERT INTO t1(a) VALUES('3');
-**   SELECT sj(a, ', ') FROM t1;
-**
-**     =>  "1, 2, 3"
-**
-*/
-struct StrBuffer {
-  char *zBuf;
-};
-typedef struct StrBuffer StrBuffer;
-static void joinFinalize(sqlite3_context *context){
-  StrBuffer *p;
-  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
-  sqlite3_result_text(context, p->zBuf, -1, SQLITE_TRANSIENT);
-  sqlite3_free(p->zBuf);
-}
-static void joinStep(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  StrBuffer *p;
-  UNUSED_PARAMETER(argc);
-  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
-  if( p->zBuf==0 ){
-    p->zBuf = sqlite3_mprintf("%s", sqlite3_value_text(argv[0]));
-  }else{
-    char *zTmp = p->zBuf;
-    p->zBuf = sqlite3_mprintf("%s%s%s",
-        zTmp, sqlite3_value_text(argv[1]), sqlite3_value_text(argv[0])
-    );
-    sqlite3_free(zTmp);
-  }
-}
-
-/*
-**   dq(zString)
-**
-** This scalar function accepts a single argument and interprets it as
-** a text value. The return value is the argument enclosed in double
-** quotes. If any double quote characters are present in the argument,
-** these are escaped.
-**
-**   dq('the raven "Nevermore."') == '"the raven ""Nevermore."""'
-*/
-static void doublequote(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  int ii;
-  char *zOut;
-  char *zCsr;
-  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
-  int nIn = sqlite3_value_bytes(argv[0]);
-
-  UNUSED_PARAMETER(argc);
-  zOut = sqlite3_malloc(nIn*2+3);
-  zCsr = zOut;
-  *zCsr++ = '"';
-  for(ii=0; ii<nIn; ii++){
-    *zCsr++ = zIn[ii];
-    if( zIn[ii]=='"' ){
-      *zCsr++ = '"';
-    }
-  }
-  *zCsr++ = '"';
-  *zCsr++ = '\0';
-
-  sqlite3_result_text(context, zOut, -1, SQLITE_TRANSIENT);
-  sqlite3_free(zOut);
-}
-
-/*
-**   multireplace(zString, zSearch1, zReplace1, ...)
-*/
-static void multireplace(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  int i = 0;
-  char *zOut = 0;
-  int nOut = 0;
-  int nMalloc = 0;
-  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
-  int nIn = sqlite3_value_bytes(argv[0]);
-
-  while( i<nIn ){
-    const char *zCopy = &zIn[i];
-    int nCopy = 1;
-    int nReplace = 1;
-    int j;
-    for(j=1; j<(argc-1); j+=2){
-      const char *z = (const char *)sqlite3_value_text(argv[j]);
-      int n = sqlite3_value_bytes(argv[j]);
-      if( n<=(nIn-i) && 0==strncmp(z, zCopy, n) ){
-        zCopy = (const char *)sqlite3_value_text(argv[j+1]);
-        nCopy = sqlite3_value_bytes(argv[j+1]);
-        nReplace = n;
-        break;
-      }
-    }
-    if( (nOut+nCopy)>nMalloc ){
-      char *zNew;
-      nMalloc = 16 + (nOut+nCopy)*2;
-      zNew = (char*)sqlite3_realloc(zOut, nMalloc);
-      if( zNew==0 ){
-        sqlite3_result_error_nomem(context);
-        return;
-      }else{
-        zOut = zNew;
-      }
-    }
-    assert( nMalloc>=(nOut+nCopy) );
-    memcpy(&zOut[nOut], zCopy, nCopy);
-    i += nReplace;
-    nOut += nCopy;
-  }
-
-  sqlite3_result_text(context, zOut, nOut, SQLITE_TRANSIENT);
-  sqlite3_free(zOut);
-}
-
-/*
-** A callback for sqlite3_exec() invokes the callback specified by the
-** GenfkeyCb structure pointed to by the void* passed as the first argument.
-*/
-static int invokeCallback(void *p, int nArg, char **azArg, char **azCol){
-  GenfkeyCb *pCb = (GenfkeyCb *)p;
-  UNUSED_PARAMETER(nArg);
-  UNUSED_PARAMETER(azCol);
-  return pCb->xData(pCb->pCtx, pCb->eType, azArg[0]);
-}
-
-static int detectSchemaProblem(
-  sqlite3 *db,                   /* Database connection */
-  const char *zMessage,          /* English language error message */
-  const char *zSql,              /* SQL statement to run */
-  GenfkeyCb *pCb
-){
-  sqlite3_stmt *pStmt;
-  int rc;
-  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-  while( SQLITE_ROW==sqlite3_step(pStmt) ){
-    char *zDel;
-    int iFk = sqlite3_column_int(pStmt, 0);
-    const char *zTab = (const char *)sqlite3_column_text(pStmt, 1);
-    zDel = sqlite3_mprintf("Error in table %s: %s", zTab, zMessage);
-    rc = pCb->xData(pCb->pCtx, pCb->eType, zDel);
-    sqlite3_free(zDel);
-    if( rc!=SQLITE_OK ) return rc;
-    zDel = sqlite3_mprintf(
-        "DELETE FROM temp.fkey WHERE from_tbl = %Q AND fkid = %d"
-        , zTab, iFk
-    );
-    sqlite3_exec(db, zDel, 0, 0, 0);
-    sqlite3_free(zDel);
-  }
-  sqlite3_finalize(pStmt);
-  return SQLITE_OK;
-}
-
-/*
-** Create and populate temporary table "fkey".
-*/
-static int populateTempTable(sqlite3 *db, GenfkeyCb *pCallback){
-  int rc;
-
-  rc = sqlite3_exec(db,
-      "CREATE VIRTUAL TABLE temp.v_fkey USING schema(foreign_key_list);"
-      "CREATE VIRTUAL TABLE temp.v_col USING schema(table_info);"
-      "CREATE VIRTUAL TABLE temp.v_idxlist USING schema(index_list);"
-      "CREATE VIRTUAL TABLE temp.v_idxinfo USING schema(index_info);"
-      "CREATE VIRTUAL TABLE temp.v_triggers USING schema(trigger_list);"
-      "CREATE TABLE temp.fkey AS "
-        "SELECT from_tbl, to_tbl, fkid, from_col, to_col, on_update, on_delete "
-        "FROM temp.v_fkey WHERE database = 'main';"
-      , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  rc = detectSchemaProblem(db, "foreign key columns do not exist",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NOT NULL AND NOT EXISTS (SELECT 1 "
-        "FROM temp.v_col WHERE tablename=to_tbl AND name==to_col"
-    ")", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* At this point the temp.fkey table is mostly populated. If any foreign
-  ** keys were specified so that they implicitly refer to they primary
-  ** key of the parent table, the "to_col" values of the temp.fkey rows
-  ** are still set to NULL.
-  **
-  ** This is easily fixed for single column primary keys, but not for
-  ** composites. With a composite primary key, there is no way to reliably
-  ** query sqlite for the order in which the columns that make up the
-  ** composite key were declared i.e. there is no way to tell if the
-  ** schema actually contains "PRIMARY KEY(a, b)" or "PRIMARY KEY(b, a)".
-  ** Therefore, this case is not handled. The following function call
-  ** detects instances of this case.
-  */
-  rc = detectSchemaProblem(db, "implicit mapping to composite primary key",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NULL "
-    "GROUP BY fkid, from_tbl HAVING count(*) > 1", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Detect attempts to implicitly map to the primary key of a table
-  ** that has no primary key column.
-  */
-  rc = detectSchemaProblem(db, "implicit mapping to non-existant primary key",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NULL AND NOT EXISTS "
-      "(SELECT 1 FROM temp.v_col WHERE pk AND tablename = temp.fkey.to_tbl)"
-    , pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Fix all the implicit primary key mappings in the temp.fkey table. */
-  rc = sqlite3_exec(db,
-    "UPDATE temp.fkey SET to_col = "
-      "(SELECT name FROM temp.v_col WHERE pk AND tablename=temp.fkey.to_tbl)"
-    " WHERE to_col IS NULL;"
-    , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Now check that all all parent keys are either primary keys or
-  ** subject to a unique constraint.
-  */
-  rc = sqlite3_exec(db,
-    "CREATE TABLE temp.idx2 AS SELECT "
-      "il.tablename AS tablename,"
-      "ii.indexname AS indexname,"
-      "ii.name AS col "
-      "FROM temp.v_idxlist AS il, temp.v_idxinfo AS ii "
-      "WHERE il.isunique AND il.database='main' AND ii.indexname = il.name;"
-    "INSERT INTO temp.idx2 "
-      "SELECT tablename, 'pk', name FROM temp.v_col WHERE pk;"
-
-    "CREATE TABLE temp.idx AS SELECT "
-      "tablename, indexname, sj(dq(col),',') AS cols "
-      "FROM (SELECT * FROM temp.idx2 ORDER BY col) "
-      "GROUP BY tablename, indexname;"
-
-    "CREATE TABLE temp.fkey2 AS SELECT "
-        "fkid, from_tbl, to_tbl, sj(dq(to_col),',') AS cols "
-        "FROM (SELECT * FROM temp.fkey ORDER BY to_col) "
-        "GROUP BY fkid, from_tbl;"
-
-    "CREATE TABLE temp.triggers AS SELECT "
-        "triggername FROM temp.v_triggers WHERE database='main' AND "
-        "triggername LIKE 'genfkey%';"
-    , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-  rc = detectSchemaProblem(db, "foreign key is not unique",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey2 "
-    "WHERE NOT EXISTS (SELECT 1 "
-        "FROM temp.idx WHERE tablename=to_tbl AND fkey2.cols==idx.cols"
-    ")", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  return rc;
-}
-
-#define GENFKEY_ERROR         1
-#define GENFKEY_DROPTRIGGER   2
-#define GENFKEY_CREATETRIGGER 3
-static int genfkey_create_triggers(
-  sqlite3 *sdb,                        /* Connection to read schema from */
-  const char *zDb,                     /* Name of db to read ("main", "temp") */
-  void *pCtx,                          /* Context pointer to pass to xData */
-  int (*xData)(void *, int, const char *)
-){
-  const char *zSql =
-    "SELECT multireplace('"
-
-      "-- Triggers for foreign key mapping:\n"
-      "--\n"
-      "--     /from_readable/ REFERENCES /to_readable/\n"
-      "--     on delete /on_delete/\n"
-      "--     on update /on_update/\n"
-      "--\n"
-
-      /* The "BEFORE INSERT ON <referencing>" trigger. This trigger's job is to
-      ** throw an exception if the user tries to insert a row into the
-      ** referencing table for which there is no corresponding row in
-      ** the referenced table.
-      */
-      "CREATE TRIGGER /name/_insert_referencing BEFORE INSERT ON /tbl/ WHEN \n"
-      "    /key_notnull/ AND NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n"
-      "BEGIN\n"
-        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
-      "END;\n"
-
-      /* The "BEFORE UPDATE ON <referencing>" trigger. This trigger's job
-      ** is to throw an exception if the user tries to update a row in the
-      ** referencing table causing it to correspond to no row in the
-      ** referenced table.
-      */
-      "CREATE TRIGGER /name/_update_referencing BEFORE\n"
-      "    UPDATE OF /rkey_list/ ON /tbl/ WHEN \n"
-      "    /key_notnull/ AND \n"
-      "    NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n"
-      "BEGIN\n"
-        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
-      "END;\n"
-
-
-      /* The "BEFORE DELETE ON <referenced>" trigger. This trigger's job
-      ** is to detect when a row is deleted from the referenced table to
-      ** which rows in the referencing table correspond. The action taken
-      ** depends on the value of the 'ON DELETE' clause.
-      */
-      "CREATE TRIGGER /name/_delete_referenced BEFORE DELETE ON /ref/ WHEN\n"
-      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
-      "BEGIN\n"
-      "  /delete_action/\n"
-      "END;\n"
-
-      /* The "AFTER UPDATE ON <referenced>" trigger. This trigger's job
-      ** is to detect when the key columns of a row in the referenced table
-      ** to which one or more rows in the referencing table correspond are
-      ** updated. The action taken depends on the value of the 'ON UPDATE'
-      ** clause.
-      */
-      "CREATE TRIGGER /name/_update_referenced AFTER\n"
-      "    UPDATE OF /fkey_list/ ON /ref/ WHEN \n"
-      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
-      "BEGIN\n"
-      "  /update_action/\n"
-      "END;\n"
-    "'"
-
-    /* These are used in the SQL comment written above each set of triggers */
-    ", '/from_readable/',  from_tbl || '(' || sj(from_col, ', ') || ')'"
-    ", '/to_readable/',    to_tbl || '(' || sj(to_col, ', ') || ')'"
-    ", '/on_delete/', on_delete"
-    ", '/on_update/', on_update"
-
-    ", '/name/',   'genfkey' || min(rowid)"
-    ", '/tbl/',    dq(from_tbl)"
-    ", '/ref/',    dq(to_tbl)"
-    ", '/key_notnull/', sj('new.' || dq(from_col) || ' IS NOT NULL', ' AND ')"
-
-    ", '/fkey_list/', sj(dq(to_col), ', ')"
-    ", '/rkey_list/', sj(dq(from_col), ', ')"
-
-    ", '/cond1/',  sj(multireplace('new./from/ == /to/'"
-                   ", '/from/', dq(from_col)"
-                   ", '/to/',   dq(to_col)"
-                   "), ' AND ')"
-    ", '/cond2/',  sj(multireplace('old./to/ == /from/'"
-                   ", '/from/', dq(from_col)"
-                   ", '/to/',   dq(to_col)"
-                   "), ' AND ')"
-
-    ", '/update_action/', CASE on_update "
-      "WHEN 'SET NULL' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = NULL',', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "WHEN 'CASCADE' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = new.'||dq(to_col),', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "ELSE "
-      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
-      "END "
-
-    ", '/delete_action/', CASE on_delete "
-      "WHEN 'SET NULL' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = NULL',', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "WHEN 'CASCADE' THEN "
-        "multireplace('DELETE FROM /tbl/ WHERE /where/;' "
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "ELSE "
-      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
-      "END "
-
-    ") FROM temp.fkey "
-    "GROUP BY from_tbl, fkid"
-  ;
-
-  int rc;
-  const int enc = SQLITE_UTF8;
-  sqlite3 *db = 0;
-
-  GenfkeyCb cb;
-  cb.xData = xData;
-  cb.pCtx = pCtx;
-
-  UNUSED_PARAMETER(zDb);
-
-  /* Open the working database handle. */
-  rc = sqlite3_open(":memory:", &db);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Create the special scalar and aggregate functions used by this program. */
-  sqlite3_create_function(db, "dq", 1, enc, 0, doublequote, 0, 0);
-  sqlite3_create_function(db, "multireplace", -1, enc, db, multireplace, 0, 0);
-  sqlite3_create_function(db, "sj", 2, enc, 0, 0, joinStep, joinFinalize);
-
-  /* Install the "schema" virtual table module */
-  installSchemaModule(db, sdb);
-
-  /* Create and populate a temp table with the information required to
-  ** build the foreign key triggers. See function populateTempTable()
-  ** for details.
-  */
-  cb.eType = GENFKEY_ERROR;
-  rc = populateTempTable(db, &cb);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Unless the --no-drop option was specified, generate DROP TRIGGER
-  ** statements to drop any triggers in the database generated by a
-  ** previous run of this program.
-  */
-  cb.eType = GENFKEY_DROPTRIGGER;
-  rc = sqlite3_exec(db,
-    "SELECT 'DROP TRIGGER main.' || dq(triggername) || ';' FROM triggers"
-    ,invokeCallback, (void *)&cb, 0
-  );
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Run the main query to create the trigger definitions. */
-  cb.eType = GENFKEY_CREATETRIGGER;
-  rc = sqlite3_exec(db, zSql, invokeCallback, (void *)&cb, 0);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-genfkey_exit:
-  sqlite3_close(db);
-  return rc;
-}
-
-
-#endif
-/* End genfkey logic. */
-/*************************************************************************/
-/*************************************************************************/
-
 /*
 ** If the following flag is set, then command execution stops
 ** at an error if we are not interactive.
@@ -1155,8 +293,8 @@
 }
 
 /*
-** A global char* and an SQL function to access its current value
-** from within an SQL statement. This program used to use the
+** A global char* and an SQL function to access its current value 
+** from within an SQL statement. This program used to use the 
 ** sqlite_exec_printf() API to substitue a string into an SQL statement.
 ** The correct way to do this with sqlite3 is to use the bind API, but
 ** since the shell is built around the callback paradigm it would be a lot
@@ -1412,11 +550,11 @@
 static void output_html_string(FILE *out, const char *z){
   int i;
   while( *z ){
-    for(i=0;   z[i]
-            && z[i]!='<'
-            && z[i]!='&'
-            && z[i]!='>'
-            && z[i]!='\"'
+    for(i=0;   z[i] 
+            && z[i]!='<' 
+            && z[i]!='&' 
+            && z[i]!='>' 
+            && z[i]!='\"' 
             && z[i]!='\'';
         i++){}
     if( i>0 ){
@@ -1444,22 +582,22 @@
 ** array, then the string must be quoted for CSV.
 */
 static const char needCsvQuote[] = {
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 0, 1, 0, 0, 0, 0, 1,   0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 0, 1, 0, 0, 0, 0, 1,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 0, 
+  0, 0, 0, 0, 0, 0, 0, 0,   0, 0, 0, 0, 0, 0, 0, 1, 
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
+  1, 1, 1, 1, 1, 1, 1, 1,   1, 1, 1, 1, 1, 1, 1, 1,   
 };
 
 /*
@@ -1476,8 +614,8 @@
     int i;
     int nSep = strlen30(p->separator);
     for(i=0; z[i]; i++){
-      if( needCsvQuote[((unsigned char*)z)[i]]
-         || (z[i]==p->separator[0] &&
+      if( needCsvQuote[((unsigned char*)z)[i]] 
+         || (z[i]==p->separator[0] && 
              (nSep==1 || memcmp(z, p->separator, nSep)==0)) ){
         i = 0;
         break;
@@ -1518,10 +656,6 @@
   int i;
   struct callback_data *p = (struct callback_data*)pArg;
 
-  if( p->echoOn && p->cnt==0  && p->pStmt){
-    printf("%s\n", sqlite3_sql(p->pStmt));
-  }
-
   switch( p->mode ){
     case MODE_Line: {
       int w = 5;
@@ -1582,7 +716,7 @@
         }else{
            w = 10;
         }
-        if( p->mode==MODE_Explain && azArg[i] &&
+        if( p->mode==MODE_Explain && azArg[i] && 
            strlen30(azArg[i])>w ){
           w = strlen30(azArg[i]);
         }
@@ -1747,7 +881,7 @@
 ** added to zIn, and the result returned in memory obtained from malloc().
 ** zIn, if it was not NULL, is freed.
 **
-** If the third argument, quote, is not '\0', then it is used as a
+** If the third argument, quote, is not '\0', then it is used as a 
 ** quote character for zAppend.
 */
 static char *appendText(char *zIn, char const *zAppend, char quote){
@@ -1834,12 +968,12 @@
 }
 
 /*
-** Execute a statement or set of statements.  Print
-** any result rows/columns depending on the current mode
+** Execute a statement or set of statements.  Print 
+** any result rows/columns depending on the current mode 
 ** set via the supplied callback.
 **
-** This is very similar to SQLite's built-in sqlite3_exec()
-** function except it takes a slightly different callback
+** This is very similar to SQLite's built-in sqlite3_exec() 
+** function except it takes a slightly different callback 
 ** and callback data argument.
 */
 static int shell_exec(
@@ -1872,6 +1006,12 @@
         continue;
       }
 
+      /* echo the sql statement if echo on */
+      if( pArg->echoOn ){
+        const char *zStmtSql = sqlite3_sql(pStmt);
+        fprintf(pArg->out,"%s\n", zStmtSql ? zStmtSql : zSql);
+      }
+
       /* perform the first step.  this will tell us if we
       ** have a result set or not and how wide it is.
       */
@@ -1890,7 +1030,7 @@
             char **azVals = &azCols[nCol];       /* Results */
             int *aiTypes = (int *)&azVals[nCol]; /* Result types */
             int i;
-            assert(sizeof(int) <= sizeof(char *));
+            assert(sizeof(int) <= sizeof(char *)); 
             /* save off ptrs to column names */
             for(i=0; i<nCol; i++){
               azCols[i] = (char *)sqlite3_column_name(pStmt, i);
@@ -1912,7 +1052,7 @@
               } /* end for */
 
               /* if data and types extracted successfully... */
-              if( SQLITE_ROW == rc ){
+              if( SQLITE_ROW == rc ){ 
                 /* call the supplied callback with the result row data */
                 if( xCallback(pArg, nCol, azVals, azCols, aiTypes) ){
                   rc = SQLITE_ABORT;
@@ -1933,7 +1073,7 @@
         }
       }
 
-      /* Finalize the statement just executed. If this fails, save a
+      /* Finalize the statement just executed. If this fails, save a 
       ** copy of the error message. Otherwise, set zSql to point to the
       ** next statement to execute. */
       rc = sqlite3_finalize(pStmt);
@@ -1969,7 +1109,7 @@
   zTable = azArg[0];
   zType = azArg[1];
   zSql = azArg[2];
-
+  
   if( strcmp(zTable, "sqlite_sequence")==0 ){
     zPrepStmt = "DELETE FROM sqlite_sequence;\n";
   }else if( strcmp(zTable, "sqlite_stat1")==0 ){
@@ -1999,7 +1139,7 @@
     char *zTableInfo = 0;
     char *zTmp = 0;
     int nRow = 0;
-
+   
     zTableInfo = appendText(zTableInfo, "PRAGMA table_info(", 0);
     zTableInfo = appendText(zTableInfo, zTable, '"');
     zTableInfo = appendText(zTableInfo, ");", 0);
@@ -2055,7 +1195,7 @@
 ** "ORDER BY rowid DESC" to the end.
 */
 static int run_schema_dump_query(
-  struct callback_data *p,
+  struct callback_data *p, 
   const char *zQuery,
   char **pzErrMsg
 ){
@@ -2074,62 +1214,6 @@
   return rc;
 }
 
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-struct GenfkeyCmd {
-  sqlite3 *db;                   /* Database handle */
-  struct callback_data *pCb;     /* Callback data */
-  int isIgnoreErrors;            /* True for --ignore-errors */
-  int isExec;                    /* True for --exec */
-  int isNoDrop;                  /* True for --no-drop */
-  int nErr;                      /* Number of errors seen so far */
-};
-typedef struct GenfkeyCmd GenfkeyCmd;
-
-static int genfkeyParseArgs(GenfkeyCmd *p, char **azArg, int nArg){
-  int ii;
-  memset(p, 0, sizeof(GenfkeyCmd));
-
-  for(ii=0; ii<nArg; ii++){
-    int n = strlen30(azArg[ii]);
-
-    if( n>2 && n<10 && 0==strncmp(azArg[ii], "--no-drop", n) ){
-      p->isNoDrop = 1;
-    }else if( n>2 && n<16 && 0==strncmp(azArg[ii], "--ignore-errors", n) ){
-      p->isIgnoreErrors = 1;
-    }else if( n>2 && n<7 && 0==strncmp(azArg[ii], "--exec", n) ){
-      p->isExec = 1;
-    }else{
-      fprintf(stderr, "unknown option: %s\n", azArg[ii]);
-      return -1;
-    }
-  }
-
-  return SQLITE_OK;
-}
-
-static int genfkeyCmdCb(void *pCtx, int eType, const char *z){
-  GenfkeyCmd *p = (GenfkeyCmd *)pCtx;
-  if( eType==GENFKEY_ERROR && !p->isIgnoreErrors ){
-    p->nErr++;
-    fprintf(stderr, "%s\n", z);
-  }
-
-  if( p->nErr==0 && (
-        (eType==GENFKEY_CREATETRIGGER)
-     || (eType==GENFKEY_DROPTRIGGER && !p->isNoDrop)
-  )){
-    if( p->isExec ){
-      sqlite3_exec(p->db, z, 0, 0, 0);
-    }else{
-      char *zCol = "sql";
-      callback((void *)p->pCb, 1, (char **)&z, (char **)&zCol);
-    }
-  }
-
-  return SQLITE_OK;
-}
-#endif
-
 /*
 ** Text of a help message
 */
@@ -2144,14 +1228,6 @@
   ".exit                  Exit this program\n"
   ".explain ?ON|OFF?      Turn output mode suitable for EXPLAIN on or off.\n"
   "                         With no args, it turns EXPLAIN on.\n"
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-  ".genfkey ?OPTIONS?     Options are:\n"
-  "                         --no-drop: Do not drop old fkey triggers.\n"
-  "                         --ignore-errors: Ignore tables with fkey errors\n"
-  "                         --exec: Execute generated SQL immediately\n"
-  "                       See file tool/genfkey.README in the source \n"
-  "                       distribution for further information.\n"
-#endif
   ".header(s) ON|OFF      Turn display of headers on or off\n"
   ".help                  Show this message\n"
   ".import FILE TABLE     Import data from FILE into TABLE\n"
@@ -2213,7 +1289,7 @@
           shellstaticFunc, 0, 0);
     }
     if( db==0 || SQLITE_OK!=sqlite3_errcode(db) ){
-      fprintf(stderr,"Error: unable to open database \"%s\": %s\n",
+      fprintf(stderr,"Error: unable to open database \"%s\": %s\n", 
           p->zDbFilename, sqlite3_errmsg(db));
       exit(1);
     }
@@ -2401,11 +1477,11 @@
     p->writableSchema = 0;
     sqlite3_exec(p->db, "PRAGMA writable_schema=ON", 0, 0, 0);
     if( nArg==1 ){
-      run_schema_dump_query(p,
+      run_schema_dump_query(p, 
         "SELECT name, type, sql FROM sqlite_master "
         "WHERE sql NOT NULL AND type=='table' AND name!='sqlite_sequence'", 0
       );
-      run_schema_dump_query(p,
+      run_schema_dump_query(p, 
         "SELECT name, type, sql FROM sqlite_master "
         "WHERE name=='sqlite_sequence'", 0
       );
@@ -2486,17 +1562,6 @@
     }
   }else
 
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-  if( c=='g' && strncmp(azArg[0], "genfkey", n)==0 ){
-    GenfkeyCmd cmd;
-    if( 0==genfkeyParseArgs(&cmd, &azArg[1], nArg-1) ){
-      cmd.db = p->db;
-      cmd.pCb = p;
-      genfkey_create_triggers(p->db, "main", (void *)&cmd, genfkeyCmdCb);
-    }
-  }else
-#endif
-
   if( c=='h' && (strncmp(azArg[0], "header", n)==0 ||
                  strncmp(azArg[0], "headers", n)==0) && nArg>1 && nArg<3 ){
     p->showHeader = booleanValue(azArg[1]);
@@ -2520,7 +1585,7 @@
     char *zSql;                 /* An SQL statement */
     char *zLine;                /* A single line of input from the file */
     char **azCol;               /* zLine[] broken up into columns */
-    char *zCommit;              /* How to commit changes */
+    char *zCommit;              /* How to commit changes */   
     FILE *in;                   /* The input file */
     int lineno = 0;             /* Line number of input file */
 
@@ -3025,11 +2090,11 @@
     open_db(p);
     sqlite3_busy_timeout(p->db, atoi(azArg[1]));
   }else
-
+    
   if( HAS_TIMER && c=='t' && n>=5 && strncmp(azArg[0], "timer", n)==0 && nArg==2 ){
     enableTimer = booleanValue(azArg[1]);
   }else
-
+  
   if( c=='w' && strncmp(azArg[0], "width", n)==0 && nArg>1 ){
     int j;
     assert( nArg<=ArraySize(azArg) );
@@ -3193,7 +2258,7 @@
       if( rc || zErrMsg ){
         char zPrefix[100];
         if( in!=0 || !stdin_is_interactive ){
-          sqlite3_snprintf(sizeof(zPrefix), zPrefix,
+          sqlite3_snprintf(sizeof(zPrefix), zPrefix, 
                            "Error: near line %d:", startline);
         }else{
           sqlite3_snprintf(sizeof(zPrefix), zPrefix, "Error:");
@@ -3332,7 +2397,7 @@
 /*
 ** Show available command line options
 */
-static const char zOptions[] =
+static const char zOptions[] = 
   "   -help                show this message\n"
   "   -init filename       read/process named file\n"
   "   -echo                print commands before execution\n"
@@ -3351,7 +2416,7 @@
 ;
 static void usage(int showDetail){
   fprintf(stderr,
-      "Usage: %s [OPTIONS] FILENAME [SQL]\n"
+      "Usage: %s [OPTIONS] FILENAME [SQL]\n"  
       "FILENAME is the name of an SQLite database. A new database is created\n"
       "if the file does not previously exist.\n", Argv0);
   if( showDetail ){
@@ -3373,6 +2438,7 @@
   sqlite3_config(SQLITE_CONFIG_LOG, shellLog, data);
   sqlite3_snprintf(sizeof(mainPrompt), mainPrompt,"sqlite> ");
   sqlite3_snprintf(sizeof(continuePrompt), continuePrompt,"   ...> ");
+  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);
 }
 
 int main(int argc, char **argv){
@@ -3409,7 +2475,7 @@
       i++;
       zInitFile = argv[i];
     /* Need to check for batch mode here to so we can avoid printing
-    ** informational messages (like from process_sqliterc) before
+    ** informational messages (like from process_sqliterc) before 
     ** we do the actual processing of arguments later in a second pass.
     */
     }else if( strcmp(argv[i],"-batch")==0 ){
@@ -3532,7 +2598,6 @@
     */
     if( zFirstCmd[0]=='.' ){
       rc = do_meta_command(zFirstCmd, &data);
-      return rc;
     }else{
       open_db(&data);
       rc = shell_exec(data.db, zFirstCmd, shell_callback, &data, &zErrMsg);
@@ -3579,9 +2644,10 @@
     }
   }
   set_table_name(&data, 0);
-  if( db ){
-    if( sqlite3_close(db)!=SQLITE_OK ){
-      fprintf(stderr,"Error: cannot close database \"%s\"\n", sqlite3_errmsg(db));
+  if( data.db ){
+    if( sqlite3_close(data.db)!=SQLITE_OK ){
+      fprintf(stderr,"Error: cannot close database \"%s\"\n",
+              sqlite3_errmsg(db));
       rc++;
     }
   }
diff --git a/dist/shell.c.orig b/dist/shell.c.orig
index c72b78d..23099b9 100644
--- a/dist/shell.c.orig
+++ b/dist/shell.c.orig
@@ -195,868 +195,6 @@
 */
 #define UNUSED_PARAMETER(x) (void)(x)
 
-
-/**************************************************************************
-***************************************************************************
-** Begin genfkey logic.
-*/
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined SQLITE_OMIT_SUBQUERY
-
-#define GENFKEY_ERROR         1
-#define GENFKEY_DROPTRIGGER   2
-#define GENFKEY_CREATETRIGGER 3
-static int genfkey_create_triggers(sqlite3 *, const char *, void *,
-  int (*)(void *, int, const char *)
-);
-
-struct GenfkeyCb {
-  void *pCtx;
-  int eType;
-  int (*xData)(void *, int, const char *);
-};
-typedef struct GenfkeyCb GenfkeyCb;
-
-/* The code in this file defines a sqlite3 virtual-table module that
-** provides a read-only view of the current database schema. There is one
-** row in the schema table for each column in the database schema.
-*/
-#define SCHEMA \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "tablename,"         /* Name of table */                                   \
-  "cid,"               /* Column number (from left-to-right, 0 upward) */    \
-  "name,"              /* Column name */                                     \
-  "type,"              /* Specified type (i.e. VARCHAR(32)) */               \
-  "not_null,"          /* Boolean. True if NOT NULL was specified */         \
-  "dflt_value,"        /* Default value for this column */                   \
-  "pk"                 /* True if this column is part of the primary key */  \
-")"
-
-#define SCHEMA2 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "from_tbl,"          /* Name of table */                                   \
-  "fkid,"                                                                    \
-  "seq,"                                                                     \
-  "to_tbl,"                                                                  \
-  "from_col,"                                                                \
-  "to_col,"                                                                  \
-  "on_update,"                                                               \
-  "on_delete,"                                                               \
-  "match"                                                                    \
-")"
-
-#define SCHEMA3 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "tablename,"         /* Name of table */                                   \
-  "seq,"                                                                     \
-  "name,"                                                                    \
-  "isunique"                                                                 \
-")"
-
-#define SCHEMA4 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "indexname,"         /* Name of table */                                   \
-  "seqno,"                                                                   \
-  "cid,"                                                                     \
-  "name"                                                                     \
-")"
-
-#define SCHEMA5 \
-"CREATE TABLE x("                                                            \
-  "database,"          /* Name of database (i.e. main, temp etc.) */         \
-  "triggername,"       /* Name of trigger */                                 \
-  "dummy"              /* Unused */                                          \
-")"
-
-typedef struct SchemaTable SchemaTable;
-static struct SchemaTable {
-  const char *zName;
-  const char *zObject;
-  const char *zPragma;
-  const char *zSchema;
-} aSchemaTable[] = {
-  { "table_info",       "table", "PRAGMA %Q.table_info(%Q)",       SCHEMA },
-  { "foreign_key_list", "table", "PRAGMA %Q.foreign_key_list(%Q)", SCHEMA2 },
-  { "index_list",       "table", "PRAGMA %Q.index_list(%Q)",       SCHEMA3 },
-  { "index_info",       "index", "PRAGMA %Q.index_info(%Q)",       SCHEMA4 },
-  { "trigger_list",     "trigger", "SELECT 1",                     SCHEMA5 },
-  { 0, 0, 0, 0 }
-};
-
-typedef struct schema_vtab schema_vtab;
-typedef struct schema_cursor schema_cursor;
-
-/* A schema table object */
-struct schema_vtab {
-  sqlite3_vtab base;
-  sqlite3 *db;
-  SchemaTable *pType;
-};
-
-/* A schema table cursor object */
-struct schema_cursor {
-  sqlite3_vtab_cursor base;
-  sqlite3_stmt *pDbList;
-  sqlite3_stmt *pTableList;
-  sqlite3_stmt *pColumnList;
-  int rowid;
-};
-
-/*
-** Table destructor for the schema module.
-*/
-static int schemaDestroy(sqlite3_vtab *pVtab){
-  sqlite3_free(pVtab);
-  return 0;
-}
-
-/*
-** Table constructor for the schema module.
-*/
-static int schemaCreate(
-  sqlite3 *db,
-  void *pAux,
-  int argc, const char *const*argv,
-  sqlite3_vtab **ppVtab,
-  char **pzErr
-){
-  int rc = SQLITE_NOMEM;
-  schema_vtab *pVtab;
-  SchemaTable *pType = &aSchemaTable[0];
-
-  UNUSED_PARAMETER(pzErr);
-  if( argc>3 ){
-    int i;
-    pType = 0;
-    for(i=0; aSchemaTable[i].zName; i++){ 
-      if( 0==strcmp(argv[3], aSchemaTable[i].zName) ){
-        pType = &aSchemaTable[i];
-      }
-    }
-    if( !pType ){
-      return SQLITE_ERROR;
-    }
-  }
-
-  pVtab = sqlite3_malloc(sizeof(schema_vtab));
-  if( pVtab ){
-    memset(pVtab, 0, sizeof(schema_vtab));
-    pVtab->db = (sqlite3 *)pAux;
-    pVtab->pType = pType;
-    rc = sqlite3_declare_vtab(db, pType->zSchema);
-  }
-  *ppVtab = (sqlite3_vtab *)pVtab;
-  return rc;
-}
-
-/*
-** Open a new cursor on the schema table.
-*/
-static int schemaOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
-  int rc = SQLITE_NOMEM;
-  schema_cursor *pCur;
-  UNUSED_PARAMETER(pVTab);
-  pCur = sqlite3_malloc(sizeof(schema_cursor));
-  if( pCur ){
-    memset(pCur, 0, sizeof(schema_cursor));
-    *ppCursor = (sqlite3_vtab_cursor *)pCur;
-    rc = SQLITE_OK;
-  }
-  return rc;
-}
-
-/*
-** Close a schema table cursor.
-*/
-static int schemaClose(sqlite3_vtab_cursor *cur){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  sqlite3_finalize(pCur->pDbList);
-  sqlite3_finalize(pCur->pTableList);
-  sqlite3_finalize(pCur->pColumnList);
-  sqlite3_free(pCur);
-  return SQLITE_OK;
-}
-
-static void columnToResult(sqlite3_context *ctx, sqlite3_stmt *pStmt, int iCol){
-  switch( sqlite3_column_type(pStmt, iCol) ){
-    case SQLITE_NULL:
-      sqlite3_result_null(ctx);
-      break;
-    case SQLITE_INTEGER:
-      sqlite3_result_int64(ctx, sqlite3_column_int64(pStmt, iCol));
-      break;
-    case SQLITE_FLOAT:
-      sqlite3_result_double(ctx, sqlite3_column_double(pStmt, iCol));
-      break;
-    case SQLITE_TEXT: {
-      const char *z = (const char *)sqlite3_column_text(pStmt, iCol);
-      sqlite3_result_text(ctx, z, -1, SQLITE_TRANSIENT);
-      break;
-    }
-  }
-}
-
-/*
-** Retrieve a column of data.
-*/
-static int schemaColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  switch( i ){
-    case 0:
-      columnToResult(ctx, pCur->pDbList, 1);
-      break;
-    case 1:
-      columnToResult(ctx, pCur->pTableList, 0);
-      break;
-    default:
-      columnToResult(ctx, pCur->pColumnList, i-2);
-      break;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Retrieve the current rowid.
-*/
-static int schemaRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  *pRowid = pCur->rowid;
-  return SQLITE_OK;
-}
-
-static int finalize(sqlite3_stmt **ppStmt){
-  int rc = sqlite3_finalize(*ppStmt);
-  *ppStmt = 0;
-  return rc;
-}
-
-static int schemaEof(sqlite3_vtab_cursor *cur){
-  schema_cursor *pCur = (schema_cursor *)cur;
-  return (pCur->pDbList ? 0 : 1);
-}
-
-/*
-** Advance the cursor to the next row.
-*/
-static int schemaNext(sqlite3_vtab_cursor *cur){
-  int rc = SQLITE_OK;
-  schema_cursor *pCur = (schema_cursor *)cur;
-  schema_vtab *pVtab = (schema_vtab *)(cur->pVtab);
-  char *zSql = 0;
-
-  while( !pCur->pColumnList || SQLITE_ROW!=sqlite3_step(pCur->pColumnList) ){
-    if( SQLITE_OK!=(rc = finalize(&pCur->pColumnList)) ) goto next_exit;
-
-    while( !pCur->pTableList || SQLITE_ROW!=sqlite3_step(pCur->pTableList) ){
-      if( SQLITE_OK!=(rc = finalize(&pCur->pTableList)) ) goto next_exit;
-
-      assert(pCur->pDbList);
-      while( SQLITE_ROW!=sqlite3_step(pCur->pDbList) ){
-        rc = finalize(&pCur->pDbList);
-        goto next_exit;
-      }
-
-      /* Set zSql to the SQL to pull the list of tables from the 
-      ** sqlite_master (or sqlite_temp_master) table of the database
-      ** identfied by the row pointed to by the SQL statement pCur->pDbList
-      ** (iterating through a "PRAGMA database_list;" statement).
-      */
-      if( sqlite3_column_int(pCur->pDbList, 0)==1 ){
-        zSql = sqlite3_mprintf(
-            "SELECT name FROM sqlite_temp_master WHERE type=%Q",
-            pVtab->pType->zObject
-        );
-      }else{
-        sqlite3_stmt *pDbList = pCur->pDbList;
-        zSql = sqlite3_mprintf(
-            "SELECT name FROM %Q.sqlite_master WHERE type=%Q",
-             sqlite3_column_text(pDbList, 1), pVtab->pType->zObject
-        );
-      }
-      if( !zSql ){
-        rc = SQLITE_NOMEM;
-        goto next_exit;
-      }
-
-      rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pTableList, 0);
-      sqlite3_free(zSql);
-      if( rc!=SQLITE_OK ) goto next_exit;
-    }
-
-    /* Set zSql to the SQL to the table_info pragma for the table currently
-    ** identified by the rows pointed to by statements pCur->pDbList and
-    ** pCur->pTableList.
-    */
-    zSql = sqlite3_mprintf(pVtab->pType->zPragma,
-        sqlite3_column_text(pCur->pDbList, 1),
-        sqlite3_column_text(pCur->pTableList, 0)
-    );
-
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-      goto next_exit;
-    }
-    rc = sqlite3_prepare(pVtab->db, zSql, -1, &pCur->pColumnList, 0);
-    sqlite3_free(zSql);
-    if( rc!=SQLITE_OK ) goto next_exit;
-  }
-  pCur->rowid++;
-
-next_exit:
-  /* TODO: Handle rc */
-  return rc;
-}
-
-/*
-** Reset a schema table cursor.
-*/
-static int schemaFilter(
-  sqlite3_vtab_cursor *pVtabCursor, 
-  int idxNum, const char *idxStr,
-  int argc, sqlite3_value **argv
-){
-  int rc;
-  schema_vtab *pVtab = (schema_vtab *)(pVtabCursor->pVtab);
-  schema_cursor *pCur = (schema_cursor *)pVtabCursor;
-  UNUSED_PARAMETER(idxNum);
-  UNUSED_PARAMETER(idxStr);
-  UNUSED_PARAMETER(argc);
-  UNUSED_PARAMETER(argv);
-  pCur->rowid = 0;
-  finalize(&pCur->pTableList);
-  finalize(&pCur->pColumnList);
-  finalize(&pCur->pDbList);
-  rc = sqlite3_prepare(pVtab->db,"SELECT 0, 'main'", -1, &pCur->pDbList, 0);
-  return (rc==SQLITE_OK ? schemaNext(pVtabCursor) : rc);
-}
-
-/*
-** Analyse the WHERE condition.
-*/
-static int schemaBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
-  UNUSED_PARAMETER(tab);
-  UNUSED_PARAMETER(pIdxInfo);
-  return SQLITE_OK;
-}
-
-/*
-** A virtual table module that merely echos method calls into TCL
-** variables.
-*/
-static sqlite3_module schemaModule = {
-  0,                           /* iVersion */
-  schemaCreate,
-  schemaCreate,
-  schemaBestIndex,
-  schemaDestroy,
-  schemaDestroy,
-  schemaOpen,                  /* xOpen - open a cursor */
-  schemaClose,                 /* xClose - close a cursor */
-  schemaFilter,                /* xFilter - configure scan constraints */
-  schemaNext,                  /* xNext - advance a cursor */
-  schemaEof,                   /* xEof */
-  schemaColumn,                /* xColumn - read data */
-  schemaRowid,                 /* xRowid - read data */
-  0,                           /* xUpdate */
-  0,                           /* xBegin */
-  0,                           /* xSync */
-  0,                           /* xCommit */
-  0,                           /* xRollback */
-  0,                           /* xFindMethod */
-  0,                           /* xRename */
-};
-
-/*
-** Extension load function.
-*/
-static int installSchemaModule(sqlite3 *db, sqlite3 *sdb){
-  sqlite3_create_module(db, "schema", &schemaModule, (void *)sdb);
-  return 0;
-}
-
-/*
-**   sj(zValue, zJoin)
-**
-** The following block contains the implementation of an aggregate 
-** function that returns a string. Each time the function is stepped, 
-** it appends data to an internal buffer. When the aggregate is finalized,
-** the contents of the buffer are returned.
-**
-** The first time the aggregate is stepped the buffer is set to a copy
-** of the first argument. The second time and subsequent times it is
-** stepped a copy of the second argument is appended to the buffer, then
-** a copy of the first.
-**
-** Example:
-**
-**   INSERT INTO t1(a) VALUES('1');
-**   INSERT INTO t1(a) VALUES('2');
-**   INSERT INTO t1(a) VALUES('3');
-**   SELECT sj(a, ', ') FROM t1;
-**
-**     =>  "1, 2, 3"
-**
-*/
-struct StrBuffer {
-  char *zBuf;
-};
-typedef struct StrBuffer StrBuffer;
-static void joinFinalize(sqlite3_context *context){
-  StrBuffer *p;
-  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
-  sqlite3_result_text(context, p->zBuf, -1, SQLITE_TRANSIENT);
-  sqlite3_free(p->zBuf);
-}
-static void joinStep(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  StrBuffer *p;
-  UNUSED_PARAMETER(argc);
-  p = (StrBuffer *)sqlite3_aggregate_context(context, sizeof(StrBuffer));
-  if( p->zBuf==0 ){
-    p->zBuf = sqlite3_mprintf("%s", sqlite3_value_text(argv[0]));
-  }else{
-    char *zTmp = p->zBuf;
-    p->zBuf = sqlite3_mprintf("%s%s%s", 
-        zTmp, sqlite3_value_text(argv[1]), sqlite3_value_text(argv[0])
-    );
-    sqlite3_free(zTmp);
-  }
-}
-
-/*
-**   dq(zString)
-**
-** This scalar function accepts a single argument and interprets it as
-** a text value. The return value is the argument enclosed in double
-** quotes. If any double quote characters are present in the argument, 
-** these are escaped.
-**
-**   dq('the raven "Nevermore."') == '"the raven ""Nevermore."""'
-*/
-static void doublequote(
-  sqlite3_context *context, 
-  int argc, 
-  sqlite3_value **argv
-){
-  int ii;
-  char *zOut;
-  char *zCsr;
-  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
-  int nIn = sqlite3_value_bytes(argv[0]);
-
-  UNUSED_PARAMETER(argc);
-  zOut = sqlite3_malloc(nIn*2+3);
-  zCsr = zOut;
-  *zCsr++ = '"';
-  for(ii=0; ii<nIn; ii++){
-    *zCsr++ = zIn[ii];
-    if( zIn[ii]=='"' ){
-      *zCsr++ = '"';
-    }
-  }
-  *zCsr++ = '"';
-  *zCsr++ = '\0';
-
-  sqlite3_result_text(context, zOut, -1, SQLITE_TRANSIENT);
-  sqlite3_free(zOut);
-}
-
-/*
-**   multireplace(zString, zSearch1, zReplace1, ...)
-*/
-static void multireplace(
-  sqlite3_context *context, 
-  int argc, 
-  sqlite3_value **argv
-){
-  int i = 0;
-  char *zOut = 0;
-  int nOut = 0;
-  int nMalloc = 0;
-  const char *zIn = (const char *)sqlite3_value_text(argv[0]);
-  int nIn = sqlite3_value_bytes(argv[0]);
-
-  while( i<nIn ){
-    const char *zCopy = &zIn[i];
-    int nCopy = 1;
-    int nReplace = 1;
-    int j;
-    for(j=1; j<(argc-1); j+=2){
-      const char *z = (const char *)sqlite3_value_text(argv[j]);
-      int n = sqlite3_value_bytes(argv[j]);
-      if( n<=(nIn-i) && 0==strncmp(z, zCopy, n) ){
-        zCopy = (const char *)sqlite3_value_text(argv[j+1]);
-        nCopy = sqlite3_value_bytes(argv[j+1]);
-        nReplace = n;
-        break;
-      }
-    }
-    if( (nOut+nCopy)>nMalloc ){
-      char *zNew;
-      nMalloc = 16 + (nOut+nCopy)*2;
-      zNew = (char*)sqlite3_realloc(zOut, nMalloc);
-      if( zNew==0 ){
-        sqlite3_result_error_nomem(context);
-        return;
-      }else{
-        zOut = zNew;
-      }
-    }
-    assert( nMalloc>=(nOut+nCopy) );
-    memcpy(&zOut[nOut], zCopy, nCopy);
-    i += nReplace;
-    nOut += nCopy;
-  }
-
-  sqlite3_result_text(context, zOut, nOut, SQLITE_TRANSIENT);
-  sqlite3_free(zOut);
-}
-
-/*
-** A callback for sqlite3_exec() invokes the callback specified by the
-** GenfkeyCb structure pointed to by the void* passed as the first argument.
-*/
-static int invokeCallback(void *p, int nArg, char **azArg, char **azCol){
-  GenfkeyCb *pCb = (GenfkeyCb *)p;
-  UNUSED_PARAMETER(nArg);
-  UNUSED_PARAMETER(azCol);
-  return pCb->xData(pCb->pCtx, pCb->eType, azArg[0]);
-}
-
-static int detectSchemaProblem(
-  sqlite3 *db,                   /* Database connection */
-  const char *zMessage,          /* English language error message */
-  const char *zSql,              /* SQL statement to run */
-  GenfkeyCb *pCb
-){
-  sqlite3_stmt *pStmt;
-  int rc;
-  rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-  while( SQLITE_ROW==sqlite3_step(pStmt) ){
-    char *zDel;
-    int iFk = sqlite3_column_int(pStmt, 0);
-    const char *zTab = (const char *)sqlite3_column_text(pStmt, 1);
-    zDel = sqlite3_mprintf("Error in table %s: %s", zTab, zMessage);
-    rc = pCb->xData(pCb->pCtx, pCb->eType, zDel);
-    sqlite3_free(zDel);
-    if( rc!=SQLITE_OK ) return rc;
-    zDel = sqlite3_mprintf(
-        "DELETE FROM temp.fkey WHERE from_tbl = %Q AND fkid = %d"
-        , zTab, iFk
-    );
-    sqlite3_exec(db, zDel, 0, 0, 0);
-    sqlite3_free(zDel);
-  }
-  sqlite3_finalize(pStmt);
-  return SQLITE_OK;
-}
-
-/*
-** Create and populate temporary table "fkey".
-*/
-static int populateTempTable(sqlite3 *db, GenfkeyCb *pCallback){
-  int rc;
-  
-  rc = sqlite3_exec(db, 
-      "CREATE VIRTUAL TABLE temp.v_fkey USING schema(foreign_key_list);"
-      "CREATE VIRTUAL TABLE temp.v_col USING schema(table_info);"
-      "CREATE VIRTUAL TABLE temp.v_idxlist USING schema(index_list);"
-      "CREATE VIRTUAL TABLE temp.v_idxinfo USING schema(index_info);"
-      "CREATE VIRTUAL TABLE temp.v_triggers USING schema(trigger_list);"
-      "CREATE TABLE temp.fkey AS "
-        "SELECT from_tbl, to_tbl, fkid, from_col, to_col, on_update, on_delete "
-        "FROM temp.v_fkey WHERE database = 'main';"
-      , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  rc = detectSchemaProblem(db, "foreign key columns do not exist",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NOT NULL AND NOT EXISTS (SELECT 1 "
-        "FROM temp.v_col WHERE tablename=to_tbl AND name==to_col"
-    ")", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* At this point the temp.fkey table is mostly populated. If any foreign
-  ** keys were specified so that they implicitly refer to they primary
-  ** key of the parent table, the "to_col" values of the temp.fkey rows
-  ** are still set to NULL.
-  **
-  ** This is easily fixed for single column primary keys, but not for
-  ** composites. With a composite primary key, there is no way to reliably
-  ** query sqlite for the order in which the columns that make up the
-  ** composite key were declared i.e. there is no way to tell if the
-  ** schema actually contains "PRIMARY KEY(a, b)" or "PRIMARY KEY(b, a)".
-  ** Therefore, this case is not handled. The following function call
-  ** detects instances of this case.
-  */
-  rc = detectSchemaProblem(db, "implicit mapping to composite primary key",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NULL "
-    "GROUP BY fkid, from_tbl HAVING count(*) > 1", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Detect attempts to implicitly map to the primary key of a table 
-  ** that has no primary key column.
-  */
-  rc = detectSchemaProblem(db, "implicit mapping to non-existant primary key",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey "
-    "WHERE to_col IS NULL AND NOT EXISTS "
-      "(SELECT 1 FROM temp.v_col WHERE pk AND tablename = temp.fkey.to_tbl)"
-    , pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Fix all the implicit primary key mappings in the temp.fkey table. */
-  rc = sqlite3_exec(db, 
-    "UPDATE temp.fkey SET to_col = "
-      "(SELECT name FROM temp.v_col WHERE pk AND tablename=temp.fkey.to_tbl)"
-    " WHERE to_col IS NULL;"
-    , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Now check that all all parent keys are either primary keys or 
-  ** subject to a unique constraint.
-  */
-  rc = sqlite3_exec(db, 
-    "CREATE TABLE temp.idx2 AS SELECT "
-      "il.tablename AS tablename,"
-      "ii.indexname AS indexname,"
-      "ii.name AS col "
-      "FROM temp.v_idxlist AS il, temp.v_idxinfo AS ii "
-      "WHERE il.isunique AND il.database='main' AND ii.indexname = il.name;"
-    "INSERT INTO temp.idx2 "
-      "SELECT tablename, 'pk', name FROM temp.v_col WHERE pk;"
-
-    "CREATE TABLE temp.idx AS SELECT "
-      "tablename, indexname, sj(dq(col),',') AS cols "
-      "FROM (SELECT * FROM temp.idx2 ORDER BY col) " 
-      "GROUP BY tablename, indexname;"
-
-    "CREATE TABLE temp.fkey2 AS SELECT "
-        "fkid, from_tbl, to_tbl, sj(dq(to_col),',') AS cols "
-        "FROM (SELECT * FROM temp.fkey ORDER BY to_col) " 
-        "GROUP BY fkid, from_tbl;"
-
-    "CREATE TABLE temp.triggers AS SELECT "
-        "triggername FROM temp.v_triggers WHERE database='main' AND "
-        "triggername LIKE 'genfkey%';"
-    , 0, 0, 0
-  );
-  if( rc!=SQLITE_OK ) return rc;
-  rc = detectSchemaProblem(db, "foreign key is not unique",
-    "SELECT fkid, from_tbl "
-    "FROM temp.fkey2 "
-    "WHERE NOT EXISTS (SELECT 1 "
-        "FROM temp.idx WHERE tablename=to_tbl AND fkey2.cols==idx.cols"
-    ")", pCallback
-  );
-  if( rc!=SQLITE_OK ) return rc;
-
-  return rc;
-}
-
-#define GENFKEY_ERROR         1
-#define GENFKEY_DROPTRIGGER   2
-#define GENFKEY_CREATETRIGGER 3
-static int genfkey_create_triggers(
-  sqlite3 *sdb,                        /* Connection to read schema from */
-  const char *zDb,                     /* Name of db to read ("main", "temp") */
-  void *pCtx,                          /* Context pointer to pass to xData */
-  int (*xData)(void *, int, const char *)
-){
-  const char *zSql =
-    "SELECT multireplace('"
-
-      "-- Triggers for foreign key mapping:\n"
-      "--\n"
-      "--     /from_readable/ REFERENCES /to_readable/\n"
-      "--     on delete /on_delete/\n"
-      "--     on update /on_update/\n"
-      "--\n"
-
-      /* The "BEFORE INSERT ON <referencing>" trigger. This trigger's job is to
-      ** throw an exception if the user tries to insert a row into the
-      ** referencing table for which there is no corresponding row in
-      ** the referenced table.
-      */
-      "CREATE TRIGGER /name/_insert_referencing BEFORE INSERT ON /tbl/ WHEN \n"
-      "    /key_notnull/ AND NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n" 
-      "BEGIN\n"
-        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
-      "END;\n"
-
-      /* The "BEFORE UPDATE ON <referencing>" trigger. This trigger's job 
-      ** is to throw an exception if the user tries to update a row in the
-      ** referencing table causing it to correspond to no row in the
-      ** referenced table.
-      */
-      "CREATE TRIGGER /name/_update_referencing BEFORE\n"
-      "    UPDATE OF /rkey_list/ ON /tbl/ WHEN \n"
-      "    /key_notnull/ AND \n"
-      "    NOT EXISTS (SELECT 1 FROM /ref/ WHERE /cond1/)\n" 
-      "BEGIN\n"
-        "  SELECT RAISE(ABORT, ''constraint failed'');\n"
-      "END;\n"
-
-
-      /* The "BEFORE DELETE ON <referenced>" trigger. This trigger's job 
-      ** is to detect when a row is deleted from the referenced table to 
-      ** which rows in the referencing table correspond. The action taken
-      ** depends on the value of the 'ON DELETE' clause.
-      */
-      "CREATE TRIGGER /name/_delete_referenced BEFORE DELETE ON /ref/ WHEN\n"
-      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
-      "BEGIN\n"
-      "  /delete_action/\n"
-      "END;\n"
-
-      /* The "AFTER UPDATE ON <referenced>" trigger. This trigger's job 
-      ** is to detect when the key columns of a row in the referenced table 
-      ** to which one or more rows in the referencing table correspond are
-      ** updated. The action taken depends on the value of the 'ON UPDATE' 
-      ** clause.
-      */
-      "CREATE TRIGGER /name/_update_referenced AFTER\n"
-      "    UPDATE OF /fkey_list/ ON /ref/ WHEN \n"
-      "    EXISTS (SELECT 1 FROM /tbl/ WHERE /cond2/)\n"
-      "BEGIN\n"
-      "  /update_action/\n"
-      "END;\n"
-    "'"
-
-    /* These are used in the SQL comment written above each set of triggers */
-    ", '/from_readable/',  from_tbl || '(' || sj(from_col, ', ') || ')'"
-    ", '/to_readable/',    to_tbl || '(' || sj(to_col, ', ') || ')'"
-    ", '/on_delete/', on_delete"
-    ", '/on_update/', on_update"
-
-    ", '/name/',   'genfkey' || min(rowid)"
-    ", '/tbl/',    dq(from_tbl)"
-    ", '/ref/',    dq(to_tbl)"
-    ", '/key_notnull/', sj('new.' || dq(from_col) || ' IS NOT NULL', ' AND ')"
-
-    ", '/fkey_list/', sj(dq(to_col), ', ')"
-    ", '/rkey_list/', sj(dq(from_col), ', ')"
-
-    ", '/cond1/',  sj(multireplace('new./from/ == /to/'"
-                   ", '/from/', dq(from_col)"
-                   ", '/to/',   dq(to_col)"
-                   "), ' AND ')"
-    ", '/cond2/',  sj(multireplace('old./to/ == /from/'"
-                   ", '/from/', dq(from_col)"
-                   ", '/to/',   dq(to_col)"
-                   "), ' AND ')"
-
-    ", '/update_action/', CASE on_update "
-      "WHEN 'SET NULL' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = NULL',', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "WHEN 'CASCADE' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = new.'||dq(to_col),', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "ELSE "
-      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
-      "END "
-
-    ", '/delete_action/', CASE on_delete "
-      "WHEN 'SET NULL' THEN "
-        "multireplace('UPDATE /tbl/ SET /setlist/ WHERE /where/;' "
-        ", '/setlist/', sj(dq(from_col)||' = NULL',', ')"
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "WHEN 'CASCADE' THEN "
-        "multireplace('DELETE FROM /tbl/ WHERE /where/;' "
-        ", '/tbl/',     dq(from_tbl)"
-        ", '/where/',   sj(dq(from_col)||' = old.'||dq(to_col),' AND ')"
-        ")"
-      "ELSE "
-      "  'SELECT RAISE(ABORT, ''constraint failed'');'"
-      "END "
-
-    ") FROM temp.fkey "
-    "GROUP BY from_tbl, fkid"
-  ;
-
-  int rc;
-  const int enc = SQLITE_UTF8;
-  sqlite3 *db = 0;
-
-  GenfkeyCb cb;
-  cb.xData = xData;
-  cb.pCtx = pCtx;
-
-  UNUSED_PARAMETER(zDb);
-
-  /* Open the working database handle. */
-  rc = sqlite3_open(":memory:", &db);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Create the special scalar and aggregate functions used by this program. */
-  sqlite3_create_function(db, "dq", 1, enc, 0, doublequote, 0, 0);
-  sqlite3_create_function(db, "multireplace", -1, enc, db, multireplace, 0, 0);
-  sqlite3_create_function(db, "sj", 2, enc, 0, 0, joinStep, joinFinalize);
-
-  /* Install the "schema" virtual table module */
-  installSchemaModule(db, sdb);
-
-  /* Create and populate a temp table with the information required to
-  ** build the foreign key triggers. See function populateTempTable()
-  ** for details.
-  */
-  cb.eType = GENFKEY_ERROR;
-  rc = populateTempTable(db, &cb);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Unless the --no-drop option was specified, generate DROP TRIGGER
-  ** statements to drop any triggers in the database generated by a
-  ** previous run of this program.
-  */
-  cb.eType = GENFKEY_DROPTRIGGER;
-  rc = sqlite3_exec(db, 
-    "SELECT 'DROP TRIGGER main.' || dq(triggername) || ';' FROM triggers"
-    ,invokeCallback, (void *)&cb, 0
-  );
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-  /* Run the main query to create the trigger definitions. */
-  cb.eType = GENFKEY_CREATETRIGGER;
-  rc = sqlite3_exec(db, zSql, invokeCallback, (void *)&cb, 0);
-  if( rc!=SQLITE_OK ) goto genfkey_exit;
-
-genfkey_exit:
-  sqlite3_close(db);
-  return rc;
-}
-
-
-#endif
-/* End genfkey logic. */
-/*************************************************************************/
-/*************************************************************************/
-
 /*
 ** If the following flag is set, then command execution stops
 ** at an error if we are not interactive.
@@ -1512,10 +650,6 @@
   int i;
   struct callback_data *p = (struct callback_data*)pArg;
 
-  if( p->echoOn && p->cnt==0  && p->pStmt){
-    printf("%s\n", sqlite3_sql(p->pStmt));
-  }
-
   switch( p->mode ){
     case MODE_Line: {
       int w = 5;
@@ -1866,6 +1000,12 @@
         continue;
       }
 
+      /* echo the sql statement if echo on */
+      if( pArg->echoOn ){
+        const char *zStmtSql = sqlite3_sql(pStmt);
+        fprintf(pArg->out,"%s\n", zStmtSql ? zStmtSql : zSql);
+      }
+
       /* perform the first step.  this will tell us if we
       ** have a result set or not and how wide it is.
       */
@@ -2068,62 +1208,6 @@
   return rc;
 }
 
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-struct GenfkeyCmd {
-  sqlite3 *db;                   /* Database handle */
-  struct callback_data *pCb;     /* Callback data */
-  int isIgnoreErrors;            /* True for --ignore-errors */
-  int isExec;                    /* True for --exec */
-  int isNoDrop;                  /* True for --no-drop */
-  int nErr;                      /* Number of errors seen so far */
-};
-typedef struct GenfkeyCmd GenfkeyCmd;
-
-static int genfkeyParseArgs(GenfkeyCmd *p, char **azArg, int nArg){
-  int ii;
-  memset(p, 0, sizeof(GenfkeyCmd));
-
-  for(ii=0; ii<nArg; ii++){
-    int n = strlen30(azArg[ii]);
-
-    if( n>2 && n<10 && 0==strncmp(azArg[ii], "--no-drop", n) ){
-      p->isNoDrop = 1;
-    }else if( n>2 && n<16 && 0==strncmp(azArg[ii], "--ignore-errors", n) ){
-      p->isIgnoreErrors = 1;
-    }else if( n>2 && n<7 && 0==strncmp(azArg[ii], "--exec", n) ){
-      p->isExec = 1;
-    }else{
-      fprintf(stderr, "unknown option: %s\n", azArg[ii]);
-      return -1;
-    }
-  }
-
-  return SQLITE_OK;
-}
-
-static int genfkeyCmdCb(void *pCtx, int eType, const char *z){
-  GenfkeyCmd *p = (GenfkeyCmd *)pCtx;
-  if( eType==GENFKEY_ERROR && !p->isIgnoreErrors ){
-    p->nErr++;
-    fprintf(stderr, "%s\n", z);
-  } 
-
-  if( p->nErr==0 && (
-        (eType==GENFKEY_CREATETRIGGER)
-     || (eType==GENFKEY_DROPTRIGGER && !p->isNoDrop)
-  )){
-    if( p->isExec ){
-      sqlite3_exec(p->db, z, 0, 0, 0);
-    }else{
-      char *zCol = "sql";
-      callback((void *)p->pCb, 1, (char **)&z, (char **)&zCol);
-    }
-  }
-
-  return SQLITE_OK;
-}
-#endif
-
 /*
 ** Text of a help message
 */
@@ -2138,14 +1222,6 @@
   ".exit                  Exit this program\n"
   ".explain ?ON|OFF?      Turn output mode suitable for EXPLAIN on or off.\n"
   "                         With no args, it turns EXPLAIN on.\n"
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-  ".genfkey ?OPTIONS?     Options are:\n"
-  "                         --no-drop: Do not drop old fkey triggers.\n"
-  "                         --ignore-errors: Ignore tables with fkey errors\n"
-  "                         --exec: Execute generated SQL immediately\n"
-  "                       See file tool/genfkey.README in the source \n"
-  "                       distribution for further information.\n"
-#endif
   ".header(s) ON|OFF      Turn display of headers on or off\n"
   ".help                  Show this message\n"
   ".import FILE TABLE     Import data from FILE into TABLE\n"
@@ -2466,17 +1542,6 @@
     }
   }else
 
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && !defined(SQLITE_OMIT_SUBQUERY)
-  if( c=='g' && strncmp(azArg[0], "genfkey", n)==0 ){
-    GenfkeyCmd cmd;
-    if( 0==genfkeyParseArgs(&cmd, &azArg[1], nArg-1) ){
-      cmd.db = p->db;
-      cmd.pCb = p;
-      genfkey_create_triggers(p->db, "main", (void *)&cmd, genfkeyCmdCb);
-    }
-  }else
-#endif
-
   if( c=='h' && (strncmp(azArg[0], "header", n)==0 ||
                  strncmp(azArg[0], "headers", n)==0) && nArg>1 && nArg<3 ){
     p->showHeader = booleanValue(azArg[1]);
@@ -3353,6 +2418,7 @@
   sqlite3_config(SQLITE_CONFIG_LOG, shellLog, data);
   sqlite3_snprintf(sizeof(mainPrompt), mainPrompt,"sqlite> ");
   sqlite3_snprintf(sizeof(continuePrompt), continuePrompt,"   ...> ");
+  sqlite3_config(SQLITE_CONFIG_SINGLETHREAD);
 }
 
 int main(int argc, char **argv){
@@ -3512,7 +2578,6 @@
     */
     if( zFirstCmd[0]=='.' ){
       rc = do_meta_command(zFirstCmd, &data);
-      return rc;
     }else{
       open_db(&data);
       rc = shell_exec(data.db, zFirstCmd, shell_callback, &data, &zErrMsg);
@@ -3559,9 +2624,10 @@
     }
   }
   set_table_name(&data, 0);
-  if( db ){
-    if( sqlite3_close(db)!=SQLITE_OK ){
-      fprintf(stderr,"Error: cannot close database \"%s\"\n", sqlite3_errmsg(db));
+  if( data.db ){
+    if( sqlite3_close(data.db)!=SQLITE_OK ){
+      fprintf(stderr,"Error: cannot close database \"%s\"\n",
+              sqlite3_errmsg(db));
       rc++;
     }
   }
diff --git a/dist/sqlite3.c b/dist/sqlite3.c
index cc77c23..0baa982 100644
--- a/dist/sqlite3.c
+++ b/dist/sqlite3.c
@@ -1,6 +1,6 @@
 /******************************************************************************
 ** This file is an amalgamation of many separate C source files from SQLite
-** version 3.6.22.  By combining all the individual C code files into this 
+** version 3.7.0.  By combining all the individual C code files into this 
 ** single large file, the entire code can be compiled as a one translation
 ** unit.  This allows many compilers to do optimizations that would not be
 ** possible if the files were compiled separately.  Performance improvements
@@ -25,6 +25,10 @@
 #ifndef SQLITE_API
 # define SQLITE_API
 #endif
+// Begin Android Add
+#define fdatasync fsync
+#undef __APPLE__
+// End Android Add
 /************** Begin file sqliteInt.h ***************************************/
 /*
 ** 2001 September 15
@@ -191,6 +195,14 @@
 #endif
 
 /*
+** The default number of frames to accumulate in the log file before
+** checkpointing the database in WAL mode.
+*/
+#ifndef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
+# define SQLITE_DEFAULT_WAL_AUTOCHECKPOINT  1000
+#endif
+
+/*
 ** The maximum number of attached databases.  This must be between 0
 ** and 30.  The upper bound on 30 is because a 32-bit integer bitmap
 ** is used internally to track attached databases.
@@ -307,41 +319,43 @@
 #include <inttypes.h>
 #endif
 
+/*
+** The number of samples of an index that SQLite takes in order to 
+** construct a histogram of the table content when running ANALYZE
+** and with SQLITE_ENABLE_STAT2
+*/
 #define SQLITE_INDEX_SAMPLES 10
 
 /*
-** This macro is used to "hide" some ugliness in casting an int
-** value to a ptr value under the MSVC 64-bit compiler.   Casting
-** non 64-bit values to ptr types results in a "hard" error with 
-** the MSVC 64-bit compiler which this attempts to avoid.  
+** The following macros are used to cast pointers to integers and
+** integers to pointers.  The way you do this varies from one compiler
+** to the next, so we have developed the following set of #if statements
+** to generate appropriate macros for a wide range of compilers.
 **
-** A simple compiler pragma or casting sequence could not be found
-** to correct this in all situations, so this macro was introduced.
-**
-** It could be argued that the intptr_t type could be used in this
-** case, but that type is not available on all compilers, or 
-** requires the #include of specific headers which differs between
-** platforms.
+** The correct "ANSI" way to do this is to use the intptr_t type. 
+** Unfortunately, that typedef is not available on all compilers, or
+** if it is available, it requires an #include of specific headers
+** that vary from one machine to the next.
 **
 ** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
 ** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
 ** So we have to define the macros in different ways depending on the
 ** compiler.
 */
-#if defined(__GNUC__)
-# if defined(HAVE_STDINT_H)
-#   define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
-#   define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
-# else
-#   define SQLITE_INT_TO_PTR(X)  ((void*)(X))
-#   define SQLITE_PTR_TO_INT(X)  ((int)(X))
-# endif
-#else
-# define SQLITE_INT_TO_PTR(X)   ((void*)&((char*)0)[X])
-# define SQLITE_PTR_TO_INT(X)   ((int)(((char*)X)-(char*)0))
+#if defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
+#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
+# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
+# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
+#elif defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
+#else                          /* Generates a warning - but it always works */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(X))
 #endif
 
-
 /*
 ** The SQLITE_THREADSAFE macro must be defined as either 0 or 1.
 ** Older versions of SQLite used an optional THREADSAFE macro.
@@ -371,23 +385,18 @@
 **
 **     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
 **     SQLITE_MEMDEBUG               // Debugging version of system malloc()
-**     SQLITE_MEMORY_SIZE            // internal allocator #1
-**     SQLITE_MMAP_HEAP_SIZE         // internal mmap() allocator
-**     SQLITE_POW2_MEMORY_SIZE       // internal power-of-two allocator
+**
+** (Historical note:  There used to be several other options, but we've
+** pared it down to just these two.)
 **
 ** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
 ** the default.
 */
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)>1
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)>1
 # error "At most one of the following compile-time configuration options\
- is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG, SQLITE_MEMORY_SIZE,\
- SQLITE_MMAP_HEAP_SIZE, SQLITE_POW2_MEMORY_SIZE"
+ is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG"
 #endif
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)==0
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)==0
 # define SQLITE_SYSTEM_MALLOC 1
 #endif
 
@@ -631,13 +640,13 @@
 ** [sqlite3_libversion_number()], [sqlite3_sourceid()],
 ** [sqlite_version()] and [sqlite_source_id()].
 */
-#define SQLITE_VERSION        "3.6.22"
-#define SQLITE_VERSION_NUMBER 3006022
-#define SQLITE_SOURCE_ID      "2010-03-22 23:55:10 82dd61fccff3e4c77e060e5734cd4b4e2eeb7c32"
+#define SQLITE_VERSION        "3.7.0"
+#define SQLITE_VERSION_NUMBER 3007000
+#define SQLITE_SOURCE_ID      "2010-06-19 15:10:10 2241788bc85fbc48e9cfecb95fe0a858338e37cb"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
-** KEYWORDS: sqlite3_version
+** KEYWORDS: sqlite3_version, sqlite3_sourceid
 **
 ** These interfaces provide the same information as the [SQLITE_VERSION],
 ** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
@@ -659,9 +668,9 @@
 ** function is provided for use in DLLs since DLL users usually do not have
 ** direct access to string constants within the DLL.  ^The
 ** sqlite3_libversion_number() function returns an integer equal to
-** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function a pointer
-** to a string constant whose value is the same as the [SQLITE_SOURCE_ID]
-** C preprocessor macro.
+** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function returns 
+** a pointer to a string constant whose value is the same as the 
+** [SQLITE_SOURCE_ID] C preprocessor macro.
 **
 ** See also: [sqlite_version()] and [sqlite_source_id()].
 */
@@ -671,6 +680,33 @@
 SQLITE_API int sqlite3_libversion_number(void);
 
 /*
+** CAPI3REF: Run-Time Library Compilation Options Diagnostics
+**
+** ^The sqlite3_compileoption_used() function returns 0 or 1 
+** indicating whether the specified option was defined at 
+** compile time.  ^The SQLITE_ prefix may be omitted from the 
+** option name passed to sqlite3_compileoption_used().  
+**
+** ^The sqlite3_compileoption_get() function allows interating
+** over the list of options that were defined at compile time by
+** returning the N-th compile time option string.  ^If N is out of range,
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_ 
+** prefix is omitted from any strings returned by 
+** sqlite3_compileoption_get().
+**
+** ^Support for the diagnostic functions sqlite3_compileoption_used()
+** and sqlite3_compileoption_get() may be omitted by specifing the 
+** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
+**
+** See also: SQL functions [sqlite_compileoption_used()] and
+** [sqlite_compileoption_get()] and the [compile_options pragma].
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+SQLITE_API int sqlite3_compileoption_used(const char *zOptName);
+SQLITE_API const char *sqlite3_compileoption_get(int N);
+#endif
+
+/*
 ** CAPI3REF: Test To See If The Library Is Threadsafe
 **
 ** ^The sqlite3_threadsafe() function returns zero if and only if
@@ -890,7 +926,7 @@
 #define SQLITE_NOTFOUND    12   /* NOT USED. Table or record not found */
 #define SQLITE_FULL        13   /* Insertion failed because database is full */
 #define SQLITE_CANTOPEN    14   /* Unable to open the database file */
-#define SQLITE_PROTOCOL    15   /* NOT USED. Database lock protocol error */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
 #define SQLITE_EMPTY       16   /* Database is empty */
 #define SQLITE_SCHEMA      17   /* The database schema changed */
 #define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
@@ -946,7 +982,12 @@
 #define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
 #define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
 #define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
-#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED | (1<<8) )
+#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
+#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
+#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
+#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
+#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
+#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
 
 /*
 ** CAPI3REF: Flags For File Open Operations
@@ -961,6 +1002,7 @@
 #define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
 #define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
 #define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
+#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
 #define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
 #define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
 #define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
@@ -1154,6 +1196,13 @@
   int (*xFileControl)(sqlite3_file*, int op, void *pArg);
   int (*xSectorSize)(sqlite3_file*);
   int (*xDeviceCharacteristics)(sqlite3_file*);
+  /* Methods above are valid for version 1 */
+  int (*xShmOpen)(sqlite3_file*);
+  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
+  int (*xShmMap)(sqlite3_file*, int iPage, int pgsz, int, void volatile**);
+  void (*xShmBarrier)(sqlite3_file*);
+  int (*xShmClose)(sqlite3_file*, int deleteFlag);
+  /* Methods above are valid for version 2 */
   /* Additional methods may be added in future releases */
 };
 
@@ -1171,11 +1220,19 @@
 ** into an integer that the pArg argument points to. This capability
 ** is used during testing and only needs to be supported when SQLITE_TEST
 ** is defined.
+**
+** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
+** layer a hint of how large the database file will grow to be during the
+** current transaction.  This hint is not guaranteed to be accurate but it
+** is often close.  The underlying VFS might choose to preallocate database
+** file space based on this hint in order to help writes to the database
+** file run faster.
 */
 #define SQLITE_FCNTL_LOCKSTATE        1
 #define SQLITE_GET_LOCKPROXYFILE      2
 #define SQLITE_SET_LOCKPROXYFILE      3
 #define SQLITE_LAST_ERRNO             4
+#define SQLITE_FCNTL_SIZE_HINT        5
 
 /*
 ** CAPI3REF: Mutex Handle
@@ -1320,7 +1377,7 @@
 */
 typedef struct sqlite3_vfs sqlite3_vfs;
 struct sqlite3_vfs {
-  int iVersion;            /* Structure version number */
+  int iVersion;            /* Structure version number (currently 2) */
   int szOsFile;            /* Size of subclassed sqlite3_file */
   int mxPathname;          /* Maximum file pathname length */
   sqlite3_vfs *pNext;      /* Next registered VFS */
@@ -1339,8 +1396,17 @@
   int (*xSleep)(sqlite3_vfs*, int microseconds);
   int (*xCurrentTime)(sqlite3_vfs*, double*);
   int (*xGetLastError)(sqlite3_vfs*, int, char *);
-  /* New fields may be appended in figure versions.  The iVersion
-  ** value will increment whenever this happens. */
+  /*
+  ** The methods above are in version 1 of the sqlite_vfs object
+  ** definition.  Those that follow are added in version 2 or later
+  */
+  int (*xRename)(sqlite3_vfs*, const char *zOld, const char *zNew, int dirSync);
+  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
+  /*
+  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
+  ** New fields may be appended in figure versions.  The iVersion
+  ** value will increment whenever this happens. 
+  */
 };
 
 /*
@@ -1361,6 +1427,44 @@
 #define SQLITE_ACCESS_READ      2
 
 /*
+** CAPI3REF: Flags for the xShmLock VFS method
+**
+** These integer constants define the various locking operations
+** allowed by the xShmLock method of [sqlite3_io_methods].  The
+** following are the only legal combinations of flags to the
+** xShmLock method:
+**
+** <ul>
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
+** </ul>
+**
+** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
+** was given no the corresponding lock.  
+**
+** The xShmLock method can transition between unlocked and SHARED or
+** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
+** and EXCLUSIVE.
+*/
+#define SQLITE_SHM_UNLOCK       1
+#define SQLITE_SHM_LOCK         2
+#define SQLITE_SHM_SHARED       4
+#define SQLITE_SHM_EXCLUSIVE    8
+
+/*
+** CAPI3REF: Maximum xShmLock index
+**
+** The xShmLock method on [sqlite3_io_methods] may use values
+** between 0 and this upper bound as its "offset" argument.
+** The SQLite core will never attempt to acquire or release a
+** lock outside of this range
+*/
+#define SQLITE_SHM_NLOCK        8
+
+
+/*
 ** CAPI3REF: Initialize The SQLite Library
 **
 ** ^The sqlite3_initialize() routine initializes the
@@ -1469,11 +1573,10 @@
 ** ^If the option is unknown or SQLite is unable to set the option
 ** then this routine returns a non-zero [error code].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_config(int, ...);
+SQLITE_API int sqlite3_config(int, ...);
 
 /*
 ** CAPI3REF: Configure database connections
-** EXPERIMENTAL
 **
 ** The sqlite3_db_config() interface is used to make configuration
 ** changes to a [database connection].  The interface is similar to
@@ -1493,11 +1596,10 @@
 ** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
 ** the call is considered successful.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_config(sqlite3*, int op, ...);
+SQLITE_API int sqlite3_db_config(sqlite3*, int op, ...);
 
 /*
 ** CAPI3REF: Memory Allocation Routines
-** EXPERIMENTAL
 **
 ** An instance of this object defines the interface between SQLite
 ** and low-level memory allocation routines.
@@ -1579,7 +1681,6 @@
 
 /*
 ** CAPI3REF: Configuration Options
-** EXPERIMENTAL
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the first argument to the [sqlite3_config()] interface.
@@ -1765,6 +1866,24 @@
 ** [sqlite3_pcache_methods] object.  SQLite copies of the current
 ** page cache implementation into that object.)^ </dd>
 **
+** <dt>SQLITE_CONFIG_LOG</dt>
+** <dd> ^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
+** function with a call signature of void(*)(void*,int,const char*), 
+** and a pointer to void. ^If the function pointer is not NULL, it is
+** invoked by [sqlite3_log()] to process each logging event.  ^If the
+** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
+** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
+** passed through as the first parameter to the application-defined logger
+** function whenever that function is invoked.  ^The second parameter to
+** the logger function is a copy of the first parameter to the corresponding
+** [sqlite3_log()] call and is intended to be a [result code] or an
+** [extended result code].  ^The third parameter passed to the logger is
+** log message after formatting via [sqlite3_snprintf()].
+** The SQLite logging interface is not reentrant; the logger function
+** supplied by the application must not invoke any SQLite interface.
+** In a multi-threaded application, the application-defined logger
+** function must be threadsafe. </dd>
+**
 ** </dl>
 */
 #define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
@@ -1785,8 +1904,7 @@
 #define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
 
 /*
-** CAPI3REF: Configuration Options
-** EXPERIMENTAL
+** CAPI3REF: Database Connection Configuration Options
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the second argument to the [sqlite3_db_config()] interface.
@@ -2562,7 +2680,6 @@
 
 /*
 ** CAPI3REF: Tracing And Profiling Functions
-** EXPERIMENTAL
 **
 ** These routines register callback functions that can be used for
 ** tracing and profiling the execution of SQL statements.
@@ -2580,7 +2697,7 @@
 ** the original statement text and an estimate of wall-clock time
 ** of how long that statement took to run.
 */
-SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
+SQLITE_API void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
 SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_profile(sqlite3*,
    void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
 
@@ -3373,6 +3490,14 @@
 ** be the case that the same database connection is being used by two or
 ** more threads at the same moment in time.
 **
+** For all versions of SQLite up to and including 3.6.23.1, it was required
+** after sqlite3_step() returned anything other than [SQLITE_ROW] that
+** [sqlite3_reset()] be called before any subsequent invocation of
+** sqlite3_step().  Failure to invoke [sqlite3_reset()] in this way would
+** result in an [SQLITE_MISUSE] return from sqlite3_step().  But after
+** version 3.6.23.1, sqlite3_step() began calling [sqlite3_reset()] 
+** automatically in this circumstance rather than returning [SQLITE_MISUSE].  
+**
 ** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
 ** API always returns a generic error code, [SQLITE_ERROR], following any
 ** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
@@ -4185,6 +4310,7 @@
   void(*)(void*,sqlite3*,int eTextRep,const void*)
 );
 
+#ifdef SQLITE_HAS_CODEC
 /*
 ** Specify the key for an encrypted database.  This routine should be
 ** called right after sqlite3_open().
@@ -4211,6 +4337,25 @@
 );
 
 /*
+** Specify the activation key for a SEE database.  Unless 
+** activated, none of the SEE routines will work.
+*/
+SQLITE_API void sqlite3_activate_see(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+#ifdef SQLITE_ENABLE_CEROD
+/*
+** Specify the activation key for a CEROD database.  Unless 
+** activated, none of the CEROD routines will work.
+*/
+SQLITE_API void sqlite3_activate_cerod(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+/*
 ** CAPI3REF: Suspend Execution For A Short Time
 **
 ** ^The sqlite3_sleep() function causes the current thread to suspend execution
@@ -4348,8 +4493,6 @@
 ** an error or constraint causes an implicit rollback to occur.
 ** ^The rollback callback is not invoked if a transaction is
 ** automatically rolled back because the database connection is closed.
-** ^The rollback callback is not invoked if a transaction is
-** rolled back because a commit callback returned non-zero.
 **
 ** See also the [sqlite3_update_hook()] interface.
 */
@@ -4635,8 +4778,6 @@
 SQLITE_API void sqlite3_reset_auto_extension(void);
 
 /*
-****** EXPERIMENTAL - subject to change without notice **************
-**
 ** The interface to the virtual-table mechanism is currently considered
 ** to be experimental.  The interface might change in incompatible ways.
 ** If this is a problem for you, do not use the interface at this time.
@@ -4656,7 +4797,6 @@
 /*
 ** CAPI3REF: Virtual Table Object
 ** KEYWORDS: sqlite3_module {virtual table module}
-** EXPERIMENTAL
 **
 ** This structure, sometimes called a a "virtual table module", 
 ** defines the implementation of a [virtual tables].  
@@ -4703,7 +4843,6 @@
 /*
 ** CAPI3REF: Virtual Table Indexing Information
 ** KEYWORDS: sqlite3_index_info
-** EXPERIMENTAL
 **
 ** The sqlite3_index_info structure and its substructures is used to
 ** pass information into and receive the reply from the [xBestIndex]
@@ -4785,7 +4924,6 @@
 
 /*
 ** CAPI3REF: Register A Virtual Table Implementation
-** EXPERIMENTAL
 **
 ** ^These routines are used to register a new [virtual table module] name.
 ** ^Module names must be registered before
@@ -4807,13 +4945,13 @@
 ** interface is equivalent to sqlite3_create_module_v2() with a NULL
 ** destructor.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module(
+SQLITE_API int sqlite3_create_module(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
   void *pClientData          /* Client data for xCreate/xConnect */
 );
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module_v2(
+SQLITE_API int sqlite3_create_module_v2(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
@@ -4824,7 +4962,6 @@
 /*
 ** CAPI3REF: Virtual Table Instance Object
 ** KEYWORDS: sqlite3_vtab
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass
 ** of this object to describe a particular instance
@@ -4850,7 +4987,6 @@
 /*
 ** CAPI3REF: Virtual Table Cursor Object
 ** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass of the
 ** following structure to describe cursors that point into the
@@ -4872,18 +5008,16 @@
 
 /*
 ** CAPI3REF: Declare The Schema Of A Virtual Table
-** EXPERIMENTAL
 **
 ** ^The [xCreate] and [xConnect] methods of a
 ** [virtual table module] call this interface
 ** to declare the format (the names and datatypes of the columns) of
 ** the virtual tables they implement.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
+SQLITE_API int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
 
 /*
 ** CAPI3REF: Overload A Function For A Virtual Table
-** EXPERIMENTAL
 **
 ** ^(Virtual tables can provide alternative implementations of functions
 ** using the [xFindFunction] method of the [virtual table module].  
@@ -4898,7 +5032,7 @@
 ** purpose is to be a placeholder function that can be overloaded
 ** by a [virtual table].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
+SQLITE_API int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
 
 /*
 ** The interface to the virtual-table mechanism defined above (back up
@@ -4908,8 +5042,6 @@
 **
 ** When the virtual-table mechanism stabilizes, we will declare the
 ** interface fixed, support it indefinitely, and remove this comment.
-**
-****** EXPERIMENTAL - subject to change without notice **************
 */
 
 /*
@@ -5252,7 +5384,6 @@
 
 /*
 ** CAPI3REF: Mutex Methods Object
-** EXPERIMENTAL
 **
 ** An instance of this structure defines the low-level routines
 ** used to allocate and use mutexes.
@@ -5465,11 +5596,11 @@
 #define SQLITE_TESTCTRL_RESERVE                 14
 #define SQLITE_TESTCTRL_OPTIMIZATIONS           15
 #define SQLITE_TESTCTRL_ISKEYWORD               16
-#define SQLITE_TESTCTRL_LAST                    16
+#define SQLITE_TESTCTRL_PGHDRSZ                 17
+#define SQLITE_TESTCTRL_LAST                    17
 
 /*
 ** CAPI3REF: SQLite Runtime Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information
 ** about the preformance of SQLite, and optionally to reset various
@@ -5497,12 +5628,11 @@
 **
 ** See also: [sqlite3_db_status()]
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+SQLITE_API int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
 
 
 /*
 ** CAPI3REF: Status Parameters
-** EXPERIMENTAL
 **
 ** These integer constants designate various run-time status parameters
 ** that can be returned by [sqlite3_status()].
@@ -5589,14 +5719,15 @@
 
 /*
 ** CAPI3REF: Database Connection Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information 
 ** about a single [database connection].  ^The first argument is the
 ** database connection object to be interrogated.  ^The second argument
-** is the parameter to interrogate.  ^Currently, the only allowed value
-** for the second parameter is [SQLITE_DBSTATUS_LOOKASIDE_USED].
-** Additional options will likely appear in future releases of SQLite.
+** is an integer constant, taken from the set of
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros, that
+** determiness the parameter to interrogate.  The set of 
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros is likely
+** to grow in future releases of SQLite.
 **
 ** ^The current value of the requested parameter is written into *pCur
 ** and the highest instantaneous value is written into *pHiwtr.  ^If
@@ -5605,11 +5736,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+SQLITE_API int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for database connections
-** EXPERIMENTAL
 **
 ** These constants are the available integer "verbs" that can be passed as
 ** the second argument to the [sqlite3_db_status()] interface.
@@ -5624,14 +5754,21 @@
 ** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
 ** <dd>This parameter returns the number of lookaside memory slots currently
 ** checked out.</dd>)^
+**
+** <dt>SQLITE_DBSTATUS_CACHE_USED</dt>
+** <dd>^This parameter returns the approximate number of of bytes of heap
+** memory used by all pager caches associated with the database connection.
+** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
+** checked out.</dd>)^
 ** </dl>
 */
 #define SQLITE_DBSTATUS_LOOKASIDE_USED     0
+#define SQLITE_DBSTATUS_CACHE_USED         1
+#define SQLITE_DBSTATUS_MAX                1   /* Largest defined DBSTATUS */
 
 
 /*
 ** CAPI3REF: Prepared Statement Status
-** EXPERIMENTAL
 **
 ** ^(Each prepared statement maintains various
 ** [SQLITE_STMTSTATUS_SORT | counters] that measure the number
@@ -5653,11 +5790,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_db_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+SQLITE_API int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for prepared statements
-** EXPERIMENTAL
 **
 ** These preprocessor macros define integer codes that name counter
 ** values associated with the [sqlite3_stmt_status()] interface.
@@ -5675,14 +5811,21 @@
 ** A non-zero value in this counter may indicate an opportunity to
 ** improvement performance through careful use of indices.</dd>
 **
+** <dt>SQLITE_STMTSTATUS_AUTOINDEX</dt>
+** <dd>^This is the number of rows inserted into transient indices that
+** were created automatically in order to help joins run faster.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance by adding permanent indices that do not
+** need to be reinitialized each time the statement is run.</dd>
+**
 ** </dl>
 */
 #define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
 #define SQLITE_STMTSTATUS_SORT              2
+#define SQLITE_STMTSTATUS_AUTOINDEX         3
 
 /*
 ** CAPI3REF: Custom Page Cache Object
-** EXPERIMENTAL
 **
 ** The sqlite3_pcache type is opaque.  It is implemented by
 ** the pluggable module.  The SQLite core has no knowledge of
@@ -5697,7 +5840,6 @@
 /*
 ** CAPI3REF: Application Defined Page Cache.
 ** KEYWORDS: {page cache}
-** EXPERIMENTAL
 **
 ** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
 ** register an alternative page cache implementation by passing in an 
@@ -5839,7 +5981,6 @@
 
 /*
 ** CAPI3REF: Online Backup Object
-** EXPERIMENTAL
 **
 ** The sqlite3_backup object records state information about an ongoing
 ** online backup operation.  ^The sqlite3_backup object is created by
@@ -5852,7 +5993,6 @@
 
 /*
 ** CAPI3REF: Online Backup API.
-** EXPERIMENTAL
 **
 ** The backup API copies the content of one database into another.
 ** It is useful either for creating backups of databases or
@@ -5921,10 +6061,14 @@
 ** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
 ** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
 **
-** ^The sqlite3_backup_step() might return [SQLITE_READONLY] if the destination
-** database was opened read-only or if
-** the destination is an in-memory database with a different page size
-** from the source database.
+** ^(The sqlite3_backup_step() might return [SQLITE_READONLY] if
+** <ol>
+** <li> the destination database was opened read-only, or
+** <li> the destination database is using write-ahead-log journaling
+** and the destination and source page sizes differ, or
+** <li> The destination database is an in-memory database and the
+** destination and source page sizes differ.
+** </ol>)^
 **
 ** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
 ** the [sqlite3_busy_handler | busy-handler function]
@@ -6040,7 +6184,6 @@
 
 /*
 ** CAPI3REF: Unlock Notification
-** EXPERIMENTAL
 **
 ** ^When running in shared-cache mode, a database operation may fail with
 ** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
@@ -6162,7 +6305,6 @@
 
 /*
 ** CAPI3REF: String Comparison
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_strnicmp()] API allows applications and extensions to
 ** compare the contents of two buffers containing UTF-8 strings in a
@@ -6173,16 +6315,19 @@
 
 /*
 ** CAPI3REF: Error Logging Interface
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_log()] interface writes a message into the error log
-** established by the [SQLITE_CONFIG_ERRORLOG] option to [sqlite3_config()].
+** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
+** ^If logging is enabled, the zFormat string and subsequent arguments are
+** used with [sqlite3_snprintf()] to generate the final output string.
 **
 ** The sqlite3_log() interface is intended for use by extensions such as
 ** virtual tables, collating functions, and SQL functions.  While there is
 ** nothing to prevent an application from calling sqlite3_log(), doing so
 ** is considered bad form.
 **
+** The zFormat string must not be NULL.
+**
 ** To avoid deadlocks and other threading problems, the sqlite3_log() routine
 ** will not use dynamically allocated memory.  The log message is stored in
 ** a fixed-length buffer on the stack.  If the log message is longer than
@@ -6192,6 +6337,89 @@
 SQLITE_API void sqlite3_log(int iErrCode, const char *zFormat, ...);
 
 /*
+** CAPI3REF: Write-Ahead Log Commit Hook
+**
+** ^The [sqlite3_wal_hook()] function is used to register a callback that
+** will be invoked each time a database connection commits data to a
+** [write-ahead log] (i.e. whenever a transaction is committed in
+** [journal_mode | journal_mode=WAL mode]). 
+**
+** ^The callback is invoked by SQLite after the commit has taken place and 
+** the associated write-lock on the database released, so the implementation 
+** may read, write or [checkpoint] the database as required.
+**
+** ^The first parameter passed to the callback function when it is invoked
+** is a copy of the third parameter passed to sqlite3_wal_hook() when
+** registering the callback. ^The second is a copy of the database handle.
+** ^The third parameter is the name of the database that was written to -
+** either "main" or the name of an [ATTACH]-ed database. ^The fourth parameter
+** is the number of pages currently in the write-ahead log file,
+** including those that were just committed.
+**
+** The callback function should normally return [SQLITE_OK].  ^If an error
+** code is returned, that error will propagate back up through the
+** SQLite code base to cause the statement that provoked the callback
+** to report an error, though the commit will have still occurred. If the
+** callback returns [SQLITE_ROW] or [SQLITE_DONE], or if it returns a value
+** that does not correspond to any valid SQLite error code, the results
+** are undefined.
+**
+** A single database handle may have at most a single write-ahead log callback 
+** registered at one time. ^Calling [sqlite3_wal_hook()] replaces any
+** previously registered write-ahead log callback. ^Note that the
+** [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] both invoke [sqlite3_wal_hook()] and will
+** those overwrite any prior [sqlite3_wal_hook()] settings.
+*/
+SQLITE_API void *sqlite3_wal_hook(
+  sqlite3*, 
+  int(*)(void *,sqlite3*,const char*,int),
+  void*
+);
+
+/*
+** CAPI3REF: Configure an auto-checkpoint
+**
+** ^The [sqlite3_wal_autocheckpoint(D,N)] is a wrapper around
+** [sqlite3_wal_hook()] that causes any database on [database connection] D
+** to automatically [checkpoint]
+** after committing a transaction if there are N or
+** more frames in the [write-ahead log] file.  ^Passing zero or 
+** a negative value as the nFrame parameter disables automatic
+** checkpoints entirely.
+**
+** ^The callback registered by this function replaces any existing callback
+** registered using [sqlite3_wal_hook()].  ^Likewise, registering a callback
+** using [sqlite3_wal_hook()] disables the automatic checkpoint mechanism
+** configured by this function.
+**
+** ^The [wal_autocheckpoint pragma] can be used to invoke this interface
+** from SQL.
+**
+** ^Every new [database connection] defaults to having the auto-checkpoint
+** enabled with a threshold of 1000 pages.  The use of this interface
+** is only necessary if the default setting is found to be suboptimal
+** for a particular application.
+*/
+SQLITE_API int sqlite3_wal_autocheckpoint(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Checkpoint a database
+**
+** ^The [sqlite3_wal_checkpoint(D,X)] interface causes database named X
+** on [database connection] D to be [checkpointed].  ^If X is NULL or an
+** empty string, then a checkpoint is run on all databases of
+** connection D.  ^If the database connection D is not in
+** [WAL | write-ahead log mode] then this interface is a harmless no-op.
+**
+** ^The [wal_checkpoint pragma] can be used to invoke this interface
+** from SQL.  ^The [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] can be used to cause this interface to be
+** run whenever the WAL reaches a certain size threshold.
+*/
+SQLITE_API int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);
+
+/*
 ** Undo the hack that converts floating point types to integer for
 ** builds on processors without floating point support.
 */
@@ -6206,11 +6434,6 @@
 
 
 /************** End of sqlite3.h *********************************************/
-// Begin Android Add
-#define SQLITE_BeginImmediate 0x00200000  /* Default BEGIN to IMMEDIATE */
-#define fdatasync fsync
-#undef __APPLE__
-// End Android Add
 /************** Continuing where we left off in sqliteInt.h ******************/
 /************** Include hash.h in the middle of sqliteInt.h ******************/
 /************** Begin file hash.h ********************************************/
@@ -6487,6 +6710,7 @@
 */
 #ifdef SQLITE_OMIT_FLOATING_POINT
 # define double sqlite_int64
+# define float sqlite_int64
 # define LONGDOUBLE_TYPE sqlite_int64
 # ifndef SQLITE_BIG_DBL
 #   define SQLITE_BIG_DBL (((sqlite3_int64)1)<<50)
@@ -6512,20 +6736,6 @@
 #endif
 
 /*
-** If the following macro is set to 1, then NULL values are considered
-** distinct when determining whether or not two entries are the same
-** in a UNIQUE index.  This is the way PostgreSQL, Oracle, DB2, MySQL,
-** OCELOT, and Firebird all work.  The SQL92 spec explicitly says this
-** is the way things are suppose to work.
-**
-** If the following macro is set to 0, the NULLs are indistinct for
-** a UNIQUE index.  In this mode, you can only have a single NULL entry
-** for a column declared UNIQUE.  This is the way Informix and SQL Server
-** work.
-*/
-#define NULL_DISTINCT_FOR_UNIQUE 1
-
-/*
 ** The "file format" number is an integer that is incremented whenever
 ** the VDBE-level file format changes.  The following macros define the
 ** the default file format for new databases and the maximum file format
@@ -6536,6 +6746,10 @@
 # define SQLITE_DEFAULT_FILE_FORMAT 1
 #endif
 
+/*
+** Determine whether triggers are recursive by default.  This can be
+** changed at run-time using a pragma.
+*/
 #ifndef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
 # define SQLITE_DEFAULT_RECURSIVE_TRIGGERS 0
 #endif
@@ -6780,7 +6994,6 @@
 typedef struct AuthContext AuthContext;
 typedef struct AutoincInfo AutoincInfo;
 typedef struct Bitvec Bitvec;
-typedef struct RowSet RowSet;
 typedef struct CollSeq CollSeq;
 typedef struct Column Column;
 typedef struct Db Db;
@@ -6801,6 +7014,7 @@
 typedef struct Module Module;
 typedef struct NameContext NameContext;
 typedef struct Parse Parse;
+typedef struct RowSet RowSet;
 typedef struct Savepoint Savepoint;
 typedef struct Select Select;
 typedef struct SrcList SrcList;
@@ -6808,9 +7022,9 @@
 typedef struct Table Table;
 typedef struct TableLock TableLock;
 typedef struct Token Token;
+typedef struct Trigger Trigger;
 typedef struct TriggerPrg TriggerPrg;
 typedef struct TriggerStep TriggerStep;
-typedef struct Trigger Trigger;
 typedef struct UnpackedRecord UnpackedRecord;
 typedef struct VTable VTable;
 typedef struct Walker Walker;
@@ -6908,6 +7122,8 @@
 SQLITE_PRIVATE int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
 SQLITE_PRIVATE int sqlite3BtreeGetPageSize(Btree*);
 SQLITE_PRIVATE int sqlite3BtreeMaxPageCount(Btree*,int);
+SQLITE_PRIVATE u32 sqlite3BtreeLastPage(Btree*);
+SQLITE_PRIVATE int sqlite3BtreeSecureDelete(Btree*,int);
 SQLITE_PRIVATE int sqlite3BtreeGetReserve(Btree*);
 SQLITE_PRIVATE int sqlite3BtreeSetAutoVacuum(Btree *, int);
 SQLITE_PRIVATE int sqlite3BtreeGetAutoVacuum(Btree *);
@@ -7011,6 +7227,8 @@
 SQLITE_PRIVATE void sqlite3BtreeCacheOverflow(BtCursor *);
 SQLITE_PRIVATE void sqlite3BtreeClearCursor(BtCursor *);
 
+SQLITE_PRIVATE int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
+
 #ifndef NDEBUG
 SQLITE_PRIVATE int sqlite3BtreeCursorIsValid(BtCursor*);
 #endif
@@ -7301,83 +7519,83 @@
 #define OP_VerifyCookie                        37
 #define OP_OpenRead                            38
 #define OP_OpenWrite                           39
-#define OP_OpenEphemeral                       40
-#define OP_OpenPseudo                          41
-#define OP_Close                               42
-#define OP_SeekLt                              43
-#define OP_SeekLe                              44
-#define OP_SeekGe                              45
-#define OP_SeekGt                              46
-#define OP_Seek                                47
-#define OP_NotFound                            48
-#define OP_Found                               49
-#define OP_IsUnique                            50
-#define OP_NotExists                           51
-#define OP_Sequence                            52
-#define OP_NewRowid                            53
-#define OP_Insert                              54
-#define OP_InsertInt                           55
-#define OP_Delete                              56
-#define OP_ResetCount                          57
-#define OP_RowKey                              58
-#define OP_RowData                             59
-#define OP_Rowid                               60
-#define OP_NullRow                             61
-#define OP_Last                                62
-#define OP_Sort                                63
-#define OP_Rewind                              64
-#define OP_Prev                                65
-#define OP_Next                                66
-#define OP_IdxInsert                           67
-#define OP_IdxDelete                           70
-#define OP_IdxRowid                            71
-#define OP_IdxLT                               72
-#define OP_IdxGE                               81
-#define OP_Destroy                             92
-#define OP_Clear                               95
-#define OP_CreateIndex                         96
-#define OP_CreateTable                         97
-#define OP_ParseSchema                         98
-#define OP_LoadAnalysis                        99
-#define OP_DropTable                          100
-#define OP_DropIndex                          101
-#define OP_DropTrigger                        102
-#define OP_IntegrityCk                        103
-#define OP_RowSetAdd                          104
-#define OP_RowSetRead                         105
-#define OP_RowSetTest                         106
-#define OP_Program                            107
-#define OP_Param                              108
-#define OP_FkCounter                          109
-#define OP_FkIfZero                           110
-#define OP_MemMax                             111
-#define OP_IfPos                              112
-#define OP_IfNeg                              113
-#define OP_IfZero                             114
-#define OP_AggStep                            115
-#define OP_AggFinal                           116
-#define OP_Vacuum                             117
-#define OP_IncrVacuum                         118
-#define OP_Expire                             119
-#define OP_TableLock                          120
-#define OP_VBegin                             121
-#define OP_VCreate                            122
-#define OP_VDestroy                           123
-#define OP_VOpen                              124
-#define OP_VFilter                            125
-#define OP_VColumn                            126
-#define OP_VNext                              127
-#define OP_VRename                            128
-#define OP_VUpdate                            129
-#define OP_Pagecount                          131
-#define OP_Trace                              132
-#define OP_Noop                               133
-#define OP_Explain                            134
+#define OP_OpenAutoindex                       40
+#define OP_OpenEphemeral                       41
+#define OP_OpenPseudo                          42
+#define OP_Close                               43
+#define OP_SeekLt                              44
+#define OP_SeekLe                              45
+#define OP_SeekGe                              46
+#define OP_SeekGt                              47
+#define OP_Seek                                48
+#define OP_NotFound                            49
+#define OP_Found                               50
+#define OP_IsUnique                            51
+#define OP_NotExists                           52
+#define OP_Sequence                            53
+#define OP_NewRowid                            54
+#define OP_Insert                              55
+#define OP_InsertInt                           56
+#define OP_Delete                              57
+#define OP_ResetCount                          58
+#define OP_RowKey                              59
+#define OP_RowData                             60
+#define OP_Rowid                               61
+#define OP_NullRow                             62
+#define OP_Last                                63
+#define OP_Sort                                64
+#define OP_Rewind                              65
+#define OP_Prev                                66
+#define OP_Next                                67
+#define OP_IdxInsert                           70
+#define OP_IdxDelete                           71
+#define OP_IdxRowid                            72
+#define OP_IdxLT                               81
+#define OP_IdxGE                               92
+#define OP_Destroy                             95
+#define OP_Clear                               96
+#define OP_CreateIndex                         97
+#define OP_CreateTable                         98
+#define OP_ParseSchema                         99
+#define OP_LoadAnalysis                       100
+#define OP_DropTable                          101
+#define OP_DropIndex                          102
+#define OP_DropTrigger                        103
+#define OP_IntegrityCk                        104
+#define OP_RowSetAdd                          105
+#define OP_RowSetRead                         106
+#define OP_RowSetTest                         107
+#define OP_Program                            108
+#define OP_Param                              109
+#define OP_FkCounter                          110
+#define OP_FkIfZero                           111
+#define OP_MemMax                             112
+#define OP_IfPos                              113
+#define OP_IfNeg                              114
+#define OP_IfZero                             115
+#define OP_AggStep                            116
+#define OP_AggFinal                           117
+#define OP_Checkpoint                         118
+#define OP_JournalMode                        119
+#define OP_Vacuum                             120
+#define OP_IncrVacuum                         121
+#define OP_Expire                             122
+#define OP_TableLock                          123
+#define OP_VBegin                             124
+#define OP_VCreate                            125
+#define OP_VDestroy                           126
+#define OP_VOpen                              127
+#define OP_VFilter                            128
+#define OP_VColumn                            129
+#define OP_VNext                              131
+#define OP_VRename                            132
+#define OP_VUpdate                            133
+#define OP_Pagecount                          134
+#define OP_Trace                              135
+#define OP_Noop                               136
+#define OP_Explain                            137
 
 /* The following opcode values are never used */
-#define OP_NotUsed_135                        135
-#define OP_NotUsed_136                        136
-#define OP_NotUsed_137                        137
 #define OP_NotUsed_138                        138
 #define OP_NotUsed_139                        139
 #define OP_NotUsed_140                        140
@@ -7396,22 +7614,22 @@
 #define OPFLG_OUT3            0x0040  /* out3:  P3 is an output */
 #define OPFLG_INITIALIZER {\
 /*   0 */ 0x00, 0x01, 0x05, 0x04, 0x04, 0x10, 0x00, 0x02,\
-/*   8 */ 0x02, 0x02, 0x02, 0x02, 0x00, 0x00, 0x24, 0x24,\
+/*   8 */ 0x02, 0x02, 0x02, 0x02, 0x02, 0x00, 0x24, 0x24,\
 /*  16 */ 0x00, 0x00, 0x00, 0x24, 0x04, 0x05, 0x04, 0x00,\
 /*  24 */ 0x00, 0x01, 0x05, 0x05, 0x00, 0x00, 0x00, 0x02,\
 /*  32 */ 0x00, 0x00, 0x00, 0x02, 0x10, 0x00, 0x00, 0x00,\
-/*  40 */ 0x00, 0x00, 0x00, 0x11, 0x11, 0x11, 0x11, 0x08,\
-/*  48 */ 0x11, 0x11, 0x11, 0x11, 0x02, 0x02, 0x00, 0x00,\
-/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x01, 0x01,\
-/*  64 */ 0x01, 0x01, 0x01, 0x08, 0x4c, 0x4c, 0x00, 0x02,\
-/*  72 */ 0x01, 0x05, 0x05, 0x15, 0x15, 0x15, 0x15, 0x15,\
+/*  40 */ 0x00, 0x00, 0x00, 0x00, 0x11, 0x11, 0x11, 0x11,\
+/*  48 */ 0x08, 0x11, 0x11, 0x11, 0x11, 0x02, 0x02, 0x00,\
+/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x01,\
+/*  64 */ 0x01, 0x01, 0x01, 0x01, 0x4c, 0x4c, 0x08, 0x00,\
+/*  72 */ 0x02, 0x05, 0x05, 0x15, 0x15, 0x15, 0x15, 0x15,\
 /*  80 */ 0x15, 0x01, 0x4c, 0x4c, 0x4c, 0x4c, 0x4c, 0x4c,\
-/*  88 */ 0x4c, 0x4c, 0x4c, 0x4c, 0x02, 0x24, 0x02, 0x00,\
-/*  96 */ 0x02, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
-/* 104 */ 0x0c, 0x45, 0x15, 0x01, 0x02, 0x00, 0x01, 0x08,\
-/* 112 */ 0x05, 0x05, 0x05, 0x00, 0x00, 0x00, 0x01, 0x00,\
-/* 120 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01,\
-/* 128 */ 0x00, 0x00, 0x02, 0x02, 0x00, 0x00, 0x00, 0x00,\
+/*  88 */ 0x4c, 0x4c, 0x4c, 0x4c, 0x01, 0x24, 0x02, 0x02,\
+/*  96 */ 0x00, 0x02, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 104 */ 0x00, 0x0c, 0x45, 0x15, 0x01, 0x02, 0x00, 0x01,\
+/* 112 */ 0x08, 0x05, 0x05, 0x05, 0x00, 0x00, 0x00, 0x02,\
+/* 120 */ 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 128 */ 0x01, 0x00, 0x02, 0x01, 0x00, 0x00, 0x02, 0x00,\
 /* 136 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x04,\
 /* 144 */ 0x04, 0x04,}
 
@@ -7557,14 +7775,15 @@
 #define PAGER_LOCKINGMODE_EXCLUSIVE   1
 
 /*
-** Valid values for the second argument to sqlite3PagerJournalMode().
+** Numeric constants that encode the journalmode.  
 */
-#define PAGER_JOURNALMODE_QUERY      -1
+#define PAGER_JOURNALMODE_QUERY     (-1)  /* Query the value of journalmode */
 #define PAGER_JOURNALMODE_DELETE      0   /* Commit by deleting journal file */
 #define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
 #define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */
 #define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
 #define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
+#define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
 
 /*
 ** The remainder of this file contains the declarations of the functions
@@ -7592,7 +7811,9 @@
 SQLITE_PRIVATE void sqlite3PagerSetCachesize(Pager*, int);
 SQLITE_PRIVATE void sqlite3PagerSetSafetyLevel(Pager*,int,int);
 SQLITE_PRIVATE int sqlite3PagerLockingMode(Pager *, int);
-SQLITE_PRIVATE int sqlite3PagerJournalMode(Pager *, int);
+SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *, int);
+SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager*);
+SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager*);
 SQLITE_PRIVATE i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
 SQLITE_PRIVATE sqlite3_backup **sqlite3PagerBackupPtr(Pager*);
 
@@ -7622,9 +7843,16 @@
 SQLITE_PRIVATE int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
 SQLITE_PRIVATE int sqlite3PagerSharedLock(Pager *pPager);
 
+SQLITE_PRIVATE int sqlite3PagerCheckpoint(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerWalSupported(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerWalCallback(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
+SQLITE_PRIVATE int sqlite3PagerCloseWal(Pager *pPager);
+
 /* Functions used to query pager state and configuration. */
 SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager*);
 SQLITE_PRIVATE int sqlite3PagerRefcount(Pager*);
+SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager*);
 SQLITE_PRIVATE const char *sqlite3PagerFilename(Pager*);
 SQLITE_PRIVATE const sqlite3_vfs *sqlite3PagerVfs(Pager*);
 SQLITE_PRIVATE sqlite3_file *sqlite3PagerFile(Pager*);
@@ -8037,7 +8265,11 @@
 ** 1GB boundary.
 **
 */
-#define PENDING_BYTE      sqlite3PendingByte
+#ifdef SQLITE_OMIT_WSD
+# define PENDING_BYTE     (0x40000000)
+#else
+# define PENDING_BYTE      sqlite3PendingByte
+#endif
 #define RESERVED_BYTE     (PENDING_BYTE+1)
 #define SHARED_FIRST      (PENDING_BYTE+2)
 #define SHARED_SIZE       510
@@ -8063,6 +8295,11 @@
 #define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
 SQLITE_PRIVATE int sqlite3OsSectorSize(sqlite3_file *id);
 SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmOpen(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
+SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmClose(sqlite3_file *id, int);
+SQLITE_PRIVATE int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
 
 /* 
 ** Functions for accessing sqlite3_vfs methods 
@@ -8079,7 +8316,7 @@
 #endif /* SQLITE_OMIT_LOAD_EXTENSION */
 SQLITE_PRIVATE int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
 SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *, int);
-SQLITE_PRIVATE int sqlite3OsCurrentTime(sqlite3_vfs *, double*);
+SQLITE_PRIVATE int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
 
 /*
 ** Convenience functions for opening and closing files using 
@@ -8214,7 +8451,7 @@
 
 /*
 ** These macros can be used to test, set, or clear bits in the 
-** Db.flags field.
+** Db.pSchema->flags field.
 */
 #define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))
 #define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->flags&(P))!=0)
@@ -8222,7 +8459,7 @@
 #define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->flags&=~(P)
 
 /*
-** Allowed values for the DB.flags field.
+** Allowed values for the DB.pSchema->flags field.
 **
 ** The DB_SchemaLoaded flag is set after the database schema has been
 ** read into internal hash tables.
@@ -8286,7 +8523,7 @@
 };
 
 /*
-** Each database is an instance of the following structure.
+** Each database connection is an instance of the following structure.
 **
 ** The sqlite.lastRowid records the last insert rowid generated by an
 ** insert statement.  Inserts on views do not affect its value.  Each
@@ -8356,6 +8593,10 @@
   void (*xRollbackCallback)(void*); /* Invoked at every commit. */
   void *pUpdateArg;
   void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);
+#ifndef SQLITE_OMIT_WAL
+  int (*xWalCallback)(void *, sqlite3 *, const char *, int);
+  void *pWalArg;
+#endif
   void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);
   void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);
   void *pCollNeededArg;
@@ -8445,6 +8686,8 @@
 #define SQLITE_ReverseOrder   0x01000000  /* Reverse unordered SELECTs */
 #define SQLITE_RecTriggers    0x02000000  /* Enable recursive triggers */
 #define SQLITE_ForeignKeys    0x04000000  /* Enforce foreign key constraints  */
+#define SQLITE_AutoIndex      0x08000000  /* Enable automatic indexes */
+#define SQLITE_PreferBuiltin  0x10000000  /* Preference to built-in funcs */
 
 /*
 ** Bits of the sqlite3.flags field that are used by the
@@ -8456,7 +8699,8 @@
 #define SQLITE_IndexSort      0x04        /* Disable indexes for sorting */
 #define SQLITE_IndexSearch    0x08        /* Disable indexes for searching */
 #define SQLITE_IndexCover     0x10        /* Disable index covering table */
-#define SQLITE_OptMask        0x1f        /* Mask of all disablable opts */
+#define SQLITE_GroupByOrder   0x20        /* Disable GROUPBY cover of ORDERBY */
+#define SQLITE_OptMask        0xff        /* Mask of all disablable opts */
 
 /*
 ** Possible values for the sqlite.magic field.
@@ -9307,6 +9551,9 @@
 ** and the next table on the list.  The parser builds the list this way.
 ** But sqlite3SrcListShiftJoinType() later shifts the jointypes so that each
 ** jointype expresses the join between the table and the previous table.
+**
+** In the colUsed field, the high-order bit (bit 63) is set if the table
+** contains more than 63 columns and the 64-th or later column is used.
 */
 struct SrcList {
   i16 nSrc;        /* Number of tables or subqueries in the FROM clause */
@@ -9418,7 +9665,7 @@
 #define WHERE_ORDERBY_MAX      0x0002 /* ORDER BY processing for max() func */
 #define WHERE_ONEPASS_DESIRED  0x0004 /* Want to do one-pass UPDATE/DELETE */
 #define WHERE_DUPLICATES_OK    0x0008 /* Ok to return a row more than once */
-#define WHERE_OMIT_OPEN        0x0010 /* Table cursor are already open */
+#define WHERE_OMIT_OPEN        0x0010 /* Table cursors are already open */
 #define WHERE_OMIT_CLOSE       0x0020 /* Omit close of table & index cursors */
 #define WHERE_FORCE_TABLE      0x0040 /* Do not use an index-only search */
 #define WHERE_ONETABLE_ONLY    0x0080 /* Only code the 1st table in pTabList */
@@ -9441,6 +9688,7 @@
   int iBreak;                    /* Jump here to break out of the loop */
   int nLevel;                    /* Number of nested loop */
   struct WhereClause *pWC;       /* Decomposition of the WHERE clause */
+  double savedNQueryLoop;        /* pParse->nQueryLoop outside the WHERE loop */
   WhereLevel a[1];               /* Information about each nest loop in WHERE */
 };
 
@@ -9682,6 +9930,7 @@
   u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
   u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
   u8 disableTriggers;  /* True to disable triggers */
+  double nQueryLoop;   /* Estimated number of iterations of a query */
 
   /* Above is constant between recursions.  Below is reset before and after
   ** each recursion */
@@ -9960,6 +10209,15 @@
 
 
 /*
+** FTS4 is really an extension for FTS3.  It is enabled using the
+** SQLITE_ENABLE_FTS3 macro.  But to avoid confusion we also all
+** the SQLITE_ENABLE_FTS4 macro to serve as an alisse for SQLITE_ENABLE_FTS3.
+*/
+#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
+# define SQLITE_ENABLE_FTS3
+#endif
+
+/*
 ** The ctype.h header is needed for non-ASCII systems.  It is also
 ** needed by FTS3 when FTS3 is included in the amalgamation.
 */
@@ -10048,7 +10306,8 @@
 
 
 #ifndef SQLITE_MUTEX_OMIT
-SQLITE_PRIVATE   sqlite3_mutex_methods *sqlite3DefaultMutex(void);
+SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3DefaultMutex(void);
+SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3NoopMutex(void);
 SQLITE_PRIVATE   sqlite3_mutex *sqlite3MutexAlloc(int);
 SQLITE_PRIVATE   int sqlite3MutexInit(void);
 SQLITE_PRIVATE   int sqlite3MutexEnd(void);
@@ -10058,7 +10317,11 @@
 SQLITE_PRIVATE void sqlite3StatusAdd(int, int);
 SQLITE_PRIVATE void sqlite3StatusSet(int, int);
 
-SQLITE_PRIVATE int sqlite3IsNaN(double);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+SQLITE_PRIVATE   int sqlite3IsNaN(double);
+#else
+# define sqlite3IsNaN(X)  0
+#endif
 
 SQLITE_PRIVATE void sqlite3VXPrintf(StrAccum*, int, const char*, va_list);
 #ifndef SQLITE_OMIT_TRACE
@@ -10176,6 +10439,7 @@
 SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**, u16);
 SQLITE_PRIVATE void sqlite3WhereEnd(WhereInfo*);
 SQLITE_PRIVATE int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int);
+SQLITE_PRIVATE void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCodeMove(Parse*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCodeCopy(Parse*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCacheStore(Parse*, int, int, int);
@@ -10202,6 +10466,7 @@
 SQLITE_PRIVATE int sqlite3RunVacuum(char**, sqlite3*);
 SQLITE_PRIVATE char *sqlite3NameFromToken(sqlite3*, Token*);
 SQLITE_PRIVATE int sqlite3ExprCompare(Expr*, Expr*);
+SQLITE_PRIVATE int sqlite3ExprListCompare(ExprList*, ExprList*);
 SQLITE_PRIVATE void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
 SQLITE_PRIVATE void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
 SQLITE_PRIVATE Vdbe *sqlite3GetVdbe(Parse*);
@@ -10379,7 +10644,7 @@
                         void(*)(void*));
 SQLITE_PRIVATE void sqlite3ValueFree(sqlite3_value*);
 SQLITE_PRIVATE sqlite3_value *sqlite3ValueNew(sqlite3 *);
-SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *, const void*, int);
+SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *, const void*, int, u8);
 #ifdef SQLITE_ENABLE_STAT2
 SQLITE_PRIVATE char *sqlite3Utf8to16(sqlite3 *, u8, char *, int, int *);
 #endif
@@ -10391,11 +10656,13 @@
 SQLITE_PRIVATE const unsigned char sqlite3CtypeMap[];
 SQLITE_PRIVATE SQLITE_WSD struct Sqlite3Config sqlite3Config;
 SQLITE_PRIVATE SQLITE_WSD FuncDefHash sqlite3GlobalFunctions;
+#ifndef SQLITE_OMIT_WSD
 SQLITE_PRIVATE int sqlite3PendingByte;
 #endif
+#endif
 SQLITE_PRIVATE void sqlite3RootPageMoved(Db*, int, int);
 SQLITE_PRIVATE void sqlite3Reindex(Parse*, Token*, Token*);
-SQLITE_PRIVATE void sqlite3AlterFunctions(sqlite3*);
+SQLITE_PRIVATE void sqlite3AlterFunctions(void);
 SQLITE_PRIVATE void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
 SQLITE_PRIVATE int sqlite3GetToken(const unsigned char *, int *);
 SQLITE_PRIVATE void sqlite3NestedParse(Parse*, const char*, ...);
@@ -10504,6 +10771,9 @@
 SQLITE_PRIVATE CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, Expr *);
 SQLITE_PRIVATE int sqlite3TempInMemory(const sqlite3*);
 SQLITE_PRIVATE VTable *sqlite3GetVTable(sqlite3*, Table*);
+SQLITE_PRIVATE const char *sqlite3JournalModename(int);
+SQLITE_PRIVATE int sqlite3Checkpoint(sqlite3*, int);
+SQLITE_PRIVATE int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);
 
 /* Declarations for functions in fkey.c. All of these are replaced by
 ** no-op macros if OMIT_FOREIGN_KEY is defined. In this case no foreign
@@ -10610,7 +10880,46 @@
 # define sqlite3VdbeIOTraceSql(X)
 #endif
 
+/*
+** These routines are available for the mem2.c debugging memory allocator
+** only.  They are used to verify that different "types" of memory
+** allocations are properly tracked by the system.
+**
+** sqlite3MemdebugSetType() sets the "type" of an allocation to one of
+** the MEMTYPE_* macros defined below.  The type must be a bitmask with
+** a single bit set.
+**
+** sqlite3MemdebugHasType() returns true if any of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+** sqlite3MemdebugHasType() is intended for use inside assert() statements.
+** For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+**
+** Perhaps the most important point is the difference between MEMTYPE_HEAP
+** and MEMTYPE_DB.  If an allocation is MEMTYPE_DB, that means it might have
+** been allocated by lookaside, except the allocation was too large or
+** lookaside was already full.  It is important to verify that allocations
+** that might have been satisfied by lookaside are not passed back to 
+** non-lookaside free() routines.  Asserts such as the example above are
+** placed on the non-lookaside free() routines to verify this constraint. 
+**
+** All of this is no-op for a production build.  It only comes into
+** play when the SQLITE_MEMDEBUG compile-time option is used.
+*/
+#ifdef SQLITE_MEMDEBUG
+SQLITE_PRIVATE   void sqlite3MemdebugSetType(void*,u8);
+SQLITE_PRIVATE   int sqlite3MemdebugHasType(void*,u8);
+#else
+# define sqlite3MemdebugSetType(X,Y)  /* no-op */
+# define sqlite3MemdebugHasType(X,Y)  1
 #endif
+#define MEMTYPE_HEAP     0x01    /* General heap allocations */
+#define MEMTYPE_DB       0x02    /* Associated with a database connection */
+#define MEMTYPE_SCRATCH  0x04    /* Scratch allocations */
+#define MEMTYPE_PCACHE   0x08    /* Page cache allocations */
+
+#endif /* _SQLITEINT_H_ */
 
 /************** End of sqliteInt.h *******************************************/
 /************** Begin file global.c ******************************************/
@@ -10809,7 +11118,9 @@
 ** Changing the pending byte during operating results in undefined
 ** and dileterious behavior.
 */
+#ifndef SQLITE_OMIT_WSD
 SQLITE_PRIVATE int sqlite3PendingByte = 0x40000000;
+#endif
 
 /*
 ** Properties of opcodes.  The OPFLG_INITIALIZER macro is
@@ -10820,6 +11131,396 @@
 SQLITE_PRIVATE const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
 
 /************** End of global.c **********************************************/
+/************** Begin file ctime.c *******************************************/
+/*
+** 2010 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements routines used to report what compile-time options
+** SQLite was built with.
+*/
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+
+
+/*
+** An array of names of all compile-time options.  This array should 
+** be sorted A-Z.
+**
+** This array looks large, but in a typical installation actually uses
+** only a handful of compile-time options, so most times this array is usually
+** rather short and uses little memory space.
+*/
+static const char * const azCompileOpt[] = {
+
+/* These macros are provided to "stringify" the value of the define
+** for those options in which the value is meaningful. */
+#define CTIMEOPT_VAL_(opt) #opt
+#define CTIMEOPT_VAL(opt) CTIMEOPT_VAL_(opt)
+
+#ifdef SQLITE_32BIT_ROWID
+  "32BIT_ROWID",
+#endif
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+  "4_BYTE_ALIGNED_MALLOC",
+#endif
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  "CASE_SENSITIVE_LIKE",
+#endif
+#ifdef SQLITE_CHECK_PAGES
+  "CHECK_PAGES",
+#endif
+#ifdef SQLITE_COVERAGE_TEST
+  "COVERAGE_TEST",
+#endif
+#ifdef SQLITE_DEBUG
+  "DEBUG",
+#endif
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  "DEFAULT_LOCKING_MODE=" CTIMEOPT_VAL(SQLITE_DEFAULT_LOCKING_MODE),
+#endif
+#ifdef SQLITE_DISABLE_DIRSYNC
+  "DISABLE_DIRSYNC",
+#endif
+#ifdef SQLITE_DISABLE_LFS
+  "DISABLE_LFS",
+#endif
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  "ENABLE_ATOMIC_WRITE",
+#endif
+#ifdef SQLITE_ENABLE_CEROD
+  "ENABLE_CEROD",
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  "ENABLE_COLUMN_METADATA",
+#endif
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  "ENABLE_EXPENSIVE_ASSERT",
+#endif
+#ifdef SQLITE_ENABLE_FTS1
+  "ENABLE_FTS1",
+#endif
+#ifdef SQLITE_ENABLE_FTS2
+  "ENABLE_FTS2",
+#endif
+#ifdef SQLITE_ENABLE_FTS3
+  "ENABLE_FTS3",
+#endif
+#ifdef SQLITE_ENABLE_FTS3_PARENTHESIS
+  "ENABLE_FTS3_PARENTHESIS",
+#endif
+#ifdef SQLITE_ENABLE_FTS4
+  "ENABLE_FTS4",
+#endif
+#ifdef SQLITE_ENABLE_ICU
+  "ENABLE_ICU",
+#endif
+#ifdef SQLITE_ENABLE_IOTRACE
+  "ENABLE_IOTRACE",
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+  "ENABLE_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+  "ENABLE_LOCKING_STYLE=" CTIMEOPT_VAL(SQLITE_ENABLE_LOCKING_STYLE),
+#endif
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  "ENABLE_MEMORY_MANAGEMENT",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS3
+  "ENABLE_MEMSYS3",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+  "ENABLE_MEMSYS5",
+#endif
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  "ENABLE_OVERSIZE_CELL_CHECK",
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+  "ENABLE_RTREE",
+#endif
+#ifdef SQLITE_ENABLE_STAT2
+  "ENABLE_STAT2",
+#endif
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  "ENABLE_UNLOCK_NOTIFY",
+#endif
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  "ENABLE_UPDATE_DELETE_LIMIT",
+#endif
+#ifdef SQLITE_HAS_CODEC
+  "HAS_CODEC",
+#endif
+#ifdef SQLITE_HAVE_ISNAN
+  "HAVE_ISNAN",
+#endif
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  "HOMEGROWN_RECURSIVE_MUTEX",
+#endif
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+  "IGNORE_AFP_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  "IGNORE_FLOCK_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_INT64_TYPE
+  "INT64_TYPE",
+#endif
+#ifdef SQLITE_LOCK_TRACE
+  "LOCK_TRACE",
+#endif
+#ifdef SQLITE_MEMDEBUG
+  "MEMDEBUG",
+#endif
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+  "MIXED_ENDIAN_64BIT_FLOAT",
+#endif
+#ifdef SQLITE_NO_SYNC
+  "NO_SYNC",
+#endif
+#ifdef SQLITE_OMIT_ALTERTABLE
+  "OMIT_ALTERTABLE",
+#endif
+#ifdef SQLITE_OMIT_ANALYZE
+  "OMIT_ANALYZE",
+#endif
+#ifdef SQLITE_OMIT_ATTACH
+  "OMIT_ATTACH",
+#endif
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  "OMIT_AUTHORIZATION",
+#endif
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  "OMIT_AUTOINCREMENT",
+#endif
+#ifdef SQLITE_OMIT_AUTOINIT
+  "OMIT_AUTOINIT",
+#endif
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  "OMIT_AUTOMATIC_INDEX",
+#endif
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  "OMIT_AUTOVACUUM",
+#endif
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  "OMIT_BETWEEN_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  "OMIT_BLOB_LITERAL",
+#endif
+#ifdef SQLITE_OMIT_BTREECOUNT
+  "OMIT_BTREECOUNT",
+#endif
+#ifdef SQLITE_OMIT_BUILTIN_TEST
+  "OMIT_BUILTIN_TEST",
+#endif
+#ifdef SQLITE_OMIT_CAST
+  "OMIT_CAST",
+#endif
+#ifdef SQLITE_OMIT_CHECK
+  "OMIT_CHECK",
+#endif
+#ifdef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  "OMIT_COMPILEOPTION_DIAGS",
+#endif
+#ifdef SQLITE_OMIT_COMPLETE
+  "OMIT_COMPLETE",
+#endif
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  "OMIT_COMPOUND_SELECT",
+#endif
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+  "OMIT_DATETIME_FUNCS",
+#endif
+#ifdef SQLITE_OMIT_DECLTYPE
+  "OMIT_DECLTYPE",
+#endif
+#ifdef SQLITE_OMIT_DEPRECATED
+  "OMIT_DEPRECATED",
+#endif
+#ifdef SQLITE_OMIT_DISKIO
+  "OMIT_DISKIO",
+#endif
+#ifdef SQLITE_OMIT_EXPLAIN
+  "OMIT_EXPLAIN",
+#endif
+#ifdef SQLITE_OMIT_FLAG_PRAGMAS
+  "OMIT_FLAG_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  "OMIT_FLOATING_POINT",
+#endif
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  "OMIT_FOREIGN_KEY",
+#endif
+#ifdef SQLITE_OMIT_GET_TABLE
+  "OMIT_GET_TABLE",
+#endif
+#ifdef SQLITE_OMIT_GLOBALRECOVER
+  "OMIT_GLOBALRECOVER",
+#endif
+#ifdef SQLITE_OMIT_INCRBLOB
+  "OMIT_INCRBLOB",
+#endif
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  "OMIT_INTEGRITY_CHECK",
+#endif
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  "OMIT_LIKE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  "OMIT_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_OMIT_LOCALTIME
+  "OMIT_LOCALTIME",
+#endif
+#ifdef SQLITE_OMIT_LOOKASIDE
+  "OMIT_LOOKASIDE",
+#endif
+#ifdef SQLITE_OMIT_MEMORYDB
+  "OMIT_MEMORYDB",
+#endif
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  "OMIT_OR_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  "OMIT_PAGER_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_PRAGMA
+  "OMIT_PRAGMA",
+#endif
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  "OMIT_PROGRESS_CALLBACK",
+#endif
+#ifdef SQLITE_OMIT_QUICKBALANCE
+  "OMIT_QUICKBALANCE",
+#endif
+#ifdef SQLITE_OMIT_REINDEX
+  "OMIT_REINDEX",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  "OMIT_SCHEMA_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  "OMIT_SCHEMA_VERSION_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  "OMIT_SHARED_CACHE",
+#endif
+#ifdef SQLITE_OMIT_SUBQUERY
+  "OMIT_SUBQUERY",
+#endif
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  "OMIT_TCL_VARIABLE",
+#endif
+#ifdef SQLITE_OMIT_TEMPDB
+  "OMIT_TEMPDB",
+#endif
+#ifdef SQLITE_OMIT_TRACE
+  "OMIT_TRACE",
+#endif
+#ifdef SQLITE_OMIT_TRIGGER
+  "OMIT_TRIGGER",
+#endif
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  "OMIT_TRUNCATE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_UTF16
+  "OMIT_UTF16",
+#endif
+#ifdef SQLITE_OMIT_VACUUM
+  "OMIT_VACUUM",
+#endif
+#ifdef SQLITE_OMIT_VIEW
+  "OMIT_VIEW",
+#endif
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  "OMIT_VIRTUALTABLE",
+#endif
+#ifdef SQLITE_OMIT_WSD
+  "OMIT_WSD",
+#endif
+#ifdef SQLITE_OMIT_XFER_OPT
+  "OMIT_XFER_OPT",
+#endif
+#ifdef SQLITE_PERFORMANCE_TRACE
+  "PERFORMANCE_TRACE",
+#endif
+#ifdef SQLITE_PROXY_DEBUG
+  "PROXY_DEBUG",
+#endif
+#ifdef SQLITE_SECURE_DELETE
+  "SECURE_DELETE",
+#endif
+#ifdef SQLITE_SMALL_STACK
+  "SMALL_STACK",
+#endif
+#ifdef SQLITE_SOUNDEX
+  "SOUNDEX",
+#endif
+#ifdef SQLITE_TCL
+  "TCL",
+#endif
+#ifdef SQLITE_TEMP_STORE
+  "TEMP_STORE=" CTIMEOPT_VAL(SQLITE_TEMP_STORE),
+#endif
+#ifdef SQLITE_TEST
+  "TEST",
+#endif
+#ifdef SQLITE_THREADSAFE
+  "THREADSAFE=" CTIMEOPT_VAL(SQLITE_THREADSAFE),
+#endif
+#ifdef SQLITE_USE_ALLOCA
+  "USE_ALLOCA",
+#endif
+#ifdef SQLITE_ZERO_MALLOC
+  "ZERO_MALLOC"
+#endif
+};
+
+/*
+** Given the name of a compile-time option, return true if that option
+** was used and false if not.
+**
+** The name can optionally begin with "SQLITE_" but the "SQLITE_" prefix
+** is not required for a match.
+*/
+SQLITE_API int sqlite3_compileoption_used(const char *zOptName){
+  int i, n;
+  if( sqlite3StrNICmp(zOptName, "SQLITE_", 7)==0 ) zOptName += 7;
+  n = sqlite3Strlen30(zOptName);
+
+  /* Since ArraySize(azCompileOpt) is normally in single digits, a
+  ** linear search is adequate.  No need for a binary search. */
+  for(i=0; i<ArraySize(azCompileOpt); i++){
+    if(   (sqlite3StrNICmp(zOptName, azCompileOpt[i], n)==0)
+       && ( (azCompileOpt[i][n]==0) || (azCompileOpt[i][n]=='=') ) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the N-th compile-time option string.  If N is out of range,
+** return a NULL pointer.
+*/
+SQLITE_API const char *sqlite3_compileoption_get(int N){
+  if( N>=0 && N<ArraySize(azCompileOpt) ){
+    return azCompileOpt[N];
+  }
+  return 0;
+}
+
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/************** End of ctime.c ***********************************************/
 /************** Begin file status.c ******************************************/
 /*
 ** 2008 June 18
@@ -10934,6 +11635,26 @@
       }
       break;
     }
+
+    /* 
+    ** Return an approximation for the amount of memory currently used
+    ** by all pagers associated with the given database connection.  The
+    ** highwater mark is meaningless and is returned as zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_USED: {
+      int totalUsed = 0;
+      int i;
+      for(i=0; i<db->nDb; i++){
+        Btree *pBt = db->aDb[i].pBt;
+        if( pBt ){
+          Pager *pPager = sqlite3BtreePager(pBt);
+          totalUsed += sqlite3PagerMemUsed(pPager);
+        }
+      }
+      *pCurrent = totalUsed;
+      *pHighwater = 0;
+      break;
+    }
     default: {
       return SQLITE_ERROR;
     }
@@ -11256,10 +11977,8 @@
 ** Set the time to the current time reported by the VFS
 */
 static void setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
-  double r;
   sqlite3 *db = sqlite3_context_db_handle(context);
-  sqlite3OsCurrentTime(db->pVfs, &r);
-  p->iJD = (sqlite3_int64)(r*86400000.0 + 0.5);
+  sqlite3OsCurrentTimeInt64(db->pVfs, &p->iJD);
   p->validJD = 1;
 }
 
@@ -11980,22 +12699,15 @@
   time_t t;
   char *zFormat = (char *)sqlite3_user_data(context);
   sqlite3 *db;
-  double rT;
+  sqlite3_int64 iT;
   char zBuf[20];
 
   UNUSED_PARAMETER(argc);
   UNUSED_PARAMETER(argv);
 
   db = sqlite3_context_db_handle(context);
-  sqlite3OsCurrentTime(db->pVfs, &rT);
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  t = 86400.0*(rT - 2440587.5) + 0.5;
-#else
-  /* without floating point support, rT will have
-  ** already lost fractional day precision.
-  */
-  t = 86400 * (rT - 2440587) - 43200;
-#endif
+  sqlite3OsCurrentTimeInt64(db->pVfs, &iT);
+  t = iT/1000 - 10000*(sqlite3_int64)21086676;
 #ifdef HAVE_GMTIME_R
   {
     struct tm sNow;
@@ -12034,8 +12746,8 @@
     FUNCTION(current_date,      0, 0, 0, cdateFunc     ),
 #else
     STR_FUNCTION(current_time,      0, "%H:%M:%S",          0, currentTimeFunc),
-    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d",          0, currentTimeFunc),
-    STR_FUNCTION(current_date,      0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
+    STR_FUNCTION(current_date,      0, "%Y-%m-%d",          0, currentTimeFunc),
+    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
 #endif
   };
   int i;
@@ -12148,6 +12860,27 @@
 SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
   return id->pMethods->xDeviceCharacteristics(id);
 }
+SQLITE_PRIVATE int sqlite3OsShmOpen(sqlite3_file *id){
+  return id->pMethods->xShmOpen(id);
+}
+SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
+  return id->pMethods->xShmLock(id, offset, n, flags);
+}
+SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id){
+  id->pMethods->xShmBarrier(id);
+}
+SQLITE_PRIVATE int sqlite3OsShmClose(sqlite3_file *id, int deleteFlag){
+  return id->pMethods->xShmClose(id, deleteFlag);
+}
+SQLITE_PRIVATE int sqlite3OsShmMap(
+  sqlite3_file *id, 
+  int iPage, 
+  int pgsz, 
+  int isWrite, 
+  void volatile **pp
+){
+  return id->pMethods->xShmMap(id, iPage, pgsz, isWrite, pp);
+}
 
 /*
 ** The next group of routines are convenience wrappers around the
@@ -12162,11 +12895,11 @@
 ){
   int rc;
   DO_OS_MALLOC_TEST(0);
-  /* 0x7f1f is a mask of SQLITE_OPEN_ flags that are valid to be passed
+  /* 0x7f3f is a mask of SQLITE_OPEN_ flags that are valid to be passed
   ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
   ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
   ** reaching the VFS. */
-  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x7f1f, pFlagsOut);
+  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x7f3f, pFlagsOut);
   assert( rc==SQLITE_OK || pFile->pMethods==0 );
   return rc;
 }
@@ -12211,8 +12944,16 @@
 SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *pVfs, int nMicro){
   return pVfs->xSleep(pVfs, nMicro);
 }
-SQLITE_PRIVATE int sqlite3OsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
-  return pVfs->xCurrentTime(pVfs, pTimeOut);
+SQLITE_PRIVATE int sqlite3OsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  int rc;
+  if( pVfs->iVersion>=2 && pVfs->xCurrentTimeInt64 ){
+    rc = pVfs->xCurrentTimeInt64(pVfs, pTimeOut);
+  }else{
+    double r;
+    rc = pVfs->xCurrentTime(pVfs, &r);
+    *pTimeOut = (sqlite3_int64)(r*86400000.0);
+  }
+  return rc;
 }
 
 SQLITE_PRIVATE int sqlite3OsOpenMalloc(
@@ -12589,7 +13330,6 @@
   sqlite3_int64 *p = (sqlite3_int64*)pPrior;
   assert( pPrior!=0 && nByte>0 );
   nByte = ROUND8(nByte);
-  p = (sqlite3_int64*)pPrior;
   p--;
   p = realloc(p, nByte+8 );
   if( p ){
@@ -12708,7 +13448,8 @@
   struct MemBlockHdr *pNext, *pPrev;  /* Linked list of all unfreed memory */
   char nBacktrace;                    /* Number of backtraces on this alloc */
   char nBacktraceSlots;               /* Available backtrace slots */
-  short nTitle;                       /* Bytes of title; includes '\0' */
+  u8 nTitle;                          /* Bytes of title; includes '\0' */
+  u8 eType;                           /* Allocation type code */
   int iForeGuard;                     /* Guard word for sanity */
 };
 
@@ -12916,6 +13657,7 @@
     }
     mem.pLast = pHdr;
     pHdr->iForeGuard = FOREGUARD;
+    pHdr->eType = MEMTYPE_HEAP;
     pHdr->nBacktraceSlots = mem.nBacktrace;
     pHdr->nTitle = mem.nTitle;
     if( mem.nBacktrace ){
@@ -12951,7 +13693,8 @@
   struct MemBlockHdr *pHdr;
   void **pBt;
   char *z;
-  assert( sqlite3GlobalConfig.bMemstat || mem.mutex!=0 );
+  assert( sqlite3GlobalConfig.bMemstat || sqlite3GlobalConfig.bCoreMutex==0 
+       || mem.mutex!=0 );
   pHdr = sqlite3MemsysGetHeader(pPrior);
   pBt = (void**)pHdr;
   pBt -= pHdr->nBacktraceSlots;
@@ -13023,6 +13766,47 @@
 }
 
 /*
+** Set the "type" of an allocation.
+*/
+SQLITE_PRIVATE void sqlite3MemdebugSetType(void *p, u8 eType){
+  if( p ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );
+    pHdr->eType = eType;
+  }
+}
+
+/*
+** Return TRUE if the mask of type in eType matches the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+*/
+SQLITE_PRIVATE int sqlite3MemdebugHasType(void *p, u8 eType){
+  int rc = 1;
+  if( p ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    assert( (pHdr->eType & (pHdr->eType-1))==0 );  /* Only one type bit set */
+    if( (pHdr->eType&eType)==0 ){
+      void **pBt;
+      pBt = (void**)pHdr;
+      pBt -= pHdr->nBacktraceSlots;
+      backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(stderr));
+      fprintf(stderr, "\n");
+      rc = 0;
+    }
+  }
+  return rc;
+}
+ 
+
+/*
 ** Set the number of backtrace levels kept for each allocation.
 ** A value of zero turns off backtracing.  The number is always rounded
 ** up to a multiple of 2.
@@ -14423,23 +15207,26 @@
 */
 SQLITE_PRIVATE int sqlite3MutexInit(void){ 
   int rc = SQLITE_OK;
-  if( sqlite3GlobalConfig.bCoreMutex ){
-    if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
-      /* If the xMutexAlloc method has not been set, then the user did not
-      ** install a mutex implementation via sqlite3_config() prior to 
-      ** sqlite3_initialize() being called. This block copies pointers to
-      ** the default implementation into the sqlite3GlobalConfig structure.
-      */
-      sqlite3_mutex_methods *pFrom = sqlite3DefaultMutex();
-      sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
+  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
+    /* If the xMutexAlloc method has not been set, then the user did not
+    ** install a mutex implementation via sqlite3_config() prior to 
+    ** sqlite3_initialize() being called. This block copies pointers to
+    ** the default implementation into the sqlite3GlobalConfig structure.
+    */
+    sqlite3_mutex_methods const *pFrom;
+    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
 
-      memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
-      memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
-             sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
-      pTo->xMutexAlloc = pFrom->xMutexAlloc;
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pFrom = sqlite3DefaultMutex();
+    }else{
+      pFrom = sqlite3NoopMutex();
     }
-    rc = sqlite3GlobalConfig.mutex.xMutexInit();
+    memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
+    memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
+           sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
+    pTo->xMutexAlloc = pFrom->xMutexAlloc;
   }
+  rc = sqlite3GlobalConfig.mutex.xMutexInit();
 
 #ifdef SQLITE_DEBUG
   GLOBAL(int, mutexIsInit) = 1;
@@ -14571,15 +15358,14 @@
 ** called correctly.
 */
 
+#ifndef SQLITE_MUTEX_OMIT
 
-#if defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG)
+#ifndef SQLITE_DEBUG
 /*
 ** Stub routines for all mutex methods.
 **
 ** This routines provide no mutual exclusion or error checking.
 */
-static int noopMutexHeld(sqlite3_mutex *p){ return 1; }
-static int noopMutexNotheld(sqlite3_mutex *p){ return 1; }
 static int noopMutexInit(void){ return SQLITE_OK; }
 static int noopMutexEnd(void){ return SQLITE_OK; }
 static sqlite3_mutex *noopMutexAlloc(int id){ return (sqlite3_mutex*)8; }
@@ -14588,8 +15374,8 @@
 static int noopMutexTry(sqlite3_mutex *p){ return SQLITE_OK; }
 static void noopMutexLeave(sqlite3_mutex *p){ return; }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     noopMutexInit,
     noopMutexEnd,
     noopMutexAlloc,
@@ -14598,15 +15384,15 @@
     noopMutexTry,
     noopMutexLeave,
 
-    noopMutexHeld,
-    noopMutexNotheld
+    0,
+    0,
   };
 
   return &sMutex;
 }
-#endif /* defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG) */
+#endif /* !SQLITE_DEBUG */
 
-#if defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG)
+#ifdef SQLITE_DEBUG
 /*
 ** In this implementation, error checking is provided for testing
 ** and debugging purposes.  The mutexes still do not provide any
@@ -14616,19 +15402,21 @@
 /*
 ** The mutex object
 */
-struct sqlite3_mutex {
+typedef struct sqlite3_debug_mutex {
   int id;     /* The mutex type */
   int cnt;    /* Number of entries without a matching leave */
-};
+} sqlite3_debug_mutex;
 
 /*
 ** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
 ** intended for use inside assert() statements.
 */
-static int debugMutexHeld(sqlite3_mutex *p){
+static int debugMutexHeld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   return p==0 || p->cnt>0;
 }
-static int debugMutexNotheld(sqlite3_mutex *p){
+static int debugMutexNotheld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   return p==0 || p->cnt==0;
 }
 
@@ -14644,8 +15432,8 @@
 ** that means that a mutex could not be allocated. 
 */
 static sqlite3_mutex *debugMutexAlloc(int id){
-  static sqlite3_mutex aStatic[6];
-  sqlite3_mutex *pNew = 0;
+  static sqlite3_debug_mutex aStatic[6];
+  sqlite3_debug_mutex *pNew = 0;
   switch( id ){
     case SQLITE_MUTEX_FAST:
     case SQLITE_MUTEX_RECURSIVE: {
@@ -14664,13 +15452,14 @@
       break;
     }
   }
-  return pNew;
+  return (sqlite3_mutex*)pNew;
 }
 
 /*
 ** This routine deallocates a previously allocated mutex.
 */
-static void debugMutexFree(sqlite3_mutex *p){
+static void debugMutexFree(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   assert( p->cnt==0 );
   assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
   sqlite3_free(p);
@@ -14687,12 +15476,14 @@
 ** can enter.  If the same thread tries to enter any other kind of mutex
 ** more than once, the behavior is undefined.
 */
-static void debugMutexEnter(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+static void debugMutexEnter(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
   p->cnt++;
 }
-static int debugMutexTry(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+static int debugMutexTry(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
   p->cnt++;
   return SQLITE_OK;
 }
@@ -14703,14 +15494,15 @@
 ** is undefined if the mutex is not currently entered or
 ** is not currently allocated.  SQLite will never do either.
 */
-static void debugMutexLeave(sqlite3_mutex *p){
-  assert( debugMutexHeld(p) );
+static void debugMutexLeave(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( debugMutexHeld(pX) );
   p->cnt--;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     debugMutexInit,
     debugMutexEnd,
     debugMutexAlloc,
@@ -14725,7 +15517,18 @@
 
   return &sMutex;
 }
-#endif /* defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG) */
+#endif /* SQLITE_DEBUG */
+
+/*
+** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
+** is used regardless of the run-time threadsafety setting.
+*/
+#ifdef SQLITE_MUTEX_NOOP
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  return sqliteNoopMutex();
+}
+#endif /* SQLITE_MUTEX_NOOP */
+#endif /* SQLITE_MUTEX_OMIT */
 
 /************** End of mutex_noop.c ******************************************/
 /************** Begin file mutex_os2.c ***************************************/
@@ -14981,8 +15784,8 @@
   DosReleaseMutexSem(p->mutex);
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     os2MutexInit,
     os2MutexEnd,
     os2MutexAlloc,
@@ -15027,23 +15830,33 @@
 
 #include <pthread.h>
 
+/*
+** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
+** are necessary under two condidtions:  (1) Debug builds and (2) using
+** home-grown mutexes.  Encapsulate these conditions into a single #define.
+*/
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
+# define SQLITE_MUTEX_NREF 1
+#else
+# define SQLITE_MUTEX_NREF 0
+#endif
 
 /*
 ** Each recursive mutex is an instance of the following structure.
 */
 struct sqlite3_mutex {
   pthread_mutex_t mutex;     /* Mutex controlling the lock */
+#if SQLITE_MUTEX_NREF
   int id;                    /* Mutex type */
-  int nRef;                  /* Number of entrances */
-  pthread_t owner;           /* Thread that is within this mutex */
-#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of entrances */
+  volatile pthread_t owner;  /* Thread that is within this mutex */
   int trace;                 /* True to trace changes */
 #endif
 };
-#ifdef SQLITE_DEBUG
+#if SQLITE_MUTEX_NREF
 #define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0, 0 }
 #else
-#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0 }
+#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
 #endif
 
 /*
@@ -15145,14 +15958,18 @@
         pthread_mutex_init(&p->mutex, &recursiveAttr);
         pthread_mutexattr_destroy(&recursiveAttr);
 #endif
+#if SQLITE_MUTEX_NREF
         p->id = iType;
+#endif
       }
       break;
     }
     case SQLITE_MUTEX_FAST: {
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){
+#if SQLITE_MUTEX_NREF
         p->id = iType;
+#endif
         pthread_mutex_init(&p->mutex, 0);
       }
       break;
@@ -15161,7 +15978,9 @@
       assert( iType-2 >= 0 );
       assert( iType-2 < ArraySize(staticMutexes) );
       p = &staticMutexes[iType-2];
+#if SQLITE_MUTEX_NREF
       p->id = iType;
+#endif
       break;
     }
   }
@@ -15221,9 +16040,11 @@
   /* Use the built-in recursive mutexes if they are available.
   */
   pthread_mutex_lock(&p->mutex);
+#if SQLITE_MUTEX_NREF
   p->owner = pthread_self();
   p->nRef++;
 #endif
+#endif
 
 #ifdef SQLITE_DEBUG
   if( p->trace ){
@@ -15264,8 +16085,10 @@
   /* Use the built-in recursive mutexes if they are available.
   */
   if( pthread_mutex_trylock(&p->mutex)==0 ){
+#if SQLITE_MUTEX_NREF
     p->owner = pthread_self();
     p->nRef++;
+#endif
     rc = SQLITE_OK;
   }else{
     rc = SQLITE_BUSY;
@@ -15288,7 +16111,9 @@
 */
 static void pthreadMutexLeave(sqlite3_mutex *p){
   assert( pthreadMutexHeld(p) );
+#if SQLITE_MUTEX_NREF
   p->nRef--;
+#endif
   assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
 
 #ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
@@ -15306,8 +16131,8 @@
 #endif
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     pthreadMutexInit,
     pthreadMutexEnd,
     pthreadMutexAlloc,
@@ -15357,9 +16182,18 @@
 struct sqlite3_mutex {
   CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
   int id;                    /* Mutex type */
-  int nRef;                  /* Number of enterances */
-  DWORD owner;               /* Thread holding this mutex */
+#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of enterances */
+  volatile DWORD owner;      /* Thread holding this mutex */
+  int trace;                 /* True to trace changes */
+#endif
 };
+#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
+#ifdef SQLITE_DEBUG
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, 0L, (DWORD)0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0 }
+#endif
 
 /*
 ** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
@@ -15403,8 +16237,12 @@
 static int winMutexHeld(sqlite3_mutex *p){
   return p->nRef!=0 && p->owner==GetCurrentThreadId();
 }
+static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
+  return p->nRef==0 || p->owner!=tid;
+}
 static int winMutexNotheld(sqlite3_mutex *p){
-  return p->nRef==0 || p->owner!=GetCurrentThreadId();
+  DWORD tid = GetCurrentThreadId(); 
+  return winMutexNotheld2(p, tid);
 }
 #endif
 
@@ -15412,7 +16250,14 @@
 /*
 ** Initialize and deinitialize the mutex subsystem.
 */
-static sqlite3_mutex winMutex_staticMutexes[6];
+static sqlite3_mutex winMutex_staticMutexes[6] = {
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER
+};
 static int winMutex_isInit = 0;
 /* As winMutexInit() and winMutexEnd() are called as part
 ** of the sqlite3_initialize and sqlite3_shutdown()
@@ -15503,7 +16348,9 @@
     case SQLITE_MUTEX_RECURSIVE: {
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){  
+#ifdef SQLITE_DEBUG
         p->id = iType;
+#endif
         InitializeCriticalSection(&p->mutex);
       }
       break;
@@ -15513,7 +16360,9 @@
       assert( iType-2 >= 0 );
       assert( iType-2 < ArraySize(winMutex_staticMutexes) );
       p = &winMutex_staticMutexes[iType-2];
+#ifdef SQLITE_DEBUG
       p->id = iType;
+#endif
       break;
     }
   }
@@ -15546,14 +16395,25 @@
 ** more than once, the behavior is undefined.
 */
 static void winMutexEnter(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld(p) );
+#ifdef SQLITE_DEBUG
+  DWORD tid = GetCurrentThreadId(); 
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+#endif
   EnterCriticalSection(&p->mutex);
-  p->owner = GetCurrentThreadId(); 
+#ifdef SQLITE_DEBUG
+  p->owner = tid; 
   p->nRef++;
+  if( p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
 }
 static int winMutexTry(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId(); 
+#endif
   int rc = SQLITE_BUSY;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld(p) );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
   /*
   ** The sqlite3_mutex_try() routine is very rarely used, and when it
   ** is used it is merely an optimization.  So it is OK for it to always
@@ -15567,13 +16427,18 @@
   */
 #if 0
   if( mutexIsNT() && TryEnterCriticalSection(&p->mutex) ){
-    p->owner = GetCurrentThreadId();
+    p->owner = tid;
     p->nRef++;
     rc = SQLITE_OK;
   }
 #else
   UNUSED_PARAMETER(p);
 #endif
+#ifdef SQLITE_DEBUG
+  if( rc==SQLITE_OK && p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
   return rc;
 }
 
@@ -15584,15 +16449,23 @@
 ** is not currently allocated.  SQLite will never do either.
 */
 static void winMutexLeave(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId();
   assert( p->nRef>0 );
-  assert( p->owner==GetCurrentThreadId() );
+  assert( p->owner==tid );
   p->nRef--;
   assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+#endif
   LeaveCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     winMutexInit,
     winMutexEnd,
     winMutexAlloc,
@@ -15971,6 +16844,7 @@
   }else{
     p = sqlite3GlobalConfig.m.xMalloc(n);
   }
+  sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
   scratchAllocOut = p!=0;
 #endif
@@ -15991,6 +16865,8 @@
     if( sqlite3GlobalConfig.pScratch==0
            || p<sqlite3GlobalConfig.pScratch
            || p>=(void*)mem0.aScratchFree ){
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
       if( sqlite3GlobalConfig.bMemstat ){
         int iSize = sqlite3MallocSize(p);
         sqlite3_mutex_enter(mem0.mutex);
@@ -16031,6 +16907,7 @@
 ** sqlite3Malloc() or sqlite3_malloc().
 */
 SQLITE_PRIVATE int sqlite3MallocSize(void *p){
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   return sqlite3GlobalConfig.m.xSize(p);
 }
 SQLITE_PRIVATE int sqlite3DbMallocSize(sqlite3 *db, void *p){
@@ -16038,6 +16915,8 @@
   if( isLookaside(db, p) ){
     return db->lookaside.sz;
   }else{
+    assert( sqlite3MemdebugHasType(p,
+             db ? (MEMTYPE_DB|MEMTYPE_HEAP) : MEMTYPE_HEAP) );
     return sqlite3GlobalConfig.m.xSize(p);
   }
 }
@@ -16047,6 +16926,7 @@
 */
 SQLITE_API void sqlite3_free(void *p){
   if( p==0 ) return;
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   if( sqlite3GlobalConfig.bMemstat ){
     sqlite3_mutex_enter(mem0.mutex);
     sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));
@@ -16069,6 +16949,8 @@
     db->lookaside.pFree = pBuf;
     db->lookaside.nOut--;
   }else{
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_DB|MEMTYPE_HEAP) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
     sqlite3_free(p);
   }
 }
@@ -16101,6 +16983,7 @@
           mem0.alarmThreshold ){
       sqlite3MallocAlarm(nNew-nOld);
     }
+    assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
     if( pNew==0 && mem0.alarmCallback ){
       sqlite3MallocAlarm(nBytes);
@@ -16198,6 +17081,8 @@
   if( !p && db ){
     db->mallocFailed = 1;
   }
+  sqlite3MemdebugSetType(p,
+            (db && db->lookaside.bEnabled) ? MEMTYPE_DB : MEMTYPE_HEAP);
   return p;
 }
 
@@ -16223,10 +17108,14 @@
         sqlite3DbFree(db, p);
       }
     }else{
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_DB|MEMTYPE_HEAP) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
       pNew = sqlite3_realloc(p, n);
       if( !pNew ){
         db->mallocFailed = 1;
       }
+      sqlite3MemdebugSetType(pNew,
+            db->lookaside.bEnabled ? MEMTYPE_DB : MEMTYPE_HEAP);
     }
   }
   return pNew;
@@ -16787,7 +17676,9 @@
       case etEXP:
       case etGENERIC:
         realvalue = va_arg(ap,double);
-#ifndef SQLITE_OMIT_FLOATING_POINT
+#ifdef SQLITE_OMIT_FLOATING_POINT
+        length = 0;
+#else
         if( precision<0 ) precision = 6;         /* Set default precision */
         if( precision>etBUFSIZE/2-10 ) precision = etBUFSIZE/2-10;
         if( realvalue<0.0 ){
@@ -16933,7 +17824,7 @@
           while( nPad-- ) bufpt[i++] = '0';
           length = width;
         }
-#endif
+#endif /* !defined(SQLITE_OMIT_FLOATING_POINT) */
         break;
       case etSIZE:
         *(va_arg(ap,int*)) = pAccum->nChar;
@@ -16980,7 +17871,7 @@
         isnull = escarg==0;
         if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
         k = precision;
-        for(i=n=0; (ch=escarg[i])!=0 && k!=0; i++, k--){
+        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
           if( ch==q )  n++;
         }
         needQuote = !isnull && xtype==etSQLESCAPE2;
@@ -17274,12 +18165,8 @@
 ** mutex is held.
 */
 static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
-  StrAccum acc;                           /* String accumulator */
-#ifdef SQLITE_SMALL_STACK
-  char zMsg[150];                         /* Complete log message */
-#else
-  char zMsg[400];                         /* Complete log message */
-#endif
+  StrAccum acc;                          /* String accumulator */
+  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */
 
   sqlite3StrAccumInit(&acc, zMsg, sizeof(zMsg), 0);
   acc.useMalloc = 0;
@@ -17832,7 +18719,7 @@
   int btreeMask;          /* Bitmask of db->aDb[] entries referenced */
   i64 startTime;          /* Time when query started - used for profiling */
   BtreeMutexArray aMutex; /* An array of Btree used here and needing locks */
-  int aCounter[2];        /* Counters used by sqlite3_stmt_status() */
+  int aCounter[3];        /* Counters used by sqlite3_stmt_status() */
   char *zSql;             /* Text of the SQL statement that generated this */
   void *pFree;            /* Free this when deleting the vdbe */
   i64 nFkConstraint;      /* Number of imm. FK constraints this VM */
@@ -17884,7 +18771,11 @@
 SQLITE_PRIVATE int sqlite3VdbeMemNulTerminate(Mem*);
 SQLITE_PRIVATE int sqlite3VdbeMemSetStr(Mem*, const char*, int, u8, void(*)(void*));
 SQLITE_PRIVATE void sqlite3VdbeMemSetInt64(Mem*, i64);
-SQLITE_PRIVATE void sqlite3VdbeMemSetDouble(Mem*, double);
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define sqlite3VdbeMemSetDouble sqlite3VdbeMemSetInt64
+#else
+SQLITE_PRIVATE   void sqlite3VdbeMemSetDouble(Mem*, double);
+#endif
 SQLITE_PRIVATE void sqlite3VdbeMemSetNull(Mem*);
 SQLITE_PRIVATE void sqlite3VdbeMemSetZeroBlob(Mem*,int);
 SQLITE_PRIVATE void sqlite3VdbeMemSetRowSet(Mem*);
@@ -18337,11 +19228,11 @@
 **
 ** NULL is returned if there is an allocation error.
 */
-SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte){
+SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte, u8 enc){
   Mem m;
   memset(&m, 0, sizeof(m));
   m.db = db;
-  sqlite3VdbeMemSetStr(&m, z, nByte, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  sqlite3VdbeMemSetStr(&m, z, nByte, enc, SQLITE_STATIC);
   sqlite3VdbeChangeEncoding(&m, SQLITE_UTF8);
   if( db->mallocFailed ){
     sqlite3VdbeMemRelease(&m);
@@ -18349,7 +19240,9 @@
   }
   assert( (m.flags & MEM_Term)!=0 || db->mallocFailed );
   assert( (m.flags & MEM_Str)!=0 || db->mallocFailed );
-  return (m.flags & MEM_Dyn)!=0 ? m.z : sqlite3DbStrDup(db, m.z);
+  assert( (m.flags & MEM_Dyn)!=0 || db->mallocFailed );
+  assert( m.z || db->mallocFailed );
+  return m.z;
 }
 
 /*
@@ -18490,6 +19383,7 @@
 }
 #endif
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Return true if the floating point value is Not a Number (NaN).
 **
@@ -18534,6 +19428,7 @@
   testcase( rc );
   return rc;
 }
+#endif /* SQLITE_OMIT_FLOATING_POINT */
 
 /*
 ** Compute a string length that is limited to what can be stored in
@@ -18711,6 +19606,7 @@
   z += incr;
   *realnum = 0;
   while( sqlite3Isdigit(*z) ){ z += incr; }
+#ifndef SQLITE_OMIT_FLOATING_POINT
   if( *z=='.' ){
     z += incr;
     if( !sqlite3Isdigit(*z) ) return 0;
@@ -18724,6 +19620,7 @@
     while( sqlite3Isdigit(*z) ){ z += incr; }
     *realnum = 1;
   }
+#endif
   return *z==0;
 }
 
@@ -18885,6 +19782,9 @@
   c = memcmp(zNum,"922337203685477580",18)*10;
   if( c==0 ){
     c = zNum[18] - '8';
+    testcase( c==(-1) );
+    testcase( c==0 );
+    testcase( c==(+1) );
   }
   return c;
 }
@@ -18921,6 +19821,9 @@
     v = v*10 + c - '0';
   }
   *pNum = neg ? -v : v;
+  testcase( i==18 );
+  testcase( i==19 );
+  testcase( i==20 );
   if( c!=0 || (i==0 && zStart==zNum) || i>19 ){
     /* zNum is empty or contains non-numeric text or is longer
     ** than 19 digits (thus guaranting that it is too large) */
@@ -18964,6 +19867,9 @@
     zNum++;   /* Skip leading zeros.  Ticket #2454 */
   }
   for(i=0; zNum[i]; i++){ assert( zNum[i]>='0' && zNum[i]<='9' ); }
+  testcase( i==18 );
+  testcase( i==19 );
+  testcase( i==20 );
   if( i<19 ){
     /* Guaranteed to fit if less than 19 digits */
     return 1;
@@ -19004,9 +19910,11 @@
   **             1234567890
   **     2^31 -> 2147483648
   */
+  testcase( i==10 );
   if( i>10 ){
     return 0;
   }
+  testcase( v-neg==2147483647 );
   if( v-neg>2147483647 ){
     return 0;
   }
@@ -19095,6 +20003,19 @@
 }
 
 /*
+** Bitmasks used by sqlite3GetVarint().  These precomputed constants
+** are defined here rather than simply putting the constant expressions
+** inline in order to work around bugs in the RVT compiler.
+**
+** SLOT_2_0     A mask for  (0x7f<<14) | 0x7f
+**
+** SLOT_4_2_0   A mask for  (0x7f<<28) | SLOT_2_0
+*/
+#define SLOT_2_0     0x001fc07f
+#define SLOT_4_2_0   0xf01fc07f
+
+
+/*
 ** Read a 64-bit variable-length integer from memory starting at p[0].
 ** Return the number of bytes read.  The value is stored in *v.
 */
@@ -19121,13 +20042,17 @@
     return 2;
   }
 
+  /* Verify that constants are precomputed correctly */
+  assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
+  assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
+
   p++;
   a = a<<14;
   a |= *p;
   /* a: p0<<14 | p2 (unmasked) */
   if (!(a&0x80))
   {
-    a &= (0x7f<<14)|(0x7f);
+    a &= SLOT_2_0;
     b &= 0x7f;
     b = b<<7;
     a |= b;
@@ -19136,14 +20061,14 @@
   }
 
   /* CSE1 from below */
-  a &= (0x7f<<14)|(0x7f);
+  a &= SLOT_2_0;
   p++;
   b = b<<14;
   b |= *p;
   /* b: p1<<14 | p3 (unmasked) */
   if (!(b&0x80))
   {
-    b &= (0x7f<<14)|(0x7f);
+    b &= SLOT_2_0;
     /* moved CSE1 up */
     /* a &= (0x7f<<14)|(0x7f); */
     a = a<<7;
@@ -19157,7 +20082,7 @@
   /* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
   /* moved CSE1 up */
   /* a &= (0x7f<<14)|(0x7f); */
-  b &= (0x7f<<14)|(0x7f);
+  b &= SLOT_2_0;
   s = a;
   /* s: p0<<14 | p2 (masked) */
 
@@ -19190,7 +20115,7 @@
   {
     /* we can skip this cause it was (effectively) done above in calc'ing s */
     /* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
-    a &= (0x7f<<14)|(0x7f);
+    a &= SLOT_2_0;
     a = a<<7;
     a |= b;
     s = s>>18;
@@ -19204,8 +20129,8 @@
   /* a: p2<<28 | p4<<14 | p6 (unmasked) */
   if (!(a&0x80))
   {
-    a &= (0x1f<<28)|(0x7f<<14)|(0x7f);
-    b &= (0x7f<<14)|(0x7f);
+    a &= SLOT_4_2_0;
+    b &= SLOT_2_0;
     b = b<<7;
     a |= b;
     s = s>>11;
@@ -19214,14 +20139,14 @@
   }
 
   /* CSE2 from below */
-  a &= (0x7f<<14)|(0x7f);
+  a &= SLOT_2_0;
   p++;
   b = b<<14;
   b |= *p;
   /* b: p3<<28 | p5<<14 | p7 (unmasked) */
   if (!(b&0x80))
   {
-    b &= (0x1f<<28)|(0x7f<<14)|(0x7f);
+    b &= SLOT_4_2_0;
     /* moved CSE2 up */
     /* a &= (0x7f<<14)|(0x7f); */
     a = a<<7;
@@ -19238,7 +20163,7 @@
 
   /* moved CSE2 up */
   /* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */
-  b &= (0x7f<<14)|(0x7f);
+  b &= SLOT_2_0;
   b = b<<8;
   a |= b;
 
@@ -19358,9 +20283,9 @@
   /* a: p0<<28 | p2<<14 | p4 (unmasked) */
   if (!(a&0x80))
   {
-    /* Walues  between 268435456 and 34359738367 */
-    a &= (0x1f<<28)|(0x7f<<14)|(0x7f);
-    b &= (0x1f<<28)|(0x7f<<14)|(0x7f);
+    /* Values  between 268435456 and 34359738367 */
+    a &= SLOT_4_2_0;
+    b &= SLOT_4_2_0;
     b = b<<7;
     *v = a | b;
     return 5;
@@ -19487,7 +20412,8 @@
   }
   magic = db->magic;
   if( magic!=SQLITE_MAGIC_OPEN ){
-    if( !sqlite3SafetyCheckSickOrOk(db) ){
+    if( sqlite3SafetyCheckSickOrOk(db) ){
+      testcase( sqlite3GlobalConfig.xLog!=0 );
       logBadConnection("unopened");
     }
     return 0;
@@ -19501,6 +20427,7 @@
   if( magic!=SQLITE_MAGIC_SICK &&
       magic!=SQLITE_MAGIC_OPEN &&
       magic!=SQLITE_MAGIC_BUSY ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
     logBadConnection("invalid");
     return 0;
   }else{
@@ -19832,39 +20759,39 @@
      /*  37 */ "VerifyCookie",
      /*  38 */ "OpenRead",
      /*  39 */ "OpenWrite",
-     /*  40 */ "OpenEphemeral",
-     /*  41 */ "OpenPseudo",
-     /*  42 */ "Close",
-     /*  43 */ "SeekLt",
-     /*  44 */ "SeekLe",
-     /*  45 */ "SeekGe",
-     /*  46 */ "SeekGt",
-     /*  47 */ "Seek",
-     /*  48 */ "NotFound",
-     /*  49 */ "Found",
-     /*  50 */ "IsUnique",
-     /*  51 */ "NotExists",
-     /*  52 */ "Sequence",
-     /*  53 */ "NewRowid",
-     /*  54 */ "Insert",
-     /*  55 */ "InsertInt",
-     /*  56 */ "Delete",
-     /*  57 */ "ResetCount",
-     /*  58 */ "RowKey",
-     /*  59 */ "RowData",
-     /*  60 */ "Rowid",
-     /*  61 */ "NullRow",
-     /*  62 */ "Last",
-     /*  63 */ "Sort",
-     /*  64 */ "Rewind",
-     /*  65 */ "Prev",
-     /*  66 */ "Next",
-     /*  67 */ "IdxInsert",
+     /*  40 */ "OpenAutoindex",
+     /*  41 */ "OpenEphemeral",
+     /*  42 */ "OpenPseudo",
+     /*  43 */ "Close",
+     /*  44 */ "SeekLt",
+     /*  45 */ "SeekLe",
+     /*  46 */ "SeekGe",
+     /*  47 */ "SeekGt",
+     /*  48 */ "Seek",
+     /*  49 */ "NotFound",
+     /*  50 */ "Found",
+     /*  51 */ "IsUnique",
+     /*  52 */ "NotExists",
+     /*  53 */ "Sequence",
+     /*  54 */ "NewRowid",
+     /*  55 */ "Insert",
+     /*  56 */ "InsertInt",
+     /*  57 */ "Delete",
+     /*  58 */ "ResetCount",
+     /*  59 */ "RowKey",
+     /*  60 */ "RowData",
+     /*  61 */ "Rowid",
+     /*  62 */ "NullRow",
+     /*  63 */ "Last",
+     /*  64 */ "Sort",
+     /*  65 */ "Rewind",
+     /*  66 */ "Prev",
+     /*  67 */ "Next",
      /*  68 */ "Or",
      /*  69 */ "And",
-     /*  70 */ "IdxDelete",
-     /*  71 */ "IdxRowid",
-     /*  72 */ "IdxLT",
+     /*  70 */ "IdxInsert",
+     /*  71 */ "IdxDelete",
+     /*  72 */ "IdxRowid",
      /*  73 */ "IsNull",
      /*  74 */ "NotNull",
      /*  75 */ "Ne",
@@ -19873,7 +20800,7 @@
      /*  78 */ "Le",
      /*  79 */ "Lt",
      /*  80 */ "Ge",
-     /*  81 */ "IdxGE",
+     /*  81 */ "IdxLT",
      /*  82 */ "BitAnd",
      /*  83 */ "BitOr",
      /*  84 */ "ShiftLeft",
@@ -19884,52 +20811,52 @@
      /*  89 */ "Divide",
      /*  90 */ "Remainder",
      /*  91 */ "Concat",
-     /*  92 */ "Destroy",
+     /*  92 */ "IdxGE",
      /*  93 */ "BitNot",
      /*  94 */ "String8",
-     /*  95 */ "Clear",
-     /*  96 */ "CreateIndex",
-     /*  97 */ "CreateTable",
-     /*  98 */ "ParseSchema",
-     /*  99 */ "LoadAnalysis",
-     /* 100 */ "DropTable",
-     /* 101 */ "DropIndex",
-     /* 102 */ "DropTrigger",
-     /* 103 */ "IntegrityCk",
-     /* 104 */ "RowSetAdd",
-     /* 105 */ "RowSetRead",
-     /* 106 */ "RowSetTest",
-     /* 107 */ "Program",
-     /* 108 */ "Param",
-     /* 109 */ "FkCounter",
-     /* 110 */ "FkIfZero",
-     /* 111 */ "MemMax",
-     /* 112 */ "IfPos",
-     /* 113 */ "IfNeg",
-     /* 114 */ "IfZero",
-     /* 115 */ "AggStep",
-     /* 116 */ "AggFinal",
-     /* 117 */ "Vacuum",
-     /* 118 */ "IncrVacuum",
-     /* 119 */ "Expire",
-     /* 120 */ "TableLock",
-     /* 121 */ "VBegin",
-     /* 122 */ "VCreate",
-     /* 123 */ "VDestroy",
-     /* 124 */ "VOpen",
-     /* 125 */ "VFilter",
-     /* 126 */ "VColumn",
-     /* 127 */ "VNext",
-     /* 128 */ "VRename",
-     /* 129 */ "VUpdate",
+     /*  95 */ "Destroy",
+     /*  96 */ "Clear",
+     /*  97 */ "CreateIndex",
+     /*  98 */ "CreateTable",
+     /*  99 */ "ParseSchema",
+     /* 100 */ "LoadAnalysis",
+     /* 101 */ "DropTable",
+     /* 102 */ "DropIndex",
+     /* 103 */ "DropTrigger",
+     /* 104 */ "IntegrityCk",
+     /* 105 */ "RowSetAdd",
+     /* 106 */ "RowSetRead",
+     /* 107 */ "RowSetTest",
+     /* 108 */ "Program",
+     /* 109 */ "Param",
+     /* 110 */ "FkCounter",
+     /* 111 */ "FkIfZero",
+     /* 112 */ "MemMax",
+     /* 113 */ "IfPos",
+     /* 114 */ "IfNeg",
+     /* 115 */ "IfZero",
+     /* 116 */ "AggStep",
+     /* 117 */ "AggFinal",
+     /* 118 */ "Checkpoint",
+     /* 119 */ "JournalMode",
+     /* 120 */ "Vacuum",
+     /* 121 */ "IncrVacuum",
+     /* 122 */ "Expire",
+     /* 123 */ "TableLock",
+     /* 124 */ "VBegin",
+     /* 125 */ "VCreate",
+     /* 126 */ "VDestroy",
+     /* 127 */ "VOpen",
+     /* 128 */ "VFilter",
+     /* 129 */ "VColumn",
      /* 130 */ "Real",
-     /* 131 */ "Pagecount",
-     /* 132 */ "Trace",
-     /* 133 */ "Noop",
-     /* 134 */ "Explain",
-     /* 135 */ "NotUsed_135",
-     /* 136 */ "NotUsed_136",
-     /* 137 */ "NotUsed_137",
+     /* 131 */ "VNext",
+     /* 132 */ "VRename",
+     /* 133 */ "VUpdate",
+     /* 134 */ "Pagecount",
+     /* 135 */ "Trace",
+     /* 136 */ "Noop",
+     /* 137 */ "Explain",
      /* 138 */ "NotUsed_138",
      /* 139 */ "NotUsed_139",
      /* 140 */ "NotUsed_140",
@@ -20034,23 +20961,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -20246,7 +21159,7 @@
   APIRET rc = NO_ERROR;
   os2File *pFile;
   if( id && (pFile = (os2File*)id) != 0 ){
-    OSTRACE2( "CLOSE %d\n", pFile->h );
+    OSTRACE(( "CLOSE %d\n", pFile->h ));
     rc = DosClose( pFile->h );
     pFile->locktype = NO_LOCK;
     if( pFile->pathToDel != NULL ){
@@ -20277,7 +21190,7 @@
   os2File *pFile = (os2File*)id;
   assert( id!=0 );
   SimulateIOError( return SQLITE_IOERR_READ );
-  OSTRACE3( "READ %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "READ %d lock=%d\n", pFile->h, pFile->locktype ));
   if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
     return SQLITE_IOERR;
   }
@@ -20310,7 +21223,7 @@
   assert( id!=0 );
   SimulateIOError( return SQLITE_IOERR_WRITE );
   SimulateDiskfullError( return SQLITE_FULL );
-  OSTRACE3( "WRITE %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "WRITE %d lock=%d\n", pFile->h, pFile->locktype ));
   if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
     return SQLITE_IOERR;
   }
@@ -20332,7 +21245,7 @@
 static int os2Truncate( sqlite3_file *id, i64 nByte ){
   APIRET rc = NO_ERROR;
   os2File *pFile = (os2File*)id;
-  OSTRACE3( "TRUNCATE %d %lld\n", pFile->h, nByte );
+  OSTRACE(( "TRUNCATE %d %lld\n", pFile->h, nByte ));
   SimulateIOError( return SQLITE_IOERR_TRUNCATE );
   rc = DosSetFileSize( pFile->h, nByte );
   return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR_TRUNCATE;
@@ -20352,7 +21265,7 @@
 */
 static int os2Sync( sqlite3_file *id, int flags ){
   os2File *pFile = (os2File*)id;
-  OSTRACE3( "SYNC %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "SYNC %d lock=%d\n", pFile->h, pFile->locktype ));
 #ifdef SQLITE_TEST
   if( flags & SQLITE_SYNC_FULL){
     sqlite3_fullsync_count++;
@@ -20402,7 +21315,7 @@
   UnlockArea.lOffset = 0L;
   UnlockArea.lRange = 0L;
   res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
-  OSTRACE3( "GETREADLOCK %d res=%d\n", pFile->h, res );
+  OSTRACE(( "GETREADLOCK %d res=%d\n", pFile->h, res ));
   return res;
 }
 
@@ -20420,7 +21333,7 @@
   UnlockArea.lOffset = SHARED_FIRST;
   UnlockArea.lRange = SHARED_SIZE;
   res = DosSetFileLocks( id->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
-  OSTRACE3( "UNLOCK-READLOCK file handle=%d res=%d?\n", id->h, res );
+  OSTRACE(( "UNLOCK-READLOCK file handle=%d res=%d?\n", id->h, res ));
   return res;
 }
 
@@ -20461,14 +21374,14 @@
   memset(&LockArea, 0, sizeof(LockArea));
   memset(&UnlockArea, 0, sizeof(UnlockArea));
   assert( pFile!=0 );
-  OSTRACE4( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype );
+  OSTRACE(( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype ));
 
   /* If there is already a lock of this type or more restrictive on the
   ** os2File, do nothing. Don't use the end_lock: exit path, as
   ** sqlite3_mutex_enter() hasn't been called yet.
   */
   if( pFile->locktype>=locktype ){
-    OSTRACE3( "LOCK %d %d ok (already held)\n", pFile->h, locktype );
+    OSTRACE(( "LOCK %d %d ok (already held)\n", pFile->h, locktype ));
     return SQLITE_OK;
   }
 
@@ -20495,7 +21408,7 @@
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, 100L, 0L );
     if( res == NO_ERROR ){
       gotPendingLock = 1;
-      OSTRACE3( "LOCK %d pending lock boolean set.  res=%d\n", pFile->h, res );
+      OSTRACE(( "LOCK %d pending lock boolean set.  res=%d\n", pFile->h, res ));
     }
   }
 
@@ -20507,7 +21420,7 @@
     if( res == NO_ERROR ){
       newLocktype = SHARED_LOCK;
     }
-    OSTRACE3( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res ));
   }
 
   /* Acquire a RESERVED lock
@@ -20522,7 +21435,7 @@
     if( res == NO_ERROR ){
       newLocktype = RESERVED_LOCK;
     }
-    OSTRACE3( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res ));
   }
 
   /* Acquire a PENDING lock
@@ -20530,7 +21443,8 @@
   if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
     newLocktype = PENDING_LOCK;
     gotPendingLock = 0;
-    OSTRACE2( "LOCK %d acquire pending lock. pending lock boolean unset.\n", pFile->h );
+    OSTRACE(( "LOCK %d acquire pending lock. pending lock boolean unset.\n",
+               pFile->h ));
   }
 
   /* Acquire an EXCLUSIVE lock
@@ -20538,7 +21452,7 @@
   if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
     assert( pFile->locktype>=SHARED_LOCK );
     res = unlockReadLock(pFile);
-    OSTRACE2( "unreadlock = %d\n", res );
+    OSTRACE(( "unreadlock = %d\n", res ));
     LockArea.lOffset = SHARED_FIRST;
     LockArea.lRange = SHARED_SIZE;
     UnlockArea.lOffset = 0L;
@@ -20547,10 +21461,10 @@
     if( res == NO_ERROR ){
       newLocktype = EXCLUSIVE_LOCK;
     }else{
-      OSTRACE2( "OS/2 error-code = %d\n", res );
+      OSTRACE(( "OS/2 error-code = %d\n", res ));
       getReadLock(pFile);
     }
-    OSTRACE3( "LOCK %d acquire exclusive lock.  res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire exclusive lock.  res=%d\n", pFile->h, res ));
   }
 
   /* If we are holding a PENDING lock that ought to be released, then
@@ -20563,7 +21477,7 @@
     UnlockArea.lOffset = PENDING_BYTE;
     UnlockArea.lRange = 1L;
     r = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r );
+    OSTRACE(( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r ));
   }
 
   /* Update the state of the lock has held in the file descriptor then
@@ -20572,12 +21486,12 @@
   if( res == NO_ERROR ){
     rc = SQLITE_OK;
   }else{
-    OSTRACE4( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
-              locktype, newLocktype );
+    OSTRACE(( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+              locktype, newLocktype ));
     rc = SQLITE_BUSY;
   }
   pFile->locktype = newLocktype;
-  OSTRACE3( "LOCK %d now %d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "LOCK %d now %d\n", pFile->h, pFile->locktype ));
   return rc;
 }
 
@@ -20592,7 +21506,7 @@
   assert( pFile!=0 );
   if( pFile->locktype>=RESERVED_LOCK ){
     r = 1;
-    OSTRACE3( "TEST WR-LOCK %d %d (local)\n", pFile->h, r );
+    OSTRACE(( "TEST WR-LOCK %d %d (local)\n", pFile->h, r ));
   }else{
     FILELOCK  LockArea,
               UnlockArea;
@@ -20604,7 +21518,7 @@
     UnlockArea.lOffset = 0L;
     UnlockArea.lRange = 0L;
     rc = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "TEST WR-LOCK %d lock reserved byte rc=%d\n", pFile->h, rc );
+    OSTRACE(( "TEST WR-LOCK %d lock reserved byte rc=%d\n", pFile->h, rc ));
     if( rc == NO_ERROR ){
       APIRET rcu = NO_ERROR; /* return code for unlocking */
       LockArea.lOffset = 0L;
@@ -20612,10 +21526,10 @@
       UnlockArea.lOffset = RESERVED_BYTE;
       UnlockArea.lRange = 1L;
       rcu = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-      OSTRACE3( "TEST WR-LOCK %d unlock reserved byte r=%d\n", pFile->h, rcu );
+      OSTRACE(( "TEST WR-LOCK %d unlock reserved byte r=%d\n", pFile->h, rcu ));
     }
     r = !(rc == NO_ERROR);
-    OSTRACE3( "TEST WR-LOCK %d %d (remote)\n", pFile->h, r );
+    OSTRACE(( "TEST WR-LOCK %d %d (remote)\n", pFile->h, r ));
   }
   *pOut = r;
   return SQLITE_OK;
@@ -20643,7 +21557,7 @@
   memset(&UnlockArea, 0, sizeof(UnlockArea));
   assert( pFile!=0 );
   assert( locktype<=SHARED_LOCK );
-  OSTRACE4( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype );
+  OSTRACE(( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype ));
   type = pFile->locktype;
   if( type>=EXCLUSIVE_LOCK ){
     LockArea.lOffset = 0L;
@@ -20651,11 +21565,11 @@
     UnlockArea.lOffset = SHARED_FIRST;
     UnlockArea.lRange = SHARED_SIZE;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res ));
     if( locktype==SHARED_LOCK && getReadLock(pFile) != NO_ERROR ){
       /* This should never happen.  We should always be able to
       ** reacquire the read lock */
-      OSTRACE3( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype );
+      OSTRACE(( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype ));
       rc = SQLITE_IOERR_UNLOCK;
     }
   }
@@ -20665,11 +21579,12 @@
     UnlockArea.lOffset = RESERVED_BYTE;
     UnlockArea.lRange = 1L;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d reserved res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d reserved res=%d\n", pFile->h, res ));
   }
   if( locktype==NO_LOCK && type>=SHARED_LOCK ){
     res = unlockReadLock(pFile);
-    OSTRACE5( "UNLOCK %d is %d want %d res=%d\n", pFile->h, type, locktype, res );
+    OSTRACE(( "UNLOCK %d is %d want %d res=%d\n",
+              pFile->h, type, locktype, res ));
   }
   if( type>=PENDING_LOCK ){
     LockArea.lOffset = 0L;
@@ -20677,10 +21592,10 @@
     UnlockArea.lOffset = PENDING_BYTE;
     UnlockArea.lRange = 1L;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d pending res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d pending res=%d\n", pFile->h, res ));
   }
   pFile->locktype = locktype;
-  OSTRACE3( "UNLOCK %d now %d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "UNLOCK %d now %d\n", pFile->h, pFile->locktype ));
   return rc;
 }
 
@@ -20691,7 +21606,8 @@
   switch( op ){
     case SQLITE_FCNTL_LOCKSTATE: {
       *(int*)pArg = ((os2File*)id)->locktype;
-      OSTRACE3( "FCNTL_LOCKSTATE %d lock=%d\n", ((os2File*)id)->h, ((os2File*)id)->locktype );
+      OSTRACE(( "FCNTL_LOCKSTATE %d lock=%d\n",
+                ((os2File*)id)->h, ((os2File*)id)->locktype ));
       return SQLITE_OK;
     }
   }
@@ -20878,7 +21794,7 @@
     zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
   }
   zBuf[j] = 0;
-  OSTRACE2( "TEMP FILENAME: %s\n", zBuf );
+  OSTRACE(( "TEMP FILENAME: %s\n", zBuf ));
   return SQLITE_OK;
 }
 
@@ -20941,30 +21857,30 @@
 
   memset( pFile, 0, sizeof(*pFile) );
 
-  OSTRACE2( "OPEN want %d\n", flags );
+  OSTRACE( "OPEN want %d\n", flags ));
 
   if( flags & SQLITE_OPEN_READWRITE ){
     ulOpenMode |= OPEN_ACCESS_READWRITE;
-    OSTRACE1( "OPEN read/write\n" );
+    OSTRACE(( "OPEN read/write\n" ));
   }else{
     ulOpenMode |= OPEN_ACCESS_READONLY;
-    OSTRACE1( "OPEN read only\n" );
+    OSTRACE(( "OPEN read only\n" ));
   }
 
   if( flags & SQLITE_OPEN_CREATE ){
     ulOpenFlags |= OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_CREATE_IF_NEW;
-    OSTRACE1( "OPEN open new/create\n" );
+    OSTRACE(( "OPEN open new/create\n" ));
   }else{
     ulOpenFlags |= OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_FAIL_IF_NEW;
-    OSTRACE1( "OPEN open existing\n" );
+    OSTRACE(( "OPEN open existing\n" ));
   }
 
   if( flags & SQLITE_OPEN_MAIN_DB ){
     ulOpenMode |= OPEN_SHARE_DENYNONE;
-    OSTRACE1( "OPEN share read/write\n" );
+    OSTRACE(( "OPEN share read/write\n" ));
   }else{
     ulOpenMode |= OPEN_SHARE_DENYWRITE;
-    OSTRACE1( "OPEN share read only\n" );
+    OSTRACE(( "OPEN share read only\n" ));
   }
 
   if( flags & SQLITE_OPEN_DELETEONCLOSE ){
@@ -20974,10 +21890,10 @@
 #endif
     os2FullPathname( pVfs, zName, CCHMAXPATH, pathUtf8 );
     pFile->pathToDel = convertUtf8PathToCp( pathUtf8 );
-    OSTRACE1( "OPEN hidden/delete on close file attributes\n" );
+    OSTRACE(( "OPEN hidden/delete on close file attributes\n" ));
   }else{
     pFile->pathToDel = NULL;
-    OSTRACE1( "OPEN normal file attribute\n" );
+    OSTRACE(( "OPEN normal file attribute\n" ));
   }
 
   /* always open in random access mode for possibly better speed */
@@ -20996,13 +21912,14 @@
                 (PEAOP2)NULL );
   free( zNameCp );
   if( rc != NO_ERROR ){
-    OSTRACE7( "OPEN Invalid handle rc=%d: zName=%s, ulAction=%#lx, ulAttr=%#lx, ulFlags=%#lx, ulMode=%#lx\n",
-              rc, zName, ulAction, ulFileAttribute, ulOpenFlags, ulOpenMode );
+    OSTRACE(( "OPEN Invalid handle rc=%d: zName=%s, ulAction=%#lx, ulAttr=%#lx, ulFlags=%#lx, ulMode=%#lx\n",
+              rc, zName, ulAction, ulFileAttribute, ulOpenFlags, ulOpenMode ));
     if( pFile->pathToDel )
       free( pFile->pathToDel );
     pFile->pathToDel = NULL;
     if( flags & SQLITE_OPEN_READWRITE ){
-      OSTRACE2( "OPEN %d Invalid handle\n", ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE) );
+      OSTRACE(( "OPEN %d Invalid handle\n",
+                ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE) ));
       return os2Open( pVfs, zName, id,
                       ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE),
                       pOutFlags );
@@ -21018,7 +21935,7 @@
   pFile->pMethod = &os2IoMethod;
   pFile->h = h;
   OpenCounter(+1);
-  OSTRACE3( "OPEN %d pOutFlags=%d\n", pFile->h, pOutFlags );
+  OSTRACE(( "OPEN %d pOutFlags=%d\n", pFile->h, pOutFlags ));
   return SQLITE_OK;
 }
 
@@ -21035,7 +21952,7 @@
   SimulateIOError( return SQLITE_IOERR_DELETE );
   rc = DosDelete( (PSZ)zFilenameCp );
   free( zFilenameCp );
-  OSTRACE2( "DELETE \"%s\"\n", zFilename );
+  OSTRACE(( "DELETE \"%s\"\n", zFilename ));
   return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR_DELETE;
 }
 
@@ -21056,17 +21973,17 @@
   rc = DosQueryPathInfo( (PSZ)zFilenameCp, FIL_STANDARD,
                          &fsts3ConfigInfo, sizeof(FILESTATUS3) );
   free( zFilenameCp );
-  OSTRACE4( "ACCESS fsts3ConfigInfo.attrFile=%d flags=%d rc=%d\n",
-            fsts3ConfigInfo.attrFile, flags, rc );
+  OSTRACE(( "ACCESS fsts3ConfigInfo.attrFile=%d flags=%d rc=%d\n",
+            fsts3ConfigInfo.attrFile, flags, rc ));
   switch( flags ){
     case SQLITE_ACCESS_READ:
     case SQLITE_ACCESS_EXISTS:
       rc = (rc == NO_ERROR);
-      OSTRACE3( "ACCESS %s access of read and exists  rc=%d\n", zFilename, rc );
+      OSTRACE(( "ACCESS %s access of read and exists  rc=%d\n", zFilename, rc));
       break;
     case SQLITE_ACCESS_READWRITE:
       rc = (rc == NO_ERROR) && ( (fsts3ConfigInfo.attrFile & FILE_READONLY) == 0 );
-      OSTRACE3( "ACCESS %s access of read/write  rc=%d\n", zFilename, rc );
+      OSTRACE(( "ACCESS %s access of read/write  rc=%d\n", zFilename, rc ));
       break;
     default:
       assert( !"Invalid flags argument" );
@@ -21276,7 +22193,7 @@
     os2Randomness,     /* xRandomness */
     os2Sleep,          /* xSleep */
     os2CurrentTime,    /* xCurrentTime */
-    os2GetLastError    /* xGetLastError */
+    os2GetLastError,   /* xGetLastError */
   };
   sqlite3_vfs_register(&os2Vfs, 1);
   initUconvObjects();
@@ -21410,6 +22327,7 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include <errno.h>
+#include <sys/mman.h>
 
 #if SQLITE_ENABLE_LOCKING_STYLE
 # include <sys/ioctl.h>
@@ -21419,10 +22337,18 @@
 # else
 #  include <sys/file.h>
 #  include <sys/param.h>
-#  include <sys/mount.h>
 # endif
 #endif /* SQLITE_ENABLE_LOCKING_STYLE */
 
+#if defined(__APPLE__) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
+# include <sys/mount.h>
+#endif
+
+/*
+** Allowed values of unixFile.fsFlags
+*/
+#define SQLITE_FSFLAGS_IS_MSDOS     0x1
+
 /*
 ** If we are to be thread-safe, include the pthreads header and define
 ** the SQLITE_UNIX_THREADS macro.
@@ -21456,6 +22382,11 @@
 */
 #define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
 
+/* Forward references */
+typedef struct unixShm unixShm;               /* Connection shared memory */
+typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
+typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
+typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
 
 /*
 ** Sometimes, after a file handle is closed by SQLite, the file descriptor
@@ -21463,7 +22394,6 @@
 ** structure are used to store the file descriptor while waiting for an
 ** opportunity to either close or reuse it.
 */
-typedef struct UnixUnusedFd UnixUnusedFd;
 struct UnixUnusedFd {
   int fd;                   /* File descriptor to close */
   int flags;                /* Flags this file descriptor was opened with */
@@ -21477,24 +22407,25 @@
 typedef struct unixFile unixFile;
 struct unixFile {
   sqlite3_io_methods const *pMethod;  /* Always the first entry */
-  struct unixOpenCnt *pOpen;       /* Info about all open fd's on this inode */
-  struct unixLockInfo *pLock;      /* Info about locks on this inode */
-  int h;                           /* The file descriptor */
-  int dirfd;                       /* File descriptor for the directory */
-  unsigned char locktype;          /* The type of lock held on this fd */
-  int lastErrno;                   /* The unix errno from the last I/O error */
-  void *lockingContext;            /* Locking style specific state */
-  UnixUnusedFd *pUnused;           /* Pre-allocated UnixUnusedFd */
-  int fileFlags;                   /* Miscellanous flags */
+  unixInodeInfo *pInode;              /* Info about locks on this inode */
+  int h;                              /* The file descriptor */
+  int dirfd;                          /* File descriptor for the directory */
+  unsigned char eFileLock;            /* The type of lock held on this fd */
+  int lastErrno;                      /* The unix errno from last I/O error */
+  void *lockingContext;               /* Locking style specific state */
+  UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
+  int fileFlags;                      /* Miscellanous flags */
+  const char *zPath;                  /* Name of the file */
+  unixShm *pShm;                      /* Shared memory segment information */
 #if SQLITE_ENABLE_LOCKING_STYLE
-  int openFlags;                   /* The flags specified at open() */
+  int openFlags;                      /* The flags specified at open() */
 #endif
-#if SQLITE_THREADSAFE && defined(__linux__)
-  pthread_t tid;                   /* The thread that "owns" this unixFile */
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
+  unsigned fsFlags;                   /* cached details from statfs() */
 #endif
 #if OS_VXWORKS
-  int isDelete;                    /* Delete on close if true */
-  struct vxworksFileId *pId;       /* Unique file ID */
+  int isDelete;                       /* Delete on close if true */
+  struct vxworksFileId *pId;          /* Unique file ID */
 #endif
 #ifndef NDEBUG
   /* The next group of variables are used to track whether or not the
@@ -21559,23 +22490,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -21785,7 +22702,7 @@
 
 /*
 ** Helper functions to obtain and relinquish the global mutex. The
-** global mutex is used to protect the unixOpenCnt, unixLockInfo and
+** global mutex is used to protect the unixInodeInfo and
 ** vxworksFileId objects used by this file, all of which may be 
 ** shared by multiple threads.
 **
@@ -21816,8 +22733,8 @@
 ** binaries. This returns the string represetation of the supplied
 ** integer lock-type.
 */
-static const char *locktypeName(int locktype){
-  switch( locktype ){
+static const char *azFileLock(int eFileLock){
+  switch( eFileLock ){
     case NO_LOCK: return "NONE";
     case SHARED_LOCK: return "SHARED";
     case RESERVED_LOCK: return "RESERVED";
@@ -22154,13 +23071,12 @@
 **
 ** If you close a file descriptor that points to a file that has locks,
 ** all locks on that file that are owned by the current process are
-** released.  To work around this problem, each unixFile structure contains
-** a pointer to an unixOpenCnt structure.  There is one unixOpenCnt structure
-** per open inode, which means that multiple unixFile can point to a single
-** unixOpenCnt.  When an attempt is made to close an unixFile, if there are
+** released.  To work around this problem, each unixInodeInfo object
+** maintains a count of the number of pending locks on tha inode.
+** When an attempt is made to close an unixFile, if there are
 ** other unixFile open on the same inode that are holding locks, the call
 ** to close() the file descriptor is deferred until all of the locks clear.
-** The unixOpenCnt structure keeps a list of file descriptors that need to
+** The unixInodeInfo structure keeps a list of file descriptors that need to
 ** be closed and that list is walked (and cleared) when the last lock
 ** clears.
 **
@@ -22175,46 +23091,19 @@
 ** in thread B.  But there is no way to know at compile-time which
 ** threading library is being used.  So there is no way to know at
 ** compile-time whether or not thread A can override locks on thread B.
-** We have to do a run-time check to discover the behavior of the
+** One has to do a run-time check to discover the behavior of the
 ** current process.
 **
-** On systems where thread A is unable to modify locks created by
-** thread B, we have to keep track of which thread created each
-** lock.  Hence there is an extra field in the key to the unixLockInfo
-** structure to record this information.  And on those systems it
-** is illegal to begin a transaction in one thread and finish it
-** in another.  For this latter restriction, there is no work-around.
-** It is a limitation of LinuxThreads.
+** SQLite used to support LinuxThreads.  But support for LinuxThreads
+** was dropped beginning with version 3.7.0.  SQLite will still work with
+** LinuxThreads provided that (1) there is no more than one connection 
+** per database file in the same process and (2) database connections
+** do not move across threads.
 */
 
 /*
-** Set or check the unixFile.tid field.  This field is set when an unixFile
-** is first opened.  All subsequent uses of the unixFile verify that the
-** same thread is operating on the unixFile.  Some operating systems do
-** not allow locks to be overridden by other threads and that restriction
-** means that sqlite3* database handles cannot be moved from one thread
-** to another while locks are held.
-**
-** Version 3.3.1 (2006-01-15):  unixFile can be moved from one thread to
-** another as long as we are running on a system that supports threads
-** overriding each others locks (which is now the most common behavior)
-** or if no locks are held.  But the unixFile.pLock field needs to be
-** recomputed because its key includes the thread-id.  See the 
-** transferOwnership() function below for additional information
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-# define SET_THREADID(X)   (X)->tid = pthread_self()
-# define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \
-                            !pthread_equal((X)->tid, pthread_self()))
-#else
-# define SET_THREADID(X)
-# define CHECK_THREADID(X) 0
-#endif
-
-/*
 ** An instance of the following structure serves as the key used
-** to locate a particular unixOpenCnt structure given its inode.  This
-** is the same as the unixLockKey except that the thread ID is omitted.
+** to locate a particular unixInodeInfo object.
 */
 struct unixFileId {
   dev_t dev;                  /* Device number */
@@ -22226,23 +23115,6 @@
 };
 
 /*
-** An instance of the following structure serves as the key used
-** to locate a particular unixLockInfo structure given its inode.
-**
-** If threads cannot override each others locks (LinuxThreads), then we
-** set the unixLockKey.tid field to the thread ID.  If threads can override
-** each others locks (Posix and NPTL) then tid is always set to zero.
-** tid is omitted if we compile without threading support or on an OS
-** other than linux.
-*/
-struct unixLockKey {
-  struct unixFileId fid;  /* Unique identifier for the file */
-#if SQLITE_THREADSAFE && defined(__linux__)
-  pthread_t tid;  /* Thread ID of lock owner. Zero if not using LinuxThreads */
-#endif
-};
-
-/*
 ** An instance of the following structure is allocated for each open
 ** inode.  Or, on LinuxThreads, there is one of these structures for
 ** each inode opened by each thread.
@@ -22251,227 +23123,109 @@
 ** structure contains a pointer to an instance of this object and this
 ** object keeps a count of the number of unixFile pointing to it.
 */
-struct unixLockInfo {
-  struct unixLockKey lockKey;     /* The lookup key */
-  int cnt;                        /* Number of SHARED locks held */
-  int locktype;                   /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+struct unixInodeInfo {
+  struct unixFileId fileId;       /* The lookup key */
+  int nShared;                    /* Number of SHARED locks held */
+  int eFileLock;                  /* One of SHARED_LOCK, RESERVED_LOCK etc. */
   int nRef;                       /* Number of pointers to this structure */
-  struct unixLockInfo *pNext;     /* List of all unixLockInfo objects */
-  struct unixLockInfo *pPrev;     /*    .... doubly linked */
-};
-
-/*
-** An instance of the following structure is allocated for each open
-** inode.  This structure keeps track of the number of locks on that
-** inode.  If a close is attempted against an inode that is holding
-** locks, the close is deferred until all locks clear by adding the
-** file descriptor to be closed to the pending list.
-**
-** TODO:  Consider changing this so that there is only a single file
-** descriptor for each open file, even when it is opened multiple times.
-** The close() system call would only occur when the last database
-** using the file closes.
-*/
-struct unixOpenCnt {
-  struct unixFileId fileId;   /* The lookup key */
-  int nRef;                   /* Number of pointers to this structure */
-  int nLock;                  /* Number of outstanding locks */
-  UnixUnusedFd *pUnused;      /* Unused file descriptors to close */
+  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
+  int nLock;                      /* Number of outstanding file locks */
+  UnixUnusedFd *pUnused;          /* Unused file descriptors to close */
+  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
+  unixInodeInfo *pPrev;           /*    .... doubly linked */
+#if defined(SQLITE_ENABLE_LOCKING_STYLE)
+  unsigned long long sharedByte;  /* for AFP simulated shared lock */
+#endif
 #if OS_VXWORKS
-  sem_t *pSem;                     /* Named POSIX semaphore */
-  char aSemName[MAX_PATHNAME+2];   /* Name of that semaphore */
+  sem_t *pSem;                    /* Named POSIX semaphore */
+  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
 #endif
-  struct unixOpenCnt *pNext, *pPrev;   /* List of all unixOpenCnt objects */
 };
 
 /*
-** Lists of all unixLockInfo and unixOpenCnt objects.  These used to be hash
-** tables.  But the number of objects is rarely more than a dozen and
-** never exceeds a few thousand.  And lookup is not on a critical
-** path so a simple linked list will suffice.
+** A lists of all unixInodeInfo objects.
 */
-static struct unixLockInfo *lockList = 0;
-static struct unixOpenCnt *openList = 0;
+static unixInodeInfo *inodeList = 0;
 
 /*
-** This variable remembers whether or not threads can override each others
-** locks.
+** Close all file descriptors accumuated in the unixInodeInfo->pUnused list.
+** If all such file descriptors are closed without error, the list is
+** cleared and SQLITE_OK returned.
 **
-**    0:  No.  Threads cannot override each others locks.  (LinuxThreads)
-**    1:  Yes.  Threads can override each others locks.  (Posix & NLPT)
-**   -1:  We don't know yet.
-**
-** On some systems, we know at compile-time if threads can override each
-** others locks.  On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro
-** will be set appropriately.  On other systems, we have to check at
-** runtime.  On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is
-** undefined.
-**
-** This variable normally has file scope only.  But during testing, we make
-** it a global so that the test code can change its value in order to verify
-** that the right stuff happens in either case.
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-#  ifndef SQLITE_THREAD_OVERRIDE_LOCK
-#    define SQLITE_THREAD_OVERRIDE_LOCK -1
-#  endif
-#  ifdef SQLITE_TEST
-int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
-#  else
-static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
-#  endif
-#endif
-
-/*
-** This structure holds information passed into individual test
-** threads by the testThreadLockingBehavior() routine.
-*/
-struct threadTestData {
-  int fd;                /* File to be locked */
-  struct flock lock;     /* The locking operation */
-  int result;            /* Result of the locking operation */
-};
-
-#if SQLITE_THREADSAFE && defined(__linux__)
-/*
-** This function is used as the main routine for a thread launched by
-** testThreadLockingBehavior(). It tests whether the shared-lock obtained
-** by the main thread in testThreadLockingBehavior() conflicts with a
-** hypothetical write-lock obtained by this thread on the same file.
-**
-** The write-lock is not actually acquired, as this is not possible if 
-** the file is open in read-only mode (see ticket #3472).
+** Otherwise, if an error occurs, then successfully closed file descriptor
+** entries are removed from the list, and SQLITE_IOERR_CLOSE returned. 
+** not deleted and SQLITE_IOERR_CLOSE returned.
 */ 
-static void *threadLockingTest(void *pArg){
-  struct threadTestData *pData = (struct threadTestData*)pArg;
-  pData->result = fcntl(pData->fd, F_GETLK, &pData->lock);
-  return pArg;
-}
-#endif /* SQLITE_THREADSAFE && defined(__linux__) */
-
-
-#if SQLITE_THREADSAFE && defined(__linux__)
-/*
-** This procedure attempts to determine whether or not threads
-** can override each others locks then sets the 
-** threadsOverrideEachOthersLocks variable appropriately.
-*/
-static void testThreadLockingBehavior(int fd_orig){
-  int fd;
-  int rc;
-  struct threadTestData d;
-  struct flock l;
-  pthread_t t;
-
-  fd = dup(fd_orig);
-  if( fd<0 ) return;
-  memset(&l, 0, sizeof(l));
-  l.l_type = F_RDLCK;
-  l.l_len = 1;
-  l.l_start = 0;
-  l.l_whence = SEEK_SET;
-  rc = fcntl(fd_orig, F_SETLK, &l);
-  if( rc!=0 ) return;
-  memset(&d, 0, sizeof(d));
-  d.fd = fd;
-  d.lock = l;
-  d.lock.l_type = F_WRLCK;
-  if( pthread_create(&t, 0, threadLockingTest, &d)==0 ){
-    pthread_join(t, 0);
+static int closePendingFds(unixFile *pFile){
+  int rc = SQLITE_OK;
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *pError = 0;
+  UnixUnusedFd *p;
+  UnixUnusedFd *pNext;
+  for(p=pInode->pUnused; p; p=pNext){
+    pNext = p->pNext;
+    if( close(p->fd) ){
+      pFile->lastErrno = errno;
+      rc = SQLITE_IOERR_CLOSE;
+      p->pNext = pError;
+      pError = p;
+    }else{
+      sqlite3_free(p);
+    }
   }
-  close(fd);
-  if( d.result!=0 ) return;
-  threadsOverrideEachOthersLocks = (d.lock.l_type==F_UNLCK);
+  pInode->pUnused = pError;
+  return rc;
 }
-#endif /* SQLITE_THREADSAFE && defined(__linux__) */
 
 /*
-** Release a unixLockInfo structure previously allocated by findLockInfo().
+** Release a unixInodeInfo structure previously allocated by findInodeInfo().
 **
 ** The mutex entered using the unixEnterMutex() function must be held
 ** when this function is called.
 */
-static void releaseLockInfo(struct unixLockInfo *pLock){
+static void releaseInodeInfo(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
   assert( unixMutexHeld() );
-  if( pLock ){
-    pLock->nRef--;
-    if( pLock->nRef==0 ){
-      if( pLock->pPrev ){
-        assert( pLock->pPrev->pNext==pLock );
-        pLock->pPrev->pNext = pLock->pNext;
+  if( pInode ){
+    pInode->nRef--;
+    if( pInode->nRef==0 ){
+      assert( pInode->pShmNode==0 );
+      closePendingFds(pFile);
+      if( pInode->pPrev ){
+        assert( pInode->pPrev->pNext==pInode );
+        pInode->pPrev->pNext = pInode->pNext;
       }else{
-        assert( lockList==pLock );
-        lockList = pLock->pNext;
+        assert( inodeList==pInode );
+        inodeList = pInode->pNext;
       }
-      if( pLock->pNext ){
-        assert( pLock->pNext->pPrev==pLock );
-        pLock->pNext->pPrev = pLock->pPrev;
+      if( pInode->pNext ){
+        assert( pInode->pNext->pPrev==pInode );
+        pInode->pNext->pPrev = pInode->pPrev;
       }
-      sqlite3_free(pLock);
+      sqlite3_free(pInode);
     }
   }
 }
 
 /*
-** Release a unixOpenCnt structure previously allocated by findLockInfo().
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-*/
-static void releaseOpenCnt(struct unixOpenCnt *pOpen){
-  assert( unixMutexHeld() );
-  if( pOpen ){
-    pOpen->nRef--;
-    if( pOpen->nRef==0 ){
-      if( pOpen->pPrev ){
-        assert( pOpen->pPrev->pNext==pOpen );
-        pOpen->pPrev->pNext = pOpen->pNext;
-      }else{
-        assert( openList==pOpen );
-        openList = pOpen->pNext;
-      }
-      if( pOpen->pNext ){
-        assert( pOpen->pNext->pPrev==pOpen );
-        pOpen->pNext->pPrev = pOpen->pPrev;
-      }
-#if SQLITE_THREADSAFE && defined(__linux__)
-      assert( !pOpen->pUnused || threadsOverrideEachOthersLocks==0 );
-#endif
-
-      /* If pOpen->pUnused is not null, then memory and file-descriptors
-      ** are leaked.
-      **
-      ** This will only happen if, under Linuxthreads, the user has opened
-      ** a transaction in one thread, then attempts to close the database
-      ** handle from another thread (without first unlocking the db file).
-      ** This is a misuse.  */
-      sqlite3_free(pOpen);
-    }
-  }
-}
-
-/*
-** Given a file descriptor, locate unixLockInfo and unixOpenCnt structures that
-** describes that file descriptor.  Create new ones if necessary.  The
-** return values might be uninitialized if an error occurs.
+** Given a file descriptor, locate the unixInodeInfo object that
+** describes that file descriptor.  Create a new one if necessary.  The
+** return value might be uninitialized if an error occurs.
 **
 ** The mutex entered using the unixEnterMutex() function must be held
 ** when this function is called.
 **
 ** Return an appropriate error code.
 */
-static int findLockInfo(
+static int findInodeInfo(
   unixFile *pFile,               /* Unix file with file desc used in the key */
-  struct unixLockInfo **ppLock,  /* Return the unixLockInfo structure here */
-  struct unixOpenCnt **ppOpen    /* Return the unixOpenCnt structure here */
+  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
 ){
   int rc;                        /* System call return code */
   int fd;                        /* The file descriptor for pFile */
-  struct unixLockKey lockKey;    /* Lookup key for the unixLockInfo structure */
-  struct unixFileId fileId;      /* Lookup key for the unixOpenCnt struct */
+  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
   struct stat statbuf;           /* Low-level file information */
-  struct unixLockInfo *pLock = 0;/* Candidate unixLockInfo object */
-  struct unixOpenCnt *pOpen;     /* Candidate unixOpenCnt object */
+  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
 
   assert( unixMutexHeld() );
 
@@ -22499,9 +23253,10 @@
   ** is a race condition such that another thread has already populated
   ** the first page of the database, no damage is done.
   */
-  if( statbuf.st_size==0 ){
+  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
     rc = write(fd, "S", 1);
     if( rc!=1 ){
+      pFile->lastErrno = errno;
       return SQLITE_IOERR;
     }
     rc = fstat(fd, &statbuf);
@@ -22512,120 +23267,36 @@
   }
 #endif
 
-  memset(&lockKey, 0, sizeof(lockKey));
-  lockKey.fid.dev = statbuf.st_dev;
+  memset(&fileId, 0, sizeof(fileId));
+  fileId.dev = statbuf.st_dev;
 #if OS_VXWORKS
-  lockKey.fid.pId = pFile->pId;
+  fileId.pId = pFile->pId;
 #else
-  lockKey.fid.ino = statbuf.st_ino;
+  fileId.ino = statbuf.st_ino;
 #endif
-#if SQLITE_THREADSAFE && defined(__linux__)
-  if( threadsOverrideEachOthersLocks<0 ){
-    testThreadLockingBehavior(fd);
+  pInode = inodeList;
+  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
+    pInode = pInode->pNext;
   }
-  lockKey.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
-#endif
-  fileId = lockKey.fid;
-  if( ppLock!=0 ){
-    pLock = lockList;
-    while( pLock && memcmp(&lockKey, &pLock->lockKey, sizeof(lockKey)) ){
-      pLock = pLock->pNext;
+  if( pInode==0 ){
+    pInode = sqlite3_malloc( sizeof(*pInode) );
+    if( pInode==0 ){
+      return SQLITE_NOMEM;
     }
-    if( pLock==0 ){
-      pLock = sqlite3_malloc( sizeof(*pLock) );
-      if( pLock==0 ){
-        rc = SQLITE_NOMEM;
-        goto exit_findlockinfo;
-      }
-      memcpy(&pLock->lockKey,&lockKey,sizeof(lockKey));
-      pLock->nRef = 1;
-      pLock->cnt = 0;
-      pLock->locktype = 0;
-      pLock->pNext = lockList;
-      pLock->pPrev = 0;
-      if( lockList ) lockList->pPrev = pLock;
-      lockList = pLock;
-    }else{
-      pLock->nRef++;
-    }
-    *ppLock = pLock;
+    memset(pInode, 0, sizeof(*pInode));
+    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
+    pInode->nRef = 1;
+    pInode->pNext = inodeList;
+    pInode->pPrev = 0;
+    if( inodeList ) inodeList->pPrev = pInode;
+    inodeList = pInode;
+  }else{
+    pInode->nRef++;
   }
-  if( ppOpen!=0 ){
-    pOpen = openList;
-    while( pOpen && memcmp(&fileId, &pOpen->fileId, sizeof(fileId)) ){
-      pOpen = pOpen->pNext;
-    }
-    if( pOpen==0 ){
-      pOpen = sqlite3_malloc( sizeof(*pOpen) );
-      if( pOpen==0 ){
-        releaseLockInfo(pLock);
-        rc = SQLITE_NOMEM;
-        goto exit_findlockinfo;
-      }
-      memset(pOpen, 0, sizeof(*pOpen));
-      pOpen->fileId = fileId;
-      pOpen->nRef = 1;
-      pOpen->pNext = openList;
-      if( openList ) openList->pPrev = pOpen;
-      openList = pOpen;
-    }else{
-      pOpen->nRef++;
-    }
-    *ppOpen = pOpen;
-  }
-
-exit_findlockinfo:
-  return rc;
+  *ppInode = pInode;
+  return SQLITE_OK;
 }
 
-/*
-** If we are currently in a different thread than the thread that the
-** unixFile argument belongs to, then transfer ownership of the unixFile
-** over to the current thread.
-**
-** A unixFile is only owned by a thread on systems that use LinuxThreads.
-**
-** Ownership transfer is only allowed if the unixFile is currently unlocked.
-** If the unixFile is locked and an ownership is wrong, then return
-** SQLITE_MISUSE.  SQLITE_OK is returned if everything works.
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-static int transferOwnership(unixFile *pFile){
-  int rc;
-  pthread_t hSelf;
-  if( threadsOverrideEachOthersLocks ){
-    /* Ownership transfers not needed on this system */
-    return SQLITE_OK;
-  }
-  hSelf = pthread_self();
-  if( pthread_equal(pFile->tid, hSelf) ){
-    /* We are still in the same thread */
-    OSTRACE1("No-transfer, same thread\n");
-    return SQLITE_OK;
-  }
-  if( pFile->locktype!=NO_LOCK ){
-    /* We cannot change ownership while we are holding a lock! */
-    return SQLITE_MISUSE_BKPT;
-  }
-  OSTRACE4("Transfer ownership of %d from %d to %d\n",
-            pFile->h, pFile->tid, hSelf);
-  pFile->tid = hSelf;
-  if (pFile->pLock != NULL) {
-    releaseLockInfo(pFile->pLock);
-    rc = findLockInfo(pFile, &pFile->pLock, 0);
-    OSTRACE5("LOCK    %d is now %s(%s,%d)\n", pFile->h,
-           locktypeName(pFile->locktype),
-           locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);
-    return rc;
-  } else {
-    return SQLITE_OK;
-  }
-}
-#else  /* if not SQLITE_THREADSAFE */
-  /* On single-threaded builds, ownership transfer is a no-op */
-# define transferOwnership(X) SQLITE_OK
-#endif /* SQLITE_THREADSAFE */
-
 
 /*
 ** This routine checks if there is a RESERVED lock held on the specified
@@ -22641,10 +23312,10 @@
   SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
 
   assert( pFile );
-  unixEnterMutex(); /* Because pFile->pLock is shared across threads */
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->pLock->locktype>SHARED_LOCK ){
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
 
@@ -22668,70 +23339,14 @@
 #endif
   
   unixLeaveMutex();
-  OSTRACE4("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
 
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Perform a file locking operation on a range of bytes in a file.
-** The "op" parameter should be one of F_RDLCK, F_WRLCK, or F_UNLCK.
-** Return 0 on success or -1 for failure.  On failure, write the error
-** code into *pErrcode.
-**
-** If the SQLITE_WHOLE_FILE_LOCKING bit is clear, then only lock
-** the range of bytes on the locking page between SHARED_FIRST and
-** SHARED_SIZE.  If SQLITE_WHOLE_FILE_LOCKING is set, then lock all
-** bytes from 0 up to but not including PENDING_BYTE, and all bytes
-** that follow SHARED_FIRST.
-**
-** In other words, of SQLITE_WHOLE_FILE_LOCKING if false (the historical
-** default case) then only lock a small range of bytes from SHARED_FIRST
-** through SHARED_FIRST+SHARED_SIZE-1.  But if SQLITE_WHOLE_FILE_LOCKING is
-** true then lock every byte in the file except for PENDING_BYTE and
-** RESERVED_BYTE.
-**
-** SQLITE_WHOLE_FILE_LOCKING=true overlaps SQLITE_WHOLE_FILE_LOCKING=false
-** and so the locking schemes are compatible.  One type of lock will
-** effectively exclude the other type.  The reason for using the
-** SQLITE_WHOLE_FILE_LOCKING=true is that by indicating the full range
-** of bytes to be read or written, we give hints to NFS to help it
-** maintain cache coherency.  On the other hand, whole file locking
-** is slower, so we don't want to use it except for NFS.
-*/
-static int rangeLock(unixFile *pFile, int op, int *pErrcode){
-  struct flock lock;
-  int rc;
-  lock.l_type = op;
-  lock.l_start = SHARED_FIRST;
-  lock.l_whence = SEEK_SET;
-  if( (pFile->fileFlags & SQLITE_WHOLE_FILE_LOCKING)==0 ){
-    lock.l_len = SHARED_SIZE;
-    rc = fcntl(pFile->h, F_SETLK, &lock);
-    *pErrcode = errno;
-  }else{
-    lock.l_len = 0;
-    rc = fcntl(pFile->h, F_SETLK, &lock);
-    *pErrcode = errno;
-    if( NEVER(op==F_UNLCK) || rc!=(-1) ){
-      lock.l_start = 0;
-      lock.l_len = PENDING_BYTE;
-      rc = fcntl(pFile->h, F_SETLK, &lock);
-      if( ALWAYS(op!=F_UNLCK) && rc==(-1) ){
-        *pErrcode = errno;
-        lock.l_type = F_UNLCK;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = 0;
-        fcntl(pFile->h, F_SETLK, &lock);
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -22754,7 +23369,7 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int unixLock(sqlite3_file *id, int locktype){
+static int unixLock(sqlite3_file *id, int eFileLock){
   /* The following describes the implementation of the various locks and
   ** lock transitions in terms of the POSIX advisory shared and exclusive
   ** lock primitives (called read-locks and write-locks below, to avoid
@@ -22795,23 +23410,23 @@
   */
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
-  struct unixLockInfo *pLock = pFile->pLock;
+  unixInodeInfo *pInode = pFile->pInode;
   struct flock lock;
   int s = 0;
-  int tErrno;
+  int tErrno = 0;
 
   assert( pFile );
-  OSTRACE7("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
-      locktypeName(locktype), locktypeName(pFile->locktype),
-      locktypeName(pLock->locktype), pLock->cnt , getpid());
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
+      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+      azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
 
   /* If there is already a lock of this type or more restrictive on the
   ** unixFile, do nothing. Don't use the end_lock: exit path, as
   ** unixEnterMutex() hasn't been called yet.
   */
-  if( pFile->locktype>=locktype ){
-    OSTRACE3("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
-            locktypeName(locktype));
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
+            azFileLock(eFileLock)));
     return SQLITE_OK;
   }
 
@@ -22820,28 +23435,20 @@
   **  (2) SQLite never explicitly requests a pendig lock.
   **  (3) A shared lock is always held when a reserve lock is requested.
   */
-  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
-  assert( locktype!=PENDING_LOCK );
-  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
 
-  /* This mutex is needed because pFile->pLock is shared across threads
+  /* This mutex is needed because pFile->pInode is shared across threads
   */
   unixEnterMutex();
-
-  /* Make sure the current thread owns the pFile.
-  */
-  rc = transferOwnership(pFile);
-  if( rc!=SQLITE_OK ){
-    unixLeaveMutex();
-    return rc;
-  }
-  pLock = pFile->pLock;
+  pInode = pFile->pInode;
 
   /* If some thread using this PID has a lock via a different unixFile*
   ** handle that precludes the requested lock, return BUSY.
   */
-  if( (pFile->locktype!=pLock->locktype && 
-          (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
   ){
     rc = SQLITE_BUSY;
     goto end_lock;
@@ -22851,14 +23458,14 @@
   ** has a SHARED or RESERVED lock, then increment reference counts and
   ** return SQLITE_OK.
   */
-  if( locktype==SHARED_LOCK && 
-      (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
-    assert( locktype==SHARED_LOCK );
-    assert( pFile->locktype==0 );
-    assert( pLock->cnt>0 );
-    pFile->locktype = SHARED_LOCK;
-    pLock->cnt++;
-    pFile->pOpen->nLock++;
+  if( eFileLock==SHARED_LOCK && 
+      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
     goto end_lock;
   }
 
@@ -22869,10 +23476,10 @@
   */
   lock.l_len = 1L;
   lock.l_whence = SEEK_SET;
-  if( locktype==SHARED_LOCK 
-      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
   ){
-    lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK);
+    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
     lock.l_start = PENDING_BYTE;
     s = fcntl(pFile->h, F_SETLK, &lock);
     if( s==(-1) ){
@@ -22889,13 +23496,16 @@
   /* If control gets to this point, then actually go ahead and make
   ** operating system calls for the specified lock.
   */
-  if( locktype==SHARED_LOCK ){
-    assert( pLock->cnt==0 );
-    assert( pLock->locktype==0 );
+  if( eFileLock==SHARED_LOCK ){
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
 
     /* Now get the read-lock */
-    s = rangeLock(pFile, F_RDLCK, &tErrno);
-
+    lock.l_start = SHARED_FIRST;
+    lock.l_len = SHARED_SIZE;
+    if( (s = fcntl(pFile->h, F_SETLK, &lock))==(-1) ){
+      tErrno = errno;
+    }
     /* Drop the temporary PENDING lock */
     lock.l_start = PENDING_BYTE;
     lock.l_len = 1L;
@@ -22917,11 +23527,11 @@
         pFile->lastErrno = tErrno;
       }
     }else{
-      pFile->locktype = SHARED_LOCK;
-      pFile->pOpen->nLock++;
-      pLock->cnt = 1;
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
     }
-  }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
     /* We are trying for an exclusive lock but another thread in this
     ** same process is still holding a shared lock. */
     rc = SQLITE_BUSY;
@@ -22930,21 +23540,22 @@
     ** assumed that there is a SHARED or greater lock on the file
     ** already.
     */
-    assert( 0!=pFile->locktype );
+    assert( 0!=pFile->eFileLock );
     lock.l_type = F_WRLCK;
-    switch( locktype ){
+    switch( eFileLock ){
       case RESERVED_LOCK:
         lock.l_start = RESERVED_BYTE;
-        s = fcntl(pFile->h, F_SETLK, &lock);
-        tErrno = errno;
         break;
       case EXCLUSIVE_LOCK:
-        s = rangeLock(pFile, F_WRLCK, &tErrno);
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
         break;
       default:
         assert(0);
     }
+    s = fcntl(pFile->h, F_SETLK, &lock);
     if( s==(-1) ){
+      tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
       if( IS_LOCK_ERROR(rc) ){
         pFile->lastErrno = tErrno;
@@ -22960,8 +23571,8 @@
   ** write operation (not a hot journal rollback).
   */
   if( rc==SQLITE_OK
-   && pFile->locktype<=SHARED_LOCK
-   && locktype==RESERVED_LOCK
+   && pFile->eFileLock<=SHARED_LOCK
+   && eFileLock==RESERVED_LOCK
   ){
     pFile->transCntrChng = 0;
     pFile->dbUpdate = 0;
@@ -22971,47 +23582,17 @@
 
 
   if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-    pLock->locktype = locktype;
-  }else if( locktype==EXCLUSIVE_LOCK ){
-    pFile->locktype = PENDING_LOCK;
-    pLock->locktype = PENDING_LOCK;
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
   }
 
 end_lock:
   unixLeaveMutex();
-  OSTRACE4("LOCK    %d %s %s (unix)\n", pFile->h, locktypeName(locktype), 
-      rc==SQLITE_OK ? "ok" : "failed");
-  return rc;
-}
-
-/*
-** Close all file descriptors accumuated in the unixOpenCnt->pUnused list.
-** If all such file descriptors are closed without error, the list is
-** cleared and SQLITE_OK returned.
-**
-** Otherwise, if an error occurs, then successfully closed file descriptor
-** entries are removed from the list, and SQLITE_IOERR_CLOSE returned. 
-** not deleted and SQLITE_IOERR_CLOSE returned.
-*/ 
-static int closePendingFds(unixFile *pFile){
-  int rc = SQLITE_OK;
-  struct unixOpenCnt *pOpen = pFile->pOpen;
-  UnixUnusedFd *pError = 0;
-  UnixUnusedFd *p;
-  UnixUnusedFd *pNext;
-  for(p=pOpen->pUnused; p; p=pNext){
-    pNext = p->pNext;
-    if( close(p->fd) ){
-      pFile->lastErrno = errno;
-      rc = SQLITE_IOERR_CLOSE;
-      p->pNext = pError;
-      pError = p;
-    }else{
-      sqlite3_free(p);
-    }
-  }
-  pOpen->pUnused = pError;
+  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), 
+      rc==SQLITE_OK ? "ok" : "failed"));
   return rc;
 }
 
@@ -23020,46 +23601,50 @@
 ** pUnused list.
 */
 static void setPendingFd(unixFile *pFile){
-  struct unixOpenCnt *pOpen = pFile->pOpen;
+  unixInodeInfo *pInode = pFile->pInode;
   UnixUnusedFd *p = pFile->pUnused;
-  p->pNext = pOpen->pUnused;
-  pOpen->pUnused = p;
+  p->pNext = pInode->pUnused;
+  pInode->pUnused = p;
   pFile->h = -1;
   pFile->pUnused = 0;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
+** 
+** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
+** the byte range is divided into 2 parts and the first part is unlocked then
+** set to a read lock, then the other part is simply unlocked.  This works 
+** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to 
+** remove the write lock on a region when a read lock is set.
 */
-static int unixUnlock(sqlite3_file *id, int locktype){
-  unixFile *pFile = (unixFile*)id; /* The open file */
-  struct unixLockInfo *pLock;      /* Structure describing current lock state */
-  struct flock lock;               /* Information passed into fcntl() */
-  int rc = SQLITE_OK;              /* Return code from this interface */
-  int h;                           /* The underlying file descriptor */
+static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int rc = SQLITE_OK;
+  int h;
   int tErrno;                      /* Error code from system call errors */
 
   assert( pFile );
-  OSTRACE7("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, locktype,
-      pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid());
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
+      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+      getpid()));
 
-  assert( locktype<=SHARED_LOCK );
-  if( pFile->locktype<=locktype ){
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
     return SQLITE_OK;
   }
-  if( CHECK_THREADID(pFile) ){
-    return SQLITE_MISUSE_BKPT;
-  }
   unixEnterMutex();
   h = pFile->h;
-  pLock = pFile->pLock;
-  assert( pLock->cnt!=0 );
-  if( pFile->locktype>SHARED_LOCK ){
-    assert( pLock->locktype==pFile->locktype );
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
     SimulateIOErrorBenign(1);
     SimulateIOError( h=(-1) )
     SimulateIOErrorBenign(0);
@@ -23073,20 +23658,76 @@
     ** the file has changed and hence might not know to flush their
     ** cache.  The use of a stale cache can lead to database corruption.
     */
+#if 0
     assert( pFile->inNormalWrite==0
          || pFile->dbUpdate==0
          || pFile->transCntrChng==1 );
+#endif
     pFile->inNormalWrite = 0;
 #endif
 
-
-    if( locktype==SHARED_LOCK ){
-      if( rangeLock(pFile, F_RDLCK, &tErrno)==(-1) ){
-        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
-        if( IS_LOCK_ERROR(rc) ){
-          pFile->lastErrno = tErrno;
+    /* downgrading to a shared lock on NFS involves clearing the write lock
+    ** before establishing the readlock - to avoid a race condition we downgrade
+    ** the lock in 2 blocks, so that part of the range will be covered by a 
+    ** write lock until the rest is covered by a read lock:
+    **  1:   [WWWWW]
+    **  2:   [....W]
+    **  3:   [RRRRW]
+    **  4:   [RRRR.]
+    */
+    if( eFileLock==SHARED_LOCK ){
+      if( handleNFSUnlock ){
+        off_t divSize = SHARED_SIZE - 1;
+        
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
         }
-        goto end_unlock;
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST+divSize;
+        lock.l_len = SHARED_SIZE-divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+      }else{
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
       }
     }
     lock.l_type = F_UNLCK;
@@ -23094,7 +23735,7 @@
     lock.l_start = PENDING_BYTE;
     lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
     if( fcntl(h, F_SETLK, &lock)!=(-1) ){
-      pLock->locktype = SHARED_LOCK;
+      pInode->eFileLock = SHARED_LOCK;
     }else{
       tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
@@ -23104,15 +23745,13 @@
       goto end_unlock;
     }
   }
-  if( locktype==NO_LOCK ){
-    struct unixOpenCnt *pOpen;
-
+  if( eFileLock==NO_LOCK ){
     /* Decrement the shared lock counter.  Release the lock using an
     ** OS call only when all threads in this same process have released
     ** the lock.
     */
-    pLock->cnt--;
-    if( pLock->cnt==0 ){
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
       lock.l_type = F_UNLCK;
       lock.l_whence = SEEK_SET;
       lock.l_start = lock.l_len = 0L;
@@ -23120,15 +23759,15 @@
       SimulateIOError( h=(-1) )
       SimulateIOErrorBenign(0);
       if( fcntl(h, F_SETLK, &lock)!=(-1) ){
-        pLock->locktype = NO_LOCK;
+        pInode->eFileLock = NO_LOCK;
       }else{
         tErrno = errno;
         rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
         if( IS_LOCK_ERROR(rc) ){
           pFile->lastErrno = tErrno;
         }
-        pLock->locktype = NO_LOCK;
-        pFile->locktype = NO_LOCK;
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
       }
     }
 
@@ -23136,10 +23775,9 @@
     ** count reaches zero, close any other file descriptors whose close
     ** was deferred because of outstanding locks.
     */
-    pOpen = pFile->pOpen;
-    pOpen->nLock--;
-    assert( pOpen->nLock>=0 );
-    if( pOpen->nLock==0 ){
+    pInode->nLock--;
+    assert( pInode->nLock>=0 );
+    if( pInode->nLock==0 ){
       int rc2 = closePendingFds(pFile);
       if( rc==SQLITE_OK ){
         rc = rc2;
@@ -23149,11 +23787,22 @@
 	
 end_unlock:
   unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->locktype = locktype;
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
   return rc;
 }
 
 /*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int unixUnlock(sqlite3_file *id, int eFileLock){
+  return _posixUnlock(id, eFileLock, 0);
+}
+
+/*
 ** This function performs the parts of the "close file" operation 
 ** common to all locking schemes. It closes the directory and file
 ** handles, if they are valid, and sets all fields of the unixFile
@@ -23191,7 +23840,7 @@
       pFile->pId = 0;
     }
 #endif
-    OSTRACE2("CLOSE   %-3d\n", pFile->h);
+    OSTRACE(("CLOSE   %-3d\n", pFile->h));
     OpenCounter(-1);
     sqlite3_free(pFile->pUnused);
     memset(pFile, 0, sizeof(unixFile));
@@ -23208,16 +23857,15 @@
     unixFile *pFile = (unixFile *)id;
     unixUnlock(id, NO_LOCK);
     unixEnterMutex();
-    if( pFile->pOpen && pFile->pOpen->nLock ){
+    if( pFile->pInode && pFile->pInode->nLock ){
       /* If there are outstanding locks, do not actually close the file just
       ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pOpen->pUnused list.  It will be automatically closed 
+      ** descriptor to pInode->pUnused list.  It will be automatically closed 
       ** when the last lock is cleared.
       */
       setPendingFd(pFile);
     }
-    releaseLockInfo(pFile->pLock);
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     rc = closeUnixFile(id);
     unixLeaveMutex();
   }
@@ -23316,7 +23964,7 @@
   assert( pFile );
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     /* Either this connection or some other connection in the same process
     ** holds a lock on the file.  No need to check further. */
     reserved = 1;
@@ -23325,13 +23973,13 @@
     const char *zLockFile = (const char*)pFile->lockingContext;
     reserved = access(zLockFile, 0)==0;
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23357,7 +24005,7 @@
 ** With dotfile locking, we really only support state (4): EXCLUSIVE.
 ** But we track the other locking levels internally.
 */
-static int dotlockLock(sqlite3_file *id, int locktype) {
+static int dotlockLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int fd;
   char *zLockFile = (char *)pFile->lockingContext;
@@ -23367,8 +24015,8 @@
   /* If we have any lock, then the lock file already exists.  All we have
   ** to do is adjust our internal record of the lock level.
   */
-  if( pFile->locktype > NO_LOCK ){
-    pFile->locktype = locktype;
+  if( pFile->eFileLock > NO_LOCK ){
+    pFile->eFileLock = eFileLock;
 #if !OS_VXWORKS
     /* Always update the timestamp on the old file */
     utimes(zLockFile, NULL);
@@ -23397,12 +24045,12 @@
   }
   
   /* got it, set the type and return ok */
-  pFile->locktype = locktype;
+  pFile->eFileLock = eFileLock;
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
@@ -23410,30 +24058,30 @@
 **
 ** When the locking level reaches NO_LOCK, delete the lock file.
 */
-static int dotlockUnlock(sqlite3_file *id, int locktype) {
+static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   char *zLockFile = (char *)pFile->lockingContext;
 
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, locktype,
-	   pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
 
   /* To downgrade to shared, simply update our internal notion of the
   ** lock state.  No need to mess with the file on disk.
   */
-  if( locktype==SHARED_LOCK ){
-    pFile->locktype = SHARED_LOCK;
+  if( eFileLock==SHARED_LOCK ){
+    pFile->eFileLock = SHARED_LOCK;
     return SQLITE_OK;
   }
   
   /* To fully unlock the database, delete the lock file */
-  assert( locktype==NO_LOCK );
+  assert( eFileLock==NO_LOCK );
   if( unlink(zLockFile) ){
     int rc = 0;
     int tErrno = errno;
@@ -23445,7 +24093,7 @@
     }
     return rc; 
   }
-  pFile->locktype = NO_LOCK;
+  pFile->eFileLock = NO_LOCK;
   return SQLITE_OK;
 }
 
@@ -23498,7 +24146,7 @@
   assert( pFile );
   
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
@@ -23529,7 +24177,7 @@
       }
     }
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
 
 #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
   if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
@@ -23542,7 +24190,7 @@
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23570,7 +24218,7 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int flockLock(sqlite3_file *id, int locktype) {
+static int flockLock(sqlite3_file *id, int eFileLock) {
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
 
@@ -23578,8 +24226,8 @@
 
   /* if we already have a lock, it is exclusive.  
   ** Just adjust level and punt on outta here. */
-  if (pFile->locktype > NO_LOCK) {
-    pFile->locktype = locktype;
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23594,10 +24242,10 @@
     }
   } else {
     /* got it, set the type and return ok */
-    pFile->locktype = locktype;
+    pFile->eFileLock = eFileLock;
   }
-  OSTRACE4("LOCK    %d %s %s (flock)\n", pFile->h, locktypeName(locktype), 
-           rc==SQLITE_OK ? "ok" : "failed");
+  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock), 
+           rc==SQLITE_OK ? "ok" : "failed"));
 #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
   if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
     rc = SQLITE_BUSY;
@@ -23608,28 +24256,28 @@
 
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int flockUnlock(sqlite3_file *id, int locktype) {
+static int flockUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, locktype,
-           pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
+           pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
   
   /* shared can just be set because we always have an exclusive */
-  if (locktype==SHARED_LOCK) {
-    pFile->locktype = locktype;
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23649,7 +24297,7 @@
     
     return r;
   } else {
-    pFile->locktype = NO_LOCK;
+    pFile->eFileLock = NO_LOCK;
     return SQLITE_OK;
   }
 }
@@ -23697,13 +24345,13 @@
   assert( pFile );
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
   /* Otherwise see if some other process holds it. */
   if( !reserved ){
-    sem_t *pSem = pFile->pOpen->pSem;
+    sem_t *pSem = pFile->pInode->pSem;
     struct stat statBuf;
 
     if( sem_trywait(pSem)==-1 ){
@@ -23713,21 +24361,21 @@
         pFile->lastErrno = tErrno;
       } else {
         /* someone else has the lock when we are in NO_LOCK */
-        reserved = (pFile->locktype < SHARED_LOCK);
+        reserved = (pFile->eFileLock < SHARED_LOCK);
       }
     }else{
       /* we could have it if we want it */
       sem_post(pSem);
     }
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
 
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23755,16 +24403,16 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int semLock(sqlite3_file *id, int locktype) {
+static int semLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int fd;
-  sem_t *pSem = pFile->pOpen->pSem;
+  sem_t *pSem = pFile->pInode->pSem;
   int rc = SQLITE_OK;
 
   /* if we already have a lock, it is exclusive.  
   ** Just adjust level and punt on outta here. */
-  if (pFile->locktype > NO_LOCK) {
-    pFile->locktype = locktype;
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
     rc = SQLITE_OK;
     goto sem_end_lock;
   }
@@ -23776,37 +24424,37 @@
   }
 
   /* got it, set the type and return ok */
-  pFile->locktype = locktype;
+  pFile->eFileLock = eFileLock;
 
  sem_end_lock:
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int semUnlock(sqlite3_file *id, int locktype) {
+static int semUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pOpen->pSem;
+  sem_t *pSem = pFile->pInode->pSem;
 
   assert( pFile );
   assert( pSem );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, locktype,
-	   pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
   
   /* shared can just be set because we always have an exclusive */
-  if (locktype==SHARED_LOCK) {
-    pFile->locktype = locktype;
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23819,7 +24467,7 @@
     }
     return rc; 
   }
-  pFile->locktype = NO_LOCK;
+  pFile->eFileLock = NO_LOCK;
   return SQLITE_OK;
 }
 
@@ -23832,8 +24480,7 @@
     semUnlock(id, NO_LOCK);
     assert( pFile );
     unixEnterMutex();
-    releaseLockInfo(pFile->pLock);
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     unixLeaveMutex();
     closeUnixFile(id);
   }
@@ -23864,7 +24511,7 @@
 */
 typedef struct afpLockingContext afpLockingContext;
 struct afpLockingContext {
-  unsigned long long sharedByte;
+  int reserved;
   const char *dbPath;             /* Name of the open file */
 };
 
@@ -23902,15 +24549,15 @@
   pb.length = length; 
   pb.fd = pFile->h;
   
-  OSTRACE6("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
+  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
     (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
-    offset, length);
+    offset, length));
   err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
   if ( err==-1 ) {
     int rc;
     int tErrno = errno;
-    OSTRACE4("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
-             path, tErrno, strerror(tErrno));
+    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
+             path, tErrno, strerror(tErrno)));
 #ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
     rc = SQLITE_BUSY;
 #else
@@ -23941,9 +24588,14 @@
   
   assert( pFile );
   afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  if( context->reserved ){
+    *pResOut = 1;
+    return SQLITE_OK;
+  }
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
   
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
@@ -23965,14 +24617,15 @@
     }
   }
   
-  OSTRACE4("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved);
+  unixLeaveMutex();
+  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
   
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23995,49 +24648,72 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int afpLock(sqlite3_file *id, int locktype){
+static int afpLock(sqlite3_file *id, int eFileLock){
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode = pFile->pInode;
   afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
   
   assert( pFile );
-  OSTRACE5("LOCK    %d %s was %s pid=%d (afp)\n", pFile->h,
-         locktypeName(locktype), locktypeName(pFile->locktype), getpid());
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
+           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+           azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
 
   /* If there is already a lock of this type or more restrictive on the
   ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
   ** unixEnterMutex() hasn't been called yet.
   */
-  if( pFile->locktype>=locktype ){
-    OSTRACE3("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
-           locktypeName(locktype));
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
+           azFileLock(eFileLock)));
     return SQLITE_OK;
   }
 
   /* Make sure the locking sequence is correct
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pendig lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
   */
-  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
-  assert( locktype!=PENDING_LOCK );
-  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
   
-  /* This mutex is needed because pFile->pLock is shared across threads
+  /* This mutex is needed because pFile->pInode is shared across threads
   */
   unixEnterMutex();
+  pInode = pFile->pInode;
 
-  /* Make sure the current thread owns the pFile.
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
   */
-  rc = transferOwnership(pFile);
-  if( rc!=SQLITE_OK ){
-    unixLeaveMutex();
-    return rc;
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+     ){
+    rc = SQLITE_BUSY;
+    goto afp_end_lock;
+  }
+  
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK && 
+     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto afp_end_lock;
   }
     
   /* A PENDING lock is needed before acquiring a SHARED lock and before
   ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
   ** be released.
   */
-  if( locktype==SHARED_LOCK 
-      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
   ){
     int failed;
     failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
@@ -24050,16 +24726,20 @@
   /* If control gets to this point, then actually go ahead and make
   ** operating system calls for the specified lock.
   */
-  if( locktype==SHARED_LOCK ){
-    int lk, lrc1, lrc2;
-    int lrc1Errno = 0;
+  if( eFileLock==SHARED_LOCK ){
+    int lrc1, lrc2, lrc1Errno;
+    long lk, mask;
     
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+        
+    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
     /* Now get the read-lock SHARED_LOCK */
     /* note that the quality of the randomness doesn't matter that much */
     lk = random(); 
-    context->sharedByte = (lk & 0x7fffffff)%(SHARED_SIZE - 1);
+    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
     lrc1 = afpSetLock(context->dbPath, pFile, 
-          SHARED_FIRST+context->sharedByte, 1, 1);
+          SHARED_FIRST+pInode->sharedByte, 1, 1);
     if( IS_LOCK_ERROR(lrc1) ){
       lrc1Errno = pFile->lastErrno;
     }
@@ -24076,34 +24756,42 @@
     } else if( lrc1 != SQLITE_OK ) {
       rc = lrc1;
     } else {
-      pFile->locktype = SHARED_LOCK;
-      pFile->pOpen->nLock++;
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
     }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+     ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
   }else{
     /* The request was for a RESERVED or EXCLUSIVE lock.  It is
     ** assumed that there is a SHARED or greater lock on the file
     ** already.
     */
     int failed = 0;
-    assert( 0!=pFile->locktype );
-    if (locktype >= RESERVED_LOCK && pFile->locktype < RESERVED_LOCK) {
+    assert( 0!=pFile->eFileLock );
+    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
         /* Acquire a RESERVED lock */
         failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
+      if( !failed ){
+        context->reserved = 1;
+      }
     }
-    if (!failed && locktype == EXCLUSIVE_LOCK) {
+    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
       /* Acquire an EXCLUSIVE lock */
         
       /* Remove the shared lock before trying the range.  we'll need to 
       ** reestablish the shared lock if we can't get the  afpUnlock
       */
       if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
-                         context->sharedByte, 1, 0)) ){
+                         pInode->sharedByte, 1, 0)) ){
         int failed2 = SQLITE_OK;
         /* now attemmpt to get the exclusive lock range */
         failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, 
                                SHARED_SIZE, 1);
         if( failed && (failed2 = afpSetLock(context->dbPath, pFile, 
-                       SHARED_FIRST + context->sharedByte, 1, 1)) ){
+                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
           /* Can't reestablish the shared lock.  Sqlite can't deal, this is
           ** a critical I/O error
           */
@@ -24121,78 +24809,124 @@
   }
   
   if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-  }else if( locktype==EXCLUSIVE_LOCK ){
-    pFile->locktype = PENDING_LOCK;
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
   }
   
 afp_end_lock:
   unixLeaveMutex();
-  OSTRACE4("LOCK    %d %s %s (afp)\n", pFile->h, locktypeName(locktype), 
-         rc==SQLITE_OK ? "ok" : "failed");
+  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), 
+         rc==SQLITE_OK ? "ok" : "failed"));
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int afpUnlock(sqlite3_file *id, int locktype) {
+static int afpUnlock(sqlite3_file *id, int eFileLock) {
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
-  afpLockingContext *pCtx = (afpLockingContext *) pFile->lockingContext;
+  unixInodeInfo *pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  int skipShared = 0;
+#ifdef SQLITE_TEST
+  int h = pFile->h;
+#endif
 
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (afp)\n", pFile->h, locktype,
-         pFile->locktype, getpid());
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
+           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+           getpid()));
 
-  assert( locktype<=SHARED_LOCK );
-  if( pFile->locktype<=locktype ){
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
     return SQLITE_OK;
   }
-  if( CHECK_THREADID(pFile) ){
-    return SQLITE_MISUSE_BKPT;
-  }
   unixEnterMutex();
-  if( pFile->locktype>SHARED_LOCK ){
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+    SimulateIOErrorBenign(1);
+    SimulateIOError( h=(-1) )
+    SimulateIOErrorBenign(0);
     
-    if( pFile->locktype==EXCLUSIVE_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
-      if( rc==SQLITE_OK && locktype==SHARED_LOCK ){
+#ifndef NDEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    assert( pFile->inNormalWrite==0
+           || pFile->dbUpdate==0
+           || pFile->transCntrChng==1 );
+    pFile->inNormalWrite = 0;
+#endif
+    
+    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
+      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
         /* only re-establish the shared lock if necessary */
-        int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
-        rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 1);
+        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
+      } else {
+        skipShared = 1;
       }
     }
-    if( rc==SQLITE_OK && pFile->locktype>=PENDING_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, PENDING_BYTE, 1, 0);
+    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
     } 
-    if( rc==SQLITE_OK && pFile->locktype>=RESERVED_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, RESERVED_BYTE, 1, 0);
+    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
+      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+      if( !rc ){ 
+        context->reserved = 0; 
+      }
     }
-  }else if( locktype==NO_LOCK ){
-    /* clear the shared lock */
-    int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
-    rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 0);
+    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
+      pInode->eFileLock = SHARED_LOCK;
+    }
   }
+  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
 
-  if( rc==SQLITE_OK ){
-    if( locktype==NO_LOCK ){
-      struct unixOpenCnt *pOpen = pFile->pOpen;
-      pOpen->nLock--;
-      assert( pOpen->nLock>=0 );
-      if( pOpen->nLock==0 ){
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      SimulateIOErrorBenign(1);
+      SimulateIOError( h=(-1) )
+      SimulateIOErrorBenign(0);
+      if( !skipShared ){
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
+      }
+      if( !rc ){
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pInode->nLock--;
+      assert( pInode->nLock>=0 );
+      if( pInode->nLock==0 ){
         rc = closePendingFds(pFile);
       }
     }
   }
+  
   unixLeaveMutex();
-  if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-  }
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
   return rc;
 }
 
@@ -24200,24 +24934,25 @@
 ** Close a file & cleanup AFP specific locking context 
 */
 static int afpClose(sqlite3_file *id) {
+  int rc = SQLITE_OK;
   if( id ){
     unixFile *pFile = (unixFile*)id;
     afpUnlock(id, NO_LOCK);
     unixEnterMutex();
-    if( pFile->pOpen && pFile->pOpen->nLock ){
+    if( pFile->pInode && pFile->pInode->nLock ){
       /* If there are outstanding locks, do not actually close the file just
       ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pOpen->aPending.  It will be automatically closed when
+      ** descriptor to pInode->aPending.  It will be automatically closed when
       ** the last lock is cleared.
       */
       setPendingFd(pFile);
     }
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     sqlite3_free(pFile->lockingContext);
-    closeUnixFile(id);
+    rc = closeUnixFile(id);
     unixLeaveMutex();
   }
-  return SQLITE_OK;
+  return rc;
 }
 
 #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
@@ -24230,6 +24965,29 @@
 ********************* End of the AFP lock implementation **********************
 ******************************************************************************/
 
+/******************************************************************************
+*************************** Begin NFS Locking ********************************/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+ ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+ ** must be either NO_LOCK or SHARED_LOCK.
+ **
+ ** If the locking level of the file descriptor is already at or below
+ ** the requested locking level, this routine is a no-op.
+ */
+static int nfsUnlock(sqlite3_file *id, int eFileLock){
+  return _posixUnlock(id, eFileLock, 1);
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the NFS lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.  
+**
+********************* End of the NFS lock implementation **********************
+******************************************************************************/
 
 /******************************************************************************
 **************** Non-locking sqlite3_file methods *****************************
@@ -24256,7 +25014,9 @@
 */
 static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
   int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
   i64 newOffset;
+#endif
   TIMER_START;
 #if defined(USE_PREAD)
   got = pread(id->h, pBuf, cnt, offset);
@@ -24281,7 +25041,7 @@
   if( got<0 ){
     ((unixFile*)id)->lastErrno = errno;
   }
-  OSTRACE5("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
+  OSTRACE(("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
   return got;
 }
 
@@ -24302,10 +25062,12 @@
 
   /* If this is a database file (not a journal, master-journal or temp
   ** file), the bytes in the locking range should never be read or written. */
+#if 0
   assert( pFile->pUnused==0
        || offset>=PENDING_BYTE+512
        || offset+amt<=PENDING_BYTE 
   );
+#endif
 
   got = seekAndRead(pFile, offset, pBuf, amt);
   if( got==amt ){
@@ -24330,7 +25092,9 @@
 */
 static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
   int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
   i64 newOffset;
+#endif
   TIMER_START;
 #if defined(USE_PREAD)
   got = pwrite(id->h, pBuf, cnt, offset);
@@ -24353,7 +25117,7 @@
     ((unixFile*)id)->lastErrno = errno;
   }
 
-  OSTRACE5("WRITE   %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
+  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
   return got;
 }
 
@@ -24375,10 +25139,12 @@
 
   /* If this is a database file (not a journal, master-journal or temp
   ** file), the bytes in the locking range should never be read or written. */
+#if 0
   assert( pFile->pUnused==0
        || offset>=PENDING_BYTE+512
        || offset+amt<=PENDING_BYTE 
   );
+#endif
 
 #ifndef NDEBUG
   /* If we are doing a normal write to a database file (as opposed to
@@ -24524,6 +25290,11 @@
   */
   if( rc ) rc = fsync(fd);
 
+#elif defined(__APPLE__)
+  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
+  ** so currently we default to the macro that redefines fdatasync to fsync
+  */
+  rc = fsync(fd);
 #else 
   rc = fdatasync(fd);
 #if OS_VXWORKS
@@ -24572,7 +25343,7 @@
   SimulateDiskfullError( return SQLITE_FULL );
 
   assert( pFile );
-  OSTRACE2("SYNC    %-3d\n", pFile->h);
+  OSTRACE(("SYNC    %-3d\n", pFile->h));
   rc = full_fsync(pFile->h, isFullsync, isDataOnly);
   SimulateIOError( rc=1 );
   if( rc ){
@@ -24581,8 +25352,8 @@
   }
   if( pFile->dirfd>=0 ){
     int err;
-    OSTRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
-            HAVE_FULLFSYNC, isFullsync);
+    OSTRACE(("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
+            HAVE_FULLFSYNC, isFullsync));
 #ifndef SQLITE_DISABLE_DIRSYNC
     /* The directory sync is only attempted if full_fsync is
     ** turned off or unavailable.  If a full_fsync occurred above,
@@ -24654,7 +25425,7 @@
   }
   *pSize = buf.st_size;
 
-  /* When opening a zero-size database, the findLockInfo() procedure
+  /* When opening a zero-size database, the findInodeInfo() procedure
   ** writes a single byte into that file in order to work around a bug
   ** in the OS-X msdos filesystem.  In order to avoid problems with upper
   ** layers, we need to report this file size as zero even though it is
@@ -24681,13 +25452,21 @@
 static int unixFileControl(sqlite3_file *id, int op, void *pArg){
   switch( op ){
     case SQLITE_FCNTL_LOCKSTATE: {
-      *(int*)pArg = ((unixFile*)id)->locktype;
+      *(int*)pArg = ((unixFile*)id)->eFileLock;
       return SQLITE_OK;
     }
     case SQLITE_LAST_ERRNO: {
       *(int*)pArg = ((unixFile*)id)->lastErrno;
       return SQLITE_OK;
     }
+    case SQLITE_FCNTL_SIZE_HINT: {
+#if 0 /* No performance advantage seen on Linux */
+      sqlite3_int64 szFile = *(sqlite3_int64*)pArg;
+      unixFile *pFile = (unixFile*)id;
+      ftruncate(pFile->h, szFile);
+#endif
+      return SQLITE_OK;
+    }
 #ifndef NDEBUG
     /* The pager calls this method to signal that it has done
     ** a rollback and that the database is therefore unchanged and
@@ -24732,6 +25511,561 @@
   return 0;
 }
 
+#ifndef SQLITE_OMIT_WAL
+
+
+/*
+** Object used to represent an shared memory buffer.  
+**
+** When multiple threads all reference the same wal-index, each thread
+** has its own unixShm object, but they all point to a single instance
+** of this unixShmNode object.  In other words, each wal-index is opened
+** only once per process.
+**
+** Each unixShmNode object is connected to a single unixInodeInfo object.
+** We could coalesce this object into unixInodeInfo, but that would mean
+** every open file that does not use shared memory (in other words, most
+** open files) would have to carry around this extra information.  So
+** the unixInodeInfo object contains a pointer to this unixShmNode object
+** and the unixShmNode object is created only when needed.
+**
+** unixMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either unixShmNode.mutex must be held or unixShmNode.nRef==0 and
+** unixMutexHeld() is true when reading or writing any other field
+** in this structure.
+*/
+struct unixShmNode {
+  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the mmapped file */
+  int h;                     /* Open file descriptor */
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  char **apRegion;           /* Array of mapped shared-memory regions */
+  int nRef;                  /* Number of unixShm objects pointing to this */
+  unixShm *pFirst;           /* All unixShm objects pointing to this */
+#ifdef SQLITE_DEBUG
+  u8 exclMask;               /* Mask of exclusive locks held */
+  u8 sharedMask;             /* Mask of shared locks held */
+  u8 nextShmId;              /* Next available unixShm.id value */
+#endif
+};
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    unixShm.pFile
+**    unixShm.id
+**
+** All other fields are read/write.  The unixShm.pFile->mutex must be held
+** while accessing any read/write fields.
+*/
+struct unixShm {
+  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
+  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
+  u8 hasMutex;               /* True if holding the unixShmNode mutex */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection within its unixShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define UNIX_SHM_BASE   ((18+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
+#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
+**
+** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
+** otherwise.
+*/
+static int unixShmSystemLock(
+  unixShmNode *pShmNode, /* Apply locks to this open shared-memory segment */
+  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
+  int ofst,              /* First byte of the locking range */
+  int n                  /* Number of bytes to lock */
+){
+  struct flock f;       /* The posix advisory locking structure */
+  int rc = SQLITE_OK;   /* Result code form fcntl() */
+
+  /* Access to the unixShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
+
+  /* Shared locks never span more than one byte */
+  assert( n==1 || lockType!=F_RDLCK );
+
+  /* Locks are within range */
+  assert( n>=1 && n<SQLITE_SHM_NLOCK );
+
+  /* Initialize the locking parameters */
+  memset(&f, 0, sizeof(f));
+  f.l_type = lockType;
+  f.l_whence = SEEK_SET;
+  f.l_start = ofst;
+  f.l_len = n;
+
+  rc = fcntl(pShmNode->h, F_SETLK, &f);
+  rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
+
+  /* Update the global lock state and do debug tracing */
+#ifdef SQLITE_DEBUG
+  { u16 mask;
+  OSTRACE(("SHM-LOCK "));
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  if( rc==SQLITE_OK ){
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask &= ~mask;
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask |= mask;
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d ok", ofst));
+      pShmNode->exclMask |= mask;
+      pShmNode->sharedMask &= ~mask;
+    }
+  }else{
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d failed", ofst));
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock failed"));
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d failed", ofst));
+    }
+  }
+  OSTRACE((" - afterwards %03x,%03x\n",
+           pShmNode->sharedMask, pShmNode->exclMask));
+  }
+#endif
+
+  return rc;        
+}
+
+
+/*
+** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void unixShmPurge(unixFile *pFd){
+  unixShmNode *p = pFd->pInode->pShmNode;
+  assert( unixMutexHeld() );
+  if( p && p->nRef==0 ){
+    int i;
+    assert( p->pInode==pFd->pInode );
+    if( p->mutex ) sqlite3_mutex_free(p->mutex);
+    for(i=0; i<p->nRegion; i++){
+      munmap(p->apRegion[i], p->szRegion);
+    }
+    sqlite3_free(p->apRegion);
+    if( p->h>=0 ) close(p->h);
+    p->pInode->pShmNode = 0;
+    sqlite3_free(p);
+  }
+}
+
+/*
+** Open a shared-memory area associated with open database file fd.  
+** This particular implementation uses mmapped files.
+**
+** The file used to implement shared-memory is in the same directory
+** as the open database file and has the same name as the open database
+** file with the "-shm" suffix added.  For example, if the database file
+** is "/home/user1/config.db" then the file that is created and mmapped
+** for shared memory will be called "/home/user1/config.db-shm".  We
+** experimented with using files in /dev/tmp or an some other tmpfs mount.
+** But if a file in a different directory from the database file is used,
+** then differing access permissions or a chroot() might cause two different 
+** processes on the same database to end up using different files for 
+** shared memory - meaning that their memory would not really be shared - 
+** resulting in database corruption.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int unixShmOpen(
+  sqlite3_file *fd      /* The file descriptor of the associated database */
+){
+  struct unixShm *p = 0;             /* The connection to be opened */
+  struct unixShmNode *pShmNode = 0;  /* The underlying mmapped file */
+  int rc;                            /* Result code */
+  struct unixFile *pDbFd;            /* Underlying database file */
+  unixInodeInfo *pInode;             /* The inode of fd */
+  char *zShmFilename;                /* Name of the file used for SHM */
+  int nShmFilename;                  /* Size of the SHM filename in bytes */
+
+  /* Allocate space for the new sqlite3_shm object.
+  */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  pDbFd = (struct unixFile*)fd;
+  assert( pDbFd->pShm==0 );
+
+  /* Check to see if a unixShmNode object already exists.  Reuse an existing
+  ** one if present.  Create a new one if necessary.
+  */
+  unixEnterMutex();
+  pInode = pDbFd->pInode;
+  pShmNode = pInode->pShmNode;
+  if( pShmNode==0 ){
+    nShmFilename = 5 + (int)strlen(pDbFd->zPath);
+    pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename );
+    if( pShmNode==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+    memset(pShmNode, 0, sizeof(*pShmNode));
+    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
+    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath);
+    pShmNode->h = -1;
+    pDbFd->pInode->pShmNode = pShmNode;
+    pShmNode->pInode = pDbFd->pInode;
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+
+    pShmNode->h = open(zShmFilename, O_RDWR|O_CREAT, 0664);
+    if( pShmNode->h<0 ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto shm_open_err;
+    }
+
+    /* Check to see if another process is holding the dead-man switch.
+    ** If not, truncate the file to zero length. 
+    */
+    rc = SQLITE_OK;
+    if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
+      if( ftruncate(pShmNode->h, 0) ){
+        rc = SQLITE_IOERR_SHMOPEN;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1);
+    }
+    if( rc ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the unixShmNode */
+  p->pShmNode = pShmNode;
+  p->pNext = pShmNode->pFirst;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->pFirst = p;
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  unixLeaveMutex();
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  unixLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+*/
+static int unixShmClose(
+  sqlite3_file *fd,          /* The underlying database file */
+  int deleteFlag             /* Delete shared-memory if true */
+){
+  unixShm *p;            /* The connection to be closed */
+  unixShmNode *pShmNode; /* The underlying shared-memory file */
+  unixShm **pp;          /* For looping over sibling connections */
+  unixFile *pDbFd;       /* The underlying database file */
+
+  pDbFd = (unixFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  unixEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    if( deleteFlag ) unlink(pShmNode->zFilename);
+    unixShmPurge(pDbFd);
+  }
+  unixLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+**
+** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
+** different here than in posix.  In xShmLock(), one can go from unlocked
+** to shared and back or from unlocked to exclusive and back.  But one may
+** not go from shared to exclusive or from exclusive to shared.
+*/
+static int unixShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
+  unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
+  unixShm *pX;                          /* For looping over all siblings */
+  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask;                             /* Mask of locks to take or release */
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  assert( n>1 || mask==(1<<ofst) );
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u16 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = unixShmSystemLock(pShmNode, F_UNLCK, ofst+UNIX_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    } 
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = unixShmSystemLock(pShmNode, F_RDLCK, ofst+UNIX_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+  
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = unixShmSystemLock(pShmNode, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
+           p->id, getpid(), p->sharedMask, p->exclMask));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void unixShmBarrier(
+  sqlite3_file *fd                /* Database file holding the shared memory */
+){
+  unixEnterMutex();
+  unixLeaveMutex();
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** isWrite is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int unixShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  unixFile *pDbFd = (unixFile*)fd;
+  unixShm *p = pDbFd->pShm;
+  unixShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    char **apNew;                      /* New apRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    struct stat sStat;                 /* Used by fstat() */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    if( fstat(pShmNode->h, &sStat) ){
+      rc = SQLITE_IOERR_SHMSIZE;
+      goto shmpage_out;
+    }
+
+    if( sStat.st_size<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      if( ftruncate(pShmNode->h, nByte) ){
+        rc = SQLITE_IOERR_SHMSIZE;
+        goto shmpage_out;
+      }  
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (char **)sqlite3_realloc(
+        pShmNode->apRegion, (iRegion+1)*sizeof(char *)
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->apRegion = apNew;
+    while(pShmNode->nRegion<=iRegion){
+      void *pMem = mmap(0, szRegion, PROT_READ|PROT_WRITE, 
+          MAP_SHARED, pShmNode->h, iRegion*szRegion
+      );
+      if( pMem==MAP_FAILED ){
+        rc = SQLITE_IOERR;
+        goto shmpage_out;
+      }
+      pShmNode->apRegion[pShmNode->nRegion] = pMem;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    *pp = pShmNode->apRegion[iRegion];
+  }else{
+    *pp = 0;
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+#else
+# define unixShmOpen    0
+# define unixShmLock    0
+# define unixShmMap     0
+# define unixShmBarrier 0
+# define unixShmClose   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
 /*
 ** Here ends the implementation of all sqlite3_file methods.
 **
@@ -24772,9 +26106,9 @@
 **   *  An I/O method finder function called FINDER that returns a pointer
 **      to the METHOD object in the previous bullet.
 */
-#define IOMETHODS(FINDER, METHOD, CLOSE, LOCK, UNLOCK, CKLOCK)               \
+#define IOMETHODS(FINDER, METHOD, VERSION, CLOSE, LOCK, UNLOCK, CKLOCK)      \
 static const sqlite3_io_methods METHOD = {                                   \
-   1,                          /* iVersion */                                \
+   VERSION,                    /* iVersion */                                \
    CLOSE,                      /* xClose */                                  \
    unixRead,                   /* xRead */                                   \
    unixWrite,                  /* xWrite */                                  \
@@ -24786,7 +26120,12 @@
    CKLOCK,                     /* xCheckReservedLock */                      \
    unixFileControl,            /* xFileControl */                            \
    unixSectorSize,             /* xSectorSize */                             \
-   unixDeviceCharacteristics   /* xDeviceCapabilities */                     \
+   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
+   unixShmOpen,                /* xShmOpen */                                \
+   unixShmLock,                /* xShmLock */                                \
+   unixShmMap,                 /* xShmMap */                                 \
+   unixShmBarrier,             /* xShmBarrier */                             \
+   unixShmClose                /* xShmClose */                               \
 };                                                                           \
 static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
   UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
@@ -24803,6 +26142,7 @@
 IOMETHODS(
   posixIoFinder,            /* Finder function name */
   posixIoMethods,           /* sqlite3_io_methods object name */
+  2,                        /* ShmOpen is enabled */
   unixClose,                /* xClose method */
   unixLock,                 /* xLock method */
   unixUnlock,               /* xUnlock method */
@@ -24811,6 +26151,7 @@
 IOMETHODS(
   nolockIoFinder,           /* Finder function name */
   nolockIoMethods,          /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   nolockClose,              /* xClose method */
   nolockLock,               /* xLock method */
   nolockUnlock,             /* xUnlock method */
@@ -24819,6 +26160,7 @@
 IOMETHODS(
   dotlockIoFinder,          /* Finder function name */
   dotlockIoMethods,         /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   dotlockClose,             /* xClose method */
   dotlockLock,              /* xLock method */
   dotlockUnlock,            /* xUnlock method */
@@ -24829,6 +26171,7 @@
 IOMETHODS(
   flockIoFinder,            /* Finder function name */
   flockIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   flockClose,               /* xClose method */
   flockLock,                /* xLock method */
   flockUnlock,              /* xUnlock method */
@@ -24840,6 +26183,7 @@
 IOMETHODS(
   semIoFinder,              /* Finder function name */
   semIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   semClose,                 /* xClose method */
   semLock,                  /* xLock method */
   semUnlock,                /* xUnlock method */
@@ -24851,6 +26195,7 @@
 IOMETHODS(
   afpIoFinder,              /* Finder function name */
   afpIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   afpClose,                 /* xClose method */
   afpLock,                  /* xLock method */
   afpUnlock,                /* xUnlock method */
@@ -24859,23 +26204,6 @@
 #endif
 
 /*
-** The "Whole File Locking" finder returns the same set of methods as
-** the posix locking finder.  But it also sets the SQLITE_WHOLE_FILE_LOCKING
-** flag to force the posix advisory locks to cover the whole file instead
-** of just a small span of bytes near the 1GiB boundary.  Whole File Locking
-** is useful on NFS-mounted files since it helps NFS to maintain cache
-** coherency.  But it is a detriment to other filesystems since it runs
-** slower.
-*/
-static const sqlite3_io_methods *posixWflIoFinderImpl(const char*z, unixFile*p){
-  UNUSED_PARAMETER(z);
-  p->fileFlags = SQLITE_WHOLE_FILE_LOCKING;
-  return &posixIoMethods;
-}
-static const sqlite3_io_methods 
-  *(*const posixWflIoFinder)(const char*,unixFile *p) = posixWflIoFinderImpl;
-
-/*
 ** The proxy locking method is a "super-method" in the sense that it
 ** opens secondary file descriptors for the conch and lock files and
 ** it uses proxy, dot-file, AFP, and flock() locking methods on those
@@ -24892,6 +26220,7 @@
 IOMETHODS(
   proxyIoFinder,            /* Finder function name */
   proxyIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   proxyClose,               /* xClose method */
   proxyLock,                /* xLock method */
   proxyUnlock,              /* xUnlock method */
@@ -24899,6 +26228,18 @@
 )
 #endif
 
+/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  nfsIoFinder,               /* Finder function name */
+  nfsIoMethods,              /* sqlite3_io_methods object name */
+  1,                         /* ShmOpen is disabled */
+  unixClose,                 /* xClose method */
+  unixLock,                  /* xLock method */
+  nfsUnlock,                 /* xUnlock method */
+  unixCheckReservedLock      /* xCheckReservedLock method */
+)
+#endif
 
 #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
 /* 
@@ -24919,11 +26260,7 @@
     { "hfs",    &posixIoMethods },
     { "ufs",    &posixIoMethods },
     { "afpfs",  &afpIoMethods },
-#ifdef SQLITE_ENABLE_AFP_LOCKING_SMB
     { "smbfs",  &afpIoMethods },
-#else
-    { "smbfs",  &flockIoMethods },
-#endif
     { "webdav", &nolockIoMethods },
     { 0, 0 }
   };
@@ -24956,8 +26293,11 @@
   lockInfo.l_whence = SEEK_SET;
   lockInfo.l_type = F_RDLCK;
   if( fcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    pNew->fileFlags = SQLITE_WHOLE_FILE_LOCKING;
-    return &posixIoMethods;
+    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
+      return &nfsIoMethods;
+    } else {
+      return &posixIoMethods;
+    }
   }else{
     return &dotlockIoMethods;
   }
@@ -25034,19 +26374,19 @@
   unixFile *pNew = (unixFile *)pId;
   int rc = SQLITE_OK;
 
-  assert( pNew->pLock==NULL );
-  assert( pNew->pOpen==NULL );
+  assert( pNew->pInode==NULL );
 
   /* Parameter isDelete is only used on vxworks. Express this explicitly 
   ** here to prevent compiler warnings about unused parameters.
   */
   UNUSED_PARAMETER(isDelete);
 
-  OSTRACE3("OPEN    %-3d %s\n", h, zFilename);    
+  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
   pNew->h = h;
   pNew->dirfd = dirfd;
-  SET_THREADID(pNew);
   pNew->fileFlags = 0;
+  assert( zFilename==0 || zFilename[0]=='/' );  /* Never a relative pathname */
+  pNew->zPath = zFilename;
 
 #if OS_VXWORKS
   pNew->pId = vxworksFindFileId(zFilename);
@@ -25068,12 +26408,16 @@
 #endif
   }
 
-  if( pLockingStyle == &posixIoMethods ){
+  if( pLockingStyle == &posixIoMethods
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+    || pLockingStyle == &nfsIoMethods
+#endif
+  ){
     unixEnterMutex();
-    rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
+    rc = findInodeInfo(pNew, &pNew->pInode);
     if( rc!=SQLITE_OK ){
-      /* If an error occured in findLockInfo(), close the file descriptor
-      ** immediately, before releasing the mutex. findLockInfo() may fail
+      /* If an error occured in findInodeInfo(), close the file descriptor
+      ** immediately, before releasing the mutex. findInodeInfo() may fail
       ** in two scenarios:
       **
       **   (a) A call to fstat() failed.
@@ -25082,7 +26426,7 @@
       ** Scenario (b) may only occur if the process is holding no other
       ** file descriptors open on the same file. If there were other file
       ** descriptors on this file, then no malloc would be required by
-      ** findLockInfo(). If this is the case, it is quite safe to close
+      ** findInodeInfo(). If this is the case, it is quite safe to close
       ** handle h - as it is guaranteed that no posix locks will be released
       ** by doing so.
       **
@@ -25110,9 +26454,15 @@
       ** according to requirement F11141.  So we do not need to make a
       ** copy of the filename. */
       pCtx->dbPath = zFilename;
+      pCtx->reserved = 0;
       srandomdev();
       unixEnterMutex();
-      rc = findLockInfo(pNew, NULL, &pNew->pOpen);
+      rc = findInodeInfo(pNew, &pNew->pInode);
+      if( rc!=SQLITE_OK ){
+        sqlite3_free(pNew->lockingContext);
+        close(h);
+        h = -1;
+      }
       unixLeaveMutex();        
     }
   }
@@ -25140,18 +26490,18 @@
     ** included in the semLockingContext
     */
     unixEnterMutex();
-    rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
-    if( (rc==SQLITE_OK) && (pNew->pOpen->pSem==NULL) ){
-      char *zSemName = pNew->pOpen->aSemName;
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
+      char *zSemName = pNew->pInode->aSemName;
       int n;
       sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
                        pNew->pId->zCanonicalName);
       for( n=1; zSemName[n]; n++ )
         if( zSemName[n]=='/' ) zSemName[n] = '_';
-      pNew->pOpen->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
-      if( pNew->pOpen->pSem == SEM_FAILED ){
+      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
+      if( pNew->pInode->pSem == SEM_FAILED ){
         rc = SQLITE_NOMEM;
-        pNew->pOpen->aSemName[0] = '\0';
+        pNew->pInode->aSemName[0] = '\0';
       }
     }
     unixLeaveMutex();
@@ -25161,6 +26511,8 @@
   pNew->lastErrno = 0;
 #if OS_VXWORKS
   if( rc!=SQLITE_OK ){
+    if( h>=0 ) close(h);
+    h = -1;
     unlink(zFilename);
     isDelete = 0;
   }
@@ -25200,7 +26552,7 @@
 #ifdef FD_CLOEXEC
       fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
 #endif
-      OSTRACE3("OPENDIR %-3d %s\n", fd, zDirname);
+      OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
     }
   }
   *pFd = fd;
@@ -25208,26 +26560,46 @@
 }
 
 /*
-** Create a temporary file name in zBuf.  zBuf must be allocated
-** by the calling process and must be big enough to hold at least
-** pVfs->mxPathname bytes.
+** Return the name of a directory in which to put temporary files.
+** If no suitable temporary file directory can be found, return NULL.
 */
-static int getTempname(int nBuf, char *zBuf){
+static const char *unixTempFileDir(void){
   static const char *azDirs[] = {
      0,
      0,
      "/var/tmp",
      "/usr/tmp",
      "/tmp",
-     ".",
+     0        /* List terminator */
   };
+  unsigned int i;
+  struct stat buf;
+  const char *zDir = 0;
+
+  azDirs[0] = sqlite3_temp_directory;
+  if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
+  for(i==0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
+    if( zDir==0 ) continue;
+    if( stat(zDir, &buf) ) continue;
+    if( !S_ISDIR(buf.st_mode) ) continue;
+    if( access(zDir, 07) ) continue;
+    break;
+  }
+  return zDir;
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be allocated
+** by the calling process and must be big enough to hold at least
+** pVfs->mxPathname bytes.
+*/
+static int unixGetTempname(int nBuf, char *zBuf){
   static const unsigned char zChars[] =
     "abcdefghijklmnopqrstuvwxyz"
     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
     "0123456789";
   unsigned int i, j;
-  struct stat buf;
-  const char *zDir = ".";
+  const char *zDir;
 
   /* It's odd to simulate an io-error here, but really this is just
   ** using the io-error infrastructure to test that SQLite handles this
@@ -25235,19 +26607,8 @@
   */
   SimulateIOError( return SQLITE_IOERR );
 
-  azDirs[0] = sqlite3_temp_directory;
-  if (NULL == azDirs[1]) {
-    azDirs[1] = getenv("TMPDIR");
-  }
-  
-  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
-    if( azDirs[i]==0 ) continue;
-    if( stat(azDirs[i], &buf) ) continue;
-    if( !S_ISDIR(buf.st_mode) ) continue;
-    if( access(azDirs[i], 07) ) continue;
-    zDir = azDirs[i];
-    break;
-  }
+  zDir = unixTempFileDir();
+  if( zDir==0 ) zDir = ".";
 
   /* Check that the output buffer is large enough for the temporary file 
   ** name. If it is not, return SQLITE_ERROR.
@@ -25313,17 +26674,17 @@
   ** Even if a subsequent open() call does succeed, the consequences of
   ** not searching for a resusable file descriptor are not dire.  */
   if( 0==stat(zPath, &sStat) ){
-    struct unixOpenCnt *pOpen;
+    unixInodeInfo *pInode;
 
     unixEnterMutex();
-    pOpen = openList;
-    while( pOpen && (pOpen->fileId.dev!=sStat.st_dev
-                     || pOpen->fileId.ino!=sStat.st_ino) ){
-       pOpen = pOpen->pNext;
+    pInode = inodeList;
+    while( pInode && (pInode->fileId.dev!=sStat.st_dev
+                     || pInode->fileId.ino!=sStat.st_ino) ){
+       pInode = pInode->pNext;
     }
-    if( pOpen ){
+    if( pInode ){
       UnixUnusedFd **pp;
-      for(pp=&pOpen->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
+      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
       pUnused = *pp;
       if( pUnused ){
         *pp = pUnused->pNext;
@@ -25377,6 +26738,9 @@
   int isCreate     = (flags & SQLITE_OPEN_CREATE);
   int isReadonly   = (flags & SQLITE_OPEN_READONLY);
   int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
+#endif
 
   /* If creating a master or main-file journal, this function will open
   ** a file-descriptor on the directory too. The first time unixSync()
@@ -25434,7 +26798,7 @@
   }else if( !zName ){
     /* If zName is NULL, the upper layer is requesting a temp file. */
     assert(isDelete && !isOpenDirectory);
-    rc = getTempname(MAX_PATHNAME+1, zTmpname);
+    rc = unixGetTempname(MAX_PATHNAME+1, zTmpname);
     if( rc!=SQLITE_OK ){
       return rc;
     }
@@ -25454,7 +26818,7 @@
   if( fd<0 ){
     mode_t openMode = (isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
     fd = open(zName, openFlags, openMode);
-    OSTRACE4("OPENX   %-3d %s 0%o\n", fd, zName, openFlags);
+    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
     if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
       /* Failed to open the file for read/write access. Try read-only. */
       flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
@@ -25510,8 +26874,25 @@
 
   noLock = eType!=SQLITE_OPEN_MAIN_DB;
 
+  
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  struct statfs fsInfo;
+  if( fstatfs(fd, &fsInfo) == -1 ){
+    ((unixFile*)pFile)->lastErrno = errno;
+    if( dirfd>=0 ) close(dirfd); /* silently leak if fail, in error */
+    close(fd); /* silently leak if fail, in error */
+    return SQLITE_IOERR_ACCESS;
+  }
+  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
+    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
+  }
+#endif
+  
+#if SQLITE_ENABLE_LOCKING_STYLE
 #if SQLITE_PREFER_PROXY_LOCKING
-  if( zPath!=NULL && !noLock && pVfs->xOpen ){
+  isAutoProxy = 1;
+#endif
+  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
     char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
     int useProxy = 0;
 
@@ -25543,6 +26924,14 @@
       rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
       if( rc==SQLITE_OK ){
         rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
+        if( rc!=SQLITE_OK ){
+          /* Use unixClose to clean up the resources added in fillInUnixFile 
+          ** and clear all the structure's references.  Specifically, 
+          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op 
+          */
+          unixClose(pFile);
+          return rc;
+        }
       }
       goto open_finished;
     }
@@ -25815,35 +27204,48 @@
 #endif
 
 /*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return 0.  Return 1 if the time and date cannot be found.
+*/
+static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#if defined(NO_GETTOD)
+  time_t t;
+  time(&t);
+  *piNow = ((sqlite3_int64)i)*1000 + unixEpoch;
+#elif OS_VXWORKS
+  struct timespec sNow;
+  clock_gettime(CLOCK_REALTIME, &sNow);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
+#else
+  struct timeval sNow;
+  gettimeofday(&sNow, 0);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+#endif
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(NotUsed);
+  return 0;
+}
+
+/*
 ** Find the current time (in Universal Coordinated Time).  Write the
 ** current time and date as a Julian Day number into *prNow and
 ** return 0.  Return 1 if the time and date cannot be found.
 */
 static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
-#if defined(SQLITE_OMIT_FLOATING_POINT)
-  time_t t;
-  time(&t);
-  *prNow = (((sqlite3_int64)t)/8640 + 24405875)/10;
-#elif defined(NO_GETTOD)
-  time_t t;
-  time(&t);
-  *prNow = t/86400.0 + 2440587.5;
-#elif OS_VXWORKS
-  struct timespec sNow;
-  clock_gettime(CLOCK_REALTIME, &sNow);
-  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_nsec/86400000000000.0;
-#else
-  struct timeval sNow;
-  gettimeofday(&sNow, 0);
-  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0;
-#endif
-
-#ifdef SQLITE_TEST
-  if( sqlite3_current_time ){
-    *prNow = sqlite3_current_time/86400.0 + 2440587.5;
-  }
-#endif
-  UNUSED_PARAMETER(NotUsed);
+  sqlite3_int64 i;
+  unixCurrentTimeInt64(0, &i);
+  *prNow = i/86400000.0;
   return 0;
 }
 
@@ -25861,6 +27263,7 @@
   return 0;
 }
 
+
 /*
 ************************ End of sqlite3_vfs methods ***************************
 ******************************************************************************/
@@ -25970,11 +27373,6 @@
 ** of the database file for multiple readers and writers on the same
 ** host (the conch ensures that they all use the same local lock file).
 **
-** There is a third file - the host ID file - used as a persistent record
-** of a unique identifier for the host, a 128-byte unique host id file
-** in the path defined by the HOSTIDPATH macro (default value is
-** /Library/Caches/.com.apple.sqliteConchHostId).
-**
 ** Requesting the lock proxy does not immediately take the conch, it is
 ** only taken when the first request to lock database file is made.  
 ** This matches the semantics of the traditional locking behavior, where
@@ -26000,10 +27398,6 @@
 **       Enables the logging of error messages during host id file
 **       retrieval and creation
 **
-**  HOSTIDPATH
-**
-**       Overrides the default host ID file path location
-**
 **  LOCKPROXYDIR
 **
 **       Overrides the default directory used for lock proxy files that
@@ -26028,11 +27422,6 @@
 */
 #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
 
-#ifdef SQLITE_TEST
-/* simulate multiple hosts by creating unique hostid file paths */
-SQLITE_API int sqlite3_hostid_num = 0;
-#endif
-
 /*
 ** The proxyLockingContext has the path and file structures for the remote 
 ** and local proxy files in it
@@ -26044,134 +27433,16 @@
   unixFile *lockProxy;         /* Open proxy lock file */
   char *lockProxyPath;         /* Name of the proxy lock file */
   char *dbPath;                /* Name of the open file */
-  int conchHeld;               /* True if the conch is currently held */
+  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
   void *oldLockingContext;     /* Original lockingcontext to restore on close */
   sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
 };
 
-/* HOSTIDLEN and CONCHLEN both include space for the string 
-** terminating nul 
+/* 
+** The proxy lock file path for the database at dbPath is written into lPath, 
+** which must point to valid, writable memory large enough for a maxLen length
+** file path. 
 */
-#define HOSTIDLEN         128
-#define CONCHLEN          (MAXPATHLEN+HOSTIDLEN+1)
-#ifndef HOSTIDPATH
-# define HOSTIDPATH       "/Library/Caches/.com.apple.sqliteConchHostId"
-#endif
-
-/* basically a copy of unixRandomness with different
-** test behavior built in */
-static int proxyGenerateHostID(char *pHostID){
-  int pid, fd, len;
-  unsigned char *key = (unsigned char *)pHostID;
-  
-  memset(key, 0, HOSTIDLEN);
-  len = 0;
-  fd = open("/dev/urandom", O_RDONLY);
-  if( fd>=0 ){
-    len = read(fd, key, HOSTIDLEN);
-    close(fd); /* silently leak the fd if it fails */
-  }
-  if( len < HOSTIDLEN ){
-    time_t t;
-    time(&t);
-    memcpy(key, &t, sizeof(t));
-    pid = getpid();
-    memcpy(&key[sizeof(t)], &pid, sizeof(pid));
-  }
-  
-#ifdef MAKE_PRETTY_HOSTID
-  {
-    int i;
-    /* filter the bytes into printable ascii characters and NUL terminate */
-    key[(HOSTIDLEN-1)] = 0x00;
-    for( i=0; i<(HOSTIDLEN-1); i++ ){
-      unsigned char pa = key[i]&0x7F;
-      if( pa<0x20 ){
-        key[i] = (key[i]&0x80 == 0x80) ? pa+0x40 : pa+0x20;
-      }else if( pa==0x7F ){
-        key[i] = (key[i]&0x80 == 0x80) ? pa=0x20 : pa+0x7E;
-      }
-    }
-  }
-#endif
-  return SQLITE_OK;
-}
-
-/* writes the host id path to path, path should be an pre-allocated buffer
-** with enough space for a path 
-*/
-static void proxyGetHostIDPath(char *path, size_t len){
-  strlcpy(path, HOSTIDPATH, len);
-#ifdef SQLITE_TEST
-  if( sqlite3_hostid_num>0 ){
-    char suffix[2] = "1";
-    suffix[0] = suffix[0] + sqlite3_hostid_num;
-    strlcat(path, suffix, len);
-  }
-#endif
-  OSTRACE3("GETHOSTIDPATH  %s pid=%d\n", path, getpid());
-}
-
-/* get the host ID from a sqlite hostid file stored in the 
-** user-specific tmp directory, create the ID if it's not there already 
-*/
-static int proxyGetHostID(char *pHostID, int *pError){
-  int fd;
-  char path[MAXPATHLEN]; 
-  size_t len;
-  int rc=SQLITE_OK;
-
-  proxyGetHostIDPath(path, MAXPATHLEN);
-  /* try to create the host ID file, if it already exists read the contents */
-  fd = open(path, O_CREAT|O_WRONLY|O_EXCL, 0644);
-  if( fd<0 ){
-    int err=errno;
-		
-    if( err!=EEXIST ){
-#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
-      fprintf(stderr, "sqlite error creating host ID file %s: %s\n",
-              path, strerror(err));
-#endif
-      return SQLITE_PERM;
-    }
-    /* couldn't create the file, read it instead */
-    fd = open(path, O_RDONLY|O_EXCL);
-    if( fd<0 ){
-#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
-      int err = errno;
-      fprintf(stderr, "sqlite error opening host ID file %s: %s\n",
-              path, strerror(err));
-#endif
-      return SQLITE_PERM;
-    }
-    len = pread(fd, pHostID, HOSTIDLEN, 0);
-    if( len<0 ){
-      *pError = errno;
-      rc = SQLITE_IOERR_READ;
-    }else if( len<HOSTIDLEN ){
-      *pError = 0;
-      rc = SQLITE_IOERR_SHORT_READ;
-    }
-    close(fd); /* silently leak the fd if it fails */
-    OSTRACE3("GETHOSTID  read %s pid=%d\n", pHostID, getpid());
-    return rc;
-  }else{
-    /* we're creating the host ID file (use a random string of bytes) */
-    proxyGenerateHostID(pHostID);
-    len = pwrite(fd, pHostID, HOSTIDLEN, 0);
-    if( len<0 ){
-      *pError = errno;
-      rc = SQLITE_IOERR_WRITE;
-    }else if( len<HOSTIDLEN ){
-      *pError = 0;
-      rc = SQLITE_IOERR_WRITE;
-    }
-    close(fd); /* silently leak the fd if it fails */
-    OSTRACE3("GETHOSTID  wrote %s pid=%d\n", pHostID, getpid());
-    return rc;
-  }
-}
-
 static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
   int len;
   int dbLen;
@@ -26182,21 +27453,12 @@
 #else
 # ifdef _CS_DARWIN_USER_TEMP_DIR
   {
-    confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen);
-    len = strlcat(lPath, "sqliteplocks", maxLen);    
-    if( mkdir(lPath, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
-      /* if mkdir fails, handle as lock file creation failure */
-#  ifdef SQLITE_DEBUG
-      int err = errno;
-      if( err!=EEXIST ){
-        fprintf(stderr, "proxyGetLockPath: mkdir(%s,0%o) error %d %s\n", lPath,
-                SQLITE_DEFAULT_PROXYDIR_PERMISSIONS, err, strerror(err));
-      }
-#  endif
-    }else{
-      OSTRACE3("GETLOCKPATH  mkdir %s pid=%d\n", lPath, getpid());
+    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
+      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
+               lPath, errno, getpid()));
+      return SQLITE_IOERR_LOCK;
     }
-    
+    len = strlcat(lPath, "sqliteplocks", maxLen);    
   }
 # else
   len = strlcpy(lPath, "/tmp/", maxLen);
@@ -26215,9 +27477,46 @@
   }
   lPath[i+len]='\0';
   strlcat(lPath, ":auto:", maxLen);
+  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, getpid()));
   return SQLITE_OK;
 }
 
+/* 
+ ** Creates the lock file and any missing directories in lockPath
+ */
+static int proxyCreateLockPath(const char *lockPath){
+  int i, len;
+  char buf[MAXPATHLEN];
+  int start = 0;
+  
+  assert(lockPath!=NULL);
+  /* try to create all the intermediate directories */
+  len = (int)strlen(lockPath);
+  buf[0] = lockPath[0];
+  for( i=1; i<len; i++ ){
+    if( lockPath[i] == '/' && (i - start > 0) ){
+      /* only mkdir if leaf dir != "." or "/" or ".." */
+      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') 
+         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
+        buf[i]='\0';
+        if( mkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
+          int err=errno;
+          if( err!=EEXIST ) {
+            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
+                     "'%s' proxy lock path=%s pid=%d\n",
+                     buf, strerror(err), lockPath, getpid()));
+            return err;
+          }
+        }
+      }
+      start=i+1;
+    }
+    buf[i] = lockPath[i];
+  }
+  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n", lockPath, getpid()));
+  return 0;
+}
+
 /*
 ** Create a new VFS file descriptor (stored in memory obtained from
 ** sqlite3_malloc) and open the file named "path" in the file descriptor.
@@ -26225,29 +27524,25 @@
 ** The caller is responsible not only for closing the file descriptor
 ** but also for freeing the memory associated with the file descriptor.
 */
-static int proxyCreateUnixFile(const char *path, unixFile **ppFile) {
+static int proxyCreateUnixFile(
+    const char *path,        /* path for the new unixFile */
+    unixFile **ppFile,       /* unixFile created and returned by ref */
+    int islockfile           /* if non zero missing dirs will be created */
+) {
+  int fd = -1;
+  int dirfd = -1;
   unixFile *pNew;
-  int flags = SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
   int rc = SQLITE_OK;
+  int openFlags = O_RDWR | O_CREAT;
   sqlite3_vfs dummyVfs;
+  int terrno = 0;
+  UnixUnusedFd *pUnused = NULL;
 
-  pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
-  if( !pNew ){
-    return SQLITE_NOMEM;
-  }
-  memset(pNew, 0, sizeof(unixFile));
-
-  /* Call unixOpen() to open the proxy file. The flags passed to unixOpen()
-  ** suggest that the file being opened is a "main database". This is
-  ** necessary as other file types do not necessarily support locking. It
-  ** is better to use unixOpen() instead of opening the file directly with
-  ** open(), as unixOpen() sets up the various mechanisms required to
-  ** make sure a call to close() does not cause the system to discard
-  ** POSIX locks prematurely.
-  **
-  ** It is important that the xOpen member of the VFS object passed to 
-  ** unixOpen() is NULL. This tells unixOpen() may try to open a proxy-file 
-  ** for the proxy-file (creating a potential infinite loop).
+  /* 1. first try to open/create the file
+  ** 2. if that fails, and this is a lock file (not-conch), try creating
+  ** the parent directories and then try again.
+  ** 3. if that fails, try to open the file read-only
+  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
   */
   pUnused = findReusableFd(path, openFlags);
   if( pUnused ){
@@ -26294,23 +27589,198 @@
   memset(pNew, 0, sizeof(unixFile));
   pNew->openFlags = openFlags;
   dummyVfs.pAppData = (void*)&autolockIoFinder;
-  dummyVfs.xOpen = 0;
-  rc = unixOpen(&dummyVfs, path, (sqlite3_file *)pNew, flags, &flags);
-  if( rc==SQLITE_OK && (flags&SQLITE_OPEN_READONLY) ){
-    pNew->pMethod->xClose((sqlite3_file *)pNew);
-    rc = SQLITE_CANTOPEN;
+  pUnused->fd = fd;
+  pUnused->flags = openFlags;
+  pNew->pUnused = pUnused;
+  
+  rc = fillInUnixFile(&dummyVfs, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0);
+  if( rc==SQLITE_OK ){
+    *ppFile = pNew;
+    return SQLITE_OK;
   }
-
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(pNew);
-    pNew = 0;
-  }
-
-  *ppFile = pNew;
+end_create_proxy:    
+  close(fd); /* silently leak fd if error, we're already in error */
+  sqlite3_free(pNew);
+  sqlite3_free(pUnused);
   return rc;
 }
 
-/* takes the conch by taking a shared lock and read the contents conch, if 
+#ifdef SQLITE_TEST
+/* simulate multiple hosts by creating unique hostid file paths */
+SQLITE_API int sqlite3_hostid_num = 0;
+#endif
+
+#define PROXY_HOSTIDLEN    16  /* conch file host id length */
+
+/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN 
+** bytes of writable memory.
+*/
+static int proxyGetHostID(unsigned char *pHostID, int *pError){
+  struct timespec timeout = {1, 0}; /* 1 sec timeout */
+  
+  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
+  memset(pHostID, 0, PROXY_HOSTIDLEN);
+  if( gethostuuid(pHostID, &timeout) ){
+    int err = errno;
+    if( pError ){
+      *pError = err;
+    }
+    return SQLITE_IOERR;
+  }
+#ifdef SQLITE_TEST
+  /* simulate multiple hosts by creating unique hostid file paths */
+  if( sqlite3_hostid_num != 0){
+    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
+  }
+#endif
+  
+  return SQLITE_OK;
+}
+
+/* The conch file contains the header, host id and lock file path
+ */
+#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
+#define PROXY_HEADERLEN    1   /* conch file header length */
+#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
+#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
+
+/* 
+** Takes an open conch file, copies the contents to a new path and then moves 
+** it back.  The newly created file's file descriptor is assigned to the
+** conch file structure and finally the original conch file descriptor is 
+** closed.  Returns zero if successful.
+*/
+static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  char tPath[MAXPATHLEN];
+  char buf[PROXY_MAXCONCHLEN];
+  char *cPath = pCtx->conchFilePath;
+  size_t readLen = 0;
+  size_t pathLen = 0;
+  char errmsg[64] = "";
+  int fd = -1;
+  int rc = -1;
+
+  /* create a new path by replace the trailing '-conch' with '-break' */
+  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
+  if( pathLen>MAXPATHLEN || pathLen<6 || 
+     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
+    sprintf(errmsg, "path error (len %d)", (int)pathLen);
+    goto end_breaklock;
+  }
+  /* read the conch content */
+  readLen = pread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
+  if( readLen<PROXY_PATHINDEX ){
+    sprintf(errmsg, "read error (len %d)", (int)readLen);
+    goto end_breaklock;
+  }
+  /* write it out to the temporary break file */
+  fd = open(tPath, (O_RDWR|O_CREAT|O_EXCL), SQLITE_DEFAULT_FILE_PERMISSIONS);
+  if( fd<0 ){
+    sprintf(errmsg, "create failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( pwrite(fd, buf, readLen, 0) != readLen ){
+    sprintf(errmsg, "write failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( rename(tPath, cPath) ){
+    sprintf(errmsg, "rename failed (%d)", errno);
+    goto end_breaklock;
+  }
+  rc = 0;
+  fprintf(stderr, "broke stale lock on %s\n", cPath);
+  close(conchFile->h);
+  conchFile->h = fd;
+  conchFile->openFlags = O_RDWR | O_CREAT;
+
+end_breaklock:
+  if( rc ){
+    if( fd>=0 ){
+      unlink(tPath);
+      close(fd);
+    }
+    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
+  }
+  return rc;
+}
+
+/* Take the requested lock on the conch file and break a stale lock if the 
+** host id matches.
+*/
+static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  int rc = SQLITE_OK;
+  int nTries = 0;
+  struct timespec conchModTime;
+  
+  do {
+    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+    nTries ++;
+    if( rc==SQLITE_BUSY ){
+      /* If the lock failed (busy):
+       * 1st try: get the mod time of the conch, wait 0.5s and try again. 
+       * 2nd try: fail if the mod time changed or host id is different, wait 
+       *           10 sec and try again
+       * 3rd try: break the lock unless the mod time has changed.
+       */
+      struct stat buf;
+      if( fstat(conchFile->h, &buf) ){
+        pFile->lastErrno = errno;
+        return SQLITE_IOERR_LOCK;
+      }
+      
+      if( nTries==1 ){
+        conchModTime = buf.st_mtimespec;
+        usleep(500000); /* wait 0.5 sec and try the lock again*/
+        continue;  
+      }
+
+      assert( nTries>1 );
+      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || 
+         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
+        return SQLITE_BUSY;
+      }
+      
+      if( nTries==2 ){  
+        char tBuf[PROXY_MAXCONCHLEN];
+        int len = pread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
+        if( len<0 ){
+          pFile->lastErrno = errno;
+          return SQLITE_IOERR_LOCK;
+        }
+        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
+          /* don't break the lock if the host id doesn't match */
+          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
+            return SQLITE_BUSY;
+          }
+        }else{
+          /* don't break the lock on short read or a version mismatch */
+          return SQLITE_BUSY;
+        }
+        usleep(10000000); /* wait 10 sec and try the lock again */
+        continue; 
+      }
+      
+      assert( nTries==3 );
+      if( 0==proxyBreakConchLock(pFile, myHostID) ){
+        rc = SQLITE_OK;
+        if( lockType==EXCLUSIVE_LOCK ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);          
+        }
+        if( !rc ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+        }
+      }
+    }
+  } while( rc==SQLITE_BUSY && nTries<3 );
+  
+  return rc;
+}
+
+/* Takes the conch by taking a shared lock and read the contents conch, if 
 ** lockPath is non-NULL, the host ID and lock file path must match.  A NULL 
 ** lockPath means that the lockPath in the conch file will be used if the 
 ** host IDs match, or a new lock path will be generated automatically 
@@ -26319,145 +27789,83 @@
 static int proxyTakeConch(unixFile *pFile){
   proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
   
-  if( pCtx->conchHeld>0 ){
+  if( pCtx->conchHeld!=0 ){
     return SQLITE_OK;
   }else{
     unixFile *conchFile = pCtx->conchFile;
-    char testValue[CONCHLEN];
-    char conchValue[CONCHLEN];
+    uuid_t myHostID;
+    int pError = 0;
+    char readBuf[PROXY_MAXCONCHLEN];
     char lockPath[MAXPATHLEN];
-    char *tLockPath = NULL;
+    char *tempLockPath = NULL;
     int rc = SQLITE_OK;
-    int readRc = SQLITE_OK;
-    int syncPerms = 0;
+    int createConch = 0;
+    int hostIdMatch = 0;
+    int readLen = 0;
+    int tryOldLockPath = 0;
+    int forceNewLockPath = 0;
+    
+    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
+             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()));
 
-    OSTRACE4("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
-             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid());
-
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);
-    if( rc==SQLITE_OK ){
-      int pError = 0;
-      memset(testValue, 0, CONCHLEN); /* conch is fixed size */
-      rc = proxyGetHostID(testValue, &pError);
-      if( (rc&0xff)==SQLITE_IOERR ){
-        pFile->lastErrno = pError;
-      }
-      if( pCtx->lockProxyPath ){
-        strlcpy(&testValue[HOSTIDLEN], pCtx->lockProxyPath, MAXPATHLEN);
-      }
+    rc = proxyGetHostID(myHostID, &pError);
+    if( (rc&0xff)==SQLITE_IOERR ){
+      pFile->lastErrno = pError;
+      goto end_takeconch;
     }
+    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
     if( rc!=SQLITE_OK ){
       goto end_takeconch;
     }
-    
-    readRc = unixRead((sqlite3_file *)conchFile, conchValue, CONCHLEN, 0);
-    if( readRc!=SQLITE_IOERR_SHORT_READ ){
-      if( readRc!=SQLITE_OK ){
-        if( (rc&0xff)==SQLITE_IOERR ){
-          pFile->lastErrno = conchFile->lastErrno;
-        }
-        rc = readRc;
-        goto end_takeconch;
-      }
-      /* if the conch has data compare the contents */
-      if( !pCtx->lockProxyPath ){
-        /* for auto-named local lock file, just check the host ID and we'll
-         ** use the local lock file path that's already in there */
-        if( !memcmp(testValue, conchValue, HOSTIDLEN) ){
-          tLockPath = (char *)&conchValue[HOSTIDLEN];
-          goto end_takeconch;
-        }
-      }else{
-        /* we've got the conch if conchValue matches our path and host ID */
-        if( !memcmp(testValue, conchValue, CONCHLEN) ){
-          goto end_takeconch;
-        }
-      }
-    }else{
-      /* a short read means we're "creating" the conch (even though it could 
-      ** have been user-intervention), if we acquire the exclusive lock,
-      ** we'll try to match the current on-disk permissions of the database
+    /* read the existing conch file */
+    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
+    if( readLen<0 ){
+      /* I/O error: lastErrno set by seekAndRead */
+      pFile->lastErrno = conchFile->lastErrno;
+      rc = SQLITE_IOERR_READ;
+      goto end_takeconch;
+    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || 
+             readBuf[0]!=(char)PROXY_CONCHVERSION ){
+      /* a short read or version format mismatch means we need to create a new 
+      ** conch file. 
       */
-      syncPerms = 1;
+      createConch = 1;
     }
-    
-    /* either conch was emtpy or didn't match */
-    if( !pCtx->lockProxyPath ){
-      proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
-      tLockPath = lockPath;
-      strlcpy(&testValue[HOSTIDLEN], lockPath, MAXPATHLEN);
-    }
-    
-    /* update conch with host and path (this will fail if other process
-     ** has a shared lock already) */
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK);
-    if( rc==SQLITE_OK ){
-      rc = unixWrite((sqlite3_file *)conchFile, testValue, CONCHLEN, 0);
-      if( rc==SQLITE_OK && syncPerms ){
-        struct stat buf;
-        int err = fstat(pFile->h, &buf);
-        if( err==0 ){
-          /* try to match the database file permissions, ignore failure */
-#ifndef SQLITE_PROXY_DEBUG
-          fchmod(conchFile->h, buf.st_mode);
-#else
-          if( fchmod(conchFile->h, buf.st_mode)!=0 ){
-            int code = errno;
-            fprintf(stderr, "fchmod %o FAILED with %d %s\n",
-                             buf.st_mode, code, strerror(code));
-          } else {
-            fprintf(stderr, "fchmod %o SUCCEDED\n",buf.st_mode);
-          }
-        }else{
-          int code = errno;
-          fprintf(stderr, "STAT FAILED[%d] with %d %s\n", 
-                          err, code, strerror(code));
-#endif
-        }
-      }
-    }
-    conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
-  
-end_takeconch:
-    OSTRACE2("TRANSPROXY: CLOSE  %d\n", pFile->h);
-    if( rc==SQLITE_OK && pFile->openFlags ){
-      if( pFile->h>=0 ){
-#ifdef STRICT_CLOSE_ERROR
-        if( close(pFile->h) ){
-          pFile->lastErrno = errno;
-          return SQLITE_IOERR_CLOSE;
-        }
-#else
-        close(pFile->h); /* silently leak fd if fail */
-#endif
-      }
-      pFile->h = -1;
-      int fd = open(pCtx->dbPath, pFile->openFlags,
-                    SQLITE_DEFAULT_FILE_PERMISSIONS);
-      OSTRACE2("TRANSPROXY: OPEN  %d\n", fd);
-      if( fd>=0 ){
-        pFile->h = fd;
-      }else{
-        rc=SQLITE_CANTOPEN; /* SQLITE_BUSY? proxyTakeConch called
-                               during locking */
-      }
-    }
-    if( rc==SQLITE_OK && !pCtx->lockProxy ){
-      char *path = tLockPath ? tLockPath : pCtx->lockProxyPath;
-      /* ACS: Need to make a copy of path sometimes */
-      rc = proxyCreateUnixFile(path, &pCtx->lockProxy);
-    }
-    if( rc==SQLITE_OK ){
-      pCtx->conchHeld = 1;
+    /* if the host id matches and the lock path already exists in the conch
+    ** we'll try to use the path there, if we can't open that path, we'll 
+    ** retry with a new auto-generated path 
+    */
+    do { /* in case we need to try again for an :auto: named lock file */
 
-      if( tLockPath ){
-        pCtx->lockProxyPath = sqlite3DbStrDup(0, tLockPath);
-        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
-          ((afpLockingContext *)pCtx->lockProxy->lockingContext)->dbPath =
-                     pCtx->lockProxyPath;
+      if( !createConch && !forceNewLockPath ){
+        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, 
+                                  PROXY_HOSTIDLEN);
+        /* if the conch has data compare the contents */
+        if( !pCtx->lockProxyPath ){
+          /* for auto-named local lock file, just check the host ID and we'll
+           ** use the local lock file path that's already in there
+           */
+          if( hostIdMatch ){
+            size_t pathLen = (readLen - PROXY_PATHINDEX);
+            
+            if( pathLen>=MAXPATHLEN ){
+              pathLen=MAXPATHLEN-1;
+            }
+            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
+            lockPath[pathLen] = 0;
+            tempLockPath = lockPath;
+            tryOldLockPath = 1;
+            /* create a copy of the lock path if the conch is taken */
+            goto end_takeconch;
+          }
+        }else if( hostIdMatch
+               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
+                           readLen-PROXY_PATHINDEX)
+        ){
+          /* conch host and lock path match */
+          goto end_takeconch; 
         }
       }
->>>>>>> BEGIN MERGE CONFLICT
       
       /* if the conch isn't writable and doesn't match, we can't take it */
       if( (conchFile->openFlags&O_RDWR) == 0 ){
@@ -26478,7 +27886,7 @@
       */
       futimes(conchFile->h, NULL);
       if( hostIdMatch && !createConch ){
-        if( conchFile->pLock && conchFile->pLock->cnt>1 ){
+        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
           /* We are trying for an exclusive lock but another thread in this
            ** same process is still holding a shared lock. */
           rc = SQLITE_BUSY;
@@ -26534,7 +27942,7 @@
       conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
       
     end_takeconch:
-      OSTRACE2("TRANSPROXY: CLOSE  %d\n", pFile->h);
+      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
       if( rc==SQLITE_OK && pFile->openFlags ){
         if( pFile->h>=0 ){
 #ifdef STRICT_CLOSE_ERROR
@@ -26549,7 +27957,7 @@
         pFile->h = -1;
         int fd = open(pCtx->dbPath, pFile->openFlags,
                       SQLITE_DEFAULT_FILE_PERMISSIONS);
-        OSTRACE2("TRANSPROXY: OPEN  %d\n", fd);
+        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
         if( fd>=0 ){
           pFile->h = fd;
         }else{
@@ -26591,16 +27999,11 @@
       } else {
         conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
       }
-      OSTRACE3("TAKECONCH  %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
+      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
+               rc==SQLITE_OK?"ok":"failed"));
       return rc;
-    } while (1); /* in case we need to retry the :auto: lock file - we should never get here except via the 'continue' call. */
-============================
-    } else {
-      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-    }
-    OSTRACE3("TAKECONCH  %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
-    return rc;
-<<<<<<< END MERGE CONFLICT
+    } while (1); /* in case we need to retry the :auto: lock file - 
+                 ** we should never get here except via the 'continue' call. */
   }
 }
 
@@ -26608,19 +28011,21 @@
 ** If pFile holds a lock on a conch file, then release that lock.
 */
 static int proxyReleaseConch(unixFile *pFile){
-  int rc;                     /* Subroutine return code */
+  int rc = SQLITE_OK;         /* Subroutine return code */
   proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
   unixFile *conchFile;        /* Name of the conch file */
 
   pCtx = (proxyLockingContext *)pFile->lockingContext;
   conchFile = pCtx->conchFile;
-  OSTRACE4("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
+  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
            (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), 
-           getpid());
+           getpid()));
+  if( pCtx->conchHeld>0 ){
+    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+  }
   pCtx->conchHeld = 0;
-  rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-  OSTRACE3("RELEASECONCH  %d %s\n", conchFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed"));
+  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
   return rc;
 }
 
@@ -26677,7 +28082,7 @@
   char *oldPath = pCtx->lockProxyPath;
   int rc = SQLITE_OK;
 
-  if( pFile->locktype!=NO_LOCK ){
+  if( pFile->eFileLock!=NO_LOCK ){
     return SQLITE_BUSY;
   }  
 
@@ -26714,8 +28119,8 @@
     /* afp style keeps a reference to the db path in the filePath field 
     ** of the struct */
     assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath);
-  }else
+    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath, MAXPATHLEN);
+  } else
 #endif
   if( pFile->pMethod == &dotlockIoMethods ){
     /* dot lock style uses the locking context to store the dot lock
@@ -26725,7 +28130,7 @@
   }else{
     /* all other styles use the locking context to store the db file path */
     assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strcpy(dbPath, (char *)pFile->lockingContext);
+    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
   }
   return SQLITE_OK;
 }
@@ -26744,7 +28149,7 @@
   char *lockPath=NULL;
   int rc = SQLITE_OK;
   
-  if( pFile->locktype!=NO_LOCK ){
+  if( pFile->eFileLock!=NO_LOCK ){
     return SQLITE_BUSY;
   }
   proxyGetDbPathForUnixFile(pFile, dbPath);
@@ -26754,8 +28159,8 @@
     lockPath=(char *)path;
   }
   
-  OSTRACE4("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
-           (lockPath ? lockPath : ":auto:"), getpid());
+  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
+           (lockPath ? lockPath : ":auto:"), getpid()));
 
   pCtx = sqlite3_malloc( sizeof(*pCtx) );
   if( pCtx==0 ){
@@ -26765,32 +28170,58 @@
 
   rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
   if( rc==SQLITE_OK ){
-    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile);
+    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
+    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
+      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
+      ** (c) the file system is read-only, then enable no-locking access.
+      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
+      ** that openFlags will have only one of O_RDONLY or O_RDWR.
+      */
+      struct statfs fsInfo;
+      struct stat conchInfo;
+      int goLockless = 0;
+
+      if( stat(pCtx->conchFilePath, &conchInfo) == -1 ) {
+        int err = errno;
+        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
+          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
+        }
+      }
+      if( goLockless ){
+        pCtx->conchHeld = -1; /* read only FS/ lockless */
+        rc = SQLITE_OK;
+      }
+    }
   }  
   if( rc==SQLITE_OK && lockPath ){
     pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
   }
 
   if( rc==SQLITE_OK ){
+    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
+    if( pCtx->dbPath==NULL ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK ){
     /* all memory is allocated, proxys are created and assigned, 
     ** switch the locking context and pMethod then return.
     */
-    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
     pCtx->oldLockingContext = pFile->lockingContext;
     pFile->lockingContext = pCtx;
     pCtx->pOldMethod = pFile->pMethod;
     pFile->pMethod = &proxyIoMethods;
   }else{
     if( pCtx->conchFile ){ 
-      rc = pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
-      if( rc ) return rc;
+      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
       sqlite3_free(pCtx->conchFile);
     }
+    sqlite3_free(pCtx->lockProxyPath);
     sqlite3_free(pCtx->conchFilePath); 
     sqlite3_free(pCtx);
   }
-  OSTRACE3("TRANSPROXY  %d %s\n", pFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed"));
+  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
   return rc;
 }
 
@@ -26874,14 +28305,18 @@
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    }else{ /* conchHeld < 0 is lockless */
+      pResOut=0;
+    }
   }
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -26904,34 +28339,42 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int proxyLock(sqlite3_file *id, int locktype) {
+static int proxyLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    rc = proxy->pMethod->xLock((sqlite3_file*)proxy, locktype);
-    pFile->locktype = proxy->locktype;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
   }
   return rc;
 }
 
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int proxyUnlock(sqlite3_file *id, int locktype) {
+static int proxyUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, locktype);
-    pFile->locktype = proxy->locktype;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
   }
   return rc;
 }
@@ -27023,7 +28466,7 @@
   ** that filesystem time.
   */
   #define UNIXVFS(VFSNAME, FINDER) {                        \
-    1,                    /* iVersion */                    \
+    2,                    /* iVersion */                    \
     sizeof(unixFile),     /* szOsFile */                    \
     MAX_PATHNAME,         /* mxPathname */                  \
     0,                    /* pNext */                       \
@@ -27040,7 +28483,9 @@
     unixRandomness,       /* xRandomness */                 \
     unixSleep,            /* xSleep */                      \
     unixCurrentTime,      /* xCurrentTime */                \
-    unixGetLastError      /* xGetLastError */               \
+    unixGetLastError,     /* xGetLastError */               \
+    0,                    /* xRename */                     \
+    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
   }
 
   /*
@@ -27058,7 +28503,6 @@
 #endif
     UNIXVFS("unix-none",     nolockIoFinder ),
     UNIXVFS("unix-dotfile",  dotlockIoFinder ),
-    UNIXVFS("unix-wfl",      posixWflIoFinder ),
 #if OS_VXWORKS
     UNIXVFS("unix-namedsem", semIoFinder ),
 #endif
@@ -27070,6 +28514,7 @@
 #endif
 #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
     UNIXVFS("unix-afp",      afpIoFinder ),
+    UNIXVFS("unix-nfs",      nfsIoFinder ),
     UNIXVFS("unix-proxy",    proxyIoFinder ),
 #endif
   };
@@ -27191,23 +28636,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -27393,6 +28824,10 @@
 # define FormatMessageW(a,b,c,d,e,f,g) 0
 #endif
 
+/* Forward references */
+typedef struct winShm winShm;           /* A connection to shared-memory */
+typedef struct winShmNode winShmNode;   /* A region of shared-memory */
+
 /*
 ** WinCE lacks native support for file locking so we have to fake it
 ** with some code of our own.
@@ -27412,12 +28847,15 @@
 */
 typedef struct winFile winFile;
 struct winFile {
-  const sqlite3_io_methods *pMethod;/* Must be first */
+  const sqlite3_io_methods *pMethod; /*** Must be first ***/
+  sqlite3_vfs *pVfs;      /* The VFS used to open this file */
   HANDLE h;               /* Handle for accessing the file */
   unsigned char locktype; /* Type of lock currently held on this file */
   short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
   DWORD lastErrno;        /* The Windows errno from the last I/O error */
   DWORD sectorSize;       /* Sector size of the device file is on */
+  winShm *pShm;           /* Instance of shared memory on this file */
+  const char *zPath;      /* Full pathname of this file */
 #if SQLITE_OS_WINCE
   WCHAR *zDeleteOnClose;  /* Name of file to delete when closing */
   HANDLE hMutex;          /* Mutex used to control access to shared lock */  
@@ -27945,7 +29383,8 @@
   winFile *pFile = (winFile*)id;
 
   assert( id!=0 );
-  OSTRACE2("CLOSE %d\n", pFile->h);
+  assert( pFile->pShm==0 );
+  OSTRACE(("CLOSE %d\n", pFile->h));
   do{
     rc = CloseHandle(pFile->h);
   }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (Sleep(100), 1) );
@@ -27964,6 +29403,7 @@
     free(pFile->zDeleteOnClose);
   }
 #endif
+  OSTRACE(("CLOSE %d %s\n", pFile->h, rc ? "ok" : "failed"));
   OpenCounter(-1);
   return rc ? SQLITE_OK : SQLITE_IOERR;
 }
@@ -27995,7 +29435,7 @@
 
   assert( id!=0 );
   SimulateIOError(return SQLITE_IOERR_READ);
-  OSTRACE3("READ %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("READ %d lock=%d\n", pFile->h, pFile->locktype));
   rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
   if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
@@ -28034,7 +29474,7 @@
   assert( id!=0 );
   SimulateIOError(return SQLITE_IOERR_WRITE);
   SimulateDiskfullError(return SQLITE_FULL);
-  OSTRACE3("WRITE %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("WRITE %d lock=%d\n", pFile->h, pFile->locktype));
   rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
   if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
@@ -28062,24 +29502,25 @@
 static int winTruncate(sqlite3_file *id, sqlite3_int64 nByte){
   LONG upperBits = (LONG)((nByte>>32) & 0x7fffffff);
   LONG lowerBits = (LONG)(nByte & 0xffffffff);
-  DWORD rc;
+  DWORD dwRet;
   winFile *pFile = (winFile*)id;
   DWORD error;
+  int rc = SQLITE_OK;
 
   assert( id!=0 );
-  OSTRACE3("TRUNCATE %d %lld\n", pFile->h, nByte);
+  OSTRACE(("TRUNCATE %d %lld\n", pFile->h, nByte));
   SimulateIOError(return SQLITE_IOERR_TRUNCATE);
-  rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
-  if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
+  dwRet = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
+  if( dwRet==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
-    return SQLITE_IOERR_TRUNCATE;
-  }
+    rc = SQLITE_IOERR_TRUNCATE;
   /* SetEndOfFile will fail if nByte is negative */
-  if( !SetEndOfFile(pFile->h) ){
+  }else if( !SetEndOfFile(pFile->h) ){
     pFile->lastErrno = GetLastError();
-    return SQLITE_IOERR_TRUNCATE;
+    rc = SQLITE_IOERR_TRUNCATE;
   }
-  return SQLITE_OK;
+  OSTRACE(("TRUNCATE %d %lld %s\n", pFile->h, nByte, rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
 }
 
 #ifdef SQLITE_TEST
@@ -28099,7 +29540,7 @@
   winFile *pFile = (winFile*)id;
 
   assert( id!=0 );
-  OSTRACE3("SYNC %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("SYNC %d lock=%d\n", pFile->h, pFile->locktype));
 #else
   UNUSED_PARAMETER(id);
 #endif
@@ -28240,8 +29681,8 @@
   DWORD error = NO_ERROR;
 
   assert( id!=0 );
-  OSTRACE5("LOCK %d %d was %d(%d)\n",
-          pFile->h, locktype, pFile->locktype, pFile->sharedLockByte);
+  OSTRACE(("LOCK %d %d was %d(%d)\n",
+           pFile->h, locktype, pFile->locktype, pFile->sharedLockByte));
 
   /* If there is already a lock of this type or more restrictive on the
   ** OsFile, do nothing. Don't use the end_lock: exit path, as
@@ -28271,7 +29712,7 @@
       /* Try 3 times to get the pending lock.  The pending lock might be
       ** held by another reader process who will release it momentarily.
       */
-      OSTRACE2("could not get a PENDING lock. cnt=%d\n", cnt);
+      OSTRACE(("could not get a PENDING lock. cnt=%d\n", cnt));
       Sleep(1);
     }
     gotPendingLock = res;
@@ -28316,13 +29757,13 @@
   if( locktype==EXCLUSIVE_LOCK && res ){
     assert( pFile->locktype>=SHARED_LOCK );
     res = unlockReadLock(pFile);
-    OSTRACE2("unreadlock = %d\n", res);
+    OSTRACE(("unreadlock = %d\n", res));
     res = LockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
     if( res ){
       newLocktype = EXCLUSIVE_LOCK;
     }else{
       error = GetLastError();
-      OSTRACE2("error-code = %d\n", error);
+      OSTRACE(("error-code = %d\n", error));
       getReadLock(pFile);
     }
   }
@@ -28340,8 +29781,8 @@
   if( res ){
     rc = SQLITE_OK;
   }else{
-    OSTRACE4("LOCK FAILED %d trying for %d but got %d\n", pFile->h,
-           locktype, newLocktype);
+    OSTRACE(("LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+           locktype, newLocktype));
     pFile->lastErrno = error;
     rc = SQLITE_BUSY;
   }
@@ -28361,14 +29802,14 @@
   assert( id!=0 );
   if( pFile->locktype>=RESERVED_LOCK ){
     rc = 1;
-    OSTRACE3("TEST WR-LOCK %d %d (local)\n", pFile->h, rc);
+    OSTRACE(("TEST WR-LOCK %d %d (local)\n", pFile->h, rc));
   }else{
     rc = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
     if( rc ){
       UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
     }
     rc = !rc;
-    OSTRACE3("TEST WR-LOCK %d %d (remote)\n", pFile->h, rc);
+    OSTRACE(("TEST WR-LOCK %d %d (remote)\n", pFile->h, rc));
   }
   *pResOut = rc;
   return SQLITE_OK;
@@ -28391,8 +29832,8 @@
   int rc = SQLITE_OK;
   assert( pFile!=0 );
   assert( locktype<=SHARED_LOCK );
-  OSTRACE5("UNLOCK %d to %d was %d(%d)\n", pFile->h, locktype,
-          pFile->locktype, pFile->sharedLockByte);
+  OSTRACE(("UNLOCK %d to %d was %d(%d)\n", pFile->h, locktype,
+          pFile->locktype, pFile->sharedLockByte));
   type = pFile->locktype;
   if( type>=EXCLUSIVE_LOCK ){
     UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
@@ -28428,6 +29869,11 @@
       *(int*)pArg = (int)((winFile*)id)->lastErrno;
       return SQLITE_OK;
     }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      sqlite3_int64 sz = *(sqlite3_int64*)pArg;
+      winTruncate(id, sz);
+      return SQLITE_OK;
+    }
   }
   return SQLITE_ERROR;
 }
@@ -28455,12 +29901,531 @@
   return 0;
 }
 
+/****************************************************************************
+********************************* Shared Memory *****************************
+**
+** The next subdivision of code manages the shared-memory primitives.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the winLockInfo objects used by 
+** this file, all of which may be shared by multiple threads.
+**
+** Function winShmMutexHeld() is used to assert() that the global mutex 
+** is held when required. This function is only used as part of assert() 
+** statements. e.g.
+**
+**   winShmEnterMutex()
+**     assert( winShmMutexHeld() );
+**   winEnterLeave()
+*/
+static void winShmEnterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void winShmLeaveMutex(void){
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#ifdef SQLITE_DEBUG
+static int winShmMutexHeld(void) {
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#endif
+
+/*
+** Object used to represent a single file opened and mmapped to provide
+** shared memory.  When multiple threads all reference the same
+** log-summary, each thread has its own winFile object, but they all
+** point to a single instance of this object.  In other words, each
+** log-summary is opened only once per process.
+**
+** winShmMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**      pNext 
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either winShmNode.mutex must be held or winShmNode.nRef==0 and
+** winShmMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+** To avoid deadlocks, mutex and mutexBuf are always released in the
+** reverse order that they are acquired.  mutexBuf is always acquired
+** first and released last.  This invariant is check by asserting
+** sqlite3_mutex_notheld() on mutex whenever mutexBuf is acquired or
+** released.
+*/
+struct winShmNode {
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the file */
+  winFile hFile;             /* File handle from winOpen */
+
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  struct ShmRegion {
+    HANDLE hMap;             /* File handle from CreateFileMapping */
+    void *pMap;
+  } *aRegion;
+  DWORD lastErrno;           /* The Windows errno from the last I/O error */
+
+  int nRef;                  /* Number of winShm objects pointing to this */
+  winShm *pFirst;            /* All winShm objects pointing to this */
+  winShmNode *pNext;         /* Next in list of all winShmNode objects */
+#ifdef SQLITE_DEBUG
+  u8 nextShmId;              /* Next available winShm.id value */
+#endif
+};
+
+/*
+** A global array of all winShmNode objects.
+**
+** The winShmMutexHeld() must be true while reading or writing this list.
+*/
+static winShmNode *winShmNodeList = 0;
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** winShm.pFile->mutex must be held while reading or writing the
+** winShm.pNext and winShm.locks[] elements.
+**
+** The winShm.pFile element is initialized when the object is created
+** and is read-only thereafter.
+*/
+struct winShm {
+  winShmNode *pShmNode;      /* The underlying winShmNode object */
+  winShm *pNext;             /* Next winShm with the same winShmNode */
+  u8 hasMutex;               /* True if holding the winShmNode mutex */
+  u8 hasMutexBuf;            /* True if holding pFile->mutexBuf */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection with its winShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define WIN_SHM_BASE   ((18+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
+#define WIN_SHM_DMS    (WIN_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply advisory locks for all n bytes beginning at ofst.
+*/
+#define _SHM_UNLCK  1
+#define _SHM_RDLCK  2
+#define _SHM_WRLCK  3
+static int winShmSystemLock(
+  winShmNode *pFile,    /* Apply locks to this open shared-memory segment */
+  int lockType,         /* _SHM_UNLCK, _SHM_RDLCK, or _SHM_WRLCK */
+  int ofst,             /* Offset to first byte to be locked/unlocked */
+  int nByte             /* Number of bytes to lock or unlock */
+){
+  OVERLAPPED ovlp;
+  DWORD dwFlags;
+  int rc = 0;           /* Result code form Lock/UnlockFileEx() */
+
+  /* Access to the winShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pFile->mutex) || pFile->nRef==0 );
+
+  /* Initialize the locking parameters */
+  dwFlags = LOCKFILE_FAIL_IMMEDIATELY;
+  if( lockType == _SHM_WRLCK ) dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
+
+  /* Find the first bit in lockMask that is set */
+  memset(&ovlp, 0, sizeof(OVERLAPPED));
+  ovlp.Offset = ofst;
+
+  /* Release/Acquire the system-level lock */
+  if( lockType==_SHM_UNLCK ){
+    rc = UnlockFileEx(pFile->hFile.h, 0, nByte, 0, &ovlp);
+  }else{
+    rc = LockFileEx(pFile->hFile.h, dwFlags, 0, nByte, 0, &ovlp);
+  }
+  if( !rc ){
+    OSTRACE(("SHM-LOCK %d %s ERROR 0x%08lx\n", 
+             pFile->hFile.h,
+             lockType==_SHM_UNLCK ? "UnlockFileEx" : "LockFileEx",
+             GetLastError()));
+  }
+  rc = (rc!=0) ? SQLITE_OK : SQLITE_BUSY;
+
+  return rc;
+}
+
+/* Forward references to VFS methods */
+static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
+static int winDelete(sqlite3_vfs *,const char*,int);
+
+/*
+** Purge the winShmNodeList list of all entries with winShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void winShmPurge(sqlite3_vfs *pVfs, int deleteFlag){
+  winShmNode **pp;
+  winShmNode *p;
+  assert( winShmMutexHeld() );
+  pp = &winShmNodeList;
+  while( (p = *pp)!=0 ){
+    if( p->nRef==0 ){
+      int i;
+      if( p->mutex ) sqlite3_mutex_free(p->mutex);
+      for(i=0; i<p->nRegion; i++){
+        UnmapViewOfFile(p->aRegion[i].pMap);
+        CloseHandle(p->aRegion[i].hMap);
+      }
+      if( p->hFile.h != INVALID_HANDLE_VALUE ) {
+        winClose((sqlite3_file *)&p->hFile);
+      }
+      if( deleteFlag ) winDelete(pVfs, p->zFilename, 0);
+      *pp = p->pNext;
+      sqlite3_free(p->aRegion);
+      sqlite3_free(p);
+    }else{
+      pp = &p->pNext;
+    }
+  }
+}
+
+/*
+** Open a shared-memory area.  This particular implementation uses
+** mmapped files.
+**
+** zName is a filename used to identify the shared-memory area.  The
+** implementation does not (and perhaps should not) use this name
+** directly, but rather use it as a template for finding an appropriate
+** name for the shared-memory storage.  In this implementation, the
+** string "-index" is appended to zName and used as the name of the
+** mmapped file.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int winShmOpen(
+  sqlite3_file *fd      /* The file to which to attach shared memory */
+){
+  struct winFile *pDbFd;             /* Database to which to attach SHM */
+  struct winShm *p;                  /* The connection to be opened */
+  struct winShmNode *pShmNode = 0;   /* The underlying mmapped file */
+  int rc;                            /* Result code */
+  struct winShmNode *pNew;           /* Newly allocated winShmNode */
+  int nName;                         /* Size of zName in bytes */
+
+  pDbFd = (winFile*)fd;
+  assert( pDbFd->pShm==0 );    /* Not previously opened */
+
+  /* Allocate space for the new sqlite3_shm object.  Also speculatively
+  ** allocate space for a new winShmNode and filename.
+  */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  nName = sqlite3Strlen30(pDbFd->zPath);
+  pNew = sqlite3_malloc( sizeof(*pShmNode) + nName + 15 );
+  if( pNew==0 ){
+    sqlite3_free(p);
+    return SQLITE_NOMEM;
+  }
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->zFilename = (char*)&pNew[1];
+  sqlite3_snprintf(nName+15, pNew->zFilename, "%s-wal-index", pDbFd->zPath);
+
+  /* Look to see if there is an existing winShmNode that can be used.
+  ** If no matching winShmNode currently exists, create a new one.
+  */
+  winShmEnterMutex();
+  for(pShmNode = winShmNodeList; pShmNode; pShmNode=pShmNode->pNext){
+    /* TBD need to come up with better match here.  Perhaps
+    ** use FILE_ID_BOTH_DIR_INFO Structure.
+    */
+    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
+  }
+  if( pShmNode ){
+    sqlite3_free(pNew);
+  }else{
+    pShmNode = pNew;
+    pNew = 0;
+    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
+    pShmNode->pNext = winShmNodeList;
+    winShmNodeList = pShmNode;
+
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+    rc = winOpen(pDbFd->pVfs,
+                 pShmNode->zFilename,             /* Name of the file (UTF-8) */
+                 (sqlite3_file*)&pShmNode->hFile,  /* File handle here */
+                 SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, /* Mode flags */
+                 0);
+    if( SQLITE_OK!=rc ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto shm_open_err;
+    }
+
+    /* Check to see if another process is holding the dead-man switch.
+    ** If not, truncate the file to zero length. 
+    */
+    if( winShmSystemLock(pShmNode, _SHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
+    }
+    if( rc==SQLITE_OK ){
+      winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
+    }
+    if( rc ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the winShmNode */
+  p->pShmNode = pShmNode;
+  p->pNext = pShmNode->pFirst;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->pFirst = p;
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  winShmLeaveMutex();
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  sqlite3_free(pNew);
+  winShmLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+*/
+static int winShmClose(
+  sqlite3_file *fd,          /* Database holding shared memory */
+  int deleteFlag             /* Delete after closing if true */
+){
+  winFile *pDbFd;       /* Database holding shared-memory */
+  winShm *p;            /* The connection to be closed */
+  winShmNode *pShmNode; /* The underlying shared-memory file */
+  winShm **pp;          /* For looping over sibling connections */
+
+  pDbFd = (winFile*)fd;
+  p = pDbFd->pShm;
+  pShmNode = p->pShmNode;
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  winShmEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    winShmPurge(pDbFd->pVfs, deleteFlag);
+  }
+  winShmLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** isWrite is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int winShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *p = pDbFd->pShm;
+  winShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    struct ShmRegion *apNew;           /* New aRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    sqlite3_int64 sz;                  /* Current size of wal-index file */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
+    if( rc!=SQLITE_OK ){
+      goto shmpage_out;
+    }
+
+    if( sz<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
+      if( rc!=SQLITE_OK ){
+        goto shmpage_out;
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (struct ShmRegion *)sqlite3_realloc(
+        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->aRegion = apNew;
+
+    while( pShmNode->nRegion<=iRegion ){
+      HANDLE hMap;                /* file-mapping handle */
+      void *pMap = 0;             /* Mapped memory region */
+     
+      hMap = CreateFileMapping(pShmNode->hFile.h, 
+          NULL, PAGE_READWRITE, 0, nByte, NULL
+      );
+      if( hMap ){
+        pMap = MapViewOfFile(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
+            0, 0, nByte
+        );
+      }
+      if( !pMap ){
+        pShmNode->lastErrno = GetLastError();
+        rc = SQLITE_IOERR;
+        if( hMap ) CloseHandle(hMap);
+        goto shmpage_out;
+      }
+
+      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
+      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
+    *pp = (void *)&p[iRegion*szRegion];
+  }else{
+    *pp = 0;
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+*/
+static int winShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *p = pDbFd->pShm;
+  winShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_PROTOCOL;
+
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    rc = winShmSystemLock(pShmNode, _SHM_UNLCK, ofst+WIN_SHM_BASE, n);
+  }else if( flags & SQLITE_SHM_SHARED ){
+    rc = winShmSystemLock(pShmNode, _SHM_RDLCK, ofst+WIN_SHM_BASE, n);
+  }else{
+    rc = winShmSystemLock(pShmNode, _SHM_WRLCK, ofst+WIN_SHM_BASE, n);
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d %s\n",
+           p->id, (int)GetCurrentProcessId(), rc ? "failed" : "ok"));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void winShmBarrier(
+  sqlite3_file *fd          /* Database holding the shared memory */
+){
+  /* MemoryBarrier(); // does not work -- do not know why not */
+  winShmEnterMutex();
+  winShmLeaveMutex();
+}
+
+#else
+# define winShmOpen    0
+# define winShmMap     0
+# define winShmLock    0
+# define winShmBarrier 0
+# define winShmClose   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+/*
+***************************** End Shared Memory *****************************
+****************************************************************************/
+
 /*
 ** This vector defines all the methods that can operate on an
 ** sqlite3_file for win32.
 */
 static const sqlite3_io_methods winIoMethod = {
-  1,                        /* iVersion */
+  2,                        /* iVersion */
   winClose,
   winRead,
   winWrite,
@@ -28472,7 +30437,12 @@
   winCheckReservedLock,
   winFileControl,
   winSectorSize,
-  winDeviceCharacteristics
+  winDeviceCharacteristics,
+  winShmOpen,              /* xShmOpen */
+  winShmLock,              /* xShmLock */
+  winShmMap,               /* xShmMap */
+  winShmBarrier,           /* xShmBarrier */
+  winShmClose              /* xShmClose */
 };
 
 /***************************************************************************
@@ -28554,7 +30524,7 @@
     zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
   }
   zBuf[j] = 0;
-  OSTRACE2("TEMP FILENAME: %s\n", zBuf);
+  OSTRACE(("TEMP FILENAME: %s\n", zBuf));
   return SQLITE_OK; 
 }
 
@@ -28646,6 +30616,8 @@
   assert( id!=0 );
   UNUSED_PARAMETER(pVfs);
 
+  pFile->h = INVALID_HANDLE_VALUE;
+
   /* If the second argument to this function is NULL, generate a 
   ** temporary file name to use 
   */
@@ -28727,6 +30699,9 @@
     );
 #endif
   }
+  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
+           h, zName, dwDesiredAccess, 
+           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));
   if( h==INVALID_HANDLE_VALUE ){
     free(zConverted);
     if( flags & SQLITE_OPEN_READWRITE ){
@@ -28747,6 +30722,9 @@
   pFile->pMethod = &winIoMethod;
   pFile->h = h;
   pFile->lastErrno = NO_ERROR;
+  pFile->pVfs = pVfs;
+  pFile->pShm = 0;
+  pFile->zPath = zName;
   pFile->sectorSize = getSectorSize(pVfs, zUtf8Name);
 #if SQLITE_OS_WINCE
   if( (flags & (SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_DB)) ==
@@ -28818,7 +30796,10 @@
 #endif
   }
   free(zConverted);
-  OSTRACE2("DELETE \"%s\"\n", zFilename);
+  OSTRACE(("DELETE \"%s\" %s\n", zFilename,
+       ( (rc==INVALID_FILE_ATTRIBUTES) && (error==ERROR_FILE_NOT_FOUND)) ?
+         "ok" : "failed" ));
+ 
   return (   (rc == INVALID_FILE_ATTRIBUTES) 
           && (error == ERROR_FILE_NOT_FOUND)) ? SQLITE_OK : SQLITE_IOERR_DELETE;
 }
@@ -29111,34 +31092,32 @@
 }
 
 /*
-** The following variable, if set to a non-zero value, becomes the result
-** returned from sqlite3OsCurrentTime().  This is used for testing.
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
 */
 #ifdef SQLITE_TEST
-SQLITE_API int sqlite3_current_time = 0;
+SQLITE_API int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
 #endif
 
 /*
-** Find the current time (in Universal Coordinated Time).  Write the
-** current time and date as a Julian Day number into *prNow and
-** return 0.  Return 1 if the time and date cannot be found.
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return 0.  Return 1 if the time and date cannot be found.
 */
-int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
-  FILETIME ft;
+static int winCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
   /* FILETIME structure is a 64-bit value representing the number of 
      100-nanosecond intervals since January 1, 1601 (= JD 2305813.5). 
   */
-  sqlite3_int64 timeW;   /* Whole days */
-  sqlite3_int64 timeF;   /* Fractional Days */
-
-  /* Number of 100-nanosecond intervals in a single day */
-  static const sqlite3_int64 ntuPerDay = 
-      10000000*(sqlite3_int64)86400;
-
-  /* Number of 100-nanosecond intervals in half of a day */
-  static const sqlite3_int64 ntuPerHalfDay = 
-      10000000*(sqlite3_int64)43200;
-
+  FILETIME ft;
+  static const sqlite3_int64 winFiletimeEpoch = 23058135*(sqlite3_int64)8640000;
+#ifdef SQLITE_TEST
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#endif
   /* 2^32 - to avoid use of LL and warnings in gcc */
   static const sqlite3_int64 max32BitValue = 
       (sqlite3_int64)2000000000 + (sqlite3_int64)2000000000 + (sqlite3_int64)294967296;
@@ -29153,24 +31132,36 @@
 #else
   GetSystemTimeAsFileTime( &ft );
 #endif
-  UNUSED_PARAMETER(pVfs);
-  timeW = (((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) + (sqlite3_int64)ft.dwLowDateTime;
-  timeF = timeW % ntuPerDay;          /* fractional days (100-nanoseconds) */
-  timeW = timeW / ntuPerDay;          /* whole days */
-  timeW = timeW + 2305813;            /* add whole days (from 2305813.5) */
-  timeF = timeF + ntuPerHalfDay;      /* add half a day (from 2305813.5) */
-  timeW = timeW + (timeF/ntuPerDay);  /* add whole day if half day made one */
-  timeF = timeF % ntuPerDay;          /* compute new fractional days */
-  *prNow = (double)timeW + ((double)timeF / (double)ntuPerDay);
+
+  *piNow = winFiletimeEpoch +
+            ((((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) + 
+               (sqlite3_int64)ft.dwLowDateTime)/(sqlite3_int64)1000;
+
 #ifdef SQLITE_TEST
   if( sqlite3_current_time ){
-    *prNow = ((double)sqlite3_current_time + (double)43200) / (double)86400 + (double)2440587;
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
   }
 #endif
+  UNUSED_PARAMETER(pVfs);
   return 0;
 }
 
 /*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
+  int rc;
+  sqlite3_int64 i;
+  rc = winCurrentTimeInt64(pVfs, &i);
+  if( !rc ){
+    *prNow = i/86400000.0;
+  }
+  return rc;
+}
+
+/*
 ** The idea is that this function works like a combination of
 ** GetLastError() and FormatMessage() on windows (or errno and
 ** strerror_r() on unix). After an error is returned by an OS
@@ -29205,30 +31196,33 @@
   return getLastErrorMsg(nBuf, zBuf);
 }
 
+
+
 /*
 ** Initialize and deinitialize the operating system interface.
 */
 SQLITE_API int sqlite3_os_init(void){
   static sqlite3_vfs winVfs = {
-    1,                 /* iVersion */
-    sizeof(winFile),   /* szOsFile */
-    MAX_PATH,          /* mxPathname */
-    0,                 /* pNext */
-    "win32",           /* zName */
-    0,                 /* pAppData */
- 
-    winOpen,           /* xOpen */
-    winDelete,         /* xDelete */
-    winAccess,         /* xAccess */
-    winFullPathname,   /* xFullPathname */
-    winDlOpen,         /* xDlOpen */
-    winDlError,        /* xDlError */
-    winDlSym,          /* xDlSym */
-    winDlClose,        /* xDlClose */
-    winRandomness,     /* xRandomness */
-    winSleep,          /* xSleep */
-    winCurrentTime,    /* xCurrentTime */
-    winGetLastError    /* xGetLastError */
+    2,                   /* iVersion */
+    sizeof(winFile),     /* szOsFile */
+    MAX_PATH,            /* mxPathname */
+    0,                   /* pNext */
+    "win32",             /* zName */
+    0,                   /* pAppData */
+    winOpen,             /* xOpen */
+    winDelete,           /* xDelete */
+    winAccess,           /* xAccess */
+    winFullPathname,     /* xFullPathname */
+    winDlOpen,           /* xDlOpen */
+    winDlError,          /* xDlError */
+    winDlSym,            /* xDlSym */
+    winDlClose,          /* xDlClose */
+    winRandomness,       /* xRandomness */
+    winSleep,            /* xSleep */
+    winCurrentTime,      /* xCurrentTime */
+    winGetLastError,     /* xGetLastError */
+    0,                   /* xRename */
+    winCurrentTimeInt64, /* xCurrentTimeInt64 */
   };
 
   sqlite3_vfs_register(&winVfs, 1);
@@ -29913,15 +31907,17 @@
 
   if( pPage ){
     if( !pPage->pData ){
-      memset(pPage, 0, sizeof(PgHdr) + pCache->szExtra);
-      pPage->pExtra = (void*)&pPage[1];
-      pPage->pData = (void *)&((char *)pPage)[sizeof(PgHdr) + pCache->szExtra];
+      memset(pPage, 0, sizeof(PgHdr));
+      pPage->pData = (void *)&pPage[1];
+      pPage->pExtra = (void*)&((char *)pPage->pData)[pCache->szPage];
+      memset(pPage->pExtra, 0, pCache->szExtra);
       pPage->pCache = pCache;
       pPage->pgno = pgno;
     }
     assert( pPage->pCache==pCache );
     assert( pPage->pgno==pgno );
-    assert( pPage->pExtra==(void *)&pPage[1] );
+    assert( pPage->pData==(void *)&pPage[1] );
+    assert( pPage->pExtra==(void *)&((char *)&pPage[1])[pCache->szPage] );
 
     if( 0==pPage->nRef ){
       pCache->nRef++;
@@ -30060,7 +32056,12 @@
     PgHdr *pNext;
     for(p=pCache->pDirty; p; p=pNext){
       pNext = p->pDirtyNext;
-      if( p->pgno>pgno ){
+      /* This routine never gets call with a positive pgno except right
+      ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
+      ** it must be that pgno==0.
+      */
+      assert( p->pgno>0 );
+      if( ALWAYS(p->pgno>pgno) ){
         assert( p->flags&PGHDR_DIRTY );
         sqlite3PcacheMakeClean(p);
       }
@@ -30404,6 +32405,7 @@
       int sz = sqlite3MallocSize(p);
       sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
     }
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
   }
   return p;
 }
@@ -30421,7 +32423,10 @@
     pSlot->pNext = pcache1.pFree;
     pcache1.pFree = pSlot;
   }else{
-    int iSize = sqlite3MallocSize(p);
+    int iSize;
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+    iSize = sqlite3MallocSize(p);
     sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
     sqlite3_free(p);
   }
@@ -30943,7 +32948,7 @@
 ** already provided an alternative.
 */
 SQLITE_PRIVATE void sqlite3PCacheSetDefault(void){
-  static sqlite3_pcache_methods defaultMethods = {
+  static const sqlite3_pcache_methods defaultMethods = {
     0,                       /* pArg */
     pcache1Init,             /* xInit */
     pcache1Shutdown,         /* xShutdown */
@@ -31456,6 +33461,197 @@
 ** another is writing.
 */
 #ifndef SQLITE_OMIT_DISKIO
+/************** Include wal.h in the middle of pager.c ***********************/
+/************** Begin file wal.h *********************************************/
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface to the write-ahead logging 
+** system. Refer to the comments below and the header comment attached to 
+** the implementation of each function in log.c for further details.
+*/
+
+#ifndef _WAL_H_
+#define _WAL_H_
+
+
+#ifdef SQLITE_OMIT_WAL
+# define sqlite3WalOpen(x,y,z)                 0
+# define sqlite3WalClose(w,x,y,z)              0
+# define sqlite3WalBeginReadTransaction(y,z)   0
+# define sqlite3WalEndReadTransaction(z)
+# define sqlite3WalRead(v,w,x,y,z)             0
+# define sqlite3WalDbsize(y,z)
+# define sqlite3WalBeginWriteTransaction(y)    0
+# define sqlite3WalEndWRiteTransaction(x)      0
+# define sqlite3WalUndo(x,y,z)                 0
+# define sqlite3WalSavepoint(y,z)
+# define sqlite3WalSavepointUndo(y,z)          0
+# define sqlite3WalFrames(u,v,w,x,y,z)         0
+# define sqlite3WalCheckpoint(u,v,w,x)         0
+# define sqlite3WalCallback(z)                 0
+#else
+
+#define WAL_SAVEPOINT_NDATA 4
+
+/* Connection to a write-ahead log (WAL) file. 
+** There is one object of this type for each pager. 
+*/
+typedef struct Wal Wal;
+
+/* Open and close a connection to a write-ahead log. */
+SQLITE_PRIVATE int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *zName, Wal**);
+SQLITE_PRIVATE int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
+
+/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
+** snapshot is like a read-transaction.  It is the state of the database
+** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
+** preserves the current state even if the other threads or processes
+** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
+** transaction and releases the lock.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
+SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal);
+
+/* Read a page from the write-ahead log, if it is present. */
+SQLITE_PRIVATE int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);
+
+/* Return the size of the database as it existed at the beginning
+** of the snapshot */
+SQLITE_PRIVATE void sqlite3WalDbsize(Wal *pWal, Pgno *pPgno);
+
+/* Obtain or release the WRITER lock. */
+SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal);
+SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal);
+
+/* Undo any frames written (but not committed) to the log */
+SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
+
+/* Return an integer that records the current (uncommitted) write
+** position in the WAL */
+SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
+
+/* Move the write position of the WAL back to iFrame.  Called in
+** response to a ROLLBACK TO command. */
+SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
+
+/* Write a frame or frames to the log. */
+SQLITE_PRIVATE int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
+
+/* Copy pages from the log to the database file */ 
+SQLITE_PRIVATE int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Write-ahead log connection */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of buffer nBuf */
+  u8 *zBuf                        /* Temporary buffer to use */
+);
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal);
+
+/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
+** by the pager layer on the database file.
+*/
+SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op);
+
+#endif /* ifndef SQLITE_OMIT_WAL */
+#endif /* _WAL_H_ */
+
+/************** End of wal.h *************************************************/
+/************** Continuing where we left off in pager.c **********************/
+
+/*
+******************** NOTES ON THE DESIGN OF THE PAGER ************************
+**
+** Within this comment block, a page is deemed to have been synced
+** automatically as soon as it is written when PRAGMA synchronous=OFF.
+** Otherwise, the page is not synced until the xSync method of the VFS
+** is called successfully on the file containing the page.
+**
+** Definition:  A page of the database file is said to be "overwriteable" if
+** one or more of the following are true about the page:
+** 
+**     (a)  The original content of the page as it was at the beginning of
+**          the transaction has been written into the rollback journal and
+**          synced.
+** 
+**     (b)  The page was a freelist leaf page at the start of the transaction.
+** 
+**     (c)  The page number is greater than the largest page that existed in
+**          the database file at the start of the transaction.
+** 
+** (1) A page of the database file is never overwritten unless one of the
+**     following are true:
+** 
+**     (a) The page and all other pages on the same sector are overwriteable.
+** 
+**     (b) The atomic page write optimization is enabled, and the entire
+**         transaction other than the update of the transaction sequence
+**         number consists of a single page change.
+** 
+** (2) The content of a page written into the rollback journal exactly matches
+**     both the content in the database when the rollback journal was written
+**     and the content in the database at the beginning of the current
+**     transaction.
+** 
+** (3) Writes to the database file are an integer multiple of the page size
+**     in length and are aligned to a page boundary.
+** 
+** (4) Reads from the database file are either aligned on a page boundary and
+**     an integer multiple of the page size in length or are taken from the
+**     first 100 bytes of the database file.
+** 
+** (5) All writes to the database file are synced prior to the rollback journal
+**     being deleted, truncated, or zeroed.
+** 
+** (6) If a master journal file is used, then all writes to the database file
+**     are synced prior to the master journal being deleted.
+** 
+** Definition: Two databases (or the same database at two points it time)
+** are said to be "logically equivalent" if they give the same answer to
+** all queries.  Note in particular the the content of freelist leaf
+** pages can be changed arbitarily without effecting the logical equivalence
+** of the database.
+** 
+** (7) At any time, if any subset, including the empty set and the total set,
+**     of the unsynced changes to a rollback journal are removed and the 
+**     journal is rolled back, the resulting database file will be logical
+**     equivalent to the database file at the beginning of the transaction.
+** 
+** (8) When a transaction is rolled back, the xTruncate method of the VFS
+**     is called to restore the database file to the same size it was at
+**     the beginning of the transaction.  (In some VFSes, the xTruncate
+**     method is a no-op, but that does not change the fact the SQLite will
+**     invoke it.)
+** 
+** (9) Whenever the database file is modified, at least one bit in the range
+**     of bytes from 24 through 39 inclusive will be changed prior to releasing
+**     the EXCLUSIVE lock.
+**
+** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
+**      than one billion transactions.
+**
+** (11) A database file is well-formed at the beginning and at the conclusion
+**      of every transaction.
+**
+** (12) An EXCLUSIVE lock is held on the database file when writing to
+**      the database file.
+**
+** (13) A SHARED lock is held on the database file while reading any
+**      content out of the database file.
+*/
 
 /*
 ** Macros for troubleshooting.  Normally turned off
@@ -31575,6 +33771,7 @@
   Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
   Pgno nOrig;                  /* Original number of pages in file */
   Pgno iSubRec;                /* Index of first record in sub-journal */
+  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
 };
 
 /*
@@ -31604,6 +33801,8 @@
 **   transaction was opened. The contents of all three of these variables is
 **   only guaranteed to be correct if the boolean Pager.dbSizeValid is true.
 **
+**   The dbFileSize value is not set or used in WAL mode.
+**
 **   TODO: Under what conditions is dbSizeValid set? Cleared?
 **
 ** changeCountDone
@@ -31633,7 +33832,8 @@
 **
 ** journalStarted
 **
-**   This flag is set whenever the the main journal is synced. 
+**   This flag is set whenever the the main journal is opened and
+**   initialized
 **
 **   The point of this flag is that it must be set after the 
 **   first journal header in a journal file has been synced to disk.
@@ -31659,7 +33859,10 @@
 **
 ** doNotSync
 **
-**   This variable is set and cleared by sqlite3PagerWrite().
+**   When enabled, cache spills are prohibited and the journal file cannot
+**   be synced.  This variable is set and cleared by sqlite3PagerWrite() 
+**   in order to prevent a journal sync from happening in between the
+**   journalling of two pages on the same sector.
 **
 ** needSync
 **
@@ -31719,6 +33922,7 @@
   sqlite3_file *sjfd;         /* File descriptor for sub-journal */
   i64 journalOff;             /* Current write offset in the journal file */
   i64 journalHdr;             /* Byte offset to previous journal header */
+  i64 journalSizeLimit;       /* Size limit for persistent journal files */
   PagerSavepoint *aSavepoint; /* Array of active savepoints */
   int nSavepoint;             /* Number of elements in aSavepoint[] */
   char dbFileVers[16];        /* Changes whenever database file changes */
@@ -31745,9 +33949,11 @@
   void *pCodec;               /* First argument to xCodec... methods */
 #endif
   char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
-  i64 journalSizeLimit;       /* Size limit for persistent journal files */
   PCache *pPCache;            /* Pointer to page cache object */
   sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
+#ifndef SQLITE_OMIT_WAL
+  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
+#endif
 };
 
 /*
@@ -32261,6 +34467,7 @@
   for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
     IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
     rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
+    assert( pPager->journalHdr <= pPager->journalOff );
     pPager->journalOff += nHeader;
   }
 
@@ -32419,6 +34626,7 @@
   }
   pPager->setMaster = 1;
   assert( isOpen(pPager->jfd) );
+  assert( pPager->journalHdr <= pPager->journalOff );
 
   /* Calculate the length in bytes and the checksum of zMaster */
   for(nMaster=0; zMaster[nMaster]; nMaster++){
@@ -32535,6 +34743,22 @@
 }
 
 /*
+** Return true if this pager uses a write-ahead log instead of the usual
+** rollback journal. Otherwise false.
+*/
+#ifndef SQLITE_OMIT_WAL
+static int pagerUseWal(Pager *pPager){
+  return (pPager->pWal!=0);
+}
+#else
+# define pagerUseWal(x) 0
+# define pagerRollbackWal(x) 0
+# define pagerWalFrames(v,w,x,y,z) 0
+# define pagerOpenWalIfPresent(z) SQLITE_OK
+# define pagerBeginReadTransaction(z) SQLITE_OK
+#endif
+
+/*
 ** Unlock the database file. This function is a no-op if the pager
 ** is in exclusive mode.
 **
@@ -32546,7 +34770,7 @@
 */
 static void pager_unlock(Pager *pPager){
   if( !pPager->exclusiveMode ){
-    int rc;                      /* Return code */
+    int rc = SQLITE_OK;          /* Return code */
 
     /* Always close the journal file when dropping the database lock.
     ** Otherwise, another connection with journal_mode=delete might
@@ -32559,12 +34783,17 @@
 
     /* If the file is unlocked, somebody else might change it. The
     ** values stored in Pager.dbSize etc. might become invalid if
-    ** this happens. TODO: Really, this doesn't need to be cleared
+    ** this happens.  One can argue that this doesn't need to be cleared
     ** until the change-counter check fails in PagerSharedLock().
+    ** Clearing the page size cache here is being conservative.
     */
     pPager->dbSizeValid = 0;
 
-    rc = osUnlock(pPager->fd, NO_LOCK);
+    if( pagerUseWal(pPager) ){
+      sqlite3WalEndReadTransaction(pPager->pWal);
+    }else{
+      rc = osUnlock(pPager->fd, NO_LOCK);
+    }
     if( rc ){
       pPager->errCode = rc;
     }
@@ -32713,6 +34942,7 @@
 
   assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
   if( isOpen(pPager->jfd) ){
+    assert( !pagerUseWal(pPager) );
 
     /* Finalize the journal file. */
     if( sqlite3IsMemJournal(pPager->jfd) ){
@@ -32726,8 +34956,8 @@
       }
       pPager->journalOff = 0;
       pPager->journalStarted = 0;
-    }else if( pPager->exclusiveMode 
-     || pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
     ){
       rc = zeroJournalHdr(pPager, hasMaster);
       pager_error(pPager, rc);
@@ -32737,9 +34967,11 @@
       /* This branch may be executed with Pager.journalMode==MEMORY if
       ** a hot-journal was just rolled back. In this case the journal
       ** file should be closed and deleted. If this connection writes to
-      ** the database file, it will do so using an in-memory journal.  */
+      ** the database file, it will do so using an in-memory journal. 
+      */
       assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
            || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
       );
       sqlite3OsClose(pPager->jfd);
       if( !pPager->tempFile ){
@@ -32750,14 +34982,30 @@
 #ifdef SQLITE_CHECK_PAGES
     sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
 #endif
-
-    sqlite3PcacheCleanAll(pPager->pPCache);
-    sqlite3BitvecDestroy(pPager->pInJournal);
-    pPager->pInJournal = 0;
-    pPager->nRec = 0;
   }
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  pPager->nRec = 0;
+  sqlite3PcacheCleanAll(pPager->pPCache);
 
-  if( !pPager->exclusiveMode ){
+  if( pagerUseWal(pPager) ){
+    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
+    assert( rc2==SQLITE_OK );
+    pPager->state = PAGER_SHARED;
+
+    /* If the connection is not in locking_mode=exclusive mode then note
+    ** that the change counter is now invalid.  Also drop the EXCLUSIVE
+    ** lock if we currently hold it.  (We might be holding the EXCLUSIVE
+    ** lock if we were in locking_mode=exclusive but recently changed back
+    ** to locking_mode=normal.)
+    */
+    if( !pPager->exclusiveMode ){
+      pPager->changeCountDone = 0;
+      if( sqlite3WalExclusiveMode(pPager->pWal, 0) ){
+        rc2 = osUnlock(pPager->fd, SHARED_LOCK);
+      }
+    }
+  }else if( !pPager->exclusiveMode ){
     rc2 = osUnlock(pPager->fd, SHARED_LOCK);
     pPager->state = PAGER_SHARED;
     pPager->changeCountDone = 0;
@@ -32848,11 +35096,10 @@
 */
 static int pager_playback_one_page(
   Pager *pPager,                /* The pager being played back */
-  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
-  int isUnsync,                 /* True if reading from unsynced main journal */
   i64 *pOffset,                 /* Offset of record to playback */
-  int isSavepnt,                /* True for a savepoint rollback */
-  Bitvec *pDone                 /* Bitvec of pages already played back */
+  Bitvec *pDone,                /* Bitvec of pages already played back */
+  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
+  int isSavepnt                 /* True for a savepoint rollback */
 ){
   int rc;
   PgHdr *pPg;                   /* An existing page in the cache */
@@ -32860,6 +35107,7 @@
   u32 cksum;                    /* Checksum used for sanity checking */
   char *aData;                  /* Temporary storage for the page */
   sqlite3_file *jfd;            /* The file descriptor for the journal file */
+  int isSynced;                 /* True if journal page is synced */
 
   assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
   assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
@@ -32868,6 +35116,7 @@
 
   aData = pPager->pTmpSpace;
   assert( aData );         /* Temp storage must have already been allocated */
+  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
 
   /* Read the page number and page data from the journal or sub-journal
   ** file. Return an error code to the caller if an IO error occurs.
@@ -32937,18 +35186,28 @@
   ** is possible to fail a statement on a database that does not yet exist.
   ** Do not attempt to write if database file has never been opened.
   */
-  pPg = pager_lookup(pPager, pgno);
+  if( pagerUseWal(pPager) ){
+    pPg = 0;
+  }else{
+    pPg = pager_lookup(pPager, pgno);
+  }
   assert( pPg || !MEMDB );
   PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
            PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
            (isMainJrnl?"main-journal":"sub-journal")
   ));
+  if( isMainJrnl ){
+    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
+  }else{
+    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
+  }
   if( (pPager->state>=PAGER_EXCLUSIVE)
-   && (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
    && isOpen(pPager->fd)
-   && !isUnsync
+   && isSynced
   ){
     i64 ofst = (pgno-1)*(i64)pPager->pageSize;
+    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
+    assert( !pagerUseWal(pPager) );
     rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst);
     if( pgno>pPager->dbFileSize ){
       pPager->dbFileSize = pgno;
@@ -32997,7 +35256,8 @@
       /* If the contents of this page were just restored from the main 
       ** journal file, then its content must be as they were when the 
       ** transaction was first opened. In this case we can mark the page
-      ** as clean, since there will be no need to write it out to the.
+      ** as clean, since there will be no need to write it out to the
+      ** database.
       **
       ** There is one exception to this rule. If the page is being rolled
       ** back as part of a savepoint (or statement) rollback from an 
@@ -33012,6 +35272,7 @@
       ** segment is synced. If a crash occurs during or following this,
       ** database corruption may ensue.
       */
+      assert( !pagerUseWal(pPager) );
       sqlite3PcacheMakeClean(pPg);
     }
 #ifdef SQLITE_CHECK_PAGES
@@ -33344,8 +35605,6 @@
   ** occurs. 
   */
   while( 1 ){
-    int isUnsync = 0;
-
     /* Read the next journal header from the journal file.  If there are
     ** not enough bytes left in the journal file for a complete header, or
     ** it is corrupted, then a process must of failed while writing it.
@@ -33386,7 +35645,6 @@
     if( nRec==0 && !isHot &&
         pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
       nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
-      isUnsync = 1;
     }
 
     /* If this is the first header read from the journal, truncate the
@@ -33408,12 +35666,20 @@
         pager_reset(pPager);
         needPagerReset = 0;
       }
-      rc = pager_playback_one_page(pPager,1,isUnsync,&pPager->journalOff,0,0);
+      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
       if( rc!=SQLITE_OK ){
         if( rc==SQLITE_DONE ){
           rc = SQLITE_OK;
           pPager->journalOff = szJ;
           break;
+        }else if( rc==SQLITE_IOERR_SHORT_READ ){
+          /* If the journal has been truncated, simply stop reading and
+          ** processing the journal. This might happen if the journal was
+          ** not completely written and synced prior to a crash.  In that
+          ** case, the database should have never been written in the
+          ** first place so it is OK to simply abandon the rollback. */
+          rc = SQLITE_OK;
+          goto end_playback;
         }else{
           /* If we are unable to rollback, quit and return the error
           ** code.  This will cause the pager to enter the error state
@@ -33458,6 +35724,9 @@
   if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){
     rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
   }
+  if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){
+    rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+  }
   if( rc==SQLITE_OK ){
     rc = pager_end_transaction(pPager, zMaster[0]!='\0');
     testcase( rc!=SQLITE_OK );
@@ -33478,6 +35747,265 @@
   return rc;
 }
 
+
+/*
+** Read the content for page pPg out of the database file and into 
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
+*/
+static int readDbPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+  Pgno pgno = pPg->pgno;       /* Page number to read */
+  int rc = SQLITE_OK;          /* Return code */
+  int isInWal = 0;             /* True if page is in log file */
+  int pgsz = pPager->pageSize; /* Number of bytes to read */
+
+  assert( pPager->state>=PAGER_SHARED && !MEMDB );
+  assert( isOpen(pPager->fd) );
+
+  if( NEVER(!isOpen(pPager->fd)) ){
+    assert( pPager->tempFile );
+    memset(pPg->pData, 0, pPager->pageSize);
+    return SQLITE_OK;
+  }
+
+  if( pagerUseWal(pPager) ){
+    /* Try to pull the page from the write-ahead log. */
+    rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pgsz, pPg->pData);
+  }
+  if( rc==SQLITE_OK && !isInWal ){
+    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
+    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+
+  if( pgno==1 ){
+    if( rc ){
+      /* If the read is unsuccessful, set the dbFileVers[] to something
+      ** that will never be a valid file version.  dbFileVers[] is a copy
+      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
+      ** zero or the size of the database in page. Bytes 32..35 and 35..39
+      ** should be page numbers which are never 0xffffffff.  So filling
+      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
+      **
+      ** For an encrypted database, the situation is more complex:  bytes
+      ** 24..39 of the database are white noise.  But the probability of
+      ** white noising equaling 16 bytes of 0xff is vanishingly small so
+      ** we should still be ok.
+      */
+      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+    }else{
+      u8 *dbFileVers = &((u8*)pPg->pData)[24];
+      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+    }
+  }
+  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
+
+  PAGER_INCR(sqlite3_pager_readdb_count);
+  PAGER_INCR(pPager->nRead);
+  IOTRACE(("PGIN %p %d\n", pPager, pgno));
+  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
+               PAGERID(pPager), pgno, pager_pagehash(pPg)));
+
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is invoked once for each page that has already been 
+** written into the log file when a WAL transaction is rolled back.
+** Parameter iPg is the page number of said page. The pCtx argument 
+** is actually a pointer to the Pager structure.
+**
+** If page iPg is present in the cache, and has no outstanding references,
+** it is discarded. Otherwise, if there are one or more outstanding
+** references, the page content is reloaded from the database. If the
+** attempt to reload content from the database is required and fails, 
+** return an SQLite error code. Otherwise, SQLITE_OK.
+*/
+static int pagerUndoCallback(void *pCtx, Pgno iPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = (Pager *)pCtx;
+  PgHdr *pPg;
+
+  pPg = sqlite3PagerLookup(pPager, iPg);
+  if( pPg ){
+    if( sqlite3PcachePageRefcount(pPg)==1 ){
+      sqlite3PcacheDrop(pPg);
+    }else{
+      rc = readDbPage(pPg);
+      if( rc==SQLITE_OK ){
+        pPager->xReiniter(pPg);
+      }
+      sqlite3PagerUnref(pPg);
+    }
+  }
+
+  /* Normally, if a transaction is rolled back, any backup processes are
+  ** updated as data is copied out of the rollback journal and into the
+  ** database. This is not generally possible with a WAL database, as
+  ** rollback involves simply truncating the log file. Therefore, if one
+  ** or more frames have already been written to the log (and therefore 
+  ** also copied into the backup databases) as part of this transaction,
+  ** the backups must be restarted.
+  */
+  sqlite3BackupRestart(pPager->pBackup);
+
+  return rc;
+}
+
+/*
+** This function is called to rollback a transaction on a WAL database.
+*/
+static int pagerRollbackWal(Pager *pPager){
+  int rc;                         /* Return Code */
+  PgHdr *pList;                   /* List of dirty pages to revert */
+
+  /* For all pages in the cache that are currently dirty or have already
+  ** been written (but not committed) to the log file, do one of the 
+  ** following:
+  **
+  **   + Discard the cached page (if refcount==0), or
+  **   + Reload page content from the database (if refcount>0).
+  */
+  pPager->dbSize = pPager->dbOrigSize;
+  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  while( pList && rc==SQLITE_OK ){
+    PgHdr *pNext = pList->pDirty;
+    rc = pagerUndoCallback((void *)pPager, pList->pgno);
+    pList = pNext;
+  }
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around sqlite3WalFrames(). As well as logging
+** the contents of the list of pages headed by pList (connected by pDirty),
+** this function notifies any active backup processes that the pages have
+** changed. 
+*/ 
+static int pagerWalFrames(
+  Pager *pPager,                  /* Pager object */
+  PgHdr *pList,                   /* List of frames to log */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Return code */
+
+  assert( pPager->pWal );
+  rc = sqlite3WalFrames(pPager->pWal, 
+      pPager->pageSize, pList, nTruncate, isCommit, sync_flags
+  );
+  if( rc==SQLITE_OK && pPager->pBackup ){
+    PgHdr *p;
+    for(p=pList; p; p=p->pDirty){
+      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
+    }
+  }
+  return rc;
+}
+
+/*
+** Begin a read transaction on the WAL.
+**
+** This routine used to be called "pagerOpenSnapshot()" because it essentially
+** makes a snapshot of the database at the current point in time and preserves
+** that snapshot for use by the reader in spite of concurrently changes by
+** other writers or checkpointers.
+*/
+static int pagerBeginReadTransaction(Pager *pPager){
+  int rc;                         /* Return code */
+  int changed = 0;                /* True if cache must be reset */
+
+  assert( pagerUseWal(pPager) );
+
+  /* sqlite3WalEndReadTransaction() was not called for the previous
+  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
+  ** are in locking_mode=NORMAL and EndRead() was previously called,
+  ** the duplicate call is harmless.
+  */
+  sqlite3WalEndReadTransaction(pPager->pWal);
+
+  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
+  if( rc==SQLITE_OK ){
+    int dummy;
+    if( changed ){
+      pager_reset(pPager);
+      assert( pPager->errCode || pPager->dbSizeValid==0 );
+    }
+    rc = sqlite3PagerPagecount(pPager, &dummy);
+  }
+  pPager->state = PAGER_SHARED;
+
+  return rc;
+}
+
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists. Assuming no error occurs, set *pExists to 1 if the file exists,
+** or 0 otherwise and return SQLITE_OK. If an IO or OOM error occurs, return
+** an SQLite error code.
+*/
+static int pagerHasWAL(Pager *pPager, int *pExists){
+  int rc;                         /* Return code */
+  char *zWal;                     /* Name of the WAL file */
+
+  assert( !pPager->tempFile );
+  zWal = sqlite3_mprintf("%s-wal", pPager->zFilename);
+  if( !zWal ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3OsAccess(pPager->pVfs, zWal, SQLITE_ACCESS_EXISTS, pExists);
+    sqlite3_free(zWal);
+  }
+  return rc;
+}
+
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists. If it does, open the pager in WAL mode. Otherwise, if no error
+** occurs, make sure Pager.journalMode is not set to PAGER_JOURNALMODE_WAL.
+** If an IO or OOM error occurs, return an SQLite error code.
+**
+** If the WAL file is opened, also open a snapshot (read transaction).
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function. Because an EXCLUSIVE lock on the db file is required to delete 
+** a WAL, this ensures there is no race condition between the xAccess() 
+** below and an xDelete() being executed by some other connection.
+*/
+static int pagerOpenWalIfPresent(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->tempFile ){
+    int isWal;                    /* True if WAL file exists */
+    rc = pagerHasWAL(pPager, &isWal);
+    if( rc==SQLITE_OK ){
+      if( isWal ){
+        pager_reset(pPager);
+        rc = sqlite3PagerOpenWal(pPager, 0);
+        if( rc==SQLITE_OK ){
+          rc = pagerBeginReadTransaction(pPager);
+        }
+      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
+      }
+    }
+  }
+  return rc;
+}
+#endif
+
 /*
 ** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
 ** the entire master journal file. The case pSavepoint==NULL occurs when 
@@ -33535,12 +36063,17 @@
   */
   pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
 
+  if( !pSavepoint && pagerUseWal(pPager) ){
+    return pagerRollbackWal(pPager);
+  }
+
   /* Use pPager->journalOff as the effective size of the main rollback
   ** journal.  The actual file might be larger than this in
   ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
   ** past pPager->journalOff is off-limits to us.
   */
   szJ = pPager->journalOff;
+  assert( pagerUseWal(pPager)==0 || szJ==0 );
 
   /* Begin by rolling back records from the main journal starting at
   ** PagerSavepoint.iOffset and continuing to the next journal header.
@@ -33549,11 +36082,11 @@
   ** will be skipped automatically.  Pages are added to pDone as they
   ** are played back.
   */
-  if( pSavepoint ){
+  if( pSavepoint && !pagerUseWal(pPager) ){
     iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
     pPager->journalOff = pSavepoint->iOffset;
     while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
-      rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
     }
     assert( rc!=SQLITE_DONE );
   }else{
@@ -33583,7 +36116,7 @@
       nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
     }
     for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
-      rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
     }
     assert( rc!=SQLITE_DONE );
   }
@@ -33596,9 +36129,13 @@
   if( pSavepoint ){
     u32 ii;            /* Loop counter */
     i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize);
+
+    if( pagerUseWal(pPager) ){
+      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
+    }
     for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
       assert( offset==ii*(4+pPager->pageSize) );
-      rc = pager_playback_one_page(pPager, 0, 0, &offset, 1, pDone);
+      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
     }
     assert( rc!=SQLITE_DONE );
   }
@@ -33607,6 +36144,7 @@
   if( rc==SQLITE_OK ){
     pPager->journalOff = szJ;
   }
+
   return rc;
 }
 
@@ -33819,10 +36357,14 @@
 ** Regardless of mxPage, return the current maximum page count.
 */
 SQLITE_PRIVATE int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
+  int nPage;
   if( mxPage>0 ){
     pPager->mxPgno = mxPage;
   }
-  sqlite3PagerPagecount(pPager, 0);
+  if( pPager->state!=PAGER_UNLOCK ){
+    sqlite3PagerPagecount(pPager, &nPage);
+    assert( pPager->mxPgno>=nPage );
+  }
   return pPager->mxPgno;
 }
 
@@ -33868,6 +36410,22 @@
   int rc = SQLITE_OK;
   memset(pDest, 0, N);
   assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  /* This routine is only called by btree immediately after creating
+  ** the Pager object.  There has not been an opportunity to transition
+  ** to WAL mode yet.
+  */
+  assert( !pagerUseWal(pPager) );
+#if 0
+  if( pagerUseWal(pPager) ){
+    int isInWal = 0;
+    rc = sqlite3WalRead(pPager->pWal, 1, &isInWal, N, pDest);
+    if( rc!=SQLITE_OK || isInWal ){
+      return rc;
+    }
+  }
+#endif
+
   if( isOpen(pPager->fd) ){
     IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
     rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
@@ -33894,12 +36452,7 @@
 ** and *pnPage is set to the number of pages in the database.
 */
 SQLITE_PRIVATE int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
-  Pgno nPage;               /* Value to return via *pnPage */
-
-  /* If the pager is already in the error state, return the error code. */
-  if( pPager->errCode ){
-    return pPager->errCode;
-  }
+  Pgno nPage = 0;           /* Value to return via *pnPage */
 
   /* Determine the number of pages in the file. Store this in nPage. */
   if( pPager->dbSizeValid ){
@@ -33908,15 +36461,23 @@
     int rc;                 /* Error returned by OsFileSize() */
     i64 n = 0;              /* File size in bytes returned by OsFileSize() */
 
-    assert( isOpen(pPager->fd) || pPager->tempFile );
-    if( isOpen(pPager->fd) && (0 != (rc = sqlite3OsFileSize(pPager->fd, &n))) ){
-      pager_error(pPager, rc);
-      return rc;
+    if( pagerUseWal(pPager) && pPager->state!=PAGER_UNLOCK ){
+      sqlite3WalDbsize(pPager->pWal, &nPage);
     }
-    if( n>0 && n<pPager->pageSize ){
-      nPage = 1;
-    }else{
-      nPage = (Pgno)(n / pPager->pageSize);
+
+    if( nPage==0 ){
+      assert( isOpen(pPager->fd) || pPager->tempFile );
+      if( isOpen(pPager->fd) ){
+        if( SQLITE_OK!=(rc = sqlite3OsFileSize(pPager->fd, &n)) ){
+          pager_error(pPager, rc);
+          return rc;
+        }
+      }
+      if( n>0 && n<pPager->pageSize ){
+        nPage = 1;
+      }else{
+        nPage = (Pgno)(n / pPager->pageSize);
+      }
     }
     if( pPager->state!=PAGER_UNLOCK ){
       pPager->dbSize = nPage;
@@ -33934,9 +36495,7 @@
   }
 
   /* Set the output variable and return SQLITE_OK */
-  if( pnPage ){
-    *pnPage = nPage;
-  }
+  *pnPage = nPage;
   return SQLITE_OK;
 }
 
@@ -34041,6 +36600,32 @@
   assertTruncateConstraint(pPager);
 }
 
+
+/*
+** This function is called before attempting a hot-journal rollback. It
+** syncs the journal file to disk, then sets pPager->journalHdr to the
+** size of the journal file so that the pager_playback() routine knows
+** that the entire journal file has been synced.
+**
+** Syncing a hot-journal to disk before attempting to roll it back ensures 
+** that if a power-failure occurs during the rollback, the process that
+** attempts rollback following system recovery sees the same journal
+** content as this process.
+**
+** If everything goes as planned, SQLITE_OK is returned. Otherwise, 
+** an SQLite error code.
+*/
+static int pagerSyncHotJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->noSync ){
+    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
+  }
+  return rc;
+}
+
 /*
 ** Shutdown the page cache.  Free all memory and close all files.
 **
@@ -34056,10 +36641,19 @@
 ** to the caller.
 */
 SQLITE_PRIVATE int sqlite3PagerClose(Pager *pPager){
+  u8 *pTmp = (u8 *)pPager->pTmpSpace;
+
   disable_simulated_io_errors();
   sqlite3BeginBenignMalloc();
   pPager->errCode = 0;
   pPager->exclusiveMode = 0;
+#ifndef SQLITE_OMIT_WAL
+  sqlite3WalClose(pPager->pWal,
+    (pPager->noSync ? 0 : pPager->sync_flags), 
+    pPager->pageSize, pTmp
+  );
+  pPager->pWal = 0;
+#endif
   pager_reset(pPager);
   if( MEMDB ){
     pager_unlock(pPager);
@@ -34070,7 +36664,9 @@
     ** be played back into the database. If a power failure occurs while
     ** this is happening, the database may become corrupt.
     */
-    pPager->journalHdr = -1;
+    if( isOpen(pPager->jfd) ){
+      pPager->errCode = pagerSyncHotJournal(pPager);
+    }
     pagerUnlockAndRollback(pPager);
   }
   sqlite3EndBenignMalloc();
@@ -34078,7 +36674,7 @@
   PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
   IOTRACE(("CLOSE %p\n", pPager))
   sqlite3OsClose(pPager->fd);
-  sqlite3PageFree(pPager->pTmpSpace);
+  sqlite3PageFree(pTmp);
   sqlite3PcacheClose(pPager->pPCache);
 
 #ifdef SQLITE_HAS_CODEC
@@ -34160,7 +36756,7 @@
         ** mode, then the journal file may at this point actually be larger
         ** than Pager.journalOff bytes. If the next thing in the journal
         ** file happens to be a journal-header (written as part of the
-        ** previous connections transaction), and a crash or power-failure 
+        ** previous connection's transaction), and a crash or power-failure 
         ** occurs after nRec is updated but before this connection writes 
         ** anything else to the journal file (or commits/rolls back its 
         ** transaction), then SQLite may become confused when doing the 
@@ -34179,10 +36775,10 @@
         */
         i64 iNextHdrOffset;
         u8 aMagic[8];
-	u8 zHeader[sizeof(aJournalMagic)+4];
+        u8 zHeader[sizeof(aJournalMagic)+4];
 
-	memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-	put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
+        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
 
         iNextHdrOffset = journalHdrOffset(pPager);
         rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
@@ -34214,7 +36810,7 @@
         IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
         rc = sqlite3OsWrite(
             pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
-	);
+        );
         if( rc!=SQLITE_OK ) return rc;
       }
       if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
@@ -34232,6 +36828,7 @@
     */
     pPager->needSync = 0;
     pPager->journalStarted = 1;
+    pPager->journalHdr = pPager->journalOff;
     sqlite3PcacheClearSyncFlags(pPager->pPCache);
   }
 
@@ -34293,6 +36890,7 @@
   ** EXCLUSIVE, it means the database file has been changed and any rollback
   ** will require a journal playback.
   */
+  assert( !pagerUseWal(pList->pPager) );
   assert( pPager->state>=PAGER_RESERVED );
   rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
 
@@ -34305,6 +36903,14 @@
     rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
   }
 
+  /* Before the first write, give the VFS a hint of what the final
+  ** file size will be.
+  */
+  if( pPager->dbSize > (pPager->dbOrigSize+1) && isOpen(pPager->fd) ){
+    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
+    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
+  }
+
   while( rc==SQLITE_OK && pList ){
     Pgno pgno = pList->pgno;
 
@@ -34314,9 +36920,7 @@
     ** any such pages to the file.
     **
     ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
-    ** set (set by sqlite3PagerDontWrite()).  Note that if compiled with
-    ** SQLITE_SECURE_DELETE the PGHDR_DONT_WRITE bit is never set and so
-    ** the second test is always true.
+    ** set (set by sqlite3PagerDontWrite()).
     */
     if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
       i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
@@ -34360,6 +36964,26 @@
 }
 
 /*
+** Ensure that the sub-journal file is open. If it is already open, this 
+** function is a no-op.
+**
+** SQLITE_OK is returned if everything goes according to plan. An 
+** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() 
+** fails.
+*/
+static int openSubJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !isOpen(pPager->sjfd) ){
+    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
+      sqlite3MemJournalOpen(pPager->sjfd);
+    }else{
+      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
+    }
+  }
+  return rc;
+}
+
+/*
 ** Append a record of the current state of page pPg to the sub-journal. 
 ** It is the callers responsibility to use subjRequiresPage() to check 
 ** that it is really required before calling this function.
@@ -34375,18 +36999,31 @@
 static int subjournalPage(PgHdr *pPg){
   int rc = SQLITE_OK;
   Pager *pPager = pPg->pPager;
-  if( isOpen(pPager->sjfd) ){
-    void *pData = pPg->pData;
-    i64 offset = pPager->nSubRec*(4+pPager->pageSize);
-    char *pData2;
+  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
 
-    CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-    PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
-  
-    assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize );
-    rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+    /* Open the sub-journal, if it has not already been opened */
+    assert( pPager->useJournal );
+    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
+    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
+    assert( pagerUseWal(pPager) 
+         || pageInJournal(pPg) 
+         || pPg->pgno>pPager->dbOrigSize 
+    );
+    rc = openSubJournal(pPager);
+
+    /* If the sub-journal was opened successfully (or was already open),
+    ** write the journal record into the file.  */
     if( rc==SQLITE_OK ){
-      rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      void *pData = pPg->pData;
+      i64 offset = pPager->nSubRec*(4+pPager->pageSize);
+      char *pData2;
+  
+      CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
+      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
+      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      }
     }
   }
   if( rc==SQLITE_OK ){
@@ -34397,7 +37034,6 @@
   return rc;
 }
 
-
 /*
 ** This function is called by the pcache layer when it has reached some
 ** soft memory limit. The first argument is a pointer to a Pager object
@@ -34424,74 +37060,84 @@
   assert( pPg->pPager==pPager );
   assert( pPg->flags&PGHDR_DIRTY );
 
-  /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
-  ** is journalling a set of two or more database pages that are stored
-  ** on the same disk sector. Syncing the journal is not allowed while
-  ** this is happening as it is important that all members of such a
-  ** set of pages are synced to disk together. So, if the page this function
-  ** is trying to make clean will require a journal sync and the doNotSync
-  ** flag is set, return without doing anything. The pcache layer will
-  ** just have to go ahead and allocate a new page buffer instead of
-  ** reusing pPg.
-  **
-  ** Similarly, if the pager has already entered the error state, do not
-  ** try to write the contents of pPg to disk.
-  */
-  if( NEVER(pPager->errCode)
-   || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC)
-  ){
-    return SQLITE_OK;
-  }
-
-  /* Sync the journal file if required. */
-  if( pPg->flags&PGHDR_NEED_SYNC ){
-    rc = syncJournal(pPager);
-    if( rc==SQLITE_OK && pPager->fullSync && 
-      !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
-      !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
-    ){
-      pPager->nRec = 0;
-      rc = writeJournalHdr(pPager);
+  pPg->pDirty = 0;
+  if( pagerUseWal(pPager) ){
+    /* Write a single frame for this page to the log. */
+    if( subjRequiresPage(pPg) ){ 
+      rc = subjournalPage(pPg); 
     }
-  }
-
-  /* If the page number of this page is larger than the current size of
-  ** the database image, it may need to be written to the sub-journal.
-  ** This is because the call to pager_write_pagelist() below will not
-  ** actually write data to the file in this case.
-  **
-  ** Consider the following sequence of events:
-  **
-  **   BEGIN;
-  **     <journal page X>
-  **     <modify page X>
-  **     SAVEPOINT sp;
-  **       <shrink database file to Y pages>
-  **       pagerStress(page X)
-  **     ROLLBACK TO sp;
-  **
-  ** If (X>Y), then when pagerStress is called page X will not be written
-  ** out to the database file, but will be dropped from the cache. Then,
-  ** following the "ROLLBACK TO sp" statement, reading page X will read
-  ** data from the database file. This will be the copy of page X as it
-  ** was when the transaction started, not as it was when "SAVEPOINT sp"
-  ** was executed.
-  **
-  ** The solution is to write the current data for page X into the 
-  ** sub-journal file now (if it is not already there), so that it will
-  ** be restored to its current value when the "ROLLBACK TO sp" is 
-  ** executed.
-  */
-  if( NEVER(
-      rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
-  ) ){
-    rc = subjournalPage(pPg);
-  }
-
-  /* Write the contents of the page out to the database file. */
-  if( rc==SQLITE_OK ){
-    pPg->pDirty = 0;
-    rc = pager_write_pagelist(pPg);
+    if( rc==SQLITE_OK ){
+      rc = pagerWalFrames(pPager, pPg, 0, 0, 0);
+    }
+  }else{
+    /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
+    ** is journalling a set of two or more database pages that are stored
+    ** on the same disk sector. Syncing the journal is not allowed while
+    ** this is happening as it is important that all members of such a
+    ** set of pages are synced to disk together. So, if the page this function
+    ** is trying to make clean will require a journal sync and the doNotSync
+    ** flag is set, return without doing anything. The pcache layer will
+    ** just have to go ahead and allocate a new page buffer instead of
+    ** reusing pPg.
+    **
+    ** Similarly, if the pager has already entered the error state, do not
+    ** try to write the contents of pPg to disk.
+    */
+    if( NEVER(pPager->errCode)
+     || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC)
+    ){
+      return SQLITE_OK;
+    }
+  
+    /* Sync the journal file if required. */
+    if( pPg->flags&PGHDR_NEED_SYNC ){
+      rc = syncJournal(pPager);
+      if( rc==SQLITE_OK && pPager->fullSync && 
+        !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
+        !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
+      ){
+        pPager->nRec = 0;
+        rc = writeJournalHdr(pPager);
+      }
+    }
+  
+    /* If the page number of this page is larger than the current size of
+    ** the database image, it may need to be written to the sub-journal.
+    ** This is because the call to pager_write_pagelist() below will not
+    ** actually write data to the file in this case.
+    **
+    ** Consider the following sequence of events:
+    **
+    **   BEGIN;
+    **     <journal page X>
+    **     <modify page X>
+    **     SAVEPOINT sp;
+    **       <shrink database file to Y pages>
+    **       pagerStress(page X)
+    **     ROLLBACK TO sp;
+    **
+    ** If (X>Y), then when pagerStress is called page X will not be written
+    ** out to the database file, but will be dropped from the cache. Then,
+    ** following the "ROLLBACK TO sp" statement, reading page X will read
+    ** data from the database file. This will be the copy of page X as it
+    ** was when the transaction started, not as it was when "SAVEPOINT sp"
+    ** was executed.
+    **
+    ** The solution is to write the current data for page X into the 
+    ** sub-journal file now (if it is not already there), so that it will
+    ** be restored to its current value when the "ROLLBACK TO sp" is 
+    ** executed.
+    */
+    if( NEVER(
+        rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
+    ) ){
+      rc = subjournalPage(pPg);
+    }
+  
+    /* Write the contents of the page out to the database file. */
+    if( rc==SQLITE_OK ){
+      rc = pager_write_pagelist(pPg);
+    }
   }
 
   /* Mark the page as clean. */
@@ -34780,6 +37426,7 @@
   /* pPager->pBusyHandlerArg = 0; */
   pPager->xReiniter = xReinit;
   /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+
   *ppPager = pPager;
   return SQLITE_OK;
 }
@@ -34899,51 +37546,6 @@
 }
 
 /*
-** Read the content for page pPg out of the database file and into 
-** pPg->pData. A shared lock or greater must be held on the database
-** file before this function is called.
-**
-** If page 1 is read, then the value of Pager.dbFileVers[] is set to
-** the value read from the database file.
-**
-** If an IO error occurs, then the IO error is returned to the caller.
-** Otherwise, SQLITE_OK is returned.
-*/
-static int readDbPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
-  Pgno pgno = pPg->pgno;       /* Page number to read */
-  int rc;                      /* Return code */
-  i64 iOffset;                 /* Byte offset of file to read from */
-
-  assert( pPager->state>=PAGER_SHARED && !MEMDB );
-  assert( isOpen(pPager->fd) );
-
-  if( NEVER(!isOpen(pPager->fd)) ){
-    assert( pPager->tempFile );
-    memset(pPg->pData, 0, pPager->pageSize);
-    return SQLITE_OK;
-  }
-  iOffset = (pgno-1)*(i64)pPager->pageSize;
-  rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
-  if( rc==SQLITE_IOERR_SHORT_READ ){
-    rc = SQLITE_OK;
-  }
-  if( pgno==1 ){
-    u8 *dbFileVers = &((u8*)pPg->pData)[24];
-    memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
-  }
-  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
-
-  PAGER_INCR(sqlite3_pager_readdb_count);
-  PAGER_INCR(pPager->nRead);
-  IOTRACE(("PGIN %p %d\n", pPager, pgno));
-  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
-               PAGERID(pPager), pgno, pager_pagehash(pPg)));
-
-  return rc;
-}
-
-/*
 ** This function is called to obtain a shared lock on the database file.
 ** It is illegal to call sqlite3PagerAcquire() until after this function
 ** has been successfully called. If a shared-lock is already held when
@@ -34996,7 +37598,9 @@
     pager_reset(pPager);
   }
 
-  if( pPager->state==PAGER_UNLOCK || isErrorReset ){
+  if( pagerUseWal(pPager) ){
+    rc = pagerBeginReadTransaction(pPager);
+  }else if( pPager->state==PAGER_UNLOCK || isErrorReset ){
     sqlite3_vfs * const pVfs = pPager->pVfs;
     int isHotJournal = 0;
     assert( !MEMDB );
@@ -35079,19 +37683,28 @@
         goto failed;
       }
 
-      /* TODO: Why are these cleared here? Is it necessary? */
+      /* Reset the journal status fields to indicates that we have no
+      ** rollback journal at this time. */
       pPager->journalStarted = 0;
       pPager->journalOff = 0;
       pPager->setMaster = 0;
       pPager->journalHdr = 0;
  
+      /* Make sure the journal file has been synced to disk. */
+ 
       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock. Purge the cache before
       ** playing back the hot-journal so that we don't end up with
-      ** an inconsistent cache.
+      ** an inconsistent cache.  Sync the hot journal before playing
+      ** it back since the process that crashed and left the hot journal
+      ** probably did not sync it and we are required to always sync
+      ** the journal before playing it back.
       */
       if( isOpen(pPager->jfd) ){
-        rc = pager_playback(pPager, 1);
+        rc = pagerSyncHotJournal(pPager);
+        if( rc==SQLITE_OK ){
+          rc = pager_playback(pPager, 1);
+        }
         if( rc!=SQLITE_OK ){
           rc = pager_error(pPager, rc);
           goto failed;
@@ -35109,7 +37722,7 @@
       ** has been modified.  If the database has changed, flush the
       ** cache.
       **
-      ** Database changes is detected by looking at 15 bytes beginning
+      ** Database changes is detected by looking at 16 bytes beginning
       ** at offset 24 into the file.  The first 4 of these 16 bytes are
       ** a 32-bit counter that is incremented with each change.  The
       ** other bytes change randomly with each file change when
@@ -35119,16 +37732,16 @@
       ** detected.  The chance of an undetected change is so small that
       ** it can be neglected.
       */
+      int nPage;
       char dbFileVers[sizeof(pPager->dbFileVers)];
-      sqlite3PagerPagecount(pPager, 0);
+      sqlite3PagerPagecount(pPager, &nPage);
 
       if( pPager->errCode ){
         rc = pPager->errCode;
         goto failed;
       }
 
-      assert( pPager->dbSizeValid );
-      if( pPager->dbSize>0 ){
+      if( nPage>0 ){
         IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
         rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
         if( rc!=SQLITE_OK ){
@@ -35143,6 +37756,11 @@
       }
     }
     assert( pPager->exclusiveMode || pPager->state==PAGER_SHARED );
+
+    /* If there is a WAL file in the file-system, open this database in WAL
+    ** mode. Otherwise, the following function call is a no-op.
+    */
+    rc = pagerOpenWalIfPresent(pPager);
   }
 
  failed:
@@ -35197,7 +37815,7 @@
 **   a) When reading a free-list leaf page from the database, and
 **
 **   b) When a savepoint is being rolled back and we need to load
-**      a new page into the cache to populate with the data read
+**      a new page into the cache to be filled with the data read
 **      from the savepoint journal.
 **
 ** If noContent is true, then the data returned is zeroed instead of
@@ -35253,7 +37871,7 @@
   assert( (*ppPage)->pgno==pgno );
   assert( (*ppPage)->pPager==pPager || (*ppPage)->pPager==0 );
 
-  if( (*ppPage)->pPager ){
+  if( (*ppPage)->pPager && !noContent ){
     /* In this case the pcache already contains an initialized copy of
     ** the page. Return without further ado.  */
     assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
@@ -35283,8 +37901,8 @@
 
     if( MEMDB || nMax<(int)pgno || noContent || !isOpen(pPager->fd) ){
       if( pgno>pPager->mxPgno ){
-	rc = SQLITE_FULL;
-	goto pager_acquire_err;
+        rc = SQLITE_FULL;
+        goto pager_acquire_err;
       }
       if( noContent ){
         /* Failure to set the bits in the InJournal bit-vectors is benign.
@@ -35369,27 +37987,6 @@
 }
 
 /*
-** If the main journal file has already been opened, ensure that the
-** sub-journal file is open too. If the main journal is not open,
-** this function is a no-op.
-**
-** SQLITE_OK is returned if everything goes according to plan. 
-** An SQLITE_IOERR_XXX error code is returned if a call to 
-** sqlite3OsOpen() fails.
-*/
-static int openSubJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ){
-    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
-      sqlite3MemJournalOpen(pPager->sjfd);
-    }else{
-      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
-    }
-  }
-  return rc;
-}
-
-/*
 ** This function is called at the start of every write transaction.
 ** There must already be a RESERVED or EXCLUSIVE lock on the database 
 ** file when this routine is called.
@@ -35413,6 +38010,7 @@
 */
 static int pager_open_journal(Pager *pPager){
   int rc = SQLITE_OK;                        /* Return code */
+  int nPage;                                 /* Size of database file */
   sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
 
   assert( pPager->state>=PAGER_RESERVED );
@@ -35425,13 +38023,10 @@
   ** an error state. */
   if( NEVER(pPager->errCode) ) return pPager->errCode;
 
-  /* TODO: Is it really possible to get here with dbSizeValid==0? If not,
-  ** the call to PagerPagecount() can be removed.
-  */
   testcase( pPager->dbSizeValid==0 );
-  sqlite3PagerPagecount(pPager, 0);
-
-  pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
+  rc = sqlite3PagerPagecount(pPager, &nPage);
+  if( rc ) return rc;
+  pPager->pInJournal = sqlite3BitvecCreate(nPage);
   if( pPager->pInJournal==0 ){
     return SQLITE_NOMEM;
   }
@@ -35473,9 +38068,6 @@
     pPager->journalHdr = 0;
     rc = writeJournalHdr(pPager);
   }
-  if( rc==SQLITE_OK && pPager->nSavepoint ){
-    rc = openSubJournal(pPager);
-  }
 
   if( rc!=SQLITE_OK ){
     sqlite3BitvecDestroy(pPager->pInJournal);
@@ -35513,29 +38105,64 @@
   int rc = SQLITE_OK;
   assert( pPager->state!=PAGER_UNLOCK );
   pPager->subjInMemory = (u8)subjInMemory;
+
   if( pPager->state==PAGER_SHARED ){
     assert( pPager->pInJournal==0 );
     assert( !MEMDB && !pPager->tempFile );
 
-    /* Obtain a RESERVED lock on the database file. If the exFlag parameter
-    ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
-    ** busy-handler callback can be used when upgrading to the EXCLUSIVE
-    ** lock, but not when obtaining the RESERVED lock.
-    */
-    rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
-    if( rc==SQLITE_OK ){
-      pPager->state = PAGER_RESERVED;
-      if( exFlag ){
-        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+    if( pagerUseWal(pPager) ){
+      /* If the pager is configured to use locking_mode=exclusive, and an
+      ** exclusive lock on the database is not already held, obtain it now.
+      */
+      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
+        rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
+        pPager->state = PAGER_SHARED;
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        sqlite3WalExclusiveMode(pPager->pWal, 1);
+      }
+
+      /* Grab the write lock on the log file. If successful, upgrade to
+      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
+      ** The busy-handler is not invoked if another connection already
+      ** holds the write-lock. If possible, the upper layer will call it.
+      **
+      ** WAL mode sets Pager.state to PAGER_RESERVED when it has an open
+      ** transaction, but never to PAGER_EXCLUSIVE. This is because in 
+      ** PAGER_EXCLUSIVE state the code to roll back savepoint transactions
+      ** may copy data from the sub-journal into the database file as well
+      ** as into the page cache. Which would be incorrect in WAL mode.
+      */
+      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
+      if( rc==SQLITE_OK ){
+        pPager->dbOrigSize = pPager->dbSize;
+        pPager->state = PAGER_RESERVED;
+        pPager->journalOff = 0;
+      }
+
+      assert( rc!=SQLITE_OK || pPager->state==PAGER_RESERVED );
+      assert( rc==SQLITE_OK || pPager->state==PAGER_SHARED );
+    }else{
+      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
+      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
+      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
+      ** lock, but not when obtaining the RESERVED lock.
+      */
+      rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
+      if( rc==SQLITE_OK ){
+        pPager->state = PAGER_RESERVED;
+        if( exFlag ){
+          rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+        }
       }
     }
 
-    /* If the required locks were successfully obtained, open the journal
-    ** file and write the first journal-header to it.
+    /* No need to open the journal file at this time.  It will be
+    ** opened before it is written to.  If we defer opening the journal,
+    ** we might save the work of creating a file if the transaction
+    ** ends up being a no-op.
     */
-    if( rc==SQLITE_OK && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-      rc = pager_open_journal(pPager);
-    }
   }else if( isOpen(pPager->jfd) && pPager->journalOff==0 ){
     /* This happens when the pager was in exclusive-access mode the last
     ** time a (read or write) transaction was successfully concluded
@@ -35543,6 +38170,7 @@
     ** kept open and either was truncated to 0 bytes or its header was
     ** overwritten with zeros.
     */
+    assert( pagerUseWal(pPager)==0 );
     assert( pPager->nRec==0 );
     assert( pPager->dbOrigSize==0 );
     assert( pPager->pInJournal==0 );
@@ -35550,7 +38178,6 @@
   }
 
   PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
-  assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK );
   if( rc!=SQLITE_OK ){
     assert( !pPager->dbModified );
     /* Ignore any IO error that occurs within pager_end_transaction(). The
@@ -35580,8 +38207,8 @@
   */
   assert( pPager->state>=PAGER_RESERVED );
 
-  /* If an error has been previously detected, we should not be
-  ** calling this routine.  Repeat the error for robustness.
+  /* If an error has been previously detected, report the same error
+  ** again.
   */
   if( NEVER(pPager->errCode) )  return pPager->errCode;
 
@@ -35598,6 +38225,7 @@
   */
   sqlite3PcacheMakeDirty(pPg);
   if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
+    assert( !pagerUseWal(pPager) );
     pPager->dbModified = 1;
   }else{
 
@@ -35606,14 +38234,17 @@
     ** or both.
     **
     ** Higher level routines should have already started a transaction,
-    ** which means they have acquired the necessary locks and opened
-    ** a rollback journal.  Double-check to makes sure this is the case.
+    ** which means they have acquired the necessary locks but the rollback
+    ** journal might not yet be open.
     */
     rc = sqlite3PagerBegin(pPager, 0, pPager->subjInMemory);
-    if( NEVER(rc!=SQLITE_OK) ){
+    if( rc!=SQLITE_OK ){
       return rc;
     }
-    if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+    if( !isOpen(pPager->jfd) 
+     && pPager->journalMode!=PAGER_JOURNALMODE_OFF 
+     && !pagerUseWal(pPager)
+    ){
       assert( pPager->useJournal );
       rc = pager_open_journal(pPager);
       if( rc!=SQLITE_OK ) return rc;
@@ -35625,6 +38256,7 @@
     ** the transaction journal if it is not there already.
     */
     if( !pageInJournal(pPg) && isOpen(pPager->jfd) ){
+      assert( !pagerUseWal(pPager) );
       if( pPg->pgno<=pPager->dbOrigSize ){
         u32 cksum;
         char *pData2;
@@ -35633,6 +38265,8 @@
         ** contains the database locks.  The following assert verifies
         ** that we do not. */
         assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
+
+        assert( pPager->journalHdr <= pPager->journalOff );
         CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
         cksum = pager_cksum(pPager, (u8*)pData2);
         rc = write32bits(pPager->jfd, pPager->journalOff, pPg->pgno);
@@ -35752,7 +38386,8 @@
     */
     pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
 
-    sqlite3PagerPagecount(pPager, (int *)&nPageCount);
+    rc = sqlite3PagerPagecount(pPager, (int *)&nPageCount);
+    if( rc ) return rc;
     if( pPg->pgno>nPageCount ){
       nPage = (pPg->pgno - pg1)+1;
     }else if( (pg1+nPagePerSector-1)>nPageCount ){
@@ -35824,7 +38459,6 @@
 }
 #endif
 
-#ifndef SQLITE_SECURE_DELETE
 /*
 ** A call to this routine tells the pager that it is not necessary to
 ** write the information on page pPg back to the disk, even though
@@ -35850,7 +38484,6 @@
 #endif
   }
 }
-#endif /* !defined(SQLITE_SECURE_DELETE) */
 
 /*
 ** This routine is called to increment the value of the database file 
@@ -35915,6 +38548,12 @@
       change_counter++;
       put32bits(((char*)pPgHdr->pData)+24, change_counter);
 
+      /* Also store the SQLite version number in bytes 96..99 and in
+      ** bytes 92..95 store the change counter for which the version number
+      ** is valid. */
+      put32bits(((char*)pPgHdr->pData)+92, change_counter);
+      put32bits(((char*)pPgHdr->pData)+96, SQLITE_VERSION_NUMBER);
+
       /* If running in direct mode, write the contents of page 1 to the file. */
       if( DIRECT_MODE ){
         const void *zBuf = pPgHdr->pData;
@@ -35988,9 +38627,7 @@
   /* The dbOrigSize is never set if journal_mode=OFF */
   assert( pPager->journalMode!=PAGER_JOURNALMODE_OFF || pPager->dbOrigSize==0 );
 
-  /* If a prior error occurred, this routine should not be called.  ROLLBACK
-  ** is the appropriate response to an error, not COMMIT.  Guard against
-  ** coding errors by repeating the prior error. */
+  /* If a prior error occurred, report that error again. */
   if( NEVER(pPager->errCode) ) return pPager->errCode;
 
   PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
@@ -36003,129 +38640,156 @@
     */
     sqlite3BackupRestart(pPager->pBackup);
   }else if( pPager->state!=PAGER_SYNCED && pPager->dbModified ){
-
-    /* The following block updates the change-counter. Exactly how it
-    ** does this depends on whether or not the atomic-update optimization
-    ** was enabled at compile time, and if this transaction meets the 
-    ** runtime criteria to use the operation: 
-    **
-    **    * The file-system supports the atomic-write property for
-    **      blocks of size page-size, and 
-    **    * This commit is not part of a multi-file transaction, and
-    **    * Exactly one page has been modified and store in the journal file.
-    **
-    ** If the optimization was not enabled at compile time, then the
-    ** pager_incr_changecounter() function is called to update the change
-    ** counter in 'indirect-mode'. If the optimization is compiled in but
-    ** is not applicable to this transaction, call sqlite3JournalCreate()
-    ** to make sure the journal file has actually been created, then call
-    ** pager_incr_changecounter() to update the change-counter in indirect
-    ** mode. 
-    **
-    ** Otherwise, if the optimization is both enabled and applicable,
-    ** then call pager_incr_changecounter() to update the change-counter
-    ** in 'direct' mode. In this case the journal file will never be
-    ** created for this transaction.
-    */
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-    PgHdr *pPg;
-    assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF );
-    if( !zMaster && isOpen(pPager->jfd) 
-     && pPager->journalOff==jrnlBufferSize(pPager) 
-     && pPager->dbSize>=pPager->dbFileSize
-     && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
-    ){
-      /* Update the db file change counter via the direct-write method. The 
-      ** following call will modify the in-memory representation of page 1 
-      ** to include the updated change counter and then write page 1 
-      ** directly to the database file. Because of the atomic-write 
-      ** property of the host file-system, this is safe.
-      */
-      rc = pager_incr_changecounter(pPager, 1);
-    }else{
-      rc = sqlite3JournalCreate(pPager->jfd);
-      if( rc==SQLITE_OK ){
-        rc = pager_incr_changecounter(pPager, 0);
-      }
-    }
-#else
-    rc = pager_incr_changecounter(pPager, 0);
-#endif
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* If this transaction has made the database smaller, then all pages
-    ** being discarded by the truncation must be written to the journal
-    ** file. This can only happen in auto-vacuum mode.
-    **
-    ** Before reading the pages with page numbers larger than the 
-    ** current value of Pager.dbSize, set dbSize back to the value
-    ** that it took at the start of the transaction. Otherwise, the
-    ** calls to sqlite3PagerGet() return zeroed pages instead of 
-    ** reading data from the database file.
-    **
-    ** When journal_mode==OFF the dbOrigSize is always zero, so this
-    ** block never runs if journal_mode=OFF.
-    */
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pPager->dbSize<pPager->dbOrigSize 
-     && ALWAYS(pPager->journalMode!=PAGER_JOURNALMODE_OFF)
-    ){
-      Pgno i;                                   /* Iterator variable */
-      const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
-      const Pgno dbSize = pPager->dbSize;       /* Database image size */ 
-      pPager->dbSize = pPager->dbOrigSize;
-      for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
-        if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
-          PgHdr *pPage;             /* Page to journal */
-          rc = sqlite3PagerGet(pPager, i, &pPage);
-          if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-          rc = sqlite3PagerWrite(pPage);
-          sqlite3PagerUnref(pPage);
-          if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+    if( pagerUseWal(pPager) ){
+      PgHdr *pList;
+      pList = sqlite3PcacheDirtyList(pPager->pPCache);
+      if( pList ){
+        /* If page 1 has been modified (for example to change file-size or
+        ** the number of freelist blocks) then it will be first on the list.
+        ** Only increment the change-counter in WAL mode if page 1 is changing
+        ** anyhow, so as to avoid unnecessarily writing copies of page 1 into
+        ** the WAL.  We do not require the change-counter for change 
+        ** detection in WAL mode since the wal-index will show when the 
+        ** database has changed and a cache flush is needed.  But it does not
+        ** hurt to increment the change-counter either.
+        */
+        if( pList->pgno==1 ){
+          testcase( pPager->changeCountDone );
+          pager_incr_changecounter(pPager, 0);
         }
-      } 
-      pPager->dbSize = dbSize;
-    }
-#endif
 
-    /* Write the master journal name into the journal file. If a master 
-    ** journal file name has already been written to the journal file, 
-    ** or if zMaster is NULL (no master journal), then this call is a no-op.
-    */
-    rc = writeMasterJournal(pPager, zMaster);
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* Sync the journal file. If the atomic-update optimization is being
-    ** used, this call will not create the journal file or perform any
-    ** real IO.
-    */
-    rc = syncJournal(pPager);
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* Write all dirty pages to the database file. */
-    rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache));
-    if( rc!=SQLITE_OK ){
-      assert( rc!=SQLITE_IOERR_BLOCKED );
-      goto commit_phase_one_exit;
-    }
-    sqlite3PcacheCleanAll(pPager->pPCache);
-
-    /* If the file on disk is not the same size as the database image,
-    ** then use pager_truncate to grow or shrink the file here.
-    */
-    if( pPager->dbSize!=pPager->dbFileSize ){
-      Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
-      assert( pPager->state>=PAGER_EXCLUSIVE );
-      rc = pager_truncate(pPager, nNew);
+        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1, 
+            (pPager->fullSync ? pPager->sync_flags : 0)
+        );
+      }
+      if( rc==SQLITE_OK ){
+        sqlite3PcacheCleanAll(pPager->pPCache);
+      }
+    }else{
+      /* The following block updates the change-counter. Exactly how it
+      ** does this depends on whether or not the atomic-update optimization
+      ** was enabled at compile time, and if this transaction meets the 
+      ** runtime criteria to use the operation: 
+      **
+      **    * The file-system supports the atomic-write property for
+      **      blocks of size page-size, and 
+      **    * This commit is not part of a multi-file transaction, and
+      **    * Exactly one page has been modified and store in the journal file.
+      **
+      ** If the atomic-update optimization was not enabled at compile time,
+      ** then the pager_incr_changecounter() function is always called to
+      ** update the change counter in 'indirect-mode' since that is the only
+      ** safe way to update the change counter if we do not have atomic-write
+      ** capability.
+      **
+      ** If the atomic-write optimization is available and if the creation
+      ** of a rollback journal file can be avoided by writing page 1 separately
+      ** from the transaction (in other words, if the tranaction only involves
+      ** changing one other page in the database) then try to update the
+      ** change counter using an atomic write.  Otherwise, we have to fall
+      ** back to using a rollback journal.
+      */
+  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
+      PgHdr *pPg;
+      assert( isOpen(pPager->jfd)
+           || pPager->journalMode==PAGER_JOURNALMODE_OFF );
+      if( !zMaster && isOpen(pPager->jfd) 
+       && pPager->journalOff==jrnlBufferSize(pPager) 
+       && pPager->dbSize>=pPager->dbFileSize
+       && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
+      ){
+        /* Update the db file change counter via the direct-write method. The 
+        ** following call will modify the in-memory representation of page 1 
+        ** to include the updated change counter and then write page 1 
+        ** directly to the database file. Because of the atomic-write 
+        ** property of the host file-system, this is safe.
+        */
+        rc = pager_incr_changecounter(pPager, 1);
+      }else{
+        rc = sqlite3JournalCreate(pPager->jfd);
+        if( rc==SQLITE_OK ){
+          rc = pager_incr_changecounter(pPager, 0);
+        }
+      }
+  #else
+      rc = pager_incr_changecounter(pPager, 0);
+  #endif
       if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* If this transaction has made the database smaller, then all pages
+      ** being discarded by the truncation must be written to the journal
+      ** file. This can only happen in auto-vacuum mode.
+      **
+      ** Before reading the pages with page numbers larger than the 
+      ** current value of Pager.dbSize, set dbSize back to the value
+      ** that it took at the start of the transaction. Otherwise, the
+      ** calls to sqlite3PagerGet() return zeroed pages instead of 
+      ** reading data from the database file.
+      **
+      ** When journal_mode==OFF the dbOrigSize is always zero, so this
+      ** block never runs if journal_mode=OFF.
+      */
+  #ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pPager->dbSize<pPager->dbOrigSize 
+       && ALWAYS(pPager->journalMode!=PAGER_JOURNALMODE_OFF)
+      ){
+        Pgno i;                                   /* Iterator variable */
+        const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
+        const Pgno dbSize = pPager->dbSize;       /* Database image size */ 
+        pPager->dbSize = pPager->dbOrigSize;
+        for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
+          if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
+            PgHdr *pPage;             /* Page to journal */
+            rc = sqlite3PagerGet(pPager, i, &pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+            rc = sqlite3PagerWrite(pPage);
+            sqlite3PagerUnref(pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+          }
+        }
+        pPager->dbSize = dbSize;
+      } 
+  #endif
+  
+      /* Write the master journal name into the journal file. If a master 
+      ** journal file name has already been written to the journal file, 
+      ** or if zMaster is NULL (no master journal), then this call is a no-op.
+      */
+      rc = writeMasterJournal(pPager, zMaster);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* Sync the journal file. If the atomic-update optimization is being
+      ** used, this call will not create the journal file or perform any
+      ** real IO.
+      */
+      rc = syncJournal(pPager);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* Write all dirty pages to the database file. */
+      rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache));
+      if( rc!=SQLITE_OK ){
+        assert( rc!=SQLITE_IOERR_BLOCKED );
+        goto commit_phase_one_exit;
+      }
+      sqlite3PcacheCleanAll(pPager->pPCache);
+  
+      /* If the file on disk is not the same size as the database image,
+      ** then use pager_truncate to grow or shrink the file here.
+      */
+      if( pPager->dbSize!=pPager->dbFileSize ){
+        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
+        assert( pPager->state>=PAGER_EXCLUSIVE );
+        rc = pager_truncate(pPager, nNew);
+        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+      }
+  
+      /* Finally, sync the database file. */
+      if( !pPager->noSync && !noSync ){
+        rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+      }
+      IOTRACE(("DBSYNC %p\n", pPager))
     }
 
-    /* Finally, sync the database file. */
-    if( !pPager->noSync && !noSync ){
-      rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
-    }
-    IOTRACE(("DBSYNC %p\n", pPager))
-
     pPager->state = PAGER_SYNCED;
   }
 
@@ -36233,7 +38897,14 @@
 SQLITE_PRIVATE int sqlite3PagerRollback(Pager *pPager){
   int rc = SQLITE_OK;                  /* Return code */
   PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
-  if( !pPager->dbModified || !isOpen(pPager->jfd) ){
+  if( pagerUseWal(pPager) ){
+    int rc2;
+
+    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
+    rc2 = pager_end_transaction(pPager, pPager->setMaster);
+    if( rc==SQLITE_OK ) rc = rc2;
+    rc = pager_error(pPager, rc);
+  }else if( !pPager->dbModified || !isOpen(pPager->jfd) ){
     rc = pager_end_transaction(pPager, pPager->setMaster);
   }else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
     if( pPager->state>=PAGER_EXCLUSIVE ){
@@ -36281,6 +38952,16 @@
 }
 
 /*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager *pPager){
+  int perPageSize = pPager->pageSize + pPager->nExtra + 20;
+  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+           + sqlite3MallocSize(pPager);
+}
+
+/*
 ** Return the number of references to the specified page.
 */
 SQLITE_PRIVATE int sqlite3PagerPageRefcount(DbPage *pPage){
@@ -36332,11 +39013,10 @@
   if( nSavepoint>nCurrent && pPager->useJournal ){
     int ii;                                 /* Iterator variable */
     PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */
+    int nPage;                              /* Size of database file */
 
-    /* Either there is no active journal or the sub-journal is open or 
-    ** the journal is always stored in memory */
-    assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) ||
-            pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
+    rc = sqlite3PagerPagecount(pPager, &nPage);
+    if( rc ) return rc;
 
     /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
     ** if the allocation fails. Otherwise, zero the new portion in case a 
@@ -36350,26 +39030,26 @@
     }
     memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
     pPager->aSavepoint = aNew;
-    pPager->nSavepoint = nSavepoint;
 
     /* Populate the PagerSavepoint structures just allocated. */
     for(ii=nCurrent; ii<nSavepoint; ii++){
-      assert( pPager->dbSizeValid );
-      aNew[ii].nOrig = pPager->dbSize;
-      if( isOpen(pPager->jfd) && ALWAYS(pPager->journalOff>0) ){
+      aNew[ii].nOrig = nPage;
+      if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
         aNew[ii].iOffset = pPager->journalOff;
       }else{
         aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
       }
       aNew[ii].iSubRec = pPager->nSubRec;
-      aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+      aNew[ii].pInSavepoint = sqlite3BitvecCreate(nPage);
       if( !aNew[ii].pInSavepoint ){
         return SQLITE_NOMEM;
       }
+      if( pagerUseWal(pPager) ){
+        sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
+      }
+      pPager->nSavepoint = ii+1;
     }
-
-    /* Open the sub-journal, if it is not already opened. */
-    rc = openSubJournal(pPager);
+    assert( pPager->nSavepoint==nSavepoint );
     assertTruncateConstraint(pPager);
   }
 
@@ -36433,6 +39113,7 @@
         /* Only truncate if it is an in-memory sub-journal. */
         if( sqlite3IsMemJournal(pPager->sjfd) ){
           rc = sqlite3OsTruncate(pPager->sjfd, 0);
+          assert( rc==SQLITE_OK );
         }
         pPager->nSubRec = 0;
       }
@@ -36442,7 +39123,7 @@
     ** not yet been opened. In this case there have been no changes to
     ** the database file, so the playback operation can be skipped.
     */
-    else if( isOpen(pPager->jfd) ){
+    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
       PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
       rc = pagerPlaybackSavepoint(pPager, pSavepoint);
       assert(rc!=SQLITE_DONE);
@@ -36711,49 +39392,132 @@
 }
 
 /*
-** Get/set the journal-mode for this pager. Parameter eMode must be one of:
+** Set the journal-mode for this pager. Parameter eMode must be one of:
 **
-**    PAGER_JOURNALMODE_QUERY
 **    PAGER_JOURNALMODE_DELETE
 **    PAGER_JOURNALMODE_TRUNCATE
 **    PAGER_JOURNALMODE_PERSIST
 **    PAGER_JOURNALMODE_OFF
 **    PAGER_JOURNALMODE_MEMORY
+**    PAGER_JOURNALMODE_WAL
 **
-** If the parameter is not _QUERY, then the journal_mode is set to the
-** value specified if the change is allowed.  The change is disallowed
-** for the following reasons:
+** The journalmode is set to the value specified if the change is allowed.
+** The change may be disallowed for the following reasons:
 **
 **   *  An in-memory database can only have its journal_mode set to _OFF
 **      or _MEMORY.
 **
-**   *  The journal mode may not be changed while a transaction is active.
+**   *  Temporary databases cannot have _WAL journalmode.
 **
 ** The returned indicate the current (possibly updated) journal-mode.
 */
-SQLITE_PRIVATE int sqlite3PagerJournalMode(Pager *pPager, int eMode){
-  assert( eMode==PAGER_JOURNALMODE_QUERY
-            || eMode==PAGER_JOURNALMODE_DELETE
+SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
+  u8 eOld = pPager->journalMode;    /* Prior journalmode */
+
+  /* The eMode parameter is always valid */
+  assert(      eMode==PAGER_JOURNALMODE_DELETE
             || eMode==PAGER_JOURNALMODE_TRUNCATE
             || eMode==PAGER_JOURNALMODE_PERSIST
             || eMode==PAGER_JOURNALMODE_OFF 
+            || eMode==PAGER_JOURNALMODE_WAL 
             || eMode==PAGER_JOURNALMODE_MEMORY );
-  assert( PAGER_JOURNALMODE_QUERY<0 );
-  if( eMode>=0
-   && (!MEMDB || eMode==PAGER_JOURNALMODE_MEMORY 
-              || eMode==PAGER_JOURNALMODE_OFF)
-   && !pPager->dbModified
-   && (!isOpen(pPager->jfd) || 0==pPager->journalOff)
-  ){
-    if( isOpen(pPager->jfd) ){
+
+  /* Do not allow the journalmode of a TEMP database to be changed to WAL
+  */
+  if( pPager->tempFile && eMode==PAGER_JOURNALMODE_WAL ){
+    assert( eOld!=PAGER_JOURNALMODE_WAL );
+    eMode = eOld;
+  }
+
+  /* Do allow the journalmode of an in-memory database to be set to
+  ** anything other than MEMORY or OFF
+  */
+  if( MEMDB ){
+    assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
+    if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
+      eMode = eOld;
+    }
+  }
+
+  if( eMode!=eOld ){
+    /* When changing between rollback modes, close the journal file prior
+    ** to the change.  But when changing from a rollback mode to WAL, keep
+    ** the journal open since there is a rollback-style transaction in play
+    ** used to convert the version numbers in the btree header.
+    */
+    if( isOpen(pPager->jfd) && eMode!=PAGER_JOURNALMODE_WAL ){
       sqlite3OsClose(pPager->jfd);
     }
+
+    /* Change the journal mode. */
     pPager->journalMode = (u8)eMode;
+
+    /* When transistioning from TRUNCATE or PERSIST to any other journal
+    ** mode except WAL (and we are not in locking_mode=EXCLUSIVE) then 
+    ** delete the journal file.
+    */
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+
+      /* In this case we would like to delete the journal file. If it is
+      ** not possible, then that is not a problem. Deleting the journal file
+      ** here is an optimization only.
+      **
+      ** Before deleting the journal file, obtain a RESERVED lock on the
+      ** database file. This ensures that the journal file is not deleted
+      ** while it is in use by some other client.
+      */
+      int rc = SQLITE_OK;
+      int state = pPager->state;
+      if( state<PAGER_SHARED ){
+        rc = sqlite3PagerSharedLock(pPager);
+      }
+      if( pPager->state==PAGER_SHARED ){
+        assert( rc==SQLITE_OK );
+        rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
+      }
+      if( rc==SQLITE_OK ){
+        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }
+      if( rc==SQLITE_OK && state==PAGER_SHARED ){
+        sqlite3OsUnlock(pPager->fd, SHARED_LOCK);
+      }else if( state==PAGER_UNLOCK ){
+        pager_unlock(pPager);
+      }
+      assert( state==pPager->state );
+    }
   }
+
+  /* Return the new journal mode */
   return (int)pPager->journalMode;
 }
 
 /*
+** Return the current journal mode.
+*/
+SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager *pPager){
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return TRUE if the pager is in a state where it is OK to change the
+** journalmode.  Journalmode changes can only happen when the database
+** is unmodified.
+*/
+SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
+  if( pPager->dbModified ) return 0;
+  if( isOpen(pPager->jfd) && pPager->journalOff>0 ) return 0;
+  return 1;
+}
+
+/*
 ** Get/set the size-limit used for persistent journal files.
 **
 ** Setting the size limit to -1 means no limit is enforced.
@@ -36776,9 +39540,2616 @@
   return &pPager->pBackup;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is called when the user invokes "PRAGMA checkpoint".
+*/
+SQLITE_PRIVATE int sqlite3PagerCheckpoint(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( pPager->pWal ){
+    u8 *zBuf = (u8 *)pPager->pTmpSpace;
+    rc = sqlite3WalCheckpoint(pPager->pWal,
+        (pPager->noSync ? 0 : pPager->sync_flags),
+        pPager->pageSize, zBuf
+    );
+  }
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3PagerWalCallback(Pager *pPager){
+  return sqlite3WalCallback(pPager->pWal);
+}
+
+/*
+** Return true if the underlying VFS for the given pager supports the
+** primitives necessary for write-ahead logging.
+*/
+SQLITE_PRIVATE int sqlite3PagerWalSupported(Pager *pPager){
+  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
+  return pMethods->iVersion>=2 && pMethods->xShmOpen!=0;
+}
+
+/*
+** Open a connection to the write-ahead log file for pager pPager. If
+** the log connection is already open, this function is a no-op.
+**
+** The caller must be holding a SHARED lock on the database file to call
+** this function.
+*/
+SQLITE_PRIVATE int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pPager->state>=PAGER_SHARED );
+  if( !pPager->pWal ){
+    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
+
+    /* Open the connection to the log file. If this operation fails, 
+    ** (e.g. due to malloc() failure), unlock the database file and 
+    ** return an error code.
+    */
+    rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,
+                        pPager->zFilename, &pPager->pWal);
+    if( rc==SQLITE_OK ){
+      pPager->journalMode = PAGER_JOURNALMODE_WAL;
+    }
+  }else{
+    *pisOpen = 1;
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to close the connection to the log file prior
+** to switching from WAL to rollback mode.
+**
+** Before closing the log file, this function attempts to take an 
+** EXCLUSIVE lock on the database file. If this cannot be obtained, an
+** error (SQLITE_BUSY) is returned and the log connection is not closed.
+** If successful, the EXCLUSIVE lock is not released before returning.
+*/
+SQLITE_PRIVATE int sqlite3PagerCloseWal(Pager *pPager){
+  int rc = SQLITE_OK;
+
+  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+
+  /* If the log file is not already open, but does exist in the file-system,
+  ** it may need to be checkpointed before the connection can switch to
+  ** rollback mode. Open it now so this can happen.
+  */
+  if( !pPager->pWal ){
+    int logexists = 0;
+    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_SHARED);
+    if( rc==SQLITE_OK ){
+      rc = pagerHasWAL(pPager, &logexists);
+    }
+    if( rc==SQLITE_OK && logexists ){
+      rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,
+                          pPager->zFilename, &pPager->pWal);
+    }
+  }
+    
+  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
+  ** the database file, the log and log-summary files will be deleted.
+  */
+  if( rc==SQLITE_OK && pPager->pWal ){
+    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_EXCLUSIVE);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3WalClose(pPager->pWal,
+                           (pPager->noSync ? 0 : pPager->sync_flags), 
+        pPager->pageSize, (u8*)pPager->pTmpSpace
+      );
+      pPager->pWal = 0;
+    }else{
+      /* If we cannot get an EXCLUSIVE lock, downgrade the PENDING lock
+      ** that we did get back to SHARED. */
+      sqlite3OsUnlock(pPager->fd, SQLITE_LOCK_SHARED);
+    }
+  }
+  return rc;
+}
+#endif
+
 #endif /* SQLITE_OMIT_DISKIO */
 
 /************** End of pager.c ***********************************************/
+/************** Begin file wal.c *********************************************/
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of a write-ahead log (WAL) used in 
+** "journal_mode=WAL" mode.
+**
+** WRITE-AHEAD LOG (WAL) FILE FORMAT
+**
+** A WAL file consists of a header followed by zero or more "frames".
+** Each frame records the revised content of a single page from the
+** database file.  All changes to the database are recorded by writing
+** frames into the WAL.  Transactions commit when a frame is written that
+** contains a commit marker.  A single WAL can and usually does record 
+** multiple transactions.  Periodically, the content of the WAL is
+** transferred back into the database file in an operation called a
+** "checkpoint".
+**
+** A single WAL file can be used multiple times.  In other words, the
+** WAL can fill up with frames and then be checkpointed and then new
+** frames can overwrite the old ones.  A WAL always grows from beginning
+** toward the end.  Checksums and counters attached to each frame are
+** used to determine which frames within the WAL are valid and which
+** are leftovers from prior checkpoints.
+**
+** The WAL header is 24 bytes in size and consists of the following six
+** big-endian 32-bit unsigned integer values:
+**
+**     0: Magic number.  0x377f0682 or 0x377f0683
+**     4: File format version.  Currently 3007000
+**     8: Database page size.  Example: 1024
+**    12: Checkpoint sequence number
+**    16: Salt-1, random integer incremented with each checkpoint
+**    20: Salt-2, a different random integer changing with each ckpt
+**
+** Immediately following the wal-header are zero or more frames. Each
+** frame consists of a 24-byte frame-header followed by a <page-size> bytes
+** of page data. The frame-header is broken into 6 big-endian 32-bit unsigned 
+** integer values, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the header)
+**    12: Salt-2 (copied from the header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+**
+** A frame is considered valid if and only if the following conditions are
+** true:
+**
+**    (1) The salt-1 and salt-2 values in the frame-header match
+**        salt values in the wal-header
+**
+**    (2) The checksum values in the final 8 bytes of the frame-header
+**        exactly match the checksum computed consecutively on the
+**        WAL header and the first 8 bytes and the content of all frames
+**        up to and including the current frame.
+**
+** The checksum is computed using 32-bit big-endian integers if the
+** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
+** is computed using little-endian if the magic number is 0x377f0682.
+** The checksum values are always stored in the frame header in a
+** big-endian format regardless of which byte order is used to compute
+** the checksum.  The checksum is computed by interpreting the input as
+** an even number of unsigned 32-bit integers: x[0] through x[N].  The
+** algorithm used for the checksum is as follows:
+** 
+**   for i from 0 to n-1 step 2:
+**     s0 += x[i] + s1;
+**     s1 += x[i+1] + s0;
+**   endfor
+**
+** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
+** WAL is transferred into the database, then the database is VFS.xSync-ed.
+** The VFS.xSync operations serve as write barriers - all writes launched
+** before the xSync must complete before any write that launches after the
+** xSync begins.
+**
+** After each checkpoint, the salt-1 value is incremented and the salt-2
+** value is randomized.  This prevents old and new frames in the WAL from
+** being considered valid at the same time and being checkpointing together
+** following a crash.
+**
+** READER ALGORITHM
+**
+** To read a page from the database (call it page number P), a reader
+** first checks the WAL to see if it contains page P.  If so, then the
+** last valid instance of page P that is a followed by a commit frame
+** or is a commit frame itself becomes the value read.  If the WAL
+** contains no copies of page P that are valid and which are a commit
+** frame or are followed by a commit frame, then page P is read from
+** the database file.
+**
+** To start a read transaction, the reader records the index of the last
+** valid frame in the WAL.  The reader uses this recorded "mxFrame" value
+** for all subsequent read operations.  New transactions can be appended
+** to the WAL, but as long as the reader uses its original mxFrame value
+** and ignores the newly appended content, it will see a consistent snapshot
+** of the database from a single point in time.  This technique allows
+** multiple concurrent readers to view different versions of the database
+** content simultaneously.
+**
+** The reader algorithm in the previous paragraphs works correctly, but 
+** because frames for page P can appear anywhere within the WAL, the
+** reader has to scan the entire WAL looking for page P frames.  If the
+** WAL is large (multiple megabytes is typical) that scan can be slow,
+** and read performance suffers.  To overcome this problem, a separate
+** data structure called the wal-index is maintained to expedite the
+** search for frames of a particular page.
+** 
+** WAL-INDEX FORMAT
+**
+** Conceptually, the wal-index is shared memory, though VFS implementations
+** might choose to implement the wal-index using a mmapped file.  Because
+** the wal-index is shared memory, SQLite does not support journal_mode=WAL 
+** on a network filesystem.  All users of the database must be able to
+** share memory.
+**
+** The wal-index is transient.  After a crash, the wal-index can (and should
+** be) reconstructed from the original WAL file.  In fact, the VFS is required
+** to either truncate or zero the header of the wal-index when the last
+** connection to it closes.  Because the wal-index is transient, it can
+** use an architecture-specific format; it does not have to be cross-platform.
+** Hence, unlike the database and WAL file formats which store all values
+** as big endian, the wal-index can store multi-byte values in the native
+** byte order of the host computer.
+**
+** The purpose of the wal-index is to answer this question quickly:  Given
+** a page number P, return the index of the last frame for page P in the WAL,
+** or return NULL if there are no frames for page P in the WAL.
+**
+** The wal-index consists of a header region, followed by an one or
+** more index blocks.  
+**
+** The wal-index header contains the total number of frames within the WAL
+** in the the mxFrame field.  
+**
+** Each index block except for the first contains information on 
+** HASHTABLE_NPAGE frames. The first index block contains information on
+** HASHTABLE_NPAGE_ONE frames. The values of HASHTABLE_NPAGE_ONE and 
+** HASHTABLE_NPAGE are selected so that together the wal-index header and
+** first index block are the same size as all other index blocks in the
+** wal-index.
+**
+** Each index block contains two sections, a page-mapping that contains the
+** database page number associated with each wal frame, and a hash-table 
+** that allows readers to query an index block for a specific page number.
+** The page-mapping is an array of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE
+** for the first index block) 32-bit page numbers. The first entry in the 
+** first index-block contains the database page number corresponding to the
+** first frame in the WAL file. The first entry in the second index block
+** in the WAL file corresponds to the (HASHTABLE_NPAGE_ONE+1)th frame in
+** the log, and so on.
+**
+** The last index block in a wal-index usually contains less than the full
+** complement of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE) page-numbers,
+** depending on the contents of the WAL file. This does not change the
+** allocated size of the page-mapping array - the page-mapping array merely
+** contains unused entries.
+**
+** Even without using the hash table, the last frame for page P
+** can be found by scanning the page-mapping sections of each index block
+** starting with the last index block and moving toward the first, and
+** within each index block, starting at the end and moving toward the
+** beginning.  The first entry that equals P corresponds to the frame
+** holding the content for that page.
+**
+** The hash table consists of HASHTABLE_NSLOT 16-bit unsigned integers.
+** HASHTABLE_NSLOT = 2*HASHTABLE_NPAGE, and there is one entry in the
+** hash table for each page number in the mapping section, so the hash 
+** table is never more than half full.  The expected number of collisions 
+** prior to finding a match is 1.  Each entry of the hash table is an
+** 1-based index of an entry in the mapping section of the same
+** index block.   Let K be the 1-based index of the largest entry in
+** the mapping section.  (For index blocks other than the last, K will
+** always be exactly HASHTABLE_NPAGE (4096) and for the last index block
+** K will be (mxFrame%HASHTABLE_NPAGE).)  Unused slots of the hash table
+** contain a value of 0.
+**
+** To look for page P in the hash table, first compute a hash iKey on
+** P as follows:
+**
+**      iKey = (P * 383) % HASHTABLE_NSLOT
+**
+** Then start scanning entries of the hash table, starting with iKey
+** (wrapping around to the beginning when the end of the hash table is
+** reached) until an unused hash slot is found. Let the first unused slot
+** be at index iUnused.  (iUnused might be less than iKey if there was
+** wrap-around.) Because the hash table is never more than half full,
+** the search is guaranteed to eventually hit an unused entry.  Let 
+** iMax be the value between iKey and iUnused, closest to iUnused,
+** where aHash[iMax]==P.  If there is no iMax entry (if there exists
+** no hash slot such that aHash[i]==p) then page P is not in the
+** current index block.  Otherwise the iMax-th mapping entry of the
+** current index block corresponds to the last entry that references 
+** page P.
+**
+** A hash search begins with the last index block and moves toward the
+** first index block, looking for entries corresponding to page P.  On
+** average, only two or three slots in each index block need to be
+** examined in order to either find the last entry for page P, or to
+** establish that no such entry exists in the block.  Each index block
+** holds over 4000 entries.  So two or three index blocks are sufficient
+** to cover a typical 10 megabyte WAL file, assuming 1K pages.  8 or 10
+** comparisons (on average) suffice to either locate a frame in the
+** WAL or to establish that the frame does not exist in the WAL.  This
+** is much faster than scanning the entire 10MB WAL.
+**
+** Note that entries are added in order of increasing K.  Hence, one
+** reader might be using some value K0 and a second reader that started
+** at a later time (after additional transactions were added to the WAL
+** and to the wal-index) might be using a different value K1, where K1>K0.
+** Both readers can use the same hash table and mapping section to get
+** the correct result.  There may be entries in the hash table with
+** K>K0 but to the first reader, those entries will appear to be unused
+** slots in the hash table and so the first reader will get an answer as
+** if no values greater than K0 had ever been inserted into the hash table
+** in the first place - which is what reader one wants.  Meanwhile, the
+** second reader using K1 will see additional values that were inserted
+** later, which is exactly what reader two wants.  
+**
+** When a rollback occurs, the value of K is decreased. Hash table entries
+** that correspond to frames greater than the new K value are removed
+** from the hash table at this point.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+SQLITE_PRIVATE int sqlite3WalTrace = 0;
+# define WALTRACE(X)  if(sqlite3WalTrace) sqlite3DebugPrintf X
+#else
+# define WALTRACE(X)
+#endif
+
+
+/*
+** Indices of various locking bytes.   WAL_NREADER is the number
+** of available reader locks and should be at least 3.
+*/
+#define WAL_WRITE_LOCK         0
+#define WAL_ALL_BUT_WRITE      1
+#define WAL_CKPT_LOCK          1
+#define WAL_RECOVER_LOCK       2
+#define WAL_READ_LOCK(I)       (3+(I))
+#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)
+
+
+/* Object declarations */
+typedef struct WalIndexHdr WalIndexHdr;
+typedef struct WalIterator WalIterator;
+typedef struct WalCkptInfo WalCkptInfo;
+
+
+/*
+** The following object holds a copy of the wal-index header content.
+**
+** The actual header in the wal-index consists of two copies of this
+** object.
+*/
+struct WalIndexHdr {
+  u32 iChange;                    /* Counter incremented each transaction */
+  u8 isInit;                      /* 1 when initialized */
+  u8 bigEndCksum;                 /* True if checksums in WAL are big-endian */
+  u16 szPage;                     /* Database page size in bytes */
+  u32 mxFrame;                    /* Index of last valid frame in the WAL */
+  u32 nPage;                      /* Size of database in pages */
+  u32 aFrameCksum[2];             /* Checksum of last frame in log */
+  u32 aSalt[2];                   /* Two salt values copied from WAL header */
+  u32 aCksum[2];                  /* Checksum over all prior fields */
+};
+
+/*
+** A copy of the following object occurs in the wal-index immediately
+** following the second copy of the WalIndexHdr.  This object stores
+** information used by checkpoint.
+**
+** nBackfill is the number of frames in the WAL that have been written
+** back into the database. (We call the act of moving content from WAL to
+** database "backfilling".)  The nBackfill number is never greater than
+** WalIndexHdr.mxFrame.  nBackfill can only be increased by threads
+** holding the WAL_CKPT_LOCK lock (which includes a recovery thread).
+** However, a WAL_WRITE_LOCK thread can move the value of nBackfill from
+** mxFrame back to zero when the WAL is reset.
+**
+** There is one entry in aReadMark[] for each reader lock.  If a reader
+** holds read-lock K, then the value in aReadMark[K] is no greater than
+** the mxFrame for that reader.  The value READMARK_NOT_USED (0xffffffff)
+** for any aReadMark[] means that entry is unused.  aReadMark[0] is 
+** a special case; its value is never used and it exists as a place-holder
+** to avoid having to offset aReadMark[] indexs by one.  Readers holding
+** WAL_READ_LOCK(0) always ignore the entire WAL and read all content
+** directly from the database.
+**
+** The value of aReadMark[K] may only be changed by a thread that
+** is holding an exclusive lock on WAL_READ_LOCK(K).  Thus, the value of
+** aReadMark[K] cannot changed while there is a reader is using that mark
+** since the reader will be holding a shared lock on WAL_READ_LOCK(K).
+**
+** The checkpointer may only transfer frames from WAL to database where
+** the frame numbers are less than or equal to every aReadMark[] that is
+** in use (that is, every aReadMark[j] for which there is a corresponding
+** WAL_READ_LOCK(j)).  New readers (usually) pick the aReadMark[] with the
+** largest value and will increase an unused aReadMark[] to mxFrame if there
+** is not already an aReadMark[] equal to mxFrame.  The exception to the
+** previous sentence is when nBackfill equals mxFrame (meaning that everything
+** in the WAL has been backfilled into the database) then new readers
+** will choose aReadMark[0] which has value 0 and hence such reader will
+** get all their all content directly from the database file and ignore 
+** the WAL.
+**
+** Writers normally append new frames to the end of the WAL.  However,
+** if nBackfill equals mxFrame (meaning that all WAL content has been
+** written back into the database) and if no readers are using the WAL
+** (in other words, if there are no WAL_READ_LOCK(i) where i>0) then
+** the writer will first "reset" the WAL back to the beginning and start
+** writing new content beginning at frame 1.
+**
+** We assume that 32-bit loads are atomic and so no locks are needed in
+** order to read from any aReadMark[] entries.
+*/
+struct WalCkptInfo {
+  u32 nBackfill;                  /* Number of WAL frames backfilled into DB */
+  u32 aReadMark[WAL_NREADER];     /* Reader marks */
+};
+#define READMARK_NOT_USED  0xffffffff
+
+
+/* A block of WALINDEX_LOCK_RESERVED bytes beginning at
+** WALINDEX_LOCK_OFFSET is reserved for locks. Since some systems
+** only support mandatory file-locks, we do not read or write data
+** from the region of the file on which locks are applied.
+*/
+#define WALINDEX_LOCK_OFFSET   (sizeof(WalIndexHdr)*2 + sizeof(WalCkptInfo))
+#define WALINDEX_LOCK_RESERVED 16
+#define WALINDEX_HDR_SIZE      (WALINDEX_LOCK_OFFSET+WALINDEX_LOCK_RESERVED)
+
+/* Size of header before each frame in wal */
+#define WAL_FRAME_HDRSIZE 24
+
+/* Size of write ahead log header */
+#define WAL_HDRSIZE 24
+
+/* WAL magic value. Either this value, or the same value with the least
+** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
+** big-endian format in the first 4 bytes of a WAL file.
+**
+** If the LSB is set, then the checksums for each frame within the WAL
+** file are calculated by treating all data as an array of 32-bit 
+** big-endian words. Otherwise, they are calculated by interpreting 
+** all data as 32-bit little-endian words.
+*/
+#define WAL_MAGIC 0x377f0682
+
+/*
+** Return the offset of frame iFrame in the write-ahead log file, 
+** assuming a database page size of szPage bytes. The offset returned
+** is to the start of the write-ahead log frame-header.
+*/
+#define walFrameOffset(iFrame, szPage) (                               \
+  WAL_HDRSIZE + ((iFrame)-1)*((szPage)+WAL_FRAME_HDRSIZE)        \
+)
+
+/*
+** An open write-ahead log file is represented by an instance of the
+** following object.
+*/
+struct Wal {
+  sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
+  sqlite3_file *pDbFd;       /* File handle for the database file */
+  sqlite3_file *pWalFd;      /* File handle for WAL file */
+  u32 iCallback;             /* Value to pass to log callback (or 0) */
+  int nWiData;               /* Size of array apWiData */
+  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
+  u16 szPage;                /* Database page size */
+  i16 readLock;              /* Which read lock is being held.  -1 for none */
+  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
+  u8 isWIndexOpen;           /* True if ShmOpen() called on pDbFd */
+  u8 writeLock;              /* True if in a write transaction */
+  u8 ckptLock;               /* True if holding a checkpoint lock */
+  WalIndexHdr hdr;           /* Wal-index header for current transaction */
+  char *zWalName;            /* Name of WAL file */
+  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
+#ifdef SQLITE_DEBUG
+  u8 lockError;              /* True if a locking error has occurred */
+#endif
+};
+
+/*
+** Each page of the wal-index mapping contains a hash-table made up of
+** an array of HASHTABLE_NSLOT elements of the following type.
+*/
+typedef u16 ht_slot;
+
+/*
+** This structure is used to implement an iterator that loops through
+** all frames in the WAL in database page order. Where two or more frames
+** correspond to the same database page, the iterator visits only the 
+** frame most recently written to the WAL (in other words, the frame with
+** the largest index).
+**
+** The internals of this structure are only accessed by:
+**
+**   walIteratorInit() - Create a new iterator,
+**   walIteratorNext() - Step an iterator,
+**   walIteratorFree() - Free an iterator.
+**
+** This functionality is used by the checkpoint code (see walCheckpoint()).
+*/
+struct WalIterator {
+  int iPrior;                     /* Last result returned from the iterator */
+  int nSegment;                   /* Size of the aSegment[] array */
+  struct WalSegment {
+    int iNext;                    /* Next slot in aIndex[] not yet returned */
+    ht_slot *aIndex;              /* i0, i1, i2... such that aPgno[iN] ascend */
+    u32 *aPgno;                   /* Array of page numbers. */
+    int nEntry;                   /* Max size of aPgno[] and aIndex[] arrays */
+    int iZero;                    /* Frame number associated with aPgno[0] */
+  } aSegment[1];                  /* One for every 32KB page in the WAL */
+};
+
+/*
+** Define the parameters of the hash tables in the wal-index file. There
+** is a hash-table following every HASHTABLE_NPAGE page numbers in the
+** wal-index.
+**
+** Changing any of these constants will alter the wal-index format and
+** create incompatibilities.
+*/
+#define HASHTABLE_NPAGE      4096                 /* Must be power of 2 */
+#define HASHTABLE_HASH_1     383                  /* Should be prime */
+#define HASHTABLE_NSLOT      (HASHTABLE_NPAGE*2)  /* Must be a power of 2 */
+
+/* 
+** The block of page numbers associated with the first hash-table in a
+** wal-index is smaller than usual. This is so that there is a complete
+** hash-table on each aligned 32KB page of the wal-index.
+*/
+#define HASHTABLE_NPAGE_ONE  (HASHTABLE_NPAGE - (WALINDEX_HDR_SIZE/sizeof(u32)))
+
+/* The wal-index is divided into pages of WALINDEX_PGSZ bytes each. */
+#define WALINDEX_PGSZ   (                                         \
+    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
+)
+
+/*
+** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
+** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
+** numbered from zero.
+**
+** If this call is successful, *ppPage is set to point to the wal-index
+** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
+** then an SQLite error code is returned and *ppPage is set to 0.
+*/
+static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
+  int rc = SQLITE_OK;
+
+  /* Enlarge the pWal->apWiData[] array if required */
+  if( pWal->nWiData<=iPage ){
+    int nByte = sizeof(u32 *)*(iPage+1);
+    volatile u32 **apNew;
+    apNew = (volatile u32 **)sqlite3_realloc(pWal->apWiData, nByte);
+    if( !apNew ){
+      *ppPage = 0;
+      return SQLITE_NOMEM;
+    }
+    memset(&apNew[pWal->nWiData], 0, sizeof(u32 *)*(iPage+1-pWal->nWiData));
+    pWal->apWiData = apNew;
+    pWal->nWiData = iPage+1;
+  }
+
+  /* Request a pointer to the required page from the VFS */
+  if( pWal->apWiData[iPage]==0 ){
+    rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
+        pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
+    );
+  }
+
+  *ppPage = pWal->apWiData[iPage];
+  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
+  return rc;
+}
+
+/*
+** Return a pointer to the WalCkptInfo structure in the wal-index.
+*/
+static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]);
+}
+
+/*
+** Return a pointer to the WalIndexHdr structure in the wal-index.
+*/
+static volatile WalIndexHdr *walIndexHdr(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalIndexHdr*)pWal->apWiData[0];
+}
+
+/*
+** The argument to this macro must be of type u32. On a little-endian
+** architecture, it returns the u32 value that results from interpreting
+** the 4 bytes as a big-endian value. On a big-endian architecture, it
+** returns the value that would be produced by intepreting the 4 bytes
+** of the input value as a little-endian integer.
+*/
+#define BYTESWAP32(x) ( \
+    (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)  \
+  + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24) \
+)
+
+/*
+** Generate or extend an 8 byte checksum based on the data in 
+** array aByte[] and the initial values of aIn[0] and aIn[1] (or
+** initial values of 0 and 0 if aIn==NULL).
+**
+** The checksum is written back into aOut[] before returning.
+**
+** nByte must be a positive multiple of 8.
+*/
+static void walChecksumBytes(
+  int nativeCksum, /* True for native byte-order, false for non-native */
+  u8 *a,           /* Content to be checksummed */
+  int nByte,       /* Bytes of content in a[].  Must be a multiple of 8. */
+  const u32 *aIn,  /* Initial checksum value input */
+  u32 *aOut        /* OUT: Final checksum value output */
+){
+  u32 s1, s2;
+  u32 *aData = (u32 *)a;
+  u32 *aEnd = (u32 *)&a[nByte];
+
+  if( aIn ){
+    s1 = aIn[0];
+    s2 = aIn[1];
+  }else{
+    s1 = s2 = 0;
+  }
+
+  assert( nByte>=8 );
+  assert( (nByte&0x00000007)==0 );
+
+  if( nativeCksum ){
+    do {
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+    }while( aData<aEnd );
+  }else{
+    do {
+      s1 += BYTESWAP32(aData[0]) + s2;
+      s2 += BYTESWAP32(aData[1]) + s1;
+      aData += 2;
+    }while( aData<aEnd );
+  }
+
+  aOut[0] = s1;
+  aOut[1] = s2;
+}
+
+/*
+** Write the header information in pWal->hdr into the wal-index.
+**
+** The checksum on pWal->hdr is updated before it is written.
+*/
+static void walIndexWriteHdr(Wal *pWal){
+  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
+  const int nCksum = offsetof(WalIndexHdr, aCksum);
+
+  assert( pWal->writeLock );
+  pWal->hdr.isInit = 1;
+  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
+  memcpy((void *)&aHdr[1], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+  sqlite3OsShmBarrier(pWal->pDbFd);
+  memcpy((void *)&aHdr[0], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+}
+
+/*
+** This function encodes a single frame header and writes it to a buffer
+** supplied by the caller. A frame-header is made up of a series of 
+** 4-byte big-endian integers, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the wal-header)
+**    12: Salt-2 (copied from the wal-header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+*/
+static void walEncodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 iPage,                      /* Database page number for frame */
+  u32 nTruncate,                  /* New db size (or 0 for non-commit frames) */
+  u8 *aData,                      /* Pointer to page data */
+  u8 *aFrame                      /* OUT: Write encoded frame here */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  assert( WAL_FRAME_HDRSIZE==24 );
+  sqlite3Put4byte(&aFrame[0], iPage);
+  sqlite3Put4byte(&aFrame[4], nTruncate);
+  memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
+
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+
+  sqlite3Put4byte(&aFrame[16], aCksum[0]);
+  sqlite3Put4byte(&aFrame[20], aCksum[1]);
+}
+
+/*
+** Check to see if the frame with header in aFrame[] and content
+** in aData[] is valid.  If it is a valid frame, fill *piPage and
+** *pnTruncate and return true.  Return if the frame is not valid.
+*/
+static int walDecodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 *piPage,                    /* OUT: Database page number for frame */
+  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
+  u8 *aData,                      /* Pointer to page data (for checksum) */
+  u8 *aFrame                      /* Frame data */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  u32 pgno;                       /* Page number of the frame */
+  assert( WAL_FRAME_HDRSIZE==24 );
+
+  /* A frame is only valid if the salt values in the frame-header
+  ** match the salt values in the wal-header. 
+  */
+  if( memcmp(&pWal->hdr.aSalt, &aFrame[8], 8)!=0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if the page number is creater than zero.
+  */
+  pgno = sqlite3Get4byte(&aFrame[0]);
+  if( pgno==0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if a checksum of the first 16 bytes
+  ** of the frame-header, and the frame-data matches
+  ** the checksum in the last 8 bytes of the frame-header.
+  */
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+  if( aCksum[0]!=sqlite3Get4byte(&aFrame[16]) 
+   || aCksum[1]!=sqlite3Get4byte(&aFrame[20]) 
+  ){
+    /* Checksum failed. */
+    return 0;
+  }
+
+  /* If we reach this point, the frame is valid.  Return the page number
+  ** and the new database size.
+  */
+  *piPage = pgno;
+  *pnTruncate = sqlite3Get4byte(&aFrame[4]);
+  return 1;
+}
+
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Names of locks.  This routine is used to provide debugging output and is not
+** a part of an ordinary build.
+*/
+static const char *walLockName(int lockIdx){
+  if( lockIdx==WAL_WRITE_LOCK ){
+    return "WRITE-LOCK";
+  }else if( lockIdx==WAL_CKPT_LOCK ){
+    return "CKPT-LOCK";
+  }else if( lockIdx==WAL_RECOVER_LOCK ){
+    return "RECOVER-LOCK";
+  }else{
+    static char zName[15];
+    sqlite3_snprintf(sizeof(zName), zName, "READ-LOCK[%d]",
+                     lockIdx-WAL_READ_LOCK(0));
+    return zName;
+  }
+}
+#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
+    
+
+/*
+** Set or release locks on the WAL.  Locks are either shared or exclusive.
+** A lock cannot be moved directly between shared and exclusive - it must go
+** through the unlocked state first.
+**
+** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
+*/
+static int walLockShared(Wal *pWal, int lockIdx){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
+            walLockName(lockIdx), rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockShared(Wal *pWal, int lockIdx){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
+}
+static int walLockExclusive(Wal *pWal, int lockIdx, int n){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
+            walLockName(lockIdx), n, rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal,
+             walLockName(lockIdx), n));
+}
+
+/*
+** Compute a hash on a page number.  The resulting hash value must land
+** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
+** the hash to the next value in the event of a collision.
+*/
+static int walHash(u32 iPage){
+  assert( iPage>0 );
+  assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 );
+  return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1);
+}
+static int walNextHash(int iPriorHash){
+  return (iPriorHash+1)&(HASHTABLE_NSLOT-1);
+}
+
+/* 
+** Return pointers to the hash table and page number array stored on
+** page iHash of the wal-index. The wal-index is broken into 32KB pages
+** numbered starting from 0.
+**
+** Set output variable *paHash to point to the start of the hash table
+** in the wal-index file. Set *piZero to one less than the frame 
+** number of the first frame indexed by this hash table. If a
+** slot in the hash table is set to N, it refers to frame number 
+** (*piZero+N) in the log.
+**
+** Finally, set *paPgno so that *paPgno[1] is the page number of the
+** first frame indexed by the hash table, frame (*piZero+1).
+*/
+static int walHashGet(
+  Wal *pWal,                      /* WAL handle */
+  int iHash,                      /* Find the iHash'th table */
+  volatile ht_slot **paHash,      /* OUT: Pointer to hash index */
+  volatile u32 **paPgno,          /* OUT: Pointer to page number array */
+  u32 *piZero                     /* OUT: Frame associated with *paPgno[0] */
+){
+  int rc;                         /* Return code */
+  volatile u32 *aPgno;
+
+  rc = walIndexPage(pWal, iHash, &aPgno);
+  assert( rc==SQLITE_OK || iHash>0 );
+
+  if( rc==SQLITE_OK ){
+    u32 iZero;
+    volatile ht_slot *aHash;
+
+    aHash = (volatile ht_slot *)&aPgno[HASHTABLE_NPAGE];
+    if( iHash==0 ){
+      aPgno = &aPgno[WALINDEX_HDR_SIZE/sizeof(u32)];
+      iZero = 0;
+    }else{
+      iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
+    }
+  
+    *paPgno = &aPgno[-1];
+    *paHash = aHash;
+    *piZero = iZero;
+  }
+  return rc;
+}
+
+/*
+** Return the number of the wal-index page that contains the hash-table
+** and page-number array that contain entries corresponding to WAL frame
+** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages 
+** are numbered starting from 0.
+*/
+static int walFramePage(u32 iFrame){
+  int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE;
+  assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE)
+       && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE)
+       && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE))
+       && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)
+       && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE))
+  );
+  return iHash;
+}
+
+/*
+** Return the page number associated with frame iFrame in this WAL.
+*/
+static u32 walFramePgno(Wal *pWal, u32 iFrame){
+  int iHash = walFramePage(iFrame);
+  if( iHash==0 ){
+    return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1];
+  }
+  return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE];
+}
+
+/*
+** Remove entries from the hash table that point to WAL slots greater
+** than pWal->hdr.mxFrame.
+**
+** This function is called whenever pWal->hdr.mxFrame is decreased due
+** to a rollback or savepoint.
+**
+** At most only the hash table containing pWal->hdr.mxFrame needs to be
+** updated.  Any later hash tables will be automatically cleared when
+** pWal->hdr.mxFrame advances to the point where those hash tables are
+** actually needed.
+*/
+static void walCleanupHash(Wal *pWal){
+  volatile ht_slot *aHash;        /* Pointer to hash table to clear */
+  volatile u32 *aPgno;            /* Page number array for hash table */
+  u32 iZero;                      /* frame == (aHash[x]+iZero) */
+  int iLimit = 0;                 /* Zero values greater than this */
+  int nByte;                      /* Number of bytes to zero in aPgno[] */
+  int i;                          /* Used to iterate through aHash[] */
+
+  assert( pWal->writeLock );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE-1 );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE+1 );
+
+  if( pWal->hdr.mxFrame==0 ) return;
+
+  /* Obtain pointers to the hash-table and page-number array containing 
+  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
+  ** that the page said hash-table and array reside on is already mapped.
+  */
+  assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) );
+  assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] );
+  walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &aHash, &aPgno, &iZero);
+
+  /* Zero all hash-table entries that correspond to frame numbers greater
+  ** than pWal->hdr.mxFrame.
+  */
+  iLimit = pWal->hdr.mxFrame - iZero;
+  assert( iLimit>0 );
+  for(i=0; i<HASHTABLE_NSLOT; i++){
+    if( aHash[i]>iLimit ){
+      aHash[i] = 0;
+    }
+  }
+  
+  /* Zero the entries in the aPgno array that correspond to frames with
+  ** frame numbers greater than pWal->hdr.mxFrame. 
+  */
+  nByte = ((char *)aHash - (char *)&aPgno[iLimit+1]);
+  memset((void *)&aPgno[iLimit+1], 0, nByte);
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* Verify that the every entry in the mapping region is still reachable
+  ** via the hash table even after the cleanup.
+  */
+  if( iLimit ){
+    int i;           /* Loop counter */
+    int iKey;        /* Hash key */
+    for(i=1; i<=iLimit; i++){
+      for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+        if( aHash[iKey]==i ) break;
+      }
+      assert( aHash[iKey]==i );
+    }
+  }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+}
+
+
+/*
+** Set an entry in the wal-index that will map database page number
+** pPage into WAL frame iFrame.
+*/
+static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
+  int rc;                         /* Return code */
+  u32 iZero;                      /* One less than frame number of aPgno[1] */
+  volatile u32 *aPgno;            /* Page number array */
+  volatile ht_slot *aHash;        /* Hash table */
+
+  rc = walHashGet(pWal, walFramePage(iFrame), &aHash, &aPgno, &iZero);
+
+  /* Assuming the wal-index file was successfully mapped, populate the
+  ** page number array and hash table entry.
+  */
+  if( rc==SQLITE_OK ){
+    int iKey;                     /* Hash table key */
+    int idx;                      /* Value to write to hash-table slot */
+    TESTONLY( int nCollide = 0;   /* Number of hash collisions */ )
+
+    idx = iFrame - iZero;
+    assert( idx <= HASHTABLE_NSLOT/2 + 1 );
+    
+    /* If this is the first entry to be added to this hash-table, zero the
+    ** entire hash table and aPgno[] array before proceding. 
+    */
+    if( idx==1 ){
+      int nByte = (u8 *)&aHash[HASHTABLE_NSLOT] - (u8 *)&aPgno[1];
+      memset((void*)&aPgno[1], 0, nByte);
+    }
+
+    /* If the entry in aPgno[] is already set, then the previous writer
+    ** must have exited unexpectedly in the middle of a transaction (after
+    ** writing one or more dirty pages to the WAL to free up memory). 
+    ** Remove the remnants of that writers uncommitted transaction from 
+    ** the hash-table before writing any new entries.
+    */
+    if( aPgno[idx] ){
+      walCleanupHash(pWal);
+      assert( !aPgno[idx] );
+    }
+
+    /* Write the aPgno[] array entry and the hash-table slot. */
+    for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
+      assert( nCollide++ < idx );
+    }
+    aPgno[idx] = iPage;
+    aHash[iKey] = idx;
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+    /* Verify that the number of entries in the hash table exactly equals
+    ** the number of entries in the mapping region.
+    */
+    {
+      int i;           /* Loop counter */
+      int nEntry = 0;  /* Number of entries in the hash table */
+      for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i] ) nEntry++; }
+      assert( nEntry==idx );
+    }
+
+    /* Verify that the every entry in the mapping region is reachable
+    ** via the hash table.  This turns out to be a really, really expensive
+    ** thing to check, so only do this occasionally - not on every
+    ** iteration.
+    */
+    if( (idx&0x3ff)==0 ){
+      int i;           /* Loop counter */
+      for(i=1; i<=idx; i++){
+        for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+          if( aHash[iKey]==i ) break;
+        }
+        assert( aHash[iKey]==i );
+      }
+    }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+  }
+
+
+  return rc;
+}
+
+
+/*
+** Recover the wal-index by reading the write-ahead log file. 
+**
+** This routine first tries to establish an exclusive lock on the
+** wal-index to prevent other threads/processes from doing anything
+** with the WAL or wal-index while recovery is running.  The
+** WAL_RECOVER_LOCK is also held so that other threads will know
+** that this thread is running recovery.  If unable to establish
+** the necessary locks, this routine returns SQLITE_BUSY.
+*/
+static int walIndexRecover(Wal *pWal){
+  int rc;                         /* Return Code */
+  i64 nSize;                      /* Size of log file */
+  u32 aFrameCksum[2] = {0, 0};
+  int iLock;                      /* Lock offset to lock for checkpoint */
+  int nLock;                      /* Number of locks to hold */
+
+  /* Obtain an exclusive lock on all byte in the locking range not already
+  ** locked by the caller. The caller is guaranteed to have locked the
+  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
+  ** If successful, the same bytes that are locked here are unlocked before
+  ** this function returns.
+  */
+  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
+  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
+  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
+  assert( pWal->writeLock );
+  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
+  nLock = SQLITE_SHM_NLOCK - iLock;
+  rc = walLockExclusive(pWal, iLock, nLock);
+  if( rc ){
+    return rc;
+  }
+  WALTRACE(("WAL%p: recovery begin...\n", pWal));
+
+  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+
+  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
+  if( rc!=SQLITE_OK ){
+    goto recovery_error;
+  }
+
+  if( nSize>WAL_HDRSIZE ){
+    u8 aBuf[WAL_HDRSIZE];         /* Buffer to load WAL header into */
+    u8 *aFrame = 0;               /* Malloc'd buffer to load entire frame */
+    int szFrame;                  /* Number of bytes in buffer aFrame[] */
+    u8 *aData;                    /* Pointer to data part of aFrame buffer */
+    int iFrame;                   /* Index of last frame read */
+    i64 iOffset;                  /* Next offset to read from log file */
+    int szPage;                   /* Page size according to the log */
+    u32 magic;                    /* Magic value read from WAL header */
+
+    /* Read in the WAL header. */
+    rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
+    if( rc!=SQLITE_OK ){
+      goto recovery_error;
+    }
+
+    /* If the database page size is not a power of two, or is greater than
+    ** SQLITE_MAX_PAGE_SIZE, conclude that the WAL file contains no valid 
+    ** data. Similarly, if the 'magic' value is invalid, ignore the whole
+    ** WAL file.
+    */
+    magic = sqlite3Get4byte(&aBuf[0]);
+    szPage = sqlite3Get4byte(&aBuf[8]);
+    if( (magic&0xFFFFFFFE)!=WAL_MAGIC 
+     || szPage&(szPage-1) 
+     || szPage>SQLITE_MAX_PAGE_SIZE 
+     || szPage<512 
+    ){
+      goto finished;
+    }
+    pWal->hdr.bigEndCksum = (magic&0x00000001);
+    pWal->szPage = szPage;
+    pWal->nCkpt = sqlite3Get4byte(&aBuf[12]);
+    memcpy(&pWal->hdr.aSalt, &aBuf[16], 8);
+    walChecksumBytes(pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN, 
+        aBuf, WAL_HDRSIZE, 0, pWal->hdr.aFrameCksum
+    );
+
+    /* Malloc a buffer to read frames into. */
+    szFrame = szPage + WAL_FRAME_HDRSIZE;
+    aFrame = (u8 *)sqlite3_malloc(szFrame);
+    if( !aFrame ){
+      rc = SQLITE_NOMEM;
+      goto recovery_error;
+    }
+    aData = &aFrame[WAL_FRAME_HDRSIZE];
+
+    /* Read all frames from the log file. */
+    iFrame = 0;
+    for(iOffset=WAL_HDRSIZE; (iOffset+szFrame)<=nSize; iOffset+=szFrame){
+      u32 pgno;                   /* Database page number for frame */
+      u32 nTruncate;              /* dbsize field from frame header */
+      int isValid;                /* True if this frame is valid */
+
+      /* Read and decode the next log frame. */
+      rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
+      if( rc!=SQLITE_OK ) break;
+      isValid = walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame);
+      if( !isValid ) break;
+      rc = walIndexAppend(pWal, ++iFrame, pgno);
+      if( rc!=SQLITE_OK ) break;
+
+      /* If nTruncate is non-zero, this is a commit record. */
+      if( nTruncate ){
+        pWal->hdr.mxFrame = iFrame;
+        pWal->hdr.nPage = nTruncate;
+        pWal->hdr.szPage = szPage;
+        aFrameCksum[0] = pWal->hdr.aFrameCksum[0];
+        aFrameCksum[1] = pWal->hdr.aFrameCksum[1];
+      }
+    }
+
+    sqlite3_free(aFrame);
+  }
+
+finished:
+  if( rc==SQLITE_OK ){
+    volatile WalCkptInfo *pInfo;
+    int i;
+    pWal->hdr.aFrameCksum[0] = aFrameCksum[0];
+    pWal->hdr.aFrameCksum[1] = aFrameCksum[1];
+    walIndexWriteHdr(pWal);
+
+    /* Reset the checkpoint-header. This is safe because this thread is 
+    ** currently holding locks that exclude all other readers, writers and
+    ** checkpointers.
+    */
+    pInfo = walCkptInfo(pWal);
+    pInfo->nBackfill = 0;
+    pInfo->aReadMark[0] = 0;
+    for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+  }
+
+recovery_error:
+  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
+  walUnlockExclusive(pWal, iLock, nLock);
+  return rc;
+}
+
+/*
+** Close an open wal-index.
+*/
+static void walIndexClose(Wal *pWal, int isDelete){
+  if( pWal->isWIndexOpen ){
+    sqlite3OsShmClose(pWal->pDbFd, isDelete);
+    pWal->isWIndexOpen = 0;
+  }
+}
+
+/* 
+** Open a connection to the WAL file associated with database zDbName.
+** The database file must already be opened on connection pDbFd.
+**
+** A SHARED lock should be held on the database file when this function
+** is called. The purpose of this SHARED lock is to prevent any other
+** client from unlinking the WAL or wal-index file. If another process
+** were to do this just after this client opened one of these files, the
+** system would be badly broken.
+**
+** If the log file is successfully opened, SQLITE_OK is returned and 
+** *ppWal is set to point to a new WAL handle. If an error occurs,
+** an SQLite error code is returned and *ppWal is left unmodified.
+*/
+SQLITE_PRIVATE int sqlite3WalOpen(
+  sqlite3_vfs *pVfs,              /* vfs module to open wal and wal-index */
+  sqlite3_file *pDbFd,            /* The open database file */
+  const char *zDbName,            /* Name of the database file */
+  Wal **ppWal                     /* OUT: Allocated Wal handle */
+){
+  int rc;                         /* Return Code */
+  Wal *pRet;                      /* Object to allocate and return */
+  int flags;                      /* Flags passed to OsOpen() */
+  char *zWal;                     /* Name of write-ahead log file */
+  int nWal;                       /* Length of zWal in bytes */
+
+  assert( zDbName && zDbName[0] );
+  assert( pDbFd );
+
+  /* In the amalgamation, the os_unix.c and os_win.c source files come before
+  ** this source file.  Verify that the #defines of the locking byte offsets
+  ** in os_unix.c and os_win.c agree with the WALINDEX_LOCK_OFFSET value.
+  */
+#ifdef WIN_SHM_BASE
+  assert( WIN_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+#ifdef UNIX_SHM_BASE
+  assert( UNIX_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+
+
+  /* Allocate an instance of struct Wal to return. */
+  *ppWal = 0;
+  nWal = sqlite3Strlen30(zDbName) + 5;
+  pRet = (Wal*)sqlite3MallocZero(sizeof(Wal) + pVfs->szOsFile + nWal);
+  if( !pRet ){
+    return SQLITE_NOMEM;
+  }
+
+  pRet->pVfs = pVfs;
+  pRet->pWalFd = (sqlite3_file *)&pRet[1];
+  pRet->pDbFd = pDbFd;
+  pRet->readLock = -1;
+  sqlite3_randomness(8, &pRet->hdr.aSalt);
+  pRet->zWalName = zWal = pVfs->szOsFile + (char*)pRet->pWalFd;
+  sqlite3_snprintf(nWal, zWal, "%s-wal", zDbName);
+  rc = sqlite3OsShmOpen(pDbFd);
+
+  /* Open file handle on the write-ahead log file. */
+  if( rc==SQLITE_OK ){
+    pRet->isWIndexOpen = 1;
+    flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_MAIN_JOURNAL);
+    rc = sqlite3OsOpen(pVfs, zWal, pRet->pWalFd, flags, &flags);
+  }
+
+  if( rc!=SQLITE_OK ){
+    walIndexClose(pRet, 0);
+    sqlite3OsClose(pRet->pWalFd);
+    sqlite3_free(pRet);
+  }else{
+    *ppWal = pRet;
+    WALTRACE(("WAL%d: opened\n", pRet));
+  }
+  return rc;
+}
+
+/*
+** Find the smallest page number out of all pages held in the WAL that
+** has not been returned by any prior invocation of this method on the
+** same WalIterator object.   Write into *piFrame the frame index where
+** that page was last written into the WAL.  Write into *piPage the page
+** number.
+**
+** Return 0 on success.  If there are no pages in the WAL with a page
+** number larger than *piPage, then return 1.
+*/
+static int walIteratorNext(
+  WalIterator *p,               /* Iterator */
+  u32 *piPage,                  /* OUT: The page number of the next page */
+  u32 *piFrame                  /* OUT: Wal frame index of next page */
+){
+  u32 iMin;                     /* Result pgno must be greater than iMin */
+  u32 iRet = 0xFFFFFFFF;        /* 0xffffffff is never a valid page number */
+  int i;                        /* For looping through segments */
+
+  iMin = p->iPrior;
+  assert( iMin<0xffffffff );
+  for(i=p->nSegment-1; i>=0; i--){
+    struct WalSegment *pSegment = &p->aSegment[i];
+    while( pSegment->iNext<pSegment->nEntry ){
+      u32 iPg = pSegment->aPgno[pSegment->aIndex[pSegment->iNext]];
+      if( iPg>iMin ){
+        if( iPg<iRet ){
+          iRet = iPg;
+          *piFrame = pSegment->iZero + pSegment->aIndex[pSegment->iNext];
+        }
+        break;
+      }
+      pSegment->iNext++;
+    }
+  }
+
+  *piPage = p->iPrior = iRet;
+  return (iRet==0xFFFFFFFF);
+}
+
+
+static void walMergesort(
+  u32 *aContent,                  /* Pages in wal */
+  ht_slot *aBuffer,               /* Buffer of at least *pnList items to use */
+  ht_slot *aList,                 /* IN/OUT: List to sort */
+  int *pnList                     /* IN/OUT: Number of elements in aList[] */
+){
+  int nList = *pnList;
+  if( nList>1 ){
+    int nLeft = nList / 2;        /* Elements in left list */
+    int nRight = nList - nLeft;   /* Elements in right list */
+    int iLeft = 0;                /* Current index in aLeft */
+    int iRight = 0;               /* Current index in aright */
+    int iOut = 0;                 /* Current index in output buffer */
+    ht_slot *aLeft = aList;       /* Left list */
+    ht_slot *aRight = aList+nLeft;/* Right list */
+
+    /* TODO: Change to non-recursive version. */
+    walMergesort(aContent, aBuffer, aLeft, &nLeft);
+    walMergesort(aContent, aBuffer, aRight, &nRight);
+
+    while( iRight<nRight || iLeft<nLeft ){
+      ht_slot logpage;
+      Pgno dbpage;
+
+      if( (iLeft<nLeft) 
+       && (iRight>=nRight || aContent[aLeft[iLeft]]<aContent[aRight[iRight]])
+      ){
+        logpage = aLeft[iLeft++];
+      }else{
+        logpage = aRight[iRight++];
+      }
+      dbpage = aContent[logpage];
+
+      aBuffer[iOut++] = logpage;
+      if( iLeft<nLeft && aContent[aLeft[iLeft]]==dbpage ) iLeft++;
+
+      assert( iLeft>=nLeft || aContent[aLeft[iLeft]]>dbpage );
+      assert( iRight>=nRight || aContent[aRight[iRight]]>dbpage );
+    }
+    memcpy(aList, aBuffer, sizeof(aList[0])*iOut);
+    *pnList = iOut;
+  }
+
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=1; i<*pnList; i++){
+      assert( aContent[aList[i]] > aContent[aList[i-1]] );
+    }
+  }
+#endif
+}
+
+/* 
+** Free an iterator allocated by walIteratorInit().
+*/
+static void walIteratorFree(WalIterator *p){
+  sqlite3_free(p);
+}
+
+/*
+** Map the wal-index into memory owned by this thread, if it is not
+** mapped already.  Then construct a WalInterator object that can be
+** used to loop over all pages in the WAL in ascending order.  
+**
+** On success, make *pp point to the newly allocated WalInterator object
+** return SQLITE_OK.  Otherwise, leave *pp unchanged and return an error
+** code.
+**
+** The calling routine should invoke walIteratorFree() to destroy the
+** WalIterator object when it has finished with it.  The caller must
+** also unmap the wal-index.  But the wal-index must not be unmapped
+** prior to the WalIterator object being destroyed.
+*/
+static int walIteratorInit(Wal *pWal, WalIterator **pp){
+  WalIterator *p;                 /* Return value */
+  int nSegment;                   /* Number of segments to merge */
+  u32 iLast;                      /* Last frame in log */
+  int nByte;                      /* Number of bytes to allocate */
+  int i;                          /* Iterator variable */
+  ht_slot *aTmp;                  /* Temp space used by merge-sort */
+  ht_slot *aSpace;                /* Space at the end of the allocation */
+
+  /* This routine only runs while holding SQLITE_SHM_CHECKPOINT.  No other
+  ** thread is able to write to shared memory while this routine is
+  ** running (or, indeed, while the WalIterator object exists).  Hence,
+  ** we can cast off the volatile qualification from shared memory
+  */
+  assert( pWal->ckptLock );
+  iLast = pWal->hdr.mxFrame;
+
+  /* Allocate space for the WalIterator object */
+  nSegment = walFramePage(iLast) + 1;
+  nByte = sizeof(WalIterator) 
+        + nSegment*(sizeof(struct WalSegment))
+        + (nSegment+1)*(HASHTABLE_NPAGE * sizeof(ht_slot));
+  p = (WalIterator *)sqlite3_malloc(nByte);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, nByte);
+
+  /* Allocate space for the WalIterator object */
+  p->nSegment = nSegment;
+  aSpace = (ht_slot *)&p->aSegment[nSegment];
+  aTmp = &aSpace[HASHTABLE_NPAGE*nSegment];
+  for(i=0; i<nSegment; i++){
+    volatile ht_slot *aHash;
+    int j;
+    u32 iZero;
+    int nEntry;
+    volatile u32 *aPgno;
+    int rc;
+
+    rc = walHashGet(pWal, i, &aHash, &aPgno, &iZero);
+    if( rc!=SQLITE_OK ){
+      walIteratorFree(p);
+      return rc;
+    }
+    aPgno++;
+    nEntry = ((i+1)==nSegment)?iLast-iZero:(u32 *)aHash-(u32 *)aPgno;
+    iZero++;
+
+    for(j=0; j<nEntry; j++){
+      aSpace[j] = j;
+    }
+    walMergesort((u32 *)aPgno, aTmp, aSpace, &nEntry);
+    p->aSegment[i].iZero = iZero;
+    p->aSegment[i].nEntry = nEntry;
+    p->aSegment[i].aIndex = aSpace;
+    p->aSegment[i].aPgno = (u32 *)aPgno;
+    aSpace += HASHTABLE_NPAGE;
+  }
+  assert( aSpace==aTmp );
+
+  /* Return the fully initialized WalIterator object */
+  *pp = p;
+  return SQLITE_OK ;
+}
+
+/*
+** Copy as much content as we can from the WAL back into the database file
+** in response to an sqlite3_wal_checkpoint() request or the equivalent.
+**
+** The amount of information copies from WAL to database might be limited
+** by active readers.  This routine will never overwrite a database page
+** that a concurrent reader might be using.
+**
+** All I/O barrier operations (a.k.a fsyncs) occur in this routine when
+** SQLite is in WAL-mode in synchronous=NORMAL.  That means that if 
+** checkpoints are always run by a background thread or background 
+** process, foreground threads will never block on a lengthy fsync call.
+**
+** Fsync is called on the WAL before writing content out of the WAL and
+** into the database.  This ensures that if the new content is persistent
+** in the WAL and can be recovered following a power-loss or hard reset.
+**
+** Fsync is also called on the database file if (and only if) the entire
+** WAL content is copied into the database file.  This second fsync makes
+** it safe to delete the WAL since the new content will persist in the
+** database file.
+**
+** This routine uses and updates the nBackfill field of the wal-index header.
+** This is the only routine tha will increase the value of nBackfill.  
+** (A WAL reset or recovery will revert nBackfill to zero, but not increase
+** its value.)
+**
+** The caller must be holding sufficient locks to ensure that no other
+** checkpoint is running (in any other thread or process) at the same
+** time.
+*/
+static int walCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int sync_flags,                 /* Flags for OsSync() (or 0) */
+  int nBuf,                       /* Size of zBuf in bytes */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc;                         /* Return code */
+  int szPage = pWal->hdr.szPage;  /* Database page-size */
+  WalIterator *pIter = 0;         /* Wal iterator context */
+  u32 iDbpage = 0;                /* Next database page to write */
+  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
+  u32 mxSafeFrame;                /* Max frame that can be backfilled */
+  int i;                          /* Loop counter */
+  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
+
+  /* Allocate the iterator */
+  rc = walIteratorInit(pWal, &pIter);
+  if( rc!=SQLITE_OK || pWal->hdr.mxFrame==0 ){
+    goto walcheckpoint_out;
+  }
+
+  /*** TODO:  Move this test out to the caller.  Make it an assert() here ***/
+  if( pWal->hdr.szPage!=nBuf ){
+    rc = SQLITE_CORRUPT_BKPT;
+    goto walcheckpoint_out;
+  }
+
+  /* Compute in mxSafeFrame the index of the last frame of the WAL that is
+  ** safe to write into the database.  Frames beyond mxSafeFrame might
+  ** overwrite database pages that are in use by active readers and thus
+  ** cannot be backfilled from the WAL.
+  */
+  mxSafeFrame = pWal->hdr.mxFrame;
+  pInfo = walCkptInfo(pWal);
+  for(i=1; i<WAL_NREADER; i++){
+    u32 y = pInfo->aReadMark[i];
+    if( mxSafeFrame>=y ){
+      assert( y<=pWal->hdr.mxFrame );
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      if( rc==SQLITE_OK ){
+        pInfo->aReadMark[i] = READMARK_NOT_USED;
+        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      }else if( rc==SQLITE_BUSY ){
+        mxSafeFrame = y;
+      }else{
+        goto walcheckpoint_out;
+      }
+    }
+  }
+
+  if( pInfo->nBackfill<mxSafeFrame
+   && (rc = walLockExclusive(pWal, WAL_READ_LOCK(0), 1))==SQLITE_OK
+  ){
+    u32 nBackfill = pInfo->nBackfill;
+
+    /* Sync the WAL to disk */
+    if( sync_flags ){
+      rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+    }
+
+    /* Iterate through the contents of the WAL, copying data to the db file. */
+    while( rc==SQLITE_OK && 0==walIteratorNext(pIter, &iDbpage, &iFrame) ){
+      assert( walFramePgno(pWal, iFrame)==iDbpage );
+      if( iFrame<=nBackfill || iFrame>mxSafeFrame ) continue;
+      rc = sqlite3OsRead(pWal->pWalFd, zBuf, szPage, 
+          walFrameOffset(iFrame, szPage) + WAL_FRAME_HDRSIZE
+      );
+      if( rc!=SQLITE_OK ) break;
+      rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, (iDbpage-1)*szPage);
+      if( rc!=SQLITE_OK ) break;
+    }
+
+    /* If work was actually accomplished... */
+    if( rc==SQLITE_OK ){
+      if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){
+        rc = sqlite3OsTruncate(pWal->pDbFd, ((i64)pWal->hdr.nPage*(i64)szPage));
+        if( rc==SQLITE_OK && sync_flags ){
+          rc = sqlite3OsSync(pWal->pDbFd, sync_flags);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        pInfo->nBackfill = mxSafeFrame;
+      }
+    }
+
+    /* Release the reader lock held while backfilling */
+    walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
+  }else if( rc==SQLITE_BUSY ){
+    /* Reset the return code so as not to report a checkpoint failure
+    ** just because active readers prevent any backfill.
+    */
+    rc = SQLITE_OK;
+  }
+
+ walcheckpoint_out:
+  walIteratorFree(pIter);
+  return rc;
+}
+
+/*
+** Close a connection to a log file.
+*/
+SQLITE_PRIVATE int sqlite3WalClose(
+  Wal *pWal,                      /* Wal to close */
+  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
+  int nBuf,
+  u8 *zBuf                        /* Buffer of at least nBuf bytes */
+){
+  int rc = SQLITE_OK;
+  if( pWal ){
+    int isDelete = 0;             /* True to unlink wal and wal-index files */
+
+    /* If an EXCLUSIVE lock can be obtained on the database file (using the
+    ** ordinary, rollback-mode locking methods, this guarantees that the
+    ** connection associated with this log file is the only connection to
+    ** the database. In this case checkpoint the database and unlink both
+    ** the wal and wal-index files.
+    **
+    ** The EXCLUSIVE lock is not released before returning.
+    */
+    rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE);
+    if( rc==SQLITE_OK ){
+      pWal->exclusiveMode = 1;
+      rc = sqlite3WalCheckpoint(pWal, sync_flags, nBuf, zBuf);
+      if( rc==SQLITE_OK ){
+        isDelete = 1;
+      }
+    }
+
+    walIndexClose(pWal, isDelete);
+    sqlite3OsClose(pWal->pWalFd);
+    if( isDelete ){
+      sqlite3OsDelete(pWal->pVfs, pWal->zWalName, 0);
+    }
+    WALTRACE(("WAL%p: closed\n", pWal));
+    sqlite3_free(pWal->apWiData);
+    sqlite3_free(pWal);
+  }
+  return rc;
+}
+
+/*
+** Try to read the wal-index header.  Return 0 on success and 1 if
+** there is a problem.
+**
+** The wal-index is in shared memory.  Another thread or process might
+** be writing the header at the same time this procedure is trying to
+** read it, which might result in inconsistency.  A dirty read is detected
+** by verifying that both copies of the header are the same and also by
+** a checksum on the header.
+**
+** If and only if the read is consistent and the header is different from
+** pWal->hdr, then pWal->hdr is updated to the content of the new header
+** and *pChanged is set to 1.
+**
+** If the checksum cannot be verified return non-zero. If the header
+** is read successfully and the checksum verified, return zero.
+*/
+int walIndexTryHdr(Wal *pWal, int *pChanged){
+  u32 aCksum[2];                  /* Checksum on the header content */
+  WalIndexHdr h1, h2;             /* Two copies of the header content */
+  WalIndexHdr volatile *aHdr;     /* Header in shared memory */
+
+  /* The first page of the wal-index must be mapped at this point. */
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+
+  /* Read the header. This might happen currently with a write to the
+  ** same area of shared memory on a different CPU in a SMP,
+  ** meaning it is possible that an inconsistent snapshot is read
+  ** from the file. If this happens, return non-zero.
+  **
+  ** There are two copies of the header at the beginning of the wal-index.
+  ** When reading, read [0] first then [1].  Writes are in the reverse order.
+  ** Memory barriers are used to prevent the compiler or the hardware from
+  ** reordering the reads and writes.
+  */
+  aHdr = walIndexHdr(pWal);
+  memcpy(&h1, (void *)&aHdr[0], sizeof(h1));
+  sqlite3OsShmBarrier(pWal->pDbFd);
+  memcpy(&h2, (void *)&aHdr[1], sizeof(h2));
+
+  if( memcmp(&h1, &h2, sizeof(h1))!=0 ){
+    return 1;   /* Dirty read */
+  }  
+  if( h1.isInit==0 ){
+    return 1;   /* Malformed header - probably all zeros */
+  }
+  walChecksumBytes(1, (u8*)&h1, sizeof(h1)-sizeof(h1.aCksum), 0, aCksum);
+  if( aCksum[0]!=h1.aCksum[0] || aCksum[1]!=h1.aCksum[1] ){
+    return 1;   /* Checksum does not match */
+  }
+
+  if( memcmp(&pWal->hdr, &h1, sizeof(WalIndexHdr)) ){
+    *pChanged = 1;
+    memcpy(&pWal->hdr, &h1, sizeof(WalIndexHdr));
+    pWal->szPage = pWal->hdr.szPage;
+  }
+
+  /* The header was successfully read. Return zero. */
+  return 0;
+}
+
+/*
+** Read the wal-index header from the wal-index and into pWal->hdr.
+** If the wal-header appears to be corrupt, try to recover the log
+** before returning.
+**
+** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
+** changed by this opertion.  If pWal->hdr is unchanged, set *pChanged
+** to 0.
+**
+** This routine also maps the wal-index content into memory and assigns
+** ownership of that mapping to the current thread.  In some implementations,
+** only one thread at a time can hold a mapping of the wal-index.  Hence,
+** the caller should strive to invoke walIndexUnmap() as soon as possible
+** after this routine returns.
+**
+** If the wal-index header is successfully read, return SQLITE_OK. 
+** Otherwise an SQLite error code.
+*/
+static int walIndexReadHdr(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int badHdr;                     /* True if a header read failed */
+  volatile u32 *page0;
+
+  /* Ensure that page 0 of the wal-index (the page that contains the 
+  ** wal-index header) is mapped. Return early if an error occurs here.
+  */
+  assert( pChanged );
+  rc = walIndexPage(pWal, 0, &page0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  };
+  assert( page0 || pWal->writeLock==0 );
+
+  /* If the first page of the wal-index has been mapped, try to read the
+  ** wal-index header immediately, without holding any lock. This usually
+  ** works, but may fail if the wal-index header is corrupt or currently 
+  ** being modified by another user.
+  */
+  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
+
+  /* If the first attempt failed, it might have been due to a race
+  ** with a writer.  So get a WRITE lock and try again.
+  */
+  assert( badHdr==0 || pWal->writeLock==0 );
+  if( badHdr && SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
+    pWal->writeLock = 1;
+    if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
+      badHdr = walIndexTryHdr(pWal, pChanged);
+      if( badHdr ){
+        /* If the wal-index header is still malformed even while holding
+        ** a WRITE lock, it can only mean that the header is corrupted and
+        ** needs to be reconstructed.  So run recovery to do exactly that.
+        */
+        rc = walIndexRecover(pWal);
+        *pChanged = 1;
+      }
+    }
+    pWal->writeLock = 0;
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  }
+
+  return rc;
+}
+
+/*
+** This is the value that walTryBeginRead returns when it needs to
+** be retried.
+*/
+#define WAL_RETRY  (-1)
+
+/*
+** Attempt to start a read transaction.  This might fail due to a race or
+** other transient condition.  When that happens, it returns WAL_RETRY to
+** indicate to the caller that it is safe to retry immediately.
+**
+** On success return SQLITE_OK.  On a permantent failure (such an
+** I/O error or an SQLITE_BUSY because another process is running
+** recovery) return a positive error code.
+**
+** On success, this routine obtains a read lock on 
+** WAL_READ_LOCK(pWal->readLock).  The pWal->readLock integer is
+** in the range 0 <= pWal->readLock < WAL_NREADER.  If pWal->readLock==(-1)
+** that means the Wal does not hold any read lock.  The reader must not
+** access any database page that is modified by a WAL frame up to and
+** including frame number aReadMark[pWal->readLock].  The reader will
+** use WAL frames up to and including pWal->hdr.mxFrame if pWal->readLock>0
+** Or if pWal->readLock==0, then the reader will ignore the WAL
+** completely and get all content directly from the database file.
+** When the read transaction is completed, the caller must release the
+** lock on WAL_READ_LOCK(pWal->readLock) and set pWal->readLock to -1.
+**
+** This routine uses the nBackfill and aReadMark[] fields of the header
+** to select a particular WAL_READ_LOCK() that strives to let the
+** checkpoint process do as much work as possible.  This routine might
+** update values of the aReadMark[] array in the header, but if it does
+** so it takes care to hold an exclusive lock on the corresponding
+** WAL_READ_LOCK() while changing values.
+*/
+static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
+  volatile WalCkptInfo *pInfo;    /* Checkpoint information in wal-index */
+  u32 mxReadMark;                 /* Largest aReadMark[] value */
+  int mxI;                        /* Index of largest aReadMark[] value */
+  int i;                          /* Loop counter */
+  int rc = SQLITE_OK;             /* Return code  */
+
+  assert( pWal->readLock<0 );     /* Not currently locked */
+
+  /* Take steps to avoid spinning forever if there is a protocol error. */
+  if( cnt>5 ){
+    if( cnt>100 ) return SQLITE_PROTOCOL;
+    sqlite3OsSleep(pWal->pVfs, 1);
+  }
+
+  if( !useWal ){
+    rc = walIndexReadHdr(pWal, pChanged);
+    if( rc==SQLITE_BUSY ){
+      /* If there is not a recovery running in another thread or process
+      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
+      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
+      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
+      ** would be technically correct.  But the race is benign since with
+      ** WAL_RETRY this routine will be called again and will probably be
+      ** right on the second iteration.
+      */
+      rc = walLockShared(pWal, WAL_RECOVER_LOCK);
+      if( rc==SQLITE_OK ){
+        walUnlockShared(pWal, WAL_RECOVER_LOCK);
+        rc = WAL_RETRY;
+      }else if( rc==SQLITE_BUSY ){
+        rc = SQLITE_BUSY_RECOVERY;
+      }
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  pInfo = walCkptInfo(pWal);
+  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){
+    /* The WAL has been completely backfilled (or it is empty).
+    ** and can be safely ignored.
+    */
+    rc = walLockShared(pWal, WAL_READ_LOCK(0));
+    sqlite3OsShmBarrier(pWal->pDbFd);
+    if( rc==SQLITE_OK ){
+      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
+        /* It is not safe to allow the reader to continue here if frames
+        ** may have been appended to the log before READ_LOCK(0) was obtained.
+        ** When holding READ_LOCK(0), the reader ignores the entire log file,
+        ** which implies that the database file contains a trustworthy
+        ** snapshoT. Since holding READ_LOCK(0) prevents a checkpoint from
+        ** happening, this is usually correct.
+        **
+        ** However, if frames have been appended to the log (or if the log 
+        ** is wrapped and written for that matter) before the READ_LOCK(0)
+        ** is obtained, that is not necessarily true. A checkpointer may
+        ** have started to backfill the appended frames but crashed before
+        ** it finished. Leaving a corrupt image in the database file.
+        */
+        walUnlockShared(pWal, WAL_READ_LOCK(0));
+        return WAL_RETRY;
+      }
+      pWal->readLock = 0;
+      return SQLITE_OK;
+    }else if( rc!=SQLITE_BUSY ){
+      return rc;
+    }
+  }
+
+  /* If we get this far, it means that the reader will want to use
+  ** the WAL to get at content from recent commits.  The job now is
+  ** to select one of the aReadMark[] entries that is closest to
+  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
+  */
+  mxReadMark = 0;
+  mxI = 0;
+  for(i=1; i<WAL_NREADER; i++){
+    u32 thisMark = pInfo->aReadMark[i];
+    if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){
+      assert( thisMark!=READMARK_NOT_USED );
+      mxReadMark = thisMark;
+      mxI = i;
+    }
+  }
+  if( mxI==0 ){
+    /* If we get here, it means that all of the aReadMark[] entries between
+    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
+    ** be mxFrame, then retry.
+    */
+    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
+    if( rc==SQLITE_OK ){
+      pInfo->aReadMark[1] = pWal->hdr.mxFrame;
+      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);
+      rc = WAL_RETRY;
+    }else if( rc==SQLITE_BUSY ){
+      rc = WAL_RETRY;
+    }
+    return rc;
+  }else{
+    if( mxReadMark < pWal->hdr.mxFrame ){
+      for(i=1; i<WAL_NREADER; i++){
+        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+        if( rc==SQLITE_OK ){
+          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
+          mxI = i;
+          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+          break;
+        }else if( rc!=SQLITE_BUSY ){
+          return rc;
+        }
+      }
+    }
+
+    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
+    if( rc ){
+      return rc==SQLITE_BUSY ? WAL_RETRY : rc;
+    }
+    /* Now that the read-lock has been obtained, check that neither the
+    ** value in the aReadMark[] array or the contents of the wal-index
+    ** header have changed.
+    **
+    ** It is necessary to check that the wal-index header did not change
+    ** between the time it was read and when the shared-lock was obtained
+    ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
+    ** that the log file may have been wrapped by a writer, or that frames
+    ** that occur later in the log than pWal->hdr.mxFrame may have been
+    ** copied into the database by a checkpointer. If either of these things
+    ** happened, then reading the database with the current value of
+    ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
+    ** instead.
+    **
+    ** This does not guarantee that the copy of the wal-index header is up to
+    ** date before proceeding. That would not be possible without somehow
+    ** blocking writers. It only guarantees that a dangerous checkpoint or 
+    ** log-wrap (either of which would require an exclusive lock on
+    ** WAL_READ_LOCK(mxI)) has not occurred since the snapshot was valid.
+    */
+    sqlite3OsShmBarrier(pWal->pDbFd);
+    if( pInfo->aReadMark[mxI]!=mxReadMark
+     || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
+    ){
+      walUnlockShared(pWal, WAL_READ_LOCK(mxI));
+      return WAL_RETRY;
+    }else{
+      assert( mxReadMark<=pWal->hdr.mxFrame );
+      pWal->readLock = mxI;
+    }
+  }
+  return rc;
+}
+
+/*
+** Begin a read transaction on the database.
+**
+** This routine used to be called sqlite3OpenSnapshot() and with good reason:
+** it takes a snapshot of the state of the WAL and wal-index for the current
+** instant in time.  The current thread will continue to use this snapshot.
+** Other threads might append new content to the WAL and wal-index but
+** that extra content is ignored by the current thread.
+**
+** If the database contents have changes since the previous read
+** transaction, then *pChanged is set to 1 before returning.  The
+** Pager layer will use this to know that is cache is stale and
+** needs to be flushed.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int cnt = 0;                    /* Number of TryBeginRead attempts */
+
+  do{
+    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
+  }while( rc==WAL_RETRY );
+  return rc;
+}
+
+/*
+** Finish with a read transaction.  All this does is release the
+** read-lock.
+*/
+SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal){
+  if( pWal->readLock>=0 ){
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->readLock = -1;
+  }
+}
+
+/*
+** Read a page from the WAL, if it is present in the WAL and if the 
+** current read transaction is configured to use the WAL.  
+**
+** The *pInWal is set to 1 if the requested page is in the WAL and
+** has been loaded.  Or *pInWal is set to 0 if the page was not in 
+** the WAL and needs to be read out of the database.
+*/
+SQLITE_PRIVATE int sqlite3WalRead(
+  Wal *pWal,                      /* WAL handle */
+  Pgno pgno,                      /* Database page number to read data for */
+  int *pInWal,                    /* OUT: True if data is read from WAL */
+  int nOut,                       /* Size of buffer pOut in bytes */
+  u8 *pOut                        /* Buffer to write page data to */
+){
+  u32 iRead = 0;                  /* If !=0, WAL frame to return data from */
+  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
+  int iHash;                      /* Used to loop through N hash tables */
+
+  /* This routine is only be called from within a read transaction. */
+  assert( pWal->readLock>=0 || pWal->lockError );
+
+  /* If the "last page" field of the wal-index header snapshot is 0, then
+  ** no data will be read from the wal under any circumstances. Return early
+  ** in this case to avoid the walIndexMap/Unmap overhead.  Likewise, if
+  ** pWal->readLock==0, then the WAL is ignored by the reader so
+  ** return early, as if the WAL were empty.
+  */
+  if( iLast==0 || pWal->readLock==0 ){
+    *pInWal = 0;
+    return SQLITE_OK;
+  }
+
+  /* Search the hash table or tables for an entry matching page number
+  ** pgno. Each iteration of the following for() loop searches one
+  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).
+  **
+  ** This code may run concurrently to the code in walIndexAppend()
+  ** that adds entries to the wal-index (and possibly to this hash 
+  ** table). This means the value just read from the hash 
+  ** slot (aHash[iKey]) may have been added before or after the 
+  ** current read transaction was opened. Values added after the
+  ** read transaction was opened may have been written incorrectly -
+  ** i.e. these slots may contain garbage data. However, we assume
+  ** that any slots written before the current read transaction was
+  ** opened remain unmodified.
+  **
+  ** For the reasons above, the if(...) condition featured in the inner
+  ** loop of the following block is more stringent that would be required 
+  ** if we had exclusive access to the hash-table:
+  **
+  **   (aPgno[iFrame]==pgno): 
+  **     This condition filters out normal hash-table collisions.
+  **
+  **   (iFrame<=iLast): 
+  **     This condition filters out entries that were added to the hash
+  **     table after the current read-transaction had started.
+  */
+  for(iHash=walFramePage(iLast); iHash>=0 && iRead==0; iHash--){
+    volatile ht_slot *aHash;      /* Pointer to hash table */
+    volatile u32 *aPgno;          /* Pointer to array of page numbers */
+    u32 iZero;                    /* Frame number corresponding to aPgno[0] */
+    int iKey;                     /* Hash slot index */
+    int rc;
+
+    rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
+      u32 iFrame = aHash[iKey] + iZero;
+      if( iFrame<=iLast && aPgno[aHash[iKey]]==pgno ){
+        assert( iFrame>iRead );
+        iRead = iFrame;
+      }
+    }
+  }
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* If expensive assert() statements are available, do a linear search
+  ** of the wal-index file content. Make sure the results agree with the
+  ** result obtained using the hash indexes above.  */
+  {
+    u32 iRead2 = 0;
+    u32 iTest;
+    for(iTest=iLast; iTest>0; iTest--){
+      if( walFramePgno(pWal, iTest)==pgno ){
+        iRead2 = iTest;
+        break;
+      }
+    }
+    assert( iRead==iRead2 );
+  }
+#endif
+
+  /* If iRead is non-zero, then it is the log frame number that contains the
+  ** required page. Read and return data from the log file.
+  */
+  if( iRead ){
+    i64 iOffset = walFrameOffset(iRead, pWal->hdr.szPage) + WAL_FRAME_HDRSIZE;
+    *pInWal = 1;
+    return sqlite3OsRead(pWal->pWalFd, pOut, nOut, iOffset);
+  }
+
+  *pInWal = 0;
+  return SQLITE_OK;
+}
+
+
+/* 
+** Set *pPgno to the size of the database file (or zero, if unknown).
+*/
+SQLITE_PRIVATE void sqlite3WalDbsize(Wal *pWal, Pgno *pPgno){
+  assert( pWal->readLock>=0 || pWal->lockError );
+  *pPgno = pWal->hdr.nPage;
+}
+
+
+/* 
+** This function starts a write transaction on the WAL.
+**
+** A read transaction must have already been started by a prior call
+** to sqlite3WalBeginReadTransaction().
+**
+** If another thread or process has written into the database since
+** the read transaction was started, then it is not possible for this
+** thread to write as doing so would cause a fork.  So this routine
+** returns SQLITE_BUSY in that case and no write transaction is started.
+**
+** There can only be a single writer active at a time.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal){
+  int rc;
+
+  /* Cannot start a write transaction without first holding a read
+  ** transaction. */
+  assert( pWal->readLock>=0 );
+
+  /* Only one writer allowed at a time.  Get the write lock.  Return
+  ** SQLITE_BUSY if unable.
+  */
+  rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  if( rc ){
+    return rc;
+  }
+  pWal->writeLock = 1;
+
+  /* If another connection has written to the database file since the
+  ** time the read transaction on this connection was started, then
+  ** the write is disallowed.
+  */
+  if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+    rc = SQLITE_BUSY;
+  }
+
+  return rc;
+}
+
+/*
+** End a write transaction.  The commit has already been done.  This
+** routine merely releases the lock.
+*/
+SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal){
+  walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  pWal->writeLock = 0;
+  return SQLITE_OK;
+}
+
+/*
+** If any data has been written (but not committed) to the log file, this
+** function moves the write-pointer back to the start of the transaction.
+**
+** Additionally, the callback function is invoked for each frame written
+** to the WAL since the start of the transaction. If the callback returns
+** other than SQLITE_OK, it is not invoked again and the error code is
+** returned to the caller.
+**
+** Otherwise, if the callback function does not return an error, this
+** function returns SQLITE_OK.
+*/
+SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
+  int rc = SQLITE_OK;
+  if( pWal->writeLock ){
+    Pgno iMax = pWal->hdr.mxFrame;
+    Pgno iFrame;
+  
+    /* Restore the clients cache of the wal-index header to the state it
+    ** was in before the client began writing to the database. 
+    */
+    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
+
+    for(iFrame=pWal->hdr.mxFrame+1; 
+        ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; 
+        iFrame++
+    ){
+      /* This call cannot fail. Unless the page for which the page number
+      ** is passed as the second argument is (a) in the cache and 
+      ** (b) has an outstanding reference, then xUndo is either a no-op
+      ** (if (a) is false) or simply expels the page from the cache (if (b)
+      ** is false).
+      **
+      ** If the upper layer is doing a rollback, it is guaranteed that there
+      ** are no outstanding references to any page other than page 1. And
+      ** page 1 is never written to the log until the transaction is
+      ** committed. As a result, the call to xUndo may not fail.
+      */
+      assert( walFramePgno(pWal, iFrame)!=1 );
+      rc = xUndo(pUndoCtx, walFramePgno(pWal, iFrame));
+    }
+    walCleanupHash(pWal);
+  }
+  assert( rc==SQLITE_OK );
+  return rc;
+}
+
+/* 
+** Argument aWalData must point to an array of WAL_SAVEPOINT_NDATA u32 
+** values. This function populates the array with values required to 
+** "rollback" the write position of the WAL handle back to the current 
+** point in the event of a savepoint rollback (via WalSavepointUndo()).
+*/
+SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
+  assert( pWal->writeLock );
+  aWalData[0] = pWal->hdr.mxFrame;
+  aWalData[1] = pWal->hdr.aFrameCksum[0];
+  aWalData[2] = pWal->hdr.aFrameCksum[1];
+  aWalData[3] = pWal->nCkpt;
+}
+
+/* 
+** Move the write position of the WAL back to the point identified by
+** the values in the aWalData[] array. aWalData must point to an array
+** of WAL_SAVEPOINT_NDATA u32 values that has been previously populated
+** by a call to WalSavepoint().
+*/
+SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
+  int rc = SQLITE_OK;
+
+  assert( pWal->writeLock );
+  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
+
+  if( aWalData[3]!=pWal->nCkpt ){
+    /* This savepoint was opened immediately after the write-transaction
+    ** was started. Right after that, the writer decided to wrap around
+    ** to the start of the log. Update the savepoint values to match.
+    */
+    aWalData[0] = 0;
+    aWalData[3] = pWal->nCkpt;
+  }
+
+  if( aWalData[0]<pWal->hdr.mxFrame ){
+    pWal->hdr.mxFrame = aWalData[0];
+    pWal->hdr.aFrameCksum[0] = aWalData[1];
+    pWal->hdr.aFrameCksum[1] = aWalData[2];
+    walCleanupHash(pWal);
+  }
+
+  return rc;
+}
+
+/*
+** This function is called just before writing a set of frames to the log
+** file (see sqlite3WalFrames()). It checks to see if, instead of appending
+** to the current log file, it is possible to overwrite the start of the
+** existing log file with the new frames (i.e. "reset" the log). If so,
+** it sets pWal->hdr.mxFrame to 0. Otherwise, pWal->hdr.mxFrame is left
+** unchanged.
+**
+** SQLITE_OK is returned if no error is encountered (regardless of whether
+** or not pWal->hdr.mxFrame is modified). An SQLite error code is returned
+** if some error 
+*/
+static int walRestartLog(Wal *pWal){
+  int rc = SQLITE_OK;
+  int cnt;
+
+  if( pWal->readLock==0 ){
+    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+    assert( pInfo->nBackfill==pWal->hdr.mxFrame );
+    if( pInfo->nBackfill>0 ){
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        /* If all readers are using WAL_READ_LOCK(0) (in other words if no
+        ** readers are currently using the WAL), then the transactions
+        ** frames will overwrite the start of the existing log. Update the
+        ** wal-index header to reflect this.
+        **
+        ** In theory it would be Ok to update the cache of the header only
+        ** at this point. But updating the actual wal-index header is also
+        ** safe and means there is no special case for sqlite3WalUndo()
+        ** to handle if this transaction is rolled back.
+        */
+        int i;                    /* Loop counter */
+        u32 *aSalt = pWal->hdr.aSalt;       /* Big-endian salt values */
+        pWal->nCkpt++;
+        pWal->hdr.mxFrame = 0;
+        sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
+        sqlite3_randomness(4, &aSalt[1]);
+        walIndexWriteHdr(pWal);
+        pInfo->nBackfill = 0;
+        for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+        assert( pInfo->aReadMark[0]==0 );
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }
+    }
+    walUnlockShared(pWal, WAL_READ_LOCK(0));
+    pWal->readLock = -1;
+    cnt = 0;
+    do{
+      int notUsed;
+      rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
+    }while( rc==WAL_RETRY );
+  }
+  return rc;
+}
+
+/* 
+** Write a set of frames to the log. The caller must hold the write-lock
+** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
+*/
+SQLITE_PRIVATE int sqlite3WalFrames(
+  Wal *pWal,                      /* Wal handle to write to */
+  int szPage,                     /* Database page-size in bytes */
+  PgHdr *pList,                   /* List of dirty pages to write */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Used to catch return codes */
+  u32 iFrame;                     /* Next frame address */
+  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-header in */
+  PgHdr *p;                       /* Iterator to run through pList with. */
+  PgHdr *pLast = 0;               /* Last frame in list */
+  int nLast = 0;                  /* Number of extra copies of last page */
+
+  assert( pList );
+  assert( pWal->writeLock );
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
+    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
+              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
+  }
+#endif
+
+  /* See if it is possible to write these frames into the start of the
+  ** log file, instead of appending to it at pWal->hdr.mxFrame.
+  */
+  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
+    return rc;
+  }
+
+  /* If this is the first frame written into the log, write the WAL
+  ** header to the start of the WAL file. See comments at the top of
+  ** this source file for a description of the WAL header format.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  if( iFrame==0 ){
+    u8 aWalHdr[WAL_HDRSIZE];        /* Buffer to assembly wal-header in */
+    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
+    sqlite3Put4byte(&aWalHdr[4], 3007000);
+    sqlite3Put4byte(&aWalHdr[8], szPage);
+    pWal->szPage = szPage;
+    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;
+    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
+    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
+    rc = sqlite3OsWrite(pWal->pWalFd, aWalHdr, sizeof(aWalHdr), 0);
+    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    walChecksumBytes(1, aWalHdr, sizeof(aWalHdr), 0, pWal->hdr.aFrameCksum);
+  }
+  assert( pWal->szPage==szPage );
+
+  /* Write the log file. */
+  for(p=pList; p; p=p->pDirty){
+    u32 nDbsize;                  /* Db-size field for frame header */
+    i64 iOffset;                  /* Write offset in log file */
+
+    iOffset = walFrameOffset(++iFrame, szPage);
+    
+    /* Populate and write the frame header */
+    nDbsize = (isCommit && p->pDirty==0) ? nTruncate : 0;
+    walEncodeFrame(pWal, p->pgno, nDbsize, p->pData, aFrame);
+    rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    /* Write the page data */
+    rc = sqlite3OsWrite(pWal->pWalFd, p->pData, szPage, iOffset+sizeof(aFrame));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    pLast = p;
+  }
+
+  /* Sync the log file if the 'isSync' flag was specified. */
+  if( sync_flags ){
+    i64 iSegment = sqlite3OsSectorSize(pWal->pWalFd);
+    i64 iOffset = walFrameOffset(iFrame+1, szPage);
+
+    assert( isCommit );
+    assert( iSegment>0 );
+
+    iSegment = (((iOffset+iSegment-1)/iSegment) * iSegment);
+    while( iOffset<iSegment ){
+      walEncodeFrame(pWal, pLast->pgno, nTruncate, pLast->pData, aFrame);
+      rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+
+      iOffset += WAL_FRAME_HDRSIZE;
+      rc = sqlite3OsWrite(pWal->pWalFd, pLast->pData, szPage, iOffset); 
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      nLast++;
+      iOffset += szPage;
+    }
+
+    rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+  }
+
+  /* Append data to the wal-index. It is not necessary to lock the 
+  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
+  ** guarantees that there are no other writers, and no data that may
+  ** be in use by existing readers is being overwritten.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
+    iFrame++;
+    rc = walIndexAppend(pWal, iFrame, p->pgno);
+  }
+  while( nLast>0 && rc==SQLITE_OK ){
+    iFrame++;
+    nLast--;
+    rc = walIndexAppend(pWal, iFrame, pLast->pgno);
+  }
+
+  if( rc==SQLITE_OK ){
+    /* Update the private copy of the header. */
+    pWal->hdr.szPage = szPage;
+    pWal->hdr.mxFrame = iFrame;
+    if( isCommit ){
+      pWal->hdr.iChange++;
+      pWal->hdr.nPage = nTruncate;
+    }
+    /* If this is a commit, update the wal-index header too. */
+    if( isCommit ){
+      walIndexWriteHdr(pWal);
+      pWal->iCallback = iFrame;
+    }
+  }
+
+  WALTRACE(("WAL%p: frame write %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* 
+** This routine is called to implement sqlite3_wal_checkpoint() and
+** related interfaces.
+**
+** Obtain a CHECKPOINT lock and then backfill as much information as
+** we can from WAL into the database.
+*/
+SQLITE_PRIVATE int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of temporary buffer */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc;                         /* Return code */
+  int isChanged = 0;              /* True if a new wal-index header is loaded */
+
+  assert( pWal->ckptLock==0 );
+
+  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
+  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  if( rc ){
+    /* Usually this is SQLITE_BUSY meaning that another thread or process
+    ** is already running a checkpoint, or maybe a recovery.  But it might
+    ** also be SQLITE_IOERR. */
+    return rc;
+  }
+  pWal->ckptLock = 1;
+
+  /* Copy data from the log to the database file. */
+  rc = walIndexReadHdr(pWal, &isChanged);
+  if( rc==SQLITE_OK ){
+    rc = walCheckpoint(pWal, sync_flags, nBuf, zBuf);
+  }
+  if( isChanged ){
+    /* If a new wal-index header was loaded before the checkpoint was 
+    ** performed, then the pager-cache associated with pWal is now
+    ** out of date. So zero the cached wal-index header to ensure that
+    ** next time the pager opens a snapshot on this database it knows that
+    ** the cache needs to be reset.
+    */
+    memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+  }
+
+  /* Release the locks. */
+  walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  pWal->ckptLock = 0;
+  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal){
+  u32 ret = 0;
+  if( pWal ){
+    ret = pWal->iCallback;
+    pWal->iCallback = 0;
+  }
+  return (int)ret;
+}
+
+/*
+** This function is called to change the WAL subsystem into or out
+** of locking_mode=EXCLUSIVE.
+**
+** If op is zero, then attempt to change from locking_mode=EXCLUSIVE
+** into locking_mode=NORMAL.  This means that we must acquire a lock
+** on the pWal->readLock byte.  If the WAL is already in locking_mode=NORMAL
+** or if the acquisition of the lock fails, then return 0.  If the
+** transition out of exclusive-mode is successful, return 1.  This
+** operation must occur while the pager is still holding the exclusive
+** lock on the main database file.
+**
+** If op is one, then change from locking_mode=NORMAL into 
+** locking_mode=EXCLUSIVE.  This means that the pWal->readLock must
+** be released.  Return 1 if the transition is made and 0 if the
+** WAL is already in exclusive-locking mode - meaning that this
+** routine is a no-op.  The pager must already hold the exclusive lock
+** on the main database file before invoking this operation.
+**
+** If op is negative, then do a dry-run of the op==1 case but do
+** not actually change anything.  The pager uses this to see if it
+** should acquire the database exclusive lock prior to invoking
+** the op==1 case.
+*/
+SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op){
+  int rc;
+  assert( pWal->writeLock==0 );
+
+  /* pWal->readLock is usually set, but might be -1 if there was a 
+  ** prior error while attempting to acquire are read-lock. This cannot 
+  ** happen if the connection is actually in exclusive mode (as no xShmLock
+  ** locks are taken in this case). Nor should the pager attempt to
+  ** upgrade to exclusive-mode following such an error.
+  */
+  assert( pWal->readLock>=0 || pWal->lockError );
+  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );
+
+  if( op==0 ){
+    if( pWal->exclusiveMode ){
+      pWal->exclusiveMode = 0;
+      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
+        pWal->exclusiveMode = 1;
+      }
+      rc = pWal->exclusiveMode==0;
+    }else{
+      /* Already in locking_mode=NORMAL */
+      rc = 0;
+    }
+  }else if( op>0 ){
+    assert( pWal->exclusiveMode==0 );
+    assert( pWal->readLock>=0 );
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->exclusiveMode = 1;
+    rc = 1;
+  }else{
+    rc = pWal->exclusiveMode==0;
+  }
+  return rc;
+}
+
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+/************** End of wal.c *************************************************/
 /************** Begin file btmutex.c *****************************************/
 /*
 ** 2007 August 27
@@ -37207,6 +42578,8 @@
   MemPage *pPage1;      /* First page of the database */
   u8 readOnly;          /* True if the underlying file is readonly */
   u8 pageSizeFixed;     /* True if the page size can no longer be changed */
+  u8 secureDelete;      /* True if secure_delete is enabled */
+  u8 initiallyEmpty;    /* Database is empty at start of transaction */
 #ifndef SQLITE_OMIT_AUTOVACUUM
   u8 autoVacuum;        /* True if auto-vacuum is enabled */
   u8 incrVacuum;        /* True if incr-vacuum is enabled */
@@ -37218,7 +42591,9 @@
   u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
   u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
   u8 inTransaction;     /* Transaction state */
+  u8 doNotUseWAL;       /* If true, do not open write-ahead-log file */
   int nTransaction;     /* Number of open transactions (read + write) */
+  u32 nPage;            /* Number of pages in the database */
   void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
   void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
   sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
@@ -38299,11 +43674,8 @@
 static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
   int rc = SQLITE_OK;
   if( !pBt->pHasContent ){
-    int nPage = 100;
-    sqlite3PagerPagecount(pBt->pPager, &nPage);
-    /* If sqlite3PagerPagecount() fails there is no harm because the
-    ** nPage variable is unchanged from its default value of 100 */
-    pBt->pHasContent = sqlite3BitvecCreate((u32)nPage);
+    assert( pgno<=pBt->nPage );
+    pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
     if( !pBt->pHasContent ){
       rc = SQLITE_NOMEM;
     }
@@ -39030,11 +44402,11 @@
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( size>=0 );   /* Minimum cell size is 4 */
 
-#ifdef SQLITE_SECURE_DELETE
-  /* Overwrite deleted information with zeros when the SECURE_DELETE 
-  ** option is enabled at compile-time */
-  memset(&data[start], 0, size);
-#endif
+  if( pPage->pBt->secureDelete ){
+    /* Overwrite deleted information with zeros when the secure_delete
+    ** option is enabled */
+    memset(&data[start], 0, size);
+  }
 
   /* Add the space back into the linked list of freeblocks.  Note that
   ** even though the freeblock list was checked by btreeInitPage(),
@@ -39266,9 +44638,9 @@
   assert( sqlite3PagerGetData(pPage->pDbPage) == data );
   assert( sqlite3PagerIswriteable(pPage->pDbPage) );
   assert( sqlite3_mutex_held(pBt->mutex) );
-#ifdef SQLITE_SECURE_DELETE
-  memset(&data[hdr], 0, pBt->usableSize - hdr);
-#endif
+  if( pBt->secureDelete ){
+    memset(&data[hdr], 0, pBt->usableSize - hdr);
+  }
   data[hdr] = (char)flags;
   first = hdr + 8 + 4*((flags&PTF_LEAF)==0 ?1:0);
   memset(&data[hdr+1], 0, 4);
@@ -39346,13 +44718,13 @@
 ** Return the size of the database file in pages. If there is any kind of
 ** error, return ((unsigned int)-1).
 */
-static Pgno pagerPagecount(BtShared *pBt){
-  int nPage = -1;
-  int rc;
-  assert( pBt->pPage1 );
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  assert( rc==SQLITE_OK || nPage==-1 );
-  return (Pgno)nPage;
+static Pgno btreePagecount(BtShared *pBt){
+  return pBt->nPage;
+}
+SQLITE_PRIVATE u32 sqlite3BtreeLastPage(Btree *p){
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( ((p->pBt->nPage)&0x8000000)==0 );
+  return (int)btreePagecount(p->pBt);
 }
 
 /*
@@ -39369,9 +44741,11 @@
   MemPage **ppPage     /* Write the page pointer here */
 ){
   int rc;
-  TESTONLY( Pgno iLastPg = pagerPagecount(pBt); )
   assert( sqlite3_mutex_held(pBt->mutex) );
 
+  if( pgno<=0 || pgno>btreePagecount(pBt) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
   rc = btreeGetPage(pBt, pgno, ppPage, 0);
   if( rc==SQLITE_OK ){
     rc = btreeInitPage(*ppPage);
@@ -39379,15 +44753,6 @@
       releasePage(*ppPage);
     }
   }
-
-  /* If the requested page number was either 0 or greater than the page
-  ** number of the last page in the database, this function should return
-  ** SQLITE_CORRUPT or some other error (i.e. SQLITE_FULL). Check that this
-  ** is the case.  */
-  assert( (pgno>0 && pgno<=iLastPg) || rc!=SQLITE_OK );
-  testcase( pgno==0 );
-  testcase( pgno==iLastPg );
-
   return rc;
 }
 
@@ -39588,6 +44953,9 @@
     pBt->pCursor = 0;
     pBt->pPage1 = 0;
     pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
+#ifdef SQLITE_SECURE_DELETE
+    pBt->secureDelete = 1;
+#endif
     pBt->pageSize = get2byte(&zDbHeader[16]);
     if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
          || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
@@ -39944,6 +45312,23 @@
   sqlite3BtreeLeave(p);
   return n;
 }
+
+/*
+** Set the secureDelete flag if newFlag is 0 or 1.  If newFlag is -1,
+** then make no changes.  Always return the value of the secureDelete
+** setting after the change.
+*/
+SQLITE_PRIVATE int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
+  int b;
+  if( p==0 ) return 0;
+  sqlite3BtreeEnter(p);
+  if( newFlag>=0 ){
+    p->pBt->secureDelete = (newFlag!=0) ? 1 : 0;
+  } 
+  b = p->pBt->secureDelete;
+  sqlite3BtreeLeave(p);
+  return b;
+}
 #endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
 
 /*
@@ -40003,9 +45388,11 @@
 ** is returned if we run out of memory. 
 */
 static int lockBtree(BtShared *pBt){
-  int rc;
-  MemPage *pPage1;
-  int nPage;
+  int rc;              /* Result code from subfunctions */
+  MemPage *pPage1;     /* Page 1 of the database file */
+  int nPage;           /* Number of pages in the database */
+  int nPageFile = 0;   /* Number of pages in the database file */
+  int nPageHeader;     /* Number of pages in the database according to hdr */
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   assert( pBt->pPage1==0 );
@@ -40017,10 +45404,14 @@
   /* Do some checking to help insure the file we opened really is
   ** a valid database file. 
   */
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  if( rc!=SQLITE_OK ){
+  nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
+  if( (rc = sqlite3PagerPagecount(pBt->pPager, &nPageFile))!=SQLITE_OK ){;
     goto page1_init_failed;
-  }else if( nPage>0 ){
+  }
+  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
+    nPage = nPageFile;
+  }
+  if( nPage>0 ){
     int pageSize;
     int usableSize;
     u8 *page1 = pPage1->aData;
@@ -40028,12 +45419,42 @@
     if( memcmp(page1, zMagicHeader, 16)!=0 ){
       goto page1_init_failed;
     }
+
+#ifdef SQLITE_OMIT_WAL
     if( page1[18]>1 ){
       pBt->readOnly = 1;
     }
     if( page1[19]>1 ){
       goto page1_init_failed;
     }
+#else
+    if( page1[18]>2 ){
+      pBt->readOnly = 1;
+    }
+    if( page1[19]>2 ){
+      goto page1_init_failed;
+    }
+
+    /* If the write version is set to 2, this database should be accessed
+    ** in WAL mode. If the log is not already open, open it now. Then 
+    ** return SQLITE_OK and return without populating BtShared.pPage1.
+    ** The caller detects this and calls this function again. This is
+    ** required as the version of page 1 currently in the page1 buffer
+    ** may not be the latest version - there may be a newer one in the log
+    ** file.
+    */
+    if( page1[19]==2 && pBt->doNotUseWAL==0 ){
+      int isOpen = 0;
+      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
+      if( rc!=SQLITE_OK ){
+        goto page1_init_failed;
+      }else if( isOpen==0 ){
+        releasePage(pPage1);
+        return SQLITE_OK;
+      }
+      rc = SQLITE_NOTADB;
+    }
+#endif
 
     /* The maximum embedded fraction must be exactly 25%.  And the minimum
     ** embedded fraction must be 12.5% for both leaf-data and non-leaf-data.
@@ -40066,6 +45487,10 @@
                                    pageSize-usableSize);
       return rc;
     }
+    if( nPageHeader>nPageFile ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto page1_init_failed;
+    }
     if( usableSize<480 ){
       goto page1_init_failed;
     }
@@ -40096,6 +45521,7 @@
   pBt->minLeaf = (pBt->usableSize-12)*32/255 - 23;
   assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
   pBt->pPage1 = pPage1;
+  pBt->nPage = nPage;
   return SQLITE_OK;
 
 page1_init_failed:
@@ -40133,12 +45559,10 @@
   MemPage *pP1;
   unsigned char *data;
   int rc;
-  int nPage;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  if( rc!=SQLITE_OK || nPage>0 ){
-    return rc;
+  if( pBt->nPage>0 ){
+    return SQLITE_OK;
   }
   pP1 = pBt->pPage1;
   assert( pP1!=0 );
@@ -40164,6 +45588,8 @@
   put4byte(&data[36 + 4*4], pBt->autoVacuum);
   put4byte(&data[36 + 7*4], pBt->incrVacuum);
 #endif
+  pBt->nPage = 1;
+  data[31] = 1;
   return SQLITE_OK;
 }
 
@@ -40253,6 +45679,7 @@
   rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
   if( SQLITE_OK!=rc ) goto trans_begun;
 
+  pBt->initiallyEmpty = pBt->nPage==0;
   do {
     /* Call lockBtree() until either pBt->pPage1 is populated or
     ** lockBtree() returns something other than SQLITE_OK. lockBtree()
@@ -40277,7 +45704,7 @@
     if( rc!=SQLITE_OK ){
       unlockBtreeIfUnused(pBt);
     }
-  }while( rc==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
+  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
           btreeInvokeBusyHandler(pBt) );
 
   if( rc==SQLITE_OK ){
@@ -40532,12 +45959,12 @@
 */
 static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
   Pgno nFreeList;           /* Number of pages still on the free-list */
+  int rc;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   assert( iLastPg>nFin );
 
   if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
-    int rc;
     u8 eType;
     Pgno iPtrPage;
 
@@ -40613,7 +46040,7 @@
     while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
       if( PTRMAP_ISPAGE(pBt, iLastPg) ){
         MemPage *pPg;
-        int rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
+        rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
         if( rc!=SQLITE_OK ){
           return rc;
         }
@@ -40626,6 +46053,7 @@
       iLastPg--;
     }
     sqlite3PagerTruncateImage(pBt->pPager, iLastPg);
+    pBt->nPage = iLastPg;
   }
   return SQLITE_OK;
 }
@@ -40648,7 +46076,11 @@
     rc = SQLITE_DONE;
   }else{
     invalidateAllOverflowCache(pBt);
-    rc = incrVacuumStep(pBt, 0, pagerPagecount(pBt));
+    rc = incrVacuumStep(pBt, 0, btreePagecount(pBt));
+    if( rc==SQLITE_OK ){
+      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+      put4byte(&pBt->pPage1->aData[28], pBt->nPage);
+    }
   }
   sqlite3BtreeLeave(p);
   return rc;
@@ -40679,7 +46111,7 @@
     int nEntry;        /* Number of entries on one ptrmap page */
     Pgno nOrig;        /* Database size before freeing */
 
-    nOrig = pagerPagecount(pBt);
+    nOrig = btreePagecount(pBt);
     if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
       /* It is not possible to create a database for which the final page
       ** is either a pointer-map page or the pending-byte page. If one
@@ -40704,11 +46136,12 @@
       rc = incrVacuumStep(pBt, nFin, iFree);
     }
     if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
-      rc = SQLITE_OK;
       rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
       put4byte(&pBt->pPage1->aData[32], 0);
       put4byte(&pBt->pPage1->aData[36], 0);
+      put4byte(&pBt->pPage1->aData[28], nFin);
       sqlite3PagerTruncateImage(pBt->pPager, nFin);
+      pBt->nPage = nFin;
     }
     if( rc!=SQLITE_OK ){
       sqlite3PagerRollback(pPager);
@@ -40958,6 +46391,11 @@
     ** call btreeGetPage() on page 1 again to make
     ** sure pPage1->aData is set correctly. */
     if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
+      int nPage = get4byte(28+(u8*)pPage1->aData);
+      testcase( nPage==0 );
+      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
+      testcase( pBt->nPage!=nPage );
+      pBt->nPage = nPage;
       releasePage(pPage1);
     }
     assert( countWriteCursors(pBt)==0 );
@@ -40995,17 +46433,13 @@
   assert( pBt->readOnly==0 );
   assert( iStatement>0 );
   assert( iStatement>p->db->nSavepoint );
-  if( NEVER(p->inTrans!=TRANS_WRITE || pBt->readOnly) ){
-    rc = SQLITE_INTERNAL;
-  }else{
-    assert( pBt->inTransaction==TRANS_WRITE );
-    /* At the pager level, a statement transaction is a savepoint with
-    ** an index greater than all savepoints created explicitly using
-    ** SQL statements. It is illegal to open, release or rollback any
-    ** such savepoints while the statement transaction savepoint is active.
-    */
-    rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
-  }
+  assert( pBt->inTransaction==TRANS_WRITE );
+  /* At the pager level, a statement transaction is a savepoint with
+  ** an index greater than all savepoints created explicitly using
+  ** SQL statements. It is illegal to open, release or rollback any
+  ** such savepoints while the statement transaction savepoint is active.
+  */
+  rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
   sqlite3BtreeLeave(p);
   return rc;
 }
@@ -41031,7 +46465,12 @@
     sqlite3BtreeEnter(p);
     rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
     if( rc==SQLITE_OK ){
+      if( iSavepoint<0 && pBt->initiallyEmpty ) pBt->nPage = 0;
       rc = newDatabase(pBt);
+      pBt->nPage = get4byte(28 + pBt->pPage1->aData);
+      if( pBt->nPage==0 ){
+        sqlite3PagerPagecount(pBt->pPager, (int*)&pBt->nPage);
+      }
     }
     sqlite3BtreeLeave(p);
   }
@@ -41097,7 +46536,7 @@
   if( NEVER(wrFlag && pBt->readOnly) ){
     return SQLITE_READONLY;
   }
-  if( iTable==1 && pagerPagecount(pBt)==0 ){
+  if( iTable==1 && btreePagecount(pBt)==0 ){
     return SQLITE_EMPTY;
   }
 
@@ -41368,7 +46807,7 @@
       iGuess++;
     }
 
-    if( iGuess<=pagerPagecount(pBt) ){
+    if( iGuess<=btreePagecount(pBt) ){
       rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
       if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
         next = iGuess;
@@ -42400,7 +47839,7 @@
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   pPage1 = pBt->pPage1;
-  mxPage = pagerPagecount(pBt);
+  mxPage = btreePagecount(pBt);
   n = get4byte(&pPage1->aData[36]);
   testcase( n==mxPage-1 );
   if( n>=mxPage ){
@@ -42596,35 +48035,35 @@
   }else{
     /* There are no pages on the freelist, so create a new page at the
     ** end of the file */
-    int nPage = pagerPagecount(pBt);
-    *pPgno = nPage + 1;
-
-    if( *pPgno==PENDING_BYTE_PAGE(pBt) ){
-      (*pPgno)++;
-    }
+    rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+    if( rc ) return rc;
+    pBt->nPage++;
+    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
 
 #ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, *pPgno) ){
+    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
       /* If *pPgno refers to a pointer-map page, allocate two new pages
       ** at the end of the file instead of one. The first allocated page
       ** becomes a new pointer-map page, the second is used by the caller.
       */
       MemPage *pPg = 0;
-      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", *pPgno));
-      assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-      rc = btreeGetPage(pBt, *pPgno, &pPg, 0);
+      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
+      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
+      rc = btreeGetPage(pBt, pBt->nPage, &pPg, 1);
       if( rc==SQLITE_OK ){
         rc = sqlite3PagerWrite(pPg->pDbPage);
         releasePage(pPg);
       }
       if( rc ) return rc;
-      (*pPgno)++;
-      if( *pPgno==PENDING_BYTE_PAGE(pBt) ){ (*pPgno)++; }
+      pBt->nPage++;
+      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
     }
 #endif
+    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
+    *pPgno = pBt->nPage;
 
     assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-    rc = btreeGetPage(pBt, *pPgno, ppPage, 0);
+    rc = btreeGetPage(pBt, *pPgno, ppPage, 1);
     if( rc ) return rc;
     rc = sqlite3PagerWrite((*ppPage)->pDbPage);
     if( rc!=SQLITE_OK ){
@@ -42687,17 +48126,17 @@
   nFree = get4byte(&pPage1->aData[36]);
   put4byte(&pPage1->aData[36], nFree+1);
 
-#ifdef SQLITE_SECURE_DELETE
-  /* If the SQLITE_SECURE_DELETE compile-time option is enabled, then
-  ** always fully overwrite deleted information with zeros.
-  */
-  if( (!pPage && (rc = btreeGetPage(pBt, iPage, &pPage, 0)))
-   ||            (rc = sqlite3PagerWrite(pPage->pDbPage))
-  ){
-    goto freepage_out;
+  if( pBt->secureDelete ){
+    /* If the secure_delete option is enabled, then
+    ** always fully overwrite deleted information with zeros.
+    */
+    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
+     ||            ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
+    ){
+      goto freepage_out;
+    }
+    memset(pPage->aData, 0, pPage->pBt->pageSize);
   }
-  memset(pPage->aData, 0, pPage->pBt->pageSize);
-#endif
 
   /* If the database supports auto-vacuum, write an entry in the pointer-map
   ** to indicate that the page is free.
@@ -42748,11 +48187,9 @@
       if( rc==SQLITE_OK ){
         put4byte(&pTrunk->aData[4], nLeaf+1);
         put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
-#ifndef SQLITE_SECURE_DELETE
-        if( pPage ){
+        if( pPage && !pBt->secureDelete ){
           sqlite3PagerDontWrite(pPage->pDbPage);
         }
-#endif
         rc = btreeSetHasContent(pBt, iPage);
       }
       TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
@@ -42816,7 +48253,7 @@
   while( nOvfl-- ){
     Pgno iNext = 0;
     MemPage *pOvfl = 0;
-    if( ovflPgno<2 || ovflPgno>pagerPagecount(pBt) ){
+    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
       /* 0 is not a legal page number and page 1 cannot be an 
       ** overflow page. Therefore if ovflPgno<2 or past the end of the 
       ** file the database must be corrupt. */
@@ -42826,7 +48263,25 @@
       rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
       if( rc ) return rc;
     }
-    rc = freePage2(pBt, pOvfl, ovflPgno);
+
+    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
+     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
+    ){
+      /* There is no reason any cursor should have an outstanding reference 
+      ** to an overflow page belonging to a cell that is being deleted/updated.
+      ** So if there exists more than one reference to this page, then it 
+      ** must not really be an overflow page and the database must be corrupt. 
+      ** It is helpful to detect this before calling freePage2(), as 
+      ** freePage2() may zero the page contents if secure-delete mode is
+      ** enabled. If this 'overflow' page happens to be a page that the
+      ** caller is iterating through or using in some other way, this
+      ** can be problematic.
+      */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = freePage2(pBt, pOvfl, ovflPgno);
+    }
+
     if( pOvfl ){
       sqlite3PagerUnref(pOvfl->pDbPage);
     }
@@ -43070,7 +48525,7 @@
   Pgno iChild,      /* If non-zero, replace first 4 bytes with this value */
   int *pRC          /* Read and write return code from here */
 ){
-  int idx;          /* Where to write new cell content in data[] */
+  int idx = 0;      /* Where to write new cell content in data[] */
   int j;            /* Loop counter */
   int end;          /* First byte past the last cell pointer in data[] */
   int ins;          /* Index in data[] where new cell pointer is inserted */
@@ -43561,10 +49016,17 @@
       ** In this case, temporarily copy the cell into the aOvflSpace[]
       ** buffer. It will be copied out again as soon as the aSpace[] buffer
       ** is allocated.  */
-#ifdef SQLITE_SECURE_DELETE
-      memcpy(&aOvflSpace[apDiv[i]-pParent->aData], apDiv[i], szNew[i]);
-      apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
-#endif
+      if( pBt->secureDelete ){
+        int iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
+        if( (iOff+szNew[i])>pBt->usableSize ){
+          rc = SQLITE_CORRUPT_BKPT;
+          memset(apOld, 0, (i+1)*sizeof(MemPage*));
+          goto balance_cleanup;
+        }else{
+          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
+          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
+        }
+      }
       dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
     }
   }
@@ -44623,8 +50085,14 @@
       releasePage(pRoot);
       return rc;
     }
+
+    /* When the new root page was allocated, page 1 was made writable in
+    ** order either to increase the database filesize, or to decrement the
+    ** freelist count.  Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
+    */
+    assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
     rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
-    if( rc ){
+    if( NEVER(rc) ){
       releasePage(pRoot);
       return rc;
     }
@@ -44664,7 +50132,7 @@
   int i;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pgno>pagerPagecount(pBt) ){
+  if( pgno>btreePagecount(pBt) ){
     return SQLITE_CORRUPT_BKPT;
   }
 
@@ -45415,7 +50883,7 @@
   nRef = sqlite3PagerRefcount(pBt->pPager);
   sCheck.pBt = pBt;
   sCheck.pPager = pBt->pPager;
-  sCheck.nPage = pagerPagecount(sCheck.pBt);
+  sCheck.nPage = btreePagecount(sCheck.pBt);
   sCheck.mxErr = mxErr;
   sCheck.nErr = 0;
   sCheck.mallocFailed = 0;
@@ -45684,6 +51152,42 @@
 }
 #endif
 
+/*
+** Set both the "read version" (single byte at byte offset 18) and 
+** "write version" (single byte at byte offset 19) fields in the database
+** header to iVersion.
+*/
+SQLITE_PRIVATE int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
+  BtShared *pBt = pBtree->pBt;
+  int rc;                         /* Return code */
+ 
+  assert( pBtree->inTrans==TRANS_NONE );
+  assert( iVersion==1 || iVersion==2 );
+
+  /* If setting the version fields to 1, do not automatically open the
+  ** WAL connection, even if the version fields are currently set to 2.
+  */
+  pBt->doNotUseWAL = (iVersion==1);
+
+  rc = sqlite3BtreeBeginTrans(pBtree, 0);
+  if( rc==SQLITE_OK ){
+    u8 *aData = pBt->pPage1->aData;
+    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
+      rc = sqlite3BtreeBeginTrans(pBtree, 2);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          aData[18] = (u8)iVersion;
+          aData[19] = (u8)iVersion;
+        }
+      }
+    }
+  }
+
+  pBt->doNotUseWAL = 0;
+  return rc;
+}
+
 /************** End of btree.c ***********************************************/
 /************** Begin file backup.c ******************************************/
 /*
@@ -45903,7 +51407,7 @@
   /* Catch the case where the destination is an in-memory database and the
   ** page sizes of the source and destination differ. 
   */
-  if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(sqlite3BtreePager(p->pDest)) ){
+  if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(pDestPager) ){
     rc = SQLITE_READONLY;
   }
 
@@ -45973,6 +51477,9 @@
 */
 SQLITE_API int sqlite3_backup_step(sqlite3_backup *p, int nPage){
   int rc;
+  int destMode;       /* Destination journal mode */
+  int pgszSrc = 0;    /* Source page size */
+  int pgszDest = 0;   /* Destination page size */
 
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
@@ -46013,13 +51520,21 @@
       rc = sqlite3BtreeBeginTrans(p->pSrc, 0);
       bCloseTrans = 1;
     }
+
+    /* Do not allow backup if the destination database is in WAL mode
+    ** and the page sizes are different between source and destination */
+    pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+    pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+    destMode = sqlite3PagerGetJournalMode(sqlite3BtreePager(p->pDest));
+    if( SQLITE_OK==rc && destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
+      rc = SQLITE_READONLY;
+    }
   
     /* Now that there is a read-lock on the source database, query the
     ** source pager for the number of pages in the database.
     */
-    if( rc==SQLITE_OK ){
-      rc = sqlite3PagerPagecount(pSrcPager, &nSrcPage);
-    }
+    nSrcPage = (int)sqlite3BtreeLastPage(p->pSrc);
+    assert( nSrcPage>=0 );
     for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
       const Pgno iSrcPg = p->iNext;                 /* Source page number */
       if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
@@ -46050,8 +51565,6 @@
     if( rc==SQLITE_DONE 
      && (rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1))==SQLITE_OK
     ){
-      const int nSrcPagesize = sqlite3BtreeGetPageSize(p->pSrc);
-      const int nDestPagesize = sqlite3BtreeGetPageSize(p->pDest);
       int nDestTruncate;
   
       if( p->pDestDb ){
@@ -46070,18 +51583,20 @@
       ** journalled by PagerCommitPhaseOne() before they are destroyed
       ** by the file truncation.
       */
-      if( nSrcPagesize<nDestPagesize ){
-        int ratio = nDestPagesize/nSrcPagesize;
+      assert( pgszSrc==sqlite3BtreeGetPageSize(p->pSrc) );
+      assert( pgszDest==sqlite3BtreeGetPageSize(p->pDest) );
+      if( pgszSrc<pgszDest ){
+        int ratio = pgszDest/pgszSrc;
         nDestTruncate = (nSrcPage+ratio-1)/ratio;
         if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
           nDestTruncate--;
         }
       }else{
-        nDestTruncate = nSrcPage * (nSrcPagesize/nDestPagesize);
+        nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
       }
       sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
 
-      if( nSrcPagesize<nDestPagesize ){
+      if( pgszSrc<pgszDest ){
         /* If the source page-size is smaller than the destination page-size,
         ** two extra things may need to happen:
         **
@@ -46091,31 +51606,31 @@
         **     pending-byte page in the source database may need to be
         **     copied into the destination database.
         */
-        const i64 iSize = (i64)nSrcPagesize * (i64)nSrcPage;
+        const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
         sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
 
         assert( pFile );
-        assert( (i64)nDestTruncate*(i64)nDestPagesize >= iSize || (
+        assert( (i64)nDestTruncate*(i64)pgszDest >= iSize || (
               nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
-           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+nDestPagesize
+           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
         ));
         if( SQLITE_OK==(rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1))
          && SQLITE_OK==(rc = backupTruncateFile(pFile, iSize))
          && SQLITE_OK==(rc = sqlite3PagerSync(pDestPager))
         ){
           i64 iOff;
-          i64 iEnd = MIN(PENDING_BYTE + nDestPagesize, iSize);
+          i64 iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
           for(
-            iOff=PENDING_BYTE+nSrcPagesize; 
+            iOff=PENDING_BYTE+pgszSrc; 
             rc==SQLITE_OK && iOff<iEnd; 
-            iOff+=nSrcPagesize
+            iOff+=pgszSrc
           ){
             PgHdr *pSrcPg = 0;
-            const Pgno iSrcPg = (Pgno)((iOff/nSrcPagesize)+1);
+            const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
             rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
             if( rc==SQLITE_OK ){
               u8 *zData = sqlite3PagerGetData(pSrcPg);
-              rc = sqlite3OsWrite(pFile, zData, nSrcPagesize, iOff);
+              rc = sqlite3OsWrite(pFile, zData, pgszSrc, iOff);
             }
             sqlite3PagerUnref(pSrcPg);
           }
@@ -46630,6 +52145,10 @@
 ** before attempting the conversion.
 */
 static i64 doubleToInt64(double r){
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  /* When floating-point is omitted, double and int64 are the same thing */
+  return r;
+#else
   /*
   ** Many compilers we encounter do not define constants for the
   ** minimum and maximum 64-bit integers, or they define them
@@ -46651,6 +52170,7 @@
   }else{
     return (i64)r;
   }
+#endif
 }
 
 /*
@@ -46778,21 +52298,26 @@
 /*
 ** Convert pMem so that it has types MEM_Real or MEM_Int or both.
 ** Invalidate any prior representations.
+**
+** Every effort is made to force the conversion, even if the input
+** is a string that does not look completely like a number.  Convert
+** as much of the string as we can and ignore the rest.
 */
 SQLITE_PRIVATE int sqlite3VdbeMemNumerify(Mem *pMem){
-  double r1, r2;
-  i64 i;
+  int rc;
   assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))==0 );
   assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
   assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
-  r1 = sqlite3VdbeRealValue(pMem);
-  i = doubleToInt64(r1);
-  r2 = (double)i;
-  if( r1==r2 ){
-    sqlite3VdbeMemIntegerify(pMem);
+  rc = sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8);
+  if( rc ) return rc;
+  rc = sqlite3VdbeMemNulTerminate(pMem);
+  if( rc ) return rc;
+  if( sqlite3Atoi64(pMem->z, &pMem->u.i) ){
+    MemSetTypeFlag(pMem, MEM_Int);
   }else{
-    pMem->r = r1;
+    pMem->r = sqlite3VdbeRealValue(pMem);
     MemSetTypeFlag(pMem, MEM_Real);
+    sqlite3VdbeIntegerAffinity(pMem);
   }
   return SQLITE_OK;
 }
@@ -46844,6 +52369,7 @@
   pMem->type = SQLITE_INTEGER;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Delete any previous value and set the value stored in *pMem to val,
 ** manifest type REAL.
@@ -46858,6 +52384,7 @@
     pMem->type = SQLITE_FLOAT;
   }
 }
+#endif
 
 /*
 ** Delete any previous value and set the value of pMem to be an
@@ -46912,7 +52439,7 @@
   sqlite3VdbeMemReleaseExternal(pTo);
   memcpy(pTo, pFrom, MEMCELLSIZE);
   pTo->xDel = 0;
-  if( (pFrom->flags&MEM_Dyn)!=0 || pFrom->z==pFrom->zMalloc ){
+  if( (pFrom->flags&MEM_Static)==0 ){
     pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
     assert( srcType==MEM_Ephem || srcType==MEM_Static );
     pTo->flags |= srcType;
@@ -47483,7 +53010,7 @@
 */
 SQLITE_API const char *sqlite3_sql(sqlite3_stmt *pStmt){
   Vdbe *p = (Vdbe *)pStmt;
-  return (p->isPrepareV2 ? p->zSql : 0);
+  return (p && p->isPrepareV2) ? p->zSql : 0;
 }
 
 /*
@@ -48160,7 +53687,7 @@
     pOp->p4.pKeyInfo = pKeyInfo;
     if( pKeyInfo ){
       u8 *aSortOrder;
-      memcpy(pKeyInfo, zP4, nByte);
+      memcpy((char*)pKeyInfo, zP4, nByte - nField);
       aSortOrder = pKeyInfo->aSortOrder;
       if( aSortOrder ){
         pKeyInfo->aSortOrder = (unsigned char*)&pKeyInfo->aColl[nField];
@@ -48231,9 +53758,12 @@
 **
 ** If a memory allocation error has occurred prior to the calling of this
 ** routine, then a pointer to a dummy VdbeOp will be returned.  That opcode
-** is readable and writable, but it has no effect.  The return of a dummy
-** opcode allows the call to continue functioning after a OOM fault without
-** having to check to see if the return from this routine is a valid pointer.
+** is readable but not writable, though it is cast to a writable value.
+** The return of a dummy opcode allows the call to continue functioning
+** after a OOM fault without having to check to see if the return from 
+** this routine is a valid pointer.  But because the dummy.opcode is 0,
+** dummy will never be written to.  This is verified by code inspection and
+** by running with Valgrind.
 **
 ** About the #ifdef SQLITE_OMIT_TRACE:  Normally, this routine is never called
 ** unless p->nOp>0.  This is because in the absense of SQLITE_OMIT_TRACE,
@@ -48244,17 +53774,17 @@
 ** check the value of p->nOp-1 before continuing.
 */
 SQLITE_PRIVATE VdbeOp *sqlite3VdbeGetOp(Vdbe *p, int addr){
-  static VdbeOp dummy;
+  static const VdbeOp dummy;
   assert( p->magic==VDBE_MAGIC_INIT );
   if( addr<0 ){
 #ifdef SQLITE_OMIT_TRACE
-    if( p->nOp==0 ) return &dummy;
+    if( p->nOp==0 ) return (VdbeOp*)&dummy;
 #endif
     addr = p->nOp - 1;
   }
   assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
   if( p->db->mallocFailed ){
-    return &dummy;
+    return (VdbeOp*)&dummy;
   }else{
     return &p->aOp[addr];
   }
@@ -48367,6 +53897,11 @@
 
 /*
 ** Declare to the Vdbe that the BTree object at db->aDb[i] is used.
+**
+** The prepared statement has to know in advance which Btree objects
+** will be used so that it can acquire mutexes on them all in sorted
+** order (via sqlite3VdbeMutexArrayEnter().  Mutexes are acquired
+** in order (and released in reverse order) to avoid deadlocks.
 */
 SQLITE_PRIVATE void sqlite3VdbeUsesBtree(Vdbe *p, int i){
   int mask;
@@ -48866,6 +54401,7 @@
   p->cacheCtr = 1;
   p->minWriteFileFormat = 255;
   p->iStatement = 0;
+  p->nFkConstraint = 0;
 #ifdef VDBE_PROFILE
   {
     int i;
@@ -49544,15 +55080,27 @@
     /* If eStatementOp is non-zero, then a statement transaction needs to
     ** be committed or rolled back. Call sqlite3VdbeCloseStatement() to
     ** do so. If this operation returns an error, and the current statement
-    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then set the error
-    ** code to the new value.
+    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then promote the
+    ** current statement error code.
+    **
+    ** Note that sqlite3VdbeCloseStatement() can only fail if eStatementOp
+    ** is SAVEPOINT_ROLLBACK.  But if p->rc==SQLITE_OK then eStatementOp
+    ** must be SAVEPOINT_RELEASE.  Hence the NEVER(p->rc==SQLITE_OK) in 
+    ** the following code.
     */
     if( eStatementOp ){
       rc = sqlite3VdbeCloseStatement(p, eStatementOp);
-      if( rc && (p->rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT) ){
-        p->rc = rc;
-        sqlite3DbFree(db, p->zErrMsg);
-        p->zErrMsg = 0;
+      if( rc ){
+        assert( eStatementOp==SAVEPOINT_ROLLBACK );
+        if( NEVER(p->rc==SQLITE_OK) || p->rc==SQLITE_CONSTRAINT ){
+          p->rc = rc;
+          sqlite3DbFree(db, p->zErrMsg);
+          p->zErrMsg = 0;
+        }
+        invalidateCursorsOnModifiedBtrees(db);
+        sqlite3RollbackAll(db);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
       }
     }
   
@@ -49754,6 +55302,7 @@
   sqlite3DbFree(db, p->zSql);
   p->magic = VDBE_MAGIC_DEAD;
   sqlite3DbFree(db, p->pFree);
+  p->db = 0;
   sqlite3DbFree(db, p);
 }
 
@@ -50837,6 +56386,27 @@
 }
 
 /*
+** This function is called after a transaction has been committed. It 
+** invokes callbacks registered with sqlite3_wal_hook() as required.
+*/
+static int doWalCallbacks(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_WAL
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      int nEntry = sqlite3PagerWalCallback(sqlite3BtreePager(pBt));
+      if( db->xWalCallback && nEntry>0 && rc==SQLITE_OK ){
+        rc = db->xWalCallback(db->pWalArg, db, db->aDb[i].zName, nEntry);
+      }
+    }
+  }
+#endif
+  return rc;
+}
+
+/*
 ** Execute the statement pStmt, either until a row of data is ready, the
 ** statement is completely executed or an error occurs.
 **
@@ -50851,21 +56421,23 @@
 
   assert(p);
   if( p->magic!=VDBE_MAGIC_RUN ){
-    sqlite3_log(SQLITE_MISUSE, 
-          "attempt to step a halted statement: [%s]", p->zSql);
-    return SQLITE_MISUSE_BKPT;
+    /* We used to require that sqlite3_reset() be called before retrying
+    ** sqlite3_step() after any error.  But after 3.6.23, we changed this
+    ** so that sqlite3_reset() would be called automatically instead of
+    ** throwing the error.
+    */
+    sqlite3_reset((sqlite3_stmt*)p);
   }
 
-  /* Assert that malloc() has not failed */
+  /* Check that malloc() has not failed. If it has, return early. */
   db = p->db;
   if( db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
     return SQLITE_NOMEM;
   }
 
   if( p->pc<=0 && p->expired ){
-    if( p->rc==SQLITE_OK ){
-      p->rc = SQLITE_SCHEMA;
-    }
+    p->rc = SQLITE_SCHEMA;
     rc = SQLITE_ERROR;
     goto end_of_step;
   }
@@ -50882,9 +56454,7 @@
 
 #ifndef SQLITE_OMIT_TRACE
     if( db->xProfile && !db->init.busy ){
-      double rNow;
-      sqlite3OsCurrentTime(db->pVfs, &rNow);
-      p->startTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
+      sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
     }
 #endif
 
@@ -50905,16 +56475,20 @@
   /* Invoke the profile callback if there is one
   */
   if( rc!=SQLITE_ROW && db->xProfile && !db->init.busy && p->zSql ){
-    double rNow;
-    u64 elapseTime;
-
-    sqlite3OsCurrentTime(db->pVfs, &rNow);
-    elapseTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
-    elapseTime -= p->startTime;
-    db->xProfile(db->pProfileArg, p->zSql, elapseTime);
+    sqlite3_int64 iNow;
+    sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
+    db->xProfile(db->pProfileArg, p->zSql, iNow - p->startTime);
   }
 #endif
 
+  if( rc==SQLITE_DONE ){
+    assert( p->rc==SQLITE_OK );
+    p->rc = doWalCallbacks(db);
+    if( p->rc!=SQLITE_OK ){
+      rc = SQLITE_ERROR;
+    }
+  }
+
   db->errCode = rc;
   if( SQLITE_NOMEM==sqlite3ApiExit(p->db, p->rc) ){
     p->rc = SQLITE_NOMEM;
@@ -50964,7 +56538,7 @@
     sqlite3_reset(pStmt);
     v->expired = 0;
   }
-  if( rc2!=SQLITE_OK && v->isPrepareV2 && db->pErr ){
+  if( rc2!=SQLITE_OK && ALWAYS(v->isPrepareV2) && ALWAYS(db->pErr) ){
     /* This case occurs after failing to recompile an sql statement. 
     ** The error message from the SQL compiler has already been loaded 
     ** into the database handle. This block copies the error message 
@@ -52168,17 +57742,30 @@
 static void applyNumericAffinity(Mem *pRec){
   if( (pRec->flags & (MEM_Real|MEM_Int))==0 ){
     int realnum;
+    u8 enc = pRec->enc;
     sqlite3VdbeMemNulTerminate(pRec);
-    if( (pRec->flags&MEM_Str)
-         && sqlite3IsNumber(pRec->z, &realnum, pRec->enc) ){
+    if( (pRec->flags&MEM_Str) && sqlite3IsNumber(pRec->z, &realnum, enc) ){
       i64 value;
-      sqlite3VdbeChangeEncoding(pRec, SQLITE_UTF8);
-      if( !realnum && sqlite3Atoi64(pRec->z, &value) ){
+      char *zUtf8 = pRec->z;
+#ifndef SQLITE_OMIT_UTF16
+      if( enc!=SQLITE_UTF8 ){
+        assert( pRec->db );
+        zUtf8 = sqlite3Utf16to8(pRec->db, pRec->z, pRec->n, enc);
+        if( !zUtf8 ) return;
+      }
+#endif
+      if( !realnum && sqlite3Atoi64(zUtf8, &value) ){
         pRec->u.i = value;
         MemSetTypeFlag(pRec, MEM_Int);
       }else{
-        sqlite3VdbeMemRealify(pRec);
+        sqlite3AtoF(zUtf8, &pRec->r);
+        MemSetTypeFlag(pRec, MEM_Real);
       }
+#ifndef SQLITE_OMIT_UTF16
+      if( enc!=SQLITE_UTF8 ){
+        sqlite3DbFree(pRec->db, zUtf8);
+      }
+#endif
     }
   }
 }
@@ -52485,22 +58072,6 @@
 #define CHECK_FOR_INTERRUPT \
    if( db->u1.isInterrupted ) goto abort_due_to_interrupt;
 
-#ifdef SQLITE_DEBUG
-static int fileExists(sqlite3 *db, const char *zFile){
-  int res = 0;
-  int rc = SQLITE_OK;
-#ifdef SQLITE_TEST
-  /* If we are currently testing IO errors, then do not call OsAccess() to
-  ** test for the presence of zFile. This is because any IO error that
-  ** occurs here will not be reported, causing the test to fail.
-  */
-  extern int sqlite3_io_error_pending;
-  if( sqlite3_io_error_pending<=0 )
-#endif
-    rc = sqlite3OsAccess(db->pVfs, zFile, SQLITE_ACCESS_EXISTS, &res);
-  return (res && rc==SQLITE_OK);
-}
-#endif
 
 #ifndef NDEBUG
 /*
@@ -52556,7 +58127,7 @@
 SQLITE_PRIVATE int sqlite3VdbeExec(
   Vdbe *p                    /* The VDBE */
 ){
-  int pc;                    /* The program counter */
+  int pc=0;                  /* The program counter */
   Op *aOp = p->aOp;          /* Copy of p->aOp */
   Op *pOp;                   /* Current operation */
   int rc = SQLITE_OK;        /* Value to return */
@@ -52591,9 +58162,6 @@
       int pcDest;
     } aa;
     struct OP_Variable_stack_vars {
-      int p1;          /* Variable to copy from */
-      int p2;          /* Register to copy to */
-      int n;           /* Number of values left to copy */
       Mem *pVar;       /* Value being transferred */
     } ab;
     struct OP_Move_stack_vars {
@@ -52630,6 +58198,8 @@
     struct OP_Ge_stack_vars {
       int res;            /* Result of the comparison of pIn1 against pIn3 */
       char affinity;      /* Affinity to use for comparison */
+      u16 flags1;         /* Copy of initial value of pIn1->flags */
+      u16 flags3;         /* Copy of initial value of pIn3->flags */
     } ai;
     struct OP_Compare_stack_vars {
       int n;
@@ -52916,18 +58486,25 @@
     struct OP_AggFinal_stack_vars {
       Mem *pMem;
     } cc;
+    struct OP_JournalMode_stack_vars {
+      Btree *pBt;                     /* Btree to change journal mode of */
+      Pager *pPager;                  /* Pager associated with pBt */
+      int eNew;                       /* New journal mode */
+      int eOld;                       /* The old journal mode */
+      const char *zFilename;          /* Name of database file for pPager */
+    } cd;
     struct OP_IncrVacuum_stack_vars {
       Btree *pBt;
-    } cd;
+    } ce;
     struct OP_VBegin_stack_vars {
       VTable *pVTab;
-    } ce;
+    } cf;
     struct OP_VOpen_stack_vars {
       VdbeCursor *pCur;
       sqlite3_vtab_cursor *pVtabCursor;
       sqlite3_vtab *pVtab;
       sqlite3_module *pModule;
-    } cf;
+    } cg;
     struct OP_VFilter_stack_vars {
       int nArg;
       int iQuery;
@@ -52940,23 +58517,23 @@
       int res;
       int i;
       Mem **apArg;
-    } cg;
+    } ch;
     struct OP_VColumn_stack_vars {
       sqlite3_vtab *pVtab;
       const sqlite3_module *pModule;
       Mem *pDest;
       sqlite3_context sContext;
-    } ch;
+    } ci;
     struct OP_VNext_stack_vars {
       sqlite3_vtab *pVtab;
       const sqlite3_module *pModule;
       int res;
       VdbeCursor *pCur;
-    } ci;
+    } cj;
     struct OP_VRename_stack_vars {
       sqlite3_vtab *pVtab;
       Mem *pName;
-    } cj;
+    } ck;
     struct OP_VUpdate_stack_vars {
       sqlite3_vtab *pVtab;
       sqlite3_module *pModule;
@@ -52965,11 +58542,6 @@
       sqlite_int64 rowid;
       Mem **apArg;
       Mem *pX;
-    } ck;
-    struct OP_Pagecount_stack_vars {
-      int p1;
-      int nPage;
-      Pager *pPager;
     } cl;
     struct OP_Trace_stack_vars {
       char *zTrace;
@@ -52997,9 +58569,7 @@
 #endif
 #ifdef SQLITE_DEBUG
   sqlite3BeginBenignMalloc();
-  if( p->pc==0 
-   && ((p->db->flags & SQLITE_VdbeListing) || fileExists(db, "vdbe_explain"))
-  ){
+  if( p->pc==0  && (p->db->flags & SQLITE_VdbeListing)!=0 ){
     int i;
     printf("VDBE Program Listing:\n");
     sqlite3VdbePrintSql(p);
@@ -53007,9 +58577,6 @@
       sqlite3VdbePrintOp(stdout, i, &aOp[i]);
     }
   }
-  if( fileExists(db, "vdbe_trace") ){
-    p->trace = stdout;
-  }
   sqlite3EndBenignMalloc();
 #endif
   for(pc=p->pc; rc==SQLITE_OK; pc++){
@@ -53031,13 +58598,6 @@
       }
       sqlite3VdbePrintOp(p->trace, pc, pOp);
     }
-    if( p->trace==0 && pc==0 ){
-      sqlite3BeginBenignMalloc();
-      if( fileExists(db, "vdbe_sqltrace") ){
-        sqlite3VdbePrintSql(p);
-      }
-      sqlite3EndBenignMalloc();
-    }
 #endif
       
 
@@ -53305,6 +58865,7 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /* Opcode: Real * P2 * P4 *
 **
 ** P4 is a pointer to a 64-bit floating point value.
@@ -53316,6 +58877,7 @@
   pOut->r = *pOp->p4.pReal;
   break;
 }
+#endif
 
 /* Opcode: String8 * P2 * P4 *
 **
@@ -53392,40 +58954,25 @@
   break;
 }
 
-/* Opcode: Variable P1 P2 P3 P4 *
+/* Opcode: Variable P1 P2 * P4 *
 **
-** Transfer the values of bound parameters P1..P1+P3-1 into registers
-** P2..P2+P3-1.
+** Transfer the values of bound parameter P1 into register P2
 **
 ** If the parameter is named, then its name appears in P4 and P3==1.
 ** The P4 value is used by sqlite3_bind_parameter_name().
 */
-case OP_Variable: {
+case OP_Variable: {            /* out2-prerelease */
 #if 0  /* local variables moved into u.ab */
-  int p1;          /* Variable to copy from */
-  int p2;          /* Register to copy to */
-  int n;           /* Number of values left to copy */
   Mem *pVar;       /* Value being transferred */
 #endif /* local variables moved into u.ab */
 
-  u.ab.p1 = pOp->p1 - 1;
-  u.ab.p2 = pOp->p2;
-  u.ab.n = pOp->p3;
-  assert( u.ab.p1>=0 && u.ab.p1+u.ab.n<=p->nVar );
-  assert( u.ab.p2>=1 && u.ab.p2+u.ab.n-1<=p->nMem );
-  assert( pOp->p4.z==0 || pOp->p3==1 || pOp->p3==0 );
-
-  while( u.ab.n-- > 0 ){
-    u.ab.pVar = &p->aVar[u.ab.p1++];
-    if( sqlite3VdbeMemTooBig(u.ab.pVar) ){
-      goto too_big;
-    }
-    pOut = &aMem[u.ab.p2++];
-    sqlite3VdbeMemReleaseExternal(pOut);
-    pOut->flags = MEM_Null;
-    sqlite3VdbeMemShallowCopy(pOut, u.ab.pVar, MEM_Static);
-    UPDATE_MAX_BLOBSIZE(pOut);
+  assert( pOp->p1>0 && pOp->p1<=p->nVar );
+  u.ab.pVar = &p->aVar[pOp->p1 - 1];
+  if( sqlite3VdbeMemTooBig(u.ab.pVar) ){
+    goto too_big;
   }
+  sqlite3VdbeMemShallowCopy(pOut, u.ab.pVar, MEM_Static);
+  UPDATE_MAX_BLOBSIZE(pOut);
   break;
 }
 
@@ -53726,6 +59273,10 @@
         break;
       }
     }
+#ifdef SQLITE_OMIT_FLOATING_POINT
+    pOut->u.i = u.af.rB;
+    MemSetTypeFlag(pOut, MEM_Int);
+#else
     if( sqlite3IsNaN(u.af.rB) ){
       goto arithmetic_result_is_null;
     }
@@ -53734,6 +59285,7 @@
     if( (u.af.flags & MEM_Real)==0 ){
       sqlite3VdbeIntegerAffinity(pOut);
     }
+#endif
   }
   break;
 
@@ -53793,7 +59345,7 @@
   for(u.ag.i=0; u.ag.i<u.ag.n; u.ag.i++, u.ag.pArg++){
     u.ag.apVal[u.ag.i] = u.ag.pArg;
     sqlite3VdbeMemStoreType(u.ag.pArg);
-    REGISTER_TRACE(pOp->p2, u.ag.pArg);
+    REGISTER_TRACE(pOp->p2+u.ag.i, u.ag.pArg);
   }
 
   assert( pOp->p4type==P4_FUNCDEF || pOp->p4type==P4_VDBEFUNC );
@@ -53956,6 +59508,7 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /* Opcode: RealAffinity P1 * * * *
 **
 ** If register P1 holds an integer convert it to a real value.
@@ -53972,6 +59525,7 @@
   }
   break;
 }
+#endif
 
 #ifndef SQLITE_OMIT_CAST
 /* Opcode: ToText P1 * * * *
@@ -54055,7 +59609,7 @@
   break;
 }
 
-#ifndef SQLITE_OMIT_CAST
+#if !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT)
 /* Opcode: ToReal P1 * * * *
 **
 ** Force the value in register P1 to be a floating point number.
@@ -54072,7 +59626,7 @@
   }
   break;
 }
-#endif /* SQLITE_OMIT_CAST */
+#endif /* !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT) */
 
 /* Opcode: Lt P1 P2 P3 P4 P5
 **
@@ -54155,10 +59709,14 @@
 #if 0  /* local variables moved into u.ai */
   int res;            /* Result of the comparison of pIn1 against pIn3 */
   char affinity;      /* Affinity to use for comparison */
+  u16 flags1;         /* Copy of initial value of pIn1->flags */
+  u16 flags3;         /* Copy of initial value of pIn3->flags */
 #endif /* local variables moved into u.ai */
 
   pIn1 = &aMem[pOp->p1];
   pIn3 = &aMem[pOp->p3];
+  u.ai.flags1 = pIn1->flags;
+  u.ai.flags3 = pIn3->flags;
   if( (pIn1->flags | pIn3->flags)&MEM_Null ){
     /* One or both operands are NULL */
     if( pOp->p5 & SQLITE_NULLEQ ){
@@ -54213,6 +59771,10 @@
   }else if( u.ai.res ){
     pc = pOp->p2-1;
   }
+
+  /* Undo any changes made by applyAffinity() to the input registers. */
+  pIn1->flags = (pIn1->flags&~MEM_TypeMask) | (u.ai.flags1&MEM_TypeMask);
+  pIn3->flags = (pIn3->flags&~MEM_TypeMask) | (u.ai.flags3&MEM_TypeMask);
   break;
 }
 
@@ -55500,10 +61062,10 @@
 **
 ** Open a new cursor P1 to a transient table.
 ** The cursor is always opened read/write even if 
-** the main database is read-only.  The transient or virtual
+** the main database is read-only.  The ephemeral
 ** table is deleted automatically when the cursor is closed.
 **
-** P2 is the number of columns in the virtual table.
+** P2 is the number of columns in the ephemeral table.
 ** The cursor points to a BTree table if P4==0 and to a BTree index
 ** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
 ** that defines the format of keys in the index.
@@ -55514,6 +61076,14 @@
 ** this opcode.  Then this opcode was call OpenVirtual.  But
 ** that created confusion with the whole virtual-table idea.
 */
+/* Opcode: OpenAutoindex P1 P2 * P4 *
+**
+** This opcode works the same as OP_OpenEphemeral.  It has a
+** different name to distinguish its use.  Tables created using
+** by this opcode will be used for automatically created transient
+** indices in joins.
+*/
+case OP_OpenAutoindex: 
 case OP_OpenEphemeral: {
 #if 0  /* local variables moved into u.ax */
   VdbeCursor *pCx;
@@ -55568,7 +61138,7 @@
 ** register P2.  In other words, cursor P1 becomes an alias for the 
 ** MEM_Blob content contained in register P2.
 **
-** A pseudo-table created by this opcode is used to hold the a single
+** A pseudo-table created by this opcode is used to hold a single
 ** row output from the sorter so that the row can be decomposed into
 ** individual columns using the OP_Column opcode.  The OP_Column opcode
 ** is the only cursor opcode that works with a pseudo-table.
@@ -56652,7 +62222,7 @@
   break;
 }
 
-/* Opcode: Next P1 P2 * * *
+/* Opcode: Next P1 P2 * * P5
 **
 ** Advance cursor P1 so that it points to the next key/data pair in its
 ** table or index.  If there are no more key/value pairs then fall through
@@ -56661,9 +62231,12 @@
 **
 ** The P1 cursor must be for a real table, not a pseudo-table.
 **
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+**
 ** See also: Prev
 */
-/* Opcode: Prev P1 P2 * * *
+/* Opcode: Prev P1 P2 * * P5
 **
 ** Back up cursor P1 so that it points to the previous key/data pair in its
 ** table or index.  If there is no previous key/value pairs then fall through
@@ -56671,6 +62244,9 @@
 ** jump immediately to P2.
 **
 ** The P1 cursor must be for a real table, not a pseudo-table.
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
 */
 case OP_Prev:          /* jump */
 case OP_Next: {        /* jump */
@@ -56682,6 +62258,7 @@
 
   CHECK_FOR_INTERRUPT;
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5<=ArraySize(p->aCounter) );
   u.bm.pC = p->apCsr[pOp->p1];
   if( u.bm.pC==0 ){
     break;  /* See ticket #2273 */
@@ -57078,7 +62655,7 @@
     u.bu.initData.iDb = pOp->p1;
     u.bu.initData.pzErrMsg = &p->zErrMsg;
     u.bu.zSql = sqlite3MPrintf(db,
-       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s",
+       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s ORDER BY rowid",
        db->aDb[u.bu.iDb].zName, u.bu.zMaster, pOp->p4.z);
     if( u.bu.zSql==0 ){
       rc = SQLITE_NOMEM;
@@ -57667,6 +63244,144 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/* Opcode: Checkpoint P1 * * * *
+**
+** Checkpoint database P1. This is a no-op if P1 is not currently in
+** WAL mode.
+*/
+case OP_Checkpoint: {
+  rc = sqlite3Checkpoint(db, pOp->p1);
+  break;
+};  
+#endif
+
+/* Opcode: JournalMode P1 P2 P3 * P5
+**
+** Change the journal mode of database P1 to P3. P3 must be one of the
+** PAGER_JOURNALMODE_XXX values. If changing between the various rollback
+** modes (delete, truncate, persist, off and memory), this is a simple
+** operation. No IO is required.
+**
+** If changing into or out of WAL mode the procedure is more complicated.
+**
+** Write a string containing the final journal-mode to register P2.
+**
+** If an attempt to change in to or out of WAL mode fails because another
+** connection also has the same database open, then an SQLITE_BUSY error
+** is raised if P5==0, or of P5!=0 the journal mode changed is skipped
+** without signaling the error.
+*/
+case OP_JournalMode: {    /* out2-prerelease */
+#if 0  /* local variables moved into u.cd */
+  Btree *pBt;                     /* Btree to change journal mode of */
+  Pager *pPager;                  /* Pager associated with pBt */
+  int eNew;                       /* New journal mode */
+  int eOld;                       /* The old journal mode */
+  const char *zFilename;          /* Name of database file for pPager */
+#endif /* local variables moved into u.cd */
+
+  u.cd.eNew = pOp->p3;
+  assert( u.cd.eNew==PAGER_JOURNALMODE_DELETE
+       || u.cd.eNew==PAGER_JOURNALMODE_TRUNCATE
+       || u.cd.eNew==PAGER_JOURNALMODE_PERSIST
+       || u.cd.eNew==PAGER_JOURNALMODE_OFF
+       || u.cd.eNew==PAGER_JOURNALMODE_MEMORY
+       || u.cd.eNew==PAGER_JOURNALMODE_WAL
+       || u.cd.eNew==PAGER_JOURNALMODE_QUERY
+  );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+
+  /* This opcode is used in two places: PRAGMA journal_mode and ATTACH.
+  ** In PRAGMA journal_mode, the sqlite3VdbeUsesBtree() routine is called
+  ** when the statment is prepared and so p->aMutex.nMutex>0.  All mutexes
+  ** are already acquired.  But when used in ATTACH, sqlite3VdbeUsesBtree()
+  ** is not called when the statement is prepared because it requires the
+  ** iDb index of the database as a parameter, and the database has not
+  ** yet been attached so that index is unavailable.  We have to wait
+  ** until runtime (now) to get the mutex on the newly attached database.
+  ** No other mutexes are required by the ATTACH command so this is safe
+  ** to do.
+  */
+  assert( (p->btreeMask & (1<<pOp->p1))!=0 || p->aMutex.nMutex==0 );
+  if( p->aMutex.nMutex==0 ){
+    /* This occurs right after ATTACH.  Get a mutex on the newly ATTACHed
+    ** database. */
+    sqlite3VdbeUsesBtree(p, pOp->p1);
+    sqlite3VdbeMutexArrayEnter(p);
+  }
+
+  u.cd.pBt = db->aDb[pOp->p1].pBt;
+  u.cd.pPager = sqlite3BtreePager(u.cd.pBt);
+  u.cd.eOld = sqlite3PagerGetJournalMode(u.cd.pPager);
+  if( u.cd.eNew==PAGER_JOURNALMODE_QUERY ) u.cd.eNew = u.cd.eOld;
+  if( !sqlite3PagerOkToChangeJournalMode(u.cd.pPager) ) u.cd.eNew = u.cd.eOld;
+
+#ifndef SQLITE_OMIT_WAL
+  u.cd.zFilename = sqlite3PagerFilename(u.cd.pPager);
+
+  /* Do not allow a transition to journal_mode=WAL for a database
+  ** in temporary storage or if the VFS does not support xShmOpen.
+  */
+  if( u.cd.eNew==PAGER_JOURNALMODE_WAL
+   && (u.cd.zFilename[0]==0                         /* Temp file */
+       || !sqlite3PagerWalSupported(u.cd.pPager))   /* No xShmOpen support */
+  ){
+    u.cd.eNew = u.cd.eOld;
+  }
+
+  if( (u.cd.eNew!=u.cd.eOld)
+   && (u.cd.eOld==PAGER_JOURNALMODE_WAL || u.cd.eNew==PAGER_JOURNALMODE_WAL)
+  ){
+    if( !db->autoCommit || db->activeVdbeCnt>1 ){
+      rc = SQLITE_ERROR;
+      sqlite3SetString(&p->zErrMsg, db,
+          "cannot change %s wal mode from within a transaction",
+          (u.cd.eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
+      );
+      break;
+    }else{
+
+      if( u.cd.eOld==PAGER_JOURNALMODE_WAL ){
+        /* If leaving WAL mode, close the log file. If successful, the call
+        ** to PagerCloseWal() checkpoints and deletes the write-ahead-log
+        ** file. An EXCLUSIVE lock may still be held on the database file
+        ** after a successful return.
+        */
+        rc = sqlite3PagerCloseWal(u.cd.pPager);
+        if( rc==SQLITE_OK ){
+          sqlite3PagerSetJournalMode(u.cd.pPager, u.cd.eNew);
+        }else if( rc==SQLITE_BUSY && pOp->p5==0 ){
+          goto abort_due_to_error;
+        }
+      }
+
+      /* Open a transaction on the database file. Regardless of the journal
+      ** mode, this transaction always uses a rollback journal.
+      */
+      assert( sqlite3BtreeIsInTrans(u.cd.pBt)==0 );
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeSetVersion(u.cd.pBt, (u.cd.eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+        if( rc==SQLITE_BUSY && pOp->p5==0 ) goto abort_due_to_error;
+      }
+      if( rc==SQLITE_BUSY ){
+        u.cd.eNew = u.cd.eOld;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+#endif /* ifndef SQLITE_OMIT_WAL */
+
+  u.cd.eNew = sqlite3PagerSetJournalMode(u.cd.pPager, u.cd.eNew);
+
+  pOut = &aMem[pOp->p2];
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = (char *)sqlite3JournalModename(u.cd.eNew);
+  pOut->n = sqlite3Strlen30(pOut->z);
+  pOut->enc = SQLITE_UTF8;
+  sqlite3VdbeChangeEncoding(pOut, encoding);
+  break;
+};  
 
 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
 /* Opcode: Vacuum * * * * *
@@ -57689,14 +63404,14 @@
 ** P2. Otherwise, fall through to the next instruction.
 */
 case OP_IncrVacuum: {        /* jump */
-#if 0  /* local variables moved into u.cd */
+#if 0  /* local variables moved into u.ce */
   Btree *pBt;
-#endif /* local variables moved into u.cd */
+#endif /* local variables moved into u.ce */
 
   assert( pOp->p1>=0 && pOp->p1<db->nDb );
   assert( (p->btreeMask & (1<<pOp->p1))!=0 );
-  u.cd.pBt = db->aDb[pOp->p1].pBt;
-  rc = sqlite3BtreeIncrVacuum(u.cd.pBt);
+  u.ce.pBt = db->aDb[pOp->p1].pBt;
+  rc = sqlite3BtreeIncrVacuum(u.ce.pBt);
   if( rc==SQLITE_DONE ){
     pc = pOp->p2 - 1;
     rc = SQLITE_OK;
@@ -57766,15 +63481,15 @@
 ** code will be set to SQLITE_LOCKED.
 */
 case OP_VBegin: {
-#if 0  /* local variables moved into u.ce */
+#if 0  /* local variables moved into u.cf */
   VTable *pVTab;
-#endif /* local variables moved into u.ce */
-  u.ce.pVTab = pOp->p4.pVtab;
-  rc = sqlite3VtabBegin(db, u.ce.pVTab);
-  if( u.ce.pVTab ){
+#endif /* local variables moved into u.cf */
+  u.cf.pVTab = pOp->p4.pVtab;
+  rc = sqlite3VtabBegin(db, u.cf.pVTab);
+  if( u.cf.pVTab ){
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.ce.pVTab->pVtab->zErrMsg;
-    u.ce.pVTab->pVtab->zErrMsg = 0;
+    p->zErrMsg = u.cf.pVTab->pVtab->zErrMsg;
+    u.cf.pVTab->pVtab->zErrMsg = 0;
   }
   break;
 }
@@ -57814,34 +63529,34 @@
 ** table and stores that cursor in P1.
 */
 case OP_VOpen: {
-#if 0  /* local variables moved into u.cf */
+#if 0  /* local variables moved into u.cg */
   VdbeCursor *pCur;
   sqlite3_vtab_cursor *pVtabCursor;
   sqlite3_vtab *pVtab;
   sqlite3_module *pModule;
-#endif /* local variables moved into u.cf */
+#endif /* local variables moved into u.cg */
 
-  u.cf.pCur = 0;
-  u.cf.pVtabCursor = 0;
-  u.cf.pVtab = pOp->p4.pVtab->pVtab;
-  u.cf.pModule = (sqlite3_module *)u.cf.pVtab->pModule;
-  assert(u.cf.pVtab && u.cf.pModule);
-  rc = u.cf.pModule->xOpen(u.cf.pVtab, &u.cf.pVtabCursor);
+  u.cg.pCur = 0;
+  u.cg.pVtabCursor = 0;
+  u.cg.pVtab = pOp->p4.pVtab->pVtab;
+  u.cg.pModule = (sqlite3_module *)u.cg.pVtab->pModule;
+  assert(u.cg.pVtab && u.cg.pModule);
+  rc = u.cg.pModule->xOpen(u.cg.pVtab, &u.cg.pVtabCursor);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.cf.pVtab->zErrMsg;
-  u.cf.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.cg.pVtab->zErrMsg;
+  u.cg.pVtab->zErrMsg = 0;
   if( SQLITE_OK==rc ){
     /* Initialize sqlite3_vtab_cursor base class */
-    u.cf.pVtabCursor->pVtab = u.cf.pVtab;
+    u.cg.pVtabCursor->pVtab = u.cg.pVtab;
 
     /* Initialise vdbe cursor object */
-    u.cf.pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
-    if( u.cf.pCur ){
-      u.cf.pCur->pVtabCursor = u.cf.pVtabCursor;
-      u.cf.pCur->pModule = u.cf.pVtabCursor->pVtab->pModule;
+    u.cg.pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
+    if( u.cg.pCur ){
+      u.cg.pCur->pVtabCursor = u.cg.pVtabCursor;
+      u.cg.pCur->pModule = u.cg.pVtabCursor->pVtab->pModule;
     }else{
       db->mallocFailed = 1;
-      u.cf.pModule->xClose(u.cf.pVtabCursor);
+      u.cg.pModule->xClose(u.cg.pVtabCursor);
     }
   }
   break;
@@ -57868,7 +63583,7 @@
 ** A jump is made to P2 if the result set after filtering would be empty.
 */
 case OP_VFilter: {   /* jump */
-#if 0  /* local variables moved into u.cg */
+#if 0  /* local variables moved into u.ch */
   int nArg;
   int iQuery;
   const sqlite3_module *pModule;
@@ -57880,46 +63595,46 @@
   int res;
   int i;
   Mem **apArg;
-#endif /* local variables moved into u.cg */
+#endif /* local variables moved into u.ch */
 
-  u.cg.pQuery = &aMem[pOp->p3];
-  u.cg.pArgc = &u.cg.pQuery[1];
-  u.cg.pCur = p->apCsr[pOp->p1];
-  REGISTER_TRACE(pOp->p3, u.cg.pQuery);
-  assert( u.cg.pCur->pVtabCursor );
-  u.cg.pVtabCursor = u.cg.pCur->pVtabCursor;
-  u.cg.pVtab = u.cg.pVtabCursor->pVtab;
-  u.cg.pModule = u.cg.pVtab->pModule;
+  u.ch.pQuery = &aMem[pOp->p3];
+  u.ch.pArgc = &u.ch.pQuery[1];
+  u.ch.pCur = p->apCsr[pOp->p1];
+  REGISTER_TRACE(pOp->p3, u.ch.pQuery);
+  assert( u.ch.pCur->pVtabCursor );
+  u.ch.pVtabCursor = u.ch.pCur->pVtabCursor;
+  u.ch.pVtab = u.ch.pVtabCursor->pVtab;
+  u.ch.pModule = u.ch.pVtab->pModule;
 
   /* Grab the index number and argc parameters */
-  assert( (u.cg.pQuery->flags&MEM_Int)!=0 && u.cg.pArgc->flags==MEM_Int );
-  u.cg.nArg = (int)u.cg.pArgc->u.i;
-  u.cg.iQuery = (int)u.cg.pQuery->u.i;
+  assert( (u.ch.pQuery->flags&MEM_Int)!=0 && u.ch.pArgc->flags==MEM_Int );
+  u.ch.nArg = (int)u.ch.pArgc->u.i;
+  u.ch.iQuery = (int)u.ch.pQuery->u.i;
 
   /* Invoke the xFilter method */
   {
-    u.cg.res = 0;
-    u.cg.apArg = p->apArg;
-    for(u.cg.i = 0; u.cg.i<u.cg.nArg; u.cg.i++){
-      u.cg.apArg[u.cg.i] = &u.cg.pArgc[u.cg.i+1];
-      sqlite3VdbeMemStoreType(u.cg.apArg[u.cg.i]);
+    u.ch.res = 0;
+    u.ch.apArg = p->apArg;
+    for(u.ch.i = 0; u.ch.i<u.ch.nArg; u.ch.i++){
+      u.ch.apArg[u.ch.i] = &u.ch.pArgc[u.ch.i+1];
+      sqlite3VdbeMemStoreType(u.ch.apArg[u.ch.i]);
     }
 
     p->inVtabMethod = 1;
-    rc = u.cg.pModule->xFilter(u.cg.pVtabCursor, u.cg.iQuery, pOp->p4.z, u.cg.nArg, u.cg.apArg);
+    rc = u.ch.pModule->xFilter(u.ch.pVtabCursor, u.ch.iQuery, pOp->p4.z, u.ch.nArg, u.ch.apArg);
     p->inVtabMethod = 0;
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.cg.pVtab->zErrMsg;
-    u.cg.pVtab->zErrMsg = 0;
+    p->zErrMsg = u.ch.pVtab->zErrMsg;
+    u.ch.pVtab->zErrMsg = 0;
     if( rc==SQLITE_OK ){
-      u.cg.res = u.cg.pModule->xEof(u.cg.pVtabCursor);
+      u.ch.res = u.ch.pModule->xEof(u.ch.pVtabCursor);
     }
 
-    if( u.cg.res ){
+    if( u.ch.res ){
       pc = pOp->p2 - 1;
     }
   }
-  u.cg.pCur->nullRow = 0;
+  u.ch.pCur->nullRow = 0;
 
   break;
 }
@@ -57933,52 +63648,52 @@
 ** P1 cursor is pointing to into register P3.
 */
 case OP_VColumn: {
-#if 0  /* local variables moved into u.ch */
+#if 0  /* local variables moved into u.ci */
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
   Mem *pDest;
   sqlite3_context sContext;
-#endif /* local variables moved into u.ch */
+#endif /* local variables moved into u.ci */
 
   VdbeCursor *pCur = p->apCsr[pOp->p1];
   assert( pCur->pVtabCursor );
   assert( pOp->p3>0 && pOp->p3<=p->nMem );
-  u.ch.pDest = &aMem[pOp->p3];
+  u.ci.pDest = &aMem[pOp->p3];
   if( pCur->nullRow ){
-    sqlite3VdbeMemSetNull(u.ch.pDest);
+    sqlite3VdbeMemSetNull(u.ci.pDest);
     break;
   }
-  u.ch.pVtab = pCur->pVtabCursor->pVtab;
-  u.ch.pModule = u.ch.pVtab->pModule;
-  assert( u.ch.pModule->xColumn );
-  memset(&u.ch.sContext, 0, sizeof(u.ch.sContext));
+  u.ci.pVtab = pCur->pVtabCursor->pVtab;
+  u.ci.pModule = u.ci.pVtab->pModule;
+  assert( u.ci.pModule->xColumn );
+  memset(&u.ci.sContext, 0, sizeof(u.ci.sContext));
 
   /* The output cell may already have a buffer allocated. Move
-  ** the current contents to u.ch.sContext.s so in case the user-function
+  ** the current contents to u.ci.sContext.s so in case the user-function
   ** can use the already allocated buffer instead of allocating a
   ** new one.
   */
-  sqlite3VdbeMemMove(&u.ch.sContext.s, u.ch.pDest);
-  MemSetTypeFlag(&u.ch.sContext.s, MEM_Null);
+  sqlite3VdbeMemMove(&u.ci.sContext.s, u.ci.pDest);
+  MemSetTypeFlag(&u.ci.sContext.s, MEM_Null);
 
-  rc = u.ch.pModule->xColumn(pCur->pVtabCursor, &u.ch.sContext, pOp->p2);
+  rc = u.ci.pModule->xColumn(pCur->pVtabCursor, &u.ci.sContext, pOp->p2);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.ch.pVtab->zErrMsg;
-  u.ch.pVtab->zErrMsg = 0;
-  if( u.ch.sContext.isError ){
-    rc = u.ch.sContext.isError;
+  p->zErrMsg = u.ci.pVtab->zErrMsg;
+  u.ci.pVtab->zErrMsg = 0;
+  if( u.ci.sContext.isError ){
+    rc = u.ci.sContext.isError;
   }
 
   /* Copy the result of the function to the P3 register. We
   ** do this regardless of whether or not an error occurred to ensure any
-  ** dynamic allocation in u.ch.sContext.s (a Mem struct) is  released.
+  ** dynamic allocation in u.ci.sContext.s (a Mem struct) is  released.
   */
-  sqlite3VdbeChangeEncoding(&u.ch.sContext.s, encoding);
-  sqlite3VdbeMemMove(u.ch.pDest, &u.ch.sContext.s);
-  REGISTER_TRACE(pOp->p3, u.ch.pDest);
-  UPDATE_MAX_BLOBSIZE(u.ch.pDest);
+  sqlite3VdbeChangeEncoding(&u.ci.sContext.s, encoding);
+  sqlite3VdbeMemMove(u.ci.pDest, &u.ci.sContext.s);
+  REGISTER_TRACE(pOp->p3, u.ci.pDest);
+  UPDATE_MAX_BLOBSIZE(u.ci.pDest);
 
-  if( sqlite3VdbeMemTooBig(u.ch.pDest) ){
+  if( sqlite3VdbeMemTooBig(u.ci.pDest) ){
     goto too_big;
   }
   break;
@@ -57993,22 +63708,22 @@
 ** the end of its result set, then fall through to the next instruction.
 */
 case OP_VNext: {   /* jump */
-#if 0  /* local variables moved into u.ci */
+#if 0  /* local variables moved into u.cj */
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
   int res;
   VdbeCursor *pCur;
-#endif /* local variables moved into u.ci */
+#endif /* local variables moved into u.cj */
 
-  u.ci.res = 0;
-  u.ci.pCur = p->apCsr[pOp->p1];
-  assert( u.ci.pCur->pVtabCursor );
-  if( u.ci.pCur->nullRow ){
+  u.cj.res = 0;
+  u.cj.pCur = p->apCsr[pOp->p1];
+  assert( u.cj.pCur->pVtabCursor );
+  if( u.cj.pCur->nullRow ){
     break;
   }
-  u.ci.pVtab = u.ci.pCur->pVtabCursor->pVtab;
-  u.ci.pModule = u.ci.pVtab->pModule;
-  assert( u.ci.pModule->xNext );
+  u.cj.pVtab = u.cj.pCur->pVtabCursor->pVtab;
+  u.cj.pModule = u.cj.pVtab->pModule;
+  assert( u.cj.pModule->xNext );
 
   /* Invoke the xNext() method of the module. There is no way for the
   ** underlying implementation to return an error if one occurs during
@@ -58017,16 +63732,16 @@
   ** some other method is next invoked on the save virtual table cursor.
   */
   p->inVtabMethod = 1;
-  rc = u.ci.pModule->xNext(u.ci.pCur->pVtabCursor);
+  rc = u.cj.pModule->xNext(u.cj.pCur->pVtabCursor);
   p->inVtabMethod = 0;
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.ci.pVtab->zErrMsg;
-  u.ci.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.cj.pVtab->zErrMsg;
+  u.cj.pVtab->zErrMsg = 0;
   if( rc==SQLITE_OK ){
-    u.ci.res = u.ci.pModule->xEof(u.ci.pCur->pVtabCursor);
+    u.cj.res = u.cj.pModule->xEof(u.cj.pCur->pVtabCursor);
   }
 
-  if( !u.ci.res ){
+  if( !u.cj.res ){
     /* If there is data, jump to P2 */
     pc = pOp->p2 - 1;
   }
@@ -58042,20 +63757,20 @@
 ** in register P1 is passed as the zName argument to the xRename method.
 */
 case OP_VRename: {
-#if 0  /* local variables moved into u.cj */
+#if 0  /* local variables moved into u.ck */
   sqlite3_vtab *pVtab;
   Mem *pName;
-#endif /* local variables moved into u.cj */
+#endif /* local variables moved into u.ck */
 
-  u.cj.pVtab = pOp->p4.pVtab->pVtab;
-  u.cj.pName = &aMem[pOp->p1];
-  assert( u.cj.pVtab->pModule->xRename );
-  REGISTER_TRACE(pOp->p1, u.cj.pName);
-  assert( u.cj.pName->flags & MEM_Str );
-  rc = u.cj.pVtab->pModule->xRename(u.cj.pVtab, u.cj.pName->z);
+  u.ck.pVtab = pOp->p4.pVtab->pVtab;
+  u.ck.pName = &aMem[pOp->p1];
+  assert( u.ck.pVtab->pModule->xRename );
+  REGISTER_TRACE(pOp->p1, u.ck.pName);
+  assert( u.ck.pName->flags & MEM_Str );
+  rc = u.ck.pVtab->pModule->xRename(u.ck.pVtab, u.ck.pName->z);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.cj.pVtab->zErrMsg;
-  u.cj.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.ck.pVtab->zErrMsg;
+  u.ck.pVtab->zErrMsg = 0;
 
   break;
 }
@@ -58086,7 +63801,7 @@
 ** is set to the value of the rowid for the row just inserted.
 */
 case OP_VUpdate: {
-#if 0  /* local variables moved into u.ck */
+#if 0  /* local variables moved into u.cl */
   sqlite3_vtab *pVtab;
   sqlite3_module *pModule;
   int nArg;
@@ -58094,27 +63809,27 @@
   sqlite_int64 rowid;
   Mem **apArg;
   Mem *pX;
-#endif /* local variables moved into u.ck */
+#endif /* local variables moved into u.cl */
 
-  u.ck.pVtab = pOp->p4.pVtab->pVtab;
-  u.ck.pModule = (sqlite3_module *)u.ck.pVtab->pModule;
-  u.ck.nArg = pOp->p2;
+  u.cl.pVtab = pOp->p4.pVtab->pVtab;
+  u.cl.pModule = (sqlite3_module *)u.cl.pVtab->pModule;
+  u.cl.nArg = pOp->p2;
   assert( pOp->p4type==P4_VTAB );
-  if( ALWAYS(u.ck.pModule->xUpdate) ){
-    u.ck.apArg = p->apArg;
-    u.ck.pX = &aMem[pOp->p3];
-    for(u.ck.i=0; u.ck.i<u.ck.nArg; u.ck.i++){
-      sqlite3VdbeMemStoreType(u.ck.pX);
-      u.ck.apArg[u.ck.i] = u.ck.pX;
-      u.ck.pX++;
+  if( ALWAYS(u.cl.pModule->xUpdate) ){
+    u.cl.apArg = p->apArg;
+    u.cl.pX = &aMem[pOp->p3];
+    for(u.cl.i=0; u.cl.i<u.cl.nArg; u.cl.i++){
+      sqlite3VdbeMemStoreType(u.cl.pX);
+      u.cl.apArg[u.cl.i] = u.cl.pX;
+      u.cl.pX++;
     }
-    rc = u.ck.pModule->xUpdate(u.ck.pVtab, u.ck.nArg, u.ck.apArg, &u.ck.rowid);
+    rc = u.cl.pModule->xUpdate(u.cl.pVtab, u.cl.nArg, u.cl.apArg, &u.cl.rowid);
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.ck.pVtab->zErrMsg;
-    u.ck.pVtab->zErrMsg = 0;
+    p->zErrMsg = u.cl.pVtab->zErrMsg;
+    u.cl.pVtab->zErrMsg = 0;
     if( rc==SQLITE_OK && pOp->p1 ){
-      assert( u.ck.nArg>1 && u.ck.apArg[0] && (u.ck.apArg[0]->flags&MEM_Null) );
-      db->lastRowid = u.ck.rowid;
+      assert( u.cl.nArg>1 && u.cl.apArg[0] && (u.cl.apArg[0]->flags&MEM_Null) );
+      db->lastRowid = u.cl.rowid;
     }
     p->nChange++;
   }
@@ -58128,21 +63843,7 @@
 ** Write the current number of pages in database P1 to memory cell P2.
 */
 case OP_Pagecount: {            /* out2-prerelease */
-#if 0  /* local variables moved into u.cl */
-  int p1;
-  int nPage;
-  Pager *pPager;
-#endif /* local variables moved into u.cl */
-
-  u.cl.p1 = pOp->p1;
-  u.cl.pPager = sqlite3BtreePager(db->aDb[u.cl.p1].pBt);
-  rc = sqlite3PagerPagecount(u.cl.pPager, &u.cl.nPage);
-  /* OP_Pagecount is always called from within a read transaction.  The
-  ** page count has already been successfully read and cached.  So the
-  ** sqlite3PagerPagecount() call above cannot fail. */
-  if( ALWAYS(rc==SQLITE_OK) ){
-    pOut->u.i = u.cl.nPage;
-  }
+  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
   break;
 }
 #endif
@@ -58188,6 +63889,7 @@
 ** the same as a no-op.  This opcodesnever appears in a real VM program.
 */
 default: {          /* This is really OP_Noop and OP_Explain */
+  assert( pOp->opcode==OP_Noop || pOp->opcode==OP_Explain );
   break;
 }
 
@@ -58239,7 +63941,9 @@
 vdbe_error_halt:
   assert( rc );
   p->rc = rc;
-  sqlite3_log(rc, "prepared statement aborts at %d: [%s]", pc, p->zSql);
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(rc, "statement aborts at %d: [%s] %s", 
+                   pc, p->zSql, p->zErrMsg);
   sqlite3VdbeHalt(p);
   if( rc==SQLITE_IOERR_NOMEM ) db->mallocFailed = 1;
   rc = SQLITE_ERROR;
@@ -59107,11 +64811,10 @@
 ** exists purely as a contingency, in case some malfunction in some other
 ** part of SQLite causes Sync to be called by mistake.
 */
-static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){   /*NO_TEST*/
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);                        /*NO_TEST*/
-  assert( 0 );                                                 /*NO_TEST*/
-  return SQLITE_OK;                                            /*NO_TEST*/
-}                                                              /*NO_TEST*/
+static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
 
 /*
 ** Query the size of the file in bytes.
@@ -59125,7 +64828,7 @@
 /*
 ** Table of methods for MemJournal sqlite3_file object.
 */
-static struct sqlite3_io_methods MemJournalMethods = {
+static const struct sqlite3_io_methods MemJournalMethods = {
   1,                /* iVersion */
   memjrnlClose,     /* xClose */
   memjrnlRead,      /* xRead */
@@ -59148,7 +64851,7 @@
   MemJournal *p = (MemJournal *)pJfd;
   assert( EIGHT_BYTE_ALIGNMENT(p) );
   memset(p, 0, sqlite3MemJournalSize());
-  p->pMethod = &MemJournalMethods;
+  p->pMethod = (sqlite3_io_methods*)&MemJournalMethods;
 }
 
 /*
@@ -59707,7 +65410,7 @@
 
 /*
 ** Allocate and return a pointer to an expression to load the column iCol
-** from datasource iSrc datasource in SrcList pSrc.
+** from datasource iSrc in SrcList pSrc.
 */
 SQLITE_PRIVATE Expr *sqlite3CreateColumnExpr(sqlite3 *db, SrcList *pSrc, int iSrc, int iCol){
   Expr *p = sqlite3ExprAlloc(db, TK_COLUMN, 0, 0);
@@ -59719,6 +65422,8 @@
       p->iColumn = -1;
     }else{
       p->iColumn = (ynVar)iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
       pItem->colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
     }
     ExprSetProperty(p, EP_Resolved);
@@ -59995,7 +65700,7 @@
   ** result-set entry.
   */
   for(i=0; i<pEList->nExpr; i++){
-    if( sqlite3ExprCompare(pEList->a[i].pExpr, pE) ){
+    if( sqlite3ExprCompare(pEList->a[i].pExpr, pE)<2 ){
       return i+1;
     }
   }
@@ -60755,10 +66460,6 @@
   addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
                            (void*)p4, P4_COLLSEQ);
   sqlite3VdbeChangeP5(pParse->pVdbe, (u8)p5);
-  if( (p5 & SQLITE_AFF_MASK)!=SQLITE_AFF_NONE ){
-    sqlite3ExprCacheAffinityChange(pParse, in1, 1);
-    sqlite3ExprCacheAffinityChange(pParse, in2, 1);
-  }
   return addr;
 }
 
@@ -62389,6 +68090,7 @@
   return out;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Generate an instruction that will put the floating point
 ** value described by z[0..n-1] into register iMem.
@@ -62408,6 +68110,7 @@
     sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);
   }
 }
+#endif
 
 
 /*
@@ -62418,7 +68121,8 @@
 ** z[n] character is guaranteed to be something that does not look
 ** like the continuation of the number.
 */
-static void codeInteger(Vdbe *v, Expr *pExpr, int negFlag, int iMem){
+static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
+  Vdbe *v = pParse->pVdbe;
   if( pExpr->flags & EP_IntValue ){
     int i = pExpr->u.iValue;
     if( negFlag ) i = -i;
@@ -62434,7 +68138,11 @@
       zV = dup8bytes(v, (char*)&value);
       sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);
     }else{
+#ifdef SQLITE_OMIT_FLOATING_POINT
+      sqlite3ErrorMsg(pParse, "oversized integer: %s%s", negFlag ? "-" : "", z);
+#else
       codeReal(v, z, negFlag, iMem);
+#endif
     }
   }
 }
@@ -62587,6 +68295,27 @@
 }
 
 /*
+** Generate code to extract the value of the iCol-th column of a table.
+*/
+SQLITE_PRIVATE void sqlite3ExprCodeGetColumnOfTable(
+  Vdbe *v,        /* The VDBE under construction */
+  Table *pTab,    /* The table containing the value */
+  int iTabCur,    /* The cursor for this table */
+  int iCol,       /* Index of the column to extract */
+  int regOut      /* Extract the valud into this register */
+){
+  if( iCol<0 || iCol==pTab->iPKey ){
+    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
+  }else{
+    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
+    sqlite3VdbeAddOp3(v, op, iTabCur, iCol, regOut);
+  }
+  if( iCol>=0 ){
+    sqlite3ColumnDefault(v, pTab, iCol, regOut);
+  }
+}
+
+/*
 ** Generate code that will extract the iColumn-th column from
 ** table pTab and store the column value in a register.  An effort
 ** is made to store the column value in register iReg, but this is
@@ -62614,13 +68343,7 @@
     }
   }  
   assert( v!=0 );
-  if( iColumn<0 ){
-    sqlite3VdbeAddOp2(v, OP_Rowid, iTable, iReg);
-  }else if( ALWAYS(pTab!=0) ){
-    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
-    sqlite3VdbeAddOp3(v, op, iTable, iColumn, iReg);
-    sqlite3ColumnDefault(v, pTab, iColumn, iReg);
-  }
+  sqlite3ExprCodeGetColumnOfTable(v, pTab, iTable, iColumn, iReg);
   sqlite3ExprCacheStore(pParse, iTable, iColumn, iReg);
   return iReg;
 }
@@ -62821,14 +68544,16 @@
       break;
     }
     case TK_INTEGER: {
-      codeInteger(v, pExpr, 0, target);
+      codeInteger(pParse, pExpr, 0, target);
       break;
     }
+#ifndef SQLITE_OMIT_FLOATING_POINT
     case TK_FLOAT: {
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       codeReal(v, pExpr->u.zToken, 0, target);
       break;
     }
+#endif
     case TK_STRING: {
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       sqlite3VdbeAddOp4(v, OP_String8, 0, target, 0, pExpr->u.zToken, 0);
@@ -62855,27 +68580,12 @@
     }
 #endif
     case TK_VARIABLE: {
-      VdbeOp *pOp;
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       assert( pExpr->u.zToken!=0 );
       assert( pExpr->u.zToken[0]!=0 );
-      if( pExpr->u.zToken[1]==0
-         && (pOp = sqlite3VdbeGetOp(v, -1))->opcode==OP_Variable
-         && pOp->p1+pOp->p3==pExpr->iColumn
-         && pOp->p2+pOp->p3==target
-         && pOp->p4.z==0
-      ){
-        /* If the previous instruction was a copy of the previous unnamed
-        ** parameter into the previous register, then simply increment the
-        ** repeat count on the prior instruction rather than making a new
-        ** instruction.
-        */
-        pOp->p3++;
-      }else{
-        sqlite3VdbeAddOp3(v, OP_Variable, pExpr->iColumn, target, 1);
-        if( pExpr->u.zToken[1]!=0 ){
-          sqlite3VdbeChangeP4(v, -1, pExpr->u.zToken, 0);
-        }
+      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iColumn, target);
+      if( pExpr->u.zToken[1]!=0 ){
+        sqlite3VdbeChangeP4(v, -1, pExpr->u.zToken, 0);
       }
       break;
     }
@@ -62998,11 +68708,13 @@
     case TK_UMINUS: {
       Expr *pLeft = pExpr->pLeft;
       assert( pLeft );
-      if( pLeft->op==TK_FLOAT ){
+      if( pLeft->op==TK_INTEGER ){
+        codeInteger(pParse, pLeft, 1, target);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      }else if( pLeft->op==TK_FLOAT ){
         assert( !ExprHasProperty(pExpr, EP_IntValue) );
         codeReal(v, pLeft->u.zToken, 1, target);
-      }else if( pLeft->op==TK_INTEGER ){
-        codeInteger(v, pLeft, 1, target);
+#endif
       }else{
         regFree1 = r1 = sqlite3GetTempReg(pParse);
         sqlite3VdbeAddOp2(v, OP_Integer, 0, r1);
@@ -63250,6 +68962,7 @@
         target
       ));
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
       /* If the column has REAL affinity, it may currently be stored as an
       ** integer. Use OP_RealAffinity to make sure it is really real.  */
       if( pExpr->iColumn>=0 
@@ -63257,6 +68970,7 @@
       ){
         sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
       }
+#endif
       break;
     }
 
@@ -63922,59 +69636,76 @@
 }
 
 /*
-** Do a deep comparison of two expression trees.  Return TRUE (non-zero)
-** if they are identical and return FALSE if they differ in any way.
+** Do a deep comparison of two expression trees.  Return 0 if the two
+** expressions are completely identical.  Return 1 if they differ only
+** by a COLLATE operator at the top level.  Return 2 if there are differences
+** other than the top-level COLLATE operator.
 **
-** Sometimes this routine will return FALSE even if the two expressions
+** Sometimes this routine will return 2 even if the two expressions
 ** really are equivalent.  If we cannot prove that the expressions are
-** identical, we return FALSE just to be safe.  So if this routine
-** returns false, then you do not really know for certain if the two
-** expressions are the same.  But if you get a TRUE return, then you
+** identical, we return 2 just to be safe.  So if this routine
+** returns 2, then you do not really know for certain if the two
+** expressions are the same.  But if you get a 0 or 1 return, then you
 ** can be sure the expressions are the same.  In the places where
-** this routine is used, it does not hurt to get an extra FALSE - that
+** this routine is used, it does not hurt to get an extra 2 - that
 ** just might result in some slightly slower code.  But returning
-** an incorrect TRUE could lead to a malfunction.
+** an incorrect 0 or 1 could lead to a malfunction.
 */
 SQLITE_PRIVATE int sqlite3ExprCompare(Expr *pA, Expr *pB){
-  int i;
   if( pA==0||pB==0 ){
-    return pB==pA;
+    return pB==pA ? 0 : 2;
   }
   assert( !ExprHasAnyProperty(pA, EP_TokenOnly|EP_Reduced) );
   assert( !ExprHasAnyProperty(pB, EP_TokenOnly|EP_Reduced) );
   if( ExprHasProperty(pA, EP_xIsSelect) || ExprHasProperty(pB, EP_xIsSelect) ){
-    return 0;
+    return 2;
   }
-  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 0;
-  if( pA->op!=pB->op ) return 0;
-  if( !sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 0;
-  if( !sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 0;
-
-  if( pA->x.pList && pB->x.pList ){
-    if( pA->x.pList->nExpr!=pB->x.pList->nExpr ) return 0;
-    for(i=0; i<pA->x.pList->nExpr; i++){
-      Expr *pExprA = pA->x.pList->a[i].pExpr;
-      Expr *pExprB = pB->x.pList->a[i].pExpr;
-      if( !sqlite3ExprCompare(pExprA, pExprB) ) return 0;
-    }
-  }else if( pA->x.pList || pB->x.pList ){
-    return 0;
-  }
-
-  if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 0;
+  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
+  if( pA->op!=pB->op ) return 2;
+  if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
+  if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
+  if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
+  if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 2;
   if( ExprHasProperty(pA, EP_IntValue) ){
     if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
-      return 0;
+      return 2;
     }
   }else if( pA->op!=TK_COLUMN && pA->u.zToken ){
-    if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 0;
+    if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 2;
     if( sqlite3StrICmp(pA->u.zToken,pB->u.zToken)!=0 ){
-      return 0;
+      return 2;
     }
   }
-  return 1;
+  if( (pA->flags & EP_ExpCollate)!=(pB->flags & EP_ExpCollate) ) return 1;
+  if( (pA->flags & EP_ExpCollate)!=0 && pA->pColl!=pB->pColl ) return 2;
+  return 0;
 }
 
+/*
+** Compare two ExprList objects.  Return 0 if they are identical and 
+** non-zero if they differ in any way.
+**
+** This routine might return non-zero for equivalent ExprLists.  The
+** only consequence will be disabled optimizations.  But this routine
+** must never return 0 if the two ExprList objects are different, or
+** a malfunction will result.
+**
+** Two NULL pointers are considered to be the same.  But a NULL pointer
+** always differs from a non-NULL pointer.
+*/
+SQLITE_PRIVATE int sqlite3ExprListCompare(ExprList *pA, ExprList *pB){
+  int i;
+  if( pA==0 && pB==0 ) return 0;
+  if( pA==0 || pB==0 ) return 1;
+  if( pA->nExpr!=pB->nExpr ) return 1;
+  for(i=0; i<pA->nExpr; i++){
+    Expr *pExprA = pA->a[i].pExpr;
+    Expr *pExprB = pB->a[i].pExpr;
+    if( pA->a[i].sortOrder!=pB->a[i].sortOrder ) return 1;
+    if( sqlite3ExprCompare(pExprA, pExprB) ) return 1;
+  }
+  return 0;
+}
 
 /*
 ** Add a new element to the pAggInfo->aCol[] array.  Return the index of
@@ -64103,7 +69834,7 @@
         */
         struct AggInfo_func *pItem = pAggInfo->aFunc;
         for(i=0; i<pAggInfo->nFunc; i++, pItem++){
-          if( sqlite3ExprCompare(pItem->pExpr, pExpr) ){
+          if( sqlite3ExprCompare(pItem->pExpr, pExpr)==0 ){
             break;
           }
         }
@@ -64471,17 +70202,23 @@
 /*
 ** Register built-in functions used to help implement ALTER TABLE
 */
-SQLITE_PRIVATE void sqlite3AlterFunctions(sqlite3 *db){
-  sqlite3CreateFunc(db, "sqlite_rename_table", 2, SQLITE_UTF8, 0,
-                         renameTableFunc, 0, 0);
+SQLITE_PRIVATE void sqlite3AlterFunctions(void){
+  static SQLITE_WSD FuncDef aAlterTableFuncs[] = {
+    FUNCTION(sqlite_rename_table,   2, 0, 0, renameTableFunc),
 #ifndef SQLITE_OMIT_TRIGGER
-  sqlite3CreateFunc(db, "sqlite_rename_trigger", 2, SQLITE_UTF8, 0,
-                         renameTriggerFunc, 0, 0);
+    FUNCTION(sqlite_rename_trigger, 2, 0, 0, renameTriggerFunc),
 #endif
 #ifndef SQLITE_OMIT_FOREIGN_KEY
-  sqlite3CreateFunc(db, "sqlite_rename_parent", 3, SQLITE_UTF8, 0,
-                         renameParentFunc, 0, 0);
+    FUNCTION(sqlite_rename_parent,  3, 0, 0, renameParentFunc),
 #endif
+  };
+  int i;
+  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aAlterTableFuncs);
+
+  for(i=0; i<ArraySize(aAlterTableFuncs); i++){
+    sqlite3FuncDefInsert(pHash, &aFunc[i]);
+  }
 }
 
 /*
@@ -64625,7 +70362,9 @@
   char *zWhere = 0;         /* Where clause to locate temp triggers */
 #endif
   VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
-  
+  int savedDbFlags;         /* Saved value of db->flags */
+
+  savedDbFlags = db->flags;  
   if( NEVER(db->mallocFailed) ) goto exit_rename_table;
   assert( pSrc->nSrc==1 );
   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
@@ -64634,6 +70373,7 @@
   if( !pTab ) goto exit_rename_table;
   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
   zDb = db->aDb[iDb].zName;
+  db->flags |= SQLITE_PreferBuiltin;
 
   /* Get a NULL terminated version of the new table name. */
   zName = sqlite3NameFromToken(db, pName);
@@ -64724,9 +70464,9 @@
     ** for which the renamed table is the parent table.  */
     if( (zWhere=whereForeignKeys(pParse, pTab))!=0 ){
       sqlite3NestedParse(pParse, 
-          "UPDATE sqlite_master SET "
+          "UPDATE \"%w\".%s SET "
               "sql = sqlite_rename_parent(sql, %Q, %Q) "
-              "WHERE %s;", zTabName, zName, zWhere);
+              "WHERE %s;", zDb, SCHEMA_TABLE(iDb), zTabName, zName, zWhere);
       sqlite3DbFree(db, zWhere);
     }
   }
@@ -64801,6 +70541,7 @@
 exit_rename_table:
   sqlite3SrcListDelete(db, pSrc);
   sqlite3DbFree(db, zName);
+  db->flags = savedDbFlags;
 }
 
 
@@ -64920,9 +70661,11 @@
   zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
   if( zCol ){
     char *zEnd = &zCol[pColDef->n-1];
+    int savedDbFlags = db->flags;
     while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
       *zEnd-- = '\0';
     }
+    db->flags |= SQLITE_PreferBuiltin;
     sqlite3NestedParse(pParse, 
         "UPDATE \"%w\".%s SET "
           "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
@@ -64931,6 +70674,7 @@
       zTab
     );
     sqlite3DbFree(db, zCol);
+    db->flags = savedDbFlags;
   }
 
   /* If the default value of the new column is NULL, then set the file
@@ -65076,7 +70820,7 @@
   int iStatCur,           /* Open the sqlite_stat1 table on this cursor */
   const char *zWhere      /* Delete entries associated with this table */
 ){
-  static struct {
+  static const struct {
     const char *zName;
     const char *zCols;
   } aTable[] = {
@@ -65658,12 +71402,16 @@
                   n = 24;
                 }
                 pSample->nByte = (u8)n;
-                pSample->u.z = sqlite3DbMallocRaw(dbMem, n);
-                if( pSample->u.z ){
-                  memcpy(pSample->u.z, z, n);
+                if( n < 1){
+                  pSample->u.z = 0;
                 }else{
-                  db->mallocFailed = 1;
-                  break;
+                  pSample->u.z = sqlite3DbMallocRaw(dbMem, n);
+                  if( pSample->u.z ){
+                    memcpy(pSample->u.z, z, n);
+                  }else{
+                    db->mallocFailed = 1;
+                    break;
+                  }
                 }
               }
             }
@@ -65812,7 +71560,7 @@
   ** or may not be initialised.
   */
   rc = sqlite3BtreeFactory(db, zFile, 0, SQLITE_DEFAULT_CACHE_SIZE,
-                           db->openFlags | SQLITE_OPEN_MAIN_DB | SQLITE_OPEN_CREATE /* Android Change */,
+                           db->openFlags | SQLITE_OPEN_MAIN_DB,
                            &aNew->pBt);
   db->nDb++;
   if( rc==SQLITE_CONSTRAINT ){
@@ -65830,7 +71578,10 @@
     }
     pPager = sqlite3BtreePager(aNew->pBt);
     sqlite3PagerLockingMode(pPager, db->dfltLockMode);
-    sqlite3PagerJournalMode(pPager, db->dfltJournalMode);
+    /* journal_mode set by the OP_JournalMode opcode that will following
+    ** the OP_Function opcode that invoked this function. */
+    sqlite3BtreeSecureDelete(aNew->pBt,
+                             sqlite3BtreeSecureDelete(db->aDb[0].pBt,-1) );
   }
   aNew->safety_level = 3;
   aNew->zName = sqlite3DbStrDup(db, zName);
@@ -65839,7 +71590,7 @@
   }
 
 
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
   if( rc==SQLITE_OK ){
     extern int sqlite3CodecAttach(sqlite3*, int, const void*, int);
     extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
@@ -65973,7 +71724,7 @@
 static void codeAttach(
   Parse *pParse,       /* The parser context */
   int type,            /* Either SQLITE_ATTACH or SQLITE_DETACH */
-  FuncDef *pFunc,      /* FuncDef wrapper for detachFunc() or attachFunc() */
+  FuncDef const *pFunc,/* FuncDef wrapper for detachFunc() or attachFunc() */
   Expr *pAuthArg,      /* Expression to pass to authorization callback */
   Expr *pFilename,     /* Name of database file */
   Expr *pDbname,       /* Name of the database to use internally */
@@ -66024,6 +71775,17 @@
     sqlite3VdbeChangeP5(v, (u8)(pFunc->nArg));
     sqlite3VdbeChangeP4(v, -1, (char *)pFunc, P4_FUNCDEF);
 
+    if( type==SQLITE_ATTACH ){
+      /* On an attach, also set the journal mode.  Note that
+      ** sqlite3VdbeUsesBtree() is not call here since the iDb index
+      ** will be out of range prior to the new database being attached.
+      ** The OP_JournalMode opcode will all sqlite3VdbeUsesBtree() for us.
+      */
+      sqlite3VdbeAddOp3(v, OP_JournalMode, db->nDb, regArgs+3, 
+                           db->dfltJournalMode);
+      sqlite3VdbeChangeP5(v, 1);
+    }
+
     /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
     ** statement only). For DETACH, set it to false (expire all existing
     ** statements).
@@ -66043,7 +71805,7 @@
 **     DETACH pDbname
 */
 SQLITE_PRIVATE void sqlite3Detach(Parse *pParse, Expr *pDbname){
-  static FuncDef detach_func = {
+  static const FuncDef detach_func = {
     1,                /* nArg */
     SQLITE_UTF8,      /* iPrefEnc */
     0,                /* flags */
@@ -66064,7 +71826,7 @@
 **     ATTACH p AS pDbname KEY pKey
 */
 SQLITE_PRIVATE void sqlite3Attach(Parse *pParse, Expr *p, Expr *pDbname, Expr *pKey){
-  static FuncDef attach_func = {
+  static const FuncDef attach_func = {
     3,                /* nArg */
     SQLITE_UTF8,      /* iPrefEnc */
     0,                /* flags */
@@ -66679,7 +72441,7 @@
                          pParse->isMultiWrite && pParse->mayAbort);
     pParse->rc = SQLITE_DONE;
     pParse->colNamesSet = 0;
-  }else if( pParse->rc==SQLITE_OK ){
+  }else{
     pParse->rc = SQLITE_ERROR;
   }
   pParse->nTab = 0;
@@ -69859,7 +75621,7 @@
   if( zName ){
     Vdbe *v = sqlite3GetVdbe(pParse);
 #ifndef SQLITE_OMIT_AUTHORIZATION
-    static const char *az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
+    static const char * const az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
     assert( !SAVEPOINT_BEGIN && SAVEPOINT_RELEASE==1 && SAVEPOINT_ROLLBACK==2 );
 #endif
     if( !v || sqlite3AuthCheck(pParse, SQLITE_SAVEPOINT, az[op], zName, 0) ){
@@ -69878,6 +75640,7 @@
   sqlite3 *db = pParse->db;
   if( db->aDb[1].pBt==0 && !pParse->explain ){
     int rc;
+    Btree *pBt;
     static const int flags = 
           SQLITE_OPEN_READWRITE |
           SQLITE_OPEN_CREATE |
@@ -69885,17 +75648,20 @@
           SQLITE_OPEN_DELETEONCLOSE |
           SQLITE_OPEN_TEMP_DB;
 
-    rc = sqlite3BtreeFactory(db, 0, 0, SQLITE_DEFAULT_CACHE_SIZE, flags,
-                                 &db->aDb[1].pBt);
+    rc = sqlite3BtreeFactory(db, 0, 0, SQLITE_DEFAULT_CACHE_SIZE, flags, &pBt);
     if( rc!=SQLITE_OK ){
       sqlite3ErrorMsg(pParse, "unable to open a temporary database "
         "file for storing temporary tables");
       pParse->rc = rc;
       return 1;
     }
+    db->aDb[1].pBt = pBt;
     assert( db->aDb[1].pSchema );
-    sqlite3PagerJournalMode(sqlite3BtreePager(db->aDb[1].pBt),
-                            db->dfltJournalMode);
+    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
+      db->mallocFailed = 1;
+      return 1;
+    }
+    sqlite3PagerSetJournalMode(sqlite3BtreePager(pBt), db->dfltJournalMode);
   }
   return 0;
 }
@@ -70535,14 +76301,19 @@
 
   /* If no match is found, search the built-in functions.
   **
+  ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
+  ** functions even if a prior app-defined function was found.  And give
+  ** priority to built-in functions.
+  **
   ** Except, if createFlag is true, that means that we are trying to
   ** install a new function.  Whatever FuncDef structure is returned will
   ** have fields overwritten with new information appropriate for the
   ** new function.  But the FuncDefs for built-in functions are read-only.
   ** So we must not search for built-ins when creating a new function.
   */ 
-  if( !createFlag && !pBest ){
+  if( !createFlag && (pBest==0 || (db->flags & SQLITE_PreferBuiltin)!=0) ){
     FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+    bestScore = 0;
     p = functionSearch(pHash, h, zName, nName);
     while( p ){
       int score = matchQuality(p, nArg, enc);
@@ -71142,9 +76913,7 @@
     sqlite3VdbeAddOp2(v, OP_Copy, iRowid, iOld);
     for(iCol=0; iCol<pTab->nCol; iCol++){
       if( mask==0xffffffff || mask&(1<<iCol) ){
-        int iTarget = iOld + iCol + 1;
-        sqlite3VdbeAddOp3(v, OP_Column, iCur, iCol, iTarget);
-        sqlite3ColumnDefault(v, pTab, iCol, iTarget);
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol, iOld+iCol+1);
       }
     }
 
@@ -71540,14 +77309,24 @@
   }
   if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
   r = sqlite3_value_double(argv[0]);
-  zBuf = sqlite3_mprintf("%.*f",n,r);
-  if( zBuf==0 ){
-    sqlite3_result_error_nomem(context);
+  /* If Y==0 and X will fit in a 64-bit int,
+  ** handle the rounding directly,
+  ** otherwise use printf.
+  */
+  if( n==0 && r>=0 && r<LARGEST_INT64-1 ){
+    r = (double)((sqlite_int64)(r+0.5));
+  }else if( n==0 && r<0 && (-r)<LARGEST_INT64-1 ){
+    r = -(double)((sqlite_int64)((-r)+0.5));
   }else{
+    zBuf = sqlite3_mprintf("%.*f",n,r);
+    if( zBuf==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
     sqlite3AtoF(zBuf, &r);
     sqlite3_free(zBuf);
-    sqlite3_result_double(context, r);
   }
+  sqlite3_result_double(context, r);
 }
 #endif
 
@@ -71709,12 +77488,18 @@
 ){
   sqlite3 *db = sqlite3_context_db_handle(context);
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-51513-12026 The last_insert_rowid() SQL function is a
+  ** wrapper around the sqlite3_last_insert_rowid() C/C++ interface
+  ** function. */
   sqlite3_result_int64(context, sqlite3_last_insert_rowid(db));
 }
 
 /*
-** Implementation of the changes() SQL function.  The return value is the
-** same as the sqlite3_changes() API function.
+** Implementation of the changes() SQL function.
+**
+** IMP: R-62073-11209 The changes() SQL function is a wrapper
+** around the sqlite3_changes() C/C++ function and hence follows the same
+** rules for counting changes.
 */
 static void changes(
   sqlite3_context *context,
@@ -71737,6 +77522,8 @@
 ){
   sqlite3 *db = sqlite3_context_db_handle(context);
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-52756-41993 This function is a wrapper around the
+  ** sqlite3_total_changes() C/C++ interface. */
   sqlite3_result_int(context, sqlite3_total_changes(db));
 }
 
@@ -72004,7 +77791,9 @@
   sqlite3_value **NotUsed2
 ){
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  sqlite3_result_text(context, sqlite3_version, -1, SQLITE_STATIC);
+  /* IMP: R-48699-48617 This function is an SQL wrapper around the
+  ** sqlite3_libversion() C-interface. */
+  sqlite3_result_text(context, sqlite3_libversion(), -1, SQLITE_STATIC);
 }
 
 /*
@@ -72018,9 +77807,54 @@
   sqlite3_value **NotUsed2
 ){
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  sqlite3_result_text(context, SQLITE_SOURCE_ID, -1, SQLITE_STATIC);
+  /* IMP: R-24470-31136 This function is an SQL wrapper around the
+  ** sqlite3_sourceid() C interface. */
+  sqlite3_result_text(context, sqlite3_sourceid(), -1, SQLITE_STATIC);
 }
 
+/*
+** Implementation of the sqlite_compileoption_used() function.
+** The result is an integer that identifies if the compiler option
+** was used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptionusedFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zOptName;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-xxxx This function is an SQL wrapper around the
+  ** sqlite3_compileoption_used() C interface. */
+  if( (zOptName = (const char*)sqlite3_value_text(argv[0]))!=0 ){
+    sqlite3_result_int(context, sqlite3_compileoption_used(zOptName));
+  }
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/*
+** Implementation of the sqlite_compileoption_get() function. 
+** The result is a string that identifies the compiler options 
+** used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptiongetFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-xxxx This function is an SQL wrapper around the
+  ** sqlite3_compileoption_get() C interface. */
+  n = sqlite3_value_int(argv[0]);
+  sqlite3_result_text(context, sqlite3_compileoption_get(n), -1, SQLITE_STATIC);
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
 /* Array for converting from half-bytes (nybbles) into ASCII hex
 ** digits. */
 static const char hexdigits[] = {
@@ -72147,7 +77981,7 @@
   if( n>db->aLimit[SQLITE_LIMIT_LENGTH] ){
     sqlite3_result_error_toobig(context);
   }else{
-    sqlite3_result_zeroblob(context, (int)n);
+    sqlite3_result_zeroblob(context, (int)n); /* IMP: R-00293-64994 */
   }
 }
 
@@ -72615,20 +78449,15 @@
 }
 
 /*
-** This function registered all of the above C functions as SQL
-** functions.  This should be the only routine in this file with
-** external linkage.
+** This routine does per-connection function registration.  Most
+** of the built-in functions above are part of the global function set.
+** This routine only deals with those that are not global.
 */
 SQLITE_PRIVATE void sqlite3RegisterBuiltinFunctions(sqlite3 *db){
-#ifndef SQLITE_OMIT_ALTERTABLE
-  sqlite3AlterFunctions(db);
-#endif
-  if( !db->mallocFailed ){
-    int rc = sqlite3_overload_function(db, "MATCH", 2);
-    assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
-    if( rc==SQLITE_NOMEM ){
-      db->mallocFailed = 1;
-    }
+  int rc = sqlite3_overload_function(db, "MATCH", 2);
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    db->mallocFailed = 1;
   }
 }
 
@@ -72752,6 +78581,10 @@
     FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
     FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
     FUNCTION(sqlite_source_id,   0, 0, 0, sourceidFunc     ),
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+    FUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
+    FUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
     FUNCTION(quote,              1, 0, 0, quoteFunc        ),
     FUNCTION(last_insert_rowid,  0, 0, 0, last_insert_rowid),
     FUNCTION(changes,            0, 0, 0, changes          ),
@@ -72792,6 +78625,9 @@
     sqlite3FuncDefInsert(pHash, &aFunc[i]);
   }
   sqlite3RegisterDateTimeFunctions();
+#ifndef SQLITE_OMIT_ALTERTABLE
+  sqlite3AlterFunctions();
+#endif
 }
 
 /************** End of func.c ************************************************/
@@ -74836,7 +80672,7 @@
           if( pColumn->a[j].idx==i ) break;
         }
       }
-      if( pColumn && j>=pColumn->nId ){
+      if( (!useTempTable && !pList) || (pColumn && j>=pColumn->nId) ){
         sqlite3ExprCode(pParse, pTab->aCol[i].pDflt, regCols+i+1);
       }else if( useTempTable ){
         sqlite3VdbeAddOp3(v, OP_Column, srcTab, j, regCols+i+1); 
@@ -75251,19 +81087,33 @@
         ** the triggers and remove both the table and index b-tree entries.
         **
         ** Otherwise, if there are no triggers or the recursive-triggers
-        ** flag is not set, call GenerateRowIndexDelete(). This removes
-        ** the index b-tree entries only. The table b-tree entry will be 
-        ** replaced by the new entry when it is inserted.  */
+        ** flag is not set, but the table has one or more indexes, call 
+        ** GenerateRowIndexDelete(). This removes the index b-tree entries 
+        ** only. The table b-tree entry will be replaced by the new entry 
+        ** when it is inserted.  
+        **
+        ** If either GenerateRowDelete() or GenerateRowIndexDelete() is called,
+        ** also invoke MultiWrite() to indicate that this VDBE may require
+        ** statement rollback (if the statement is aborted after the delete
+        ** takes place). Earlier versions called sqlite3MultiWrite() regardless,
+        ** but being more selective here allows statements like:
+        **
+        **   REPLACE INTO t(rowid) VALUES($newrowid)
+        **
+        ** to run without a statement journal if there are no indexes on the
+        ** table.
+        */
         Trigger *pTrigger = 0;
         if( pParse->db->flags&SQLITE_RecTriggers ){
           pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
         }
-        sqlite3MultiWrite(pParse);
         if( pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0) ){
+          sqlite3MultiWrite(pParse);
           sqlite3GenerateRowDelete(
               pParse, pTab, baseCur, regRowid, 0, pTrigger, OE_Replace
           );
-        }else{
+        }else if( pTab->pIndex ){
+          sqlite3MultiWrite(pParse);
           sqlite3GenerateRowIndexDelete(pParse, pTab, baseCur, 0);
         }
         seenReplace = 1;
@@ -75705,7 +81555,7 @@
     }
   }
 #ifndef SQLITE_OMIT_CHECK
-  if( pDest->pCheck && !sqlite3ExprCompare(pSrc->pCheck, pDest->pCheck) ){
+  if( pDest->pCheck && sqlite3ExprCompare(pSrc->pCheck, pDest->pCheck) ){
     return 0;   /* Tables have different CHECK constraints.  Ticket #2252 */
   }
 #endif
@@ -75848,6 +81698,7 @@
   int nRetry = 0;             /* Number of retry attempts */
   int callbackIsInit;         /* True if callback data is initialized */
 
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
   if( zSql==0 ) zSql = "";
 
   sqlite3_mutex_enter(db->mutex);
@@ -77117,6 +82968,9 @@
     { "legacy_file_format",       SQLITE_LegacyFileFmt },
     { "fullfsync",                SQLITE_FullFSync     },
     { "reverse_unordered_selects", SQLITE_ReverseOrder  },
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    { "automatic_index",          SQLITE_AutoIndex     },
+#endif
 #ifdef SQLITE_DEBUG
     { "sql_trace",                SQLITE_SqlTrace      },
     { "vdbe_listing",             SQLITE_VdbeListing   },
@@ -77198,6 +83052,31 @@
 }
 #endif
 
+
+/*
+** Parameter eMode must be one of the PAGER_JOURNALMODE_XXX constants
+** defined in pager.h. This function returns the associated lowercase
+** journal-mode name.
+*/
+SQLITE_PRIVATE const char *sqlite3JournalModename(int eMode){
+  static char * const azModeName[] = {
+    "delete", "persist", "off", "truncate", "memory"
+#ifndef SQLITE_OMIT_WAL
+     , "wal"
+#endif
+  };
+  assert( PAGER_JOURNALMODE_DELETE==0 );
+  assert( PAGER_JOURNALMODE_PERSIST==1 );
+  assert( PAGER_JOURNALMODE_OFF==2 );
+  assert( PAGER_JOURNALMODE_TRUNCATE==3 );
+  assert( PAGER_JOURNALMODE_MEMORY==4 );
+  assert( PAGER_JOURNALMODE_WAL==5 );
+  assert( eMode>=0 && eMode<=ArraySize(azModeName) );
+
+  if( eMode==ArraySize(azModeName) ) return 0;
+  return azModeName[eMode];
+}
+
 /*
 ** Process a pragma statement.  
 **
@@ -77270,11 +83149,11 @@
   ** page cache size value and the persistent page cache size value
   ** stored in the database file.
   **
-  ** The default cache size is stored in meta-value 2 of page 1 of the
-  ** database file.  The cache size is actually the absolute value of
-  ** this memory location.  The sign of meta-value 2 determines the
-  ** synchronous setting.  A negative value means synchronous is off
-  ** and a positive value means synchronous is on.
+  ** Older versions of SQLite would set the default cache size to a
+  ** negative number to indicate synchronous=OFF.  These days, synchronous
+  ** is always on by default regardless of the sign of the default cache
+  ** size.  But continue to take the absolute value of the default cache
+  ** size of historical compatibility.
   */
   if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){
     static const VdbeOpList getCacheSize[] = {
@@ -77303,10 +83182,6 @@
       if( size<0 ) size = -size;
       sqlite3BeginWriteOperation(pParse, 0, iDb);
       sqlite3VdbeAddOp2(v, OP_Integer, size, 1);
-      sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, 2, BTREE_DEFAULT_CACHE_SIZE);
-      addr = sqlite3VdbeAddOp2(v, OP_IfPos, 2, 0);
-      sqlite3VdbeAddOp2(v, OP_Integer, -size, 1);
-      sqlite3VdbeJumpHere(v, addr);
       sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_DEFAULT_CACHE_SIZE, 1);
       pDb->pSchema->cache_size = size;
       sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
@@ -77362,6 +83237,31 @@
   }else
 
   /*
+  **  PRAGMA [database.]secure_delete
+  **  PRAGMA [database.]secure_delete=ON/OFF
+  **
+  ** The first form reports the current setting for the
+  ** secure_delete flag.  The second form changes the secure_delete
+  ** flag setting and reports thenew value.
+  */
+  if( sqlite3StrICmp(zLeft,"secure_delete")==0 ){
+    Btree *pBt = pDb->pBt;
+    int b = -1;
+    assert( pBt!=0 );
+    if( zRight ){
+      b = getBoolean(zRight);
+    }
+    if( pId2->n==0 && b>=0 ){
+      int ii;
+      for(ii=0; ii<db->nDb; ii++){
+        sqlite3BtreeSecureDelete(db->aDb[ii].pBt, b);
+      }
+    }
+    b = sqlite3BtreeSecureDelete(pBt, b);
+    returnSingleInt(pParse, "secure_delete", b);
+  }else
+
+  /*
   **  PRAGMA [database.]page_count
   **
   ** Return the number of pages in the specified database.
@@ -77426,21 +83326,25 @@
 
   /*
   **  PRAGMA [database.]journal_mode
-  **  PRAGMA [database.]journal_mode = (delete|persist|off|truncate|memory)
+  **  PRAGMA [database.]journal_mode =
+  **                      (delete|persist|off|truncate|memory|wal|off)
   */
   if( sqlite3StrICmp(zLeft,"journal_mode")==0 ){
-    int eMode;
-    static char * const azModeName[] = {
-      "delete", "persist", "off", "truncate", "memory"
-    };
+    int eMode;                    /* One of the PAGER_JOURNALMODE_XXX symbols */
+
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "journal_mode", SQLITE_STATIC);
 
     if( zRight==0 ){
       eMode = PAGER_JOURNALMODE_QUERY;
     }else{
+      const char *zMode;
       int n = sqlite3Strlen30(zRight);
-      eMode = sizeof(azModeName)/sizeof(azModeName[0]) - 1;
-      while( eMode>=0 && sqlite3StrNICmp(zRight, azModeName[eMode], n)!=0 ){
-        eMode--;
+      for(eMode=0; (zMode = sqlite3JournalModename(eMode)); eMode++){
+        if( sqlite3StrNICmp(zRight, zMode, n)==0 ) break;
+      }
+      if( !zMode ){
+        eMode = PAGER_JOURNALMODE_QUERY;
       }
     }
     if( pId2->n==0 && eMode==PAGER_JOURNALMODE_QUERY ){
@@ -77449,39 +83353,31 @@
       ** the journal-mode of the main database).
       */
       eMode = db->dfltJournalMode;
+      sqlite3VdbeAddOp2(v, OP_String8, 0, 1);
+      sqlite3VdbeChangeP4(v, -1, sqlite3JournalModename(eMode), P4_STATIC);
     }else{
-      Pager *pPager;
+      int ii;
+
       if( pId2->n==0 ){
-        /* This indicates that no database name was specified as part
-        ** of the PRAGMA command. In this case the journal-mode must be
-        ** set on all attached databases, as well as the main db file.
+        /* When there is no database name before the "journal_mode" keyword
+        ** in the PRAGMA, then the journal-mode will be set on
+        ** all attached databases, as well as the main db file.
         **
         ** Also, the sqlite3.dfltJournalMode variable is set so that
         ** any subsequently attached databases also use the specified
         ** journal mode.
         */
-        int ii;
-        assert(pDb==&db->aDb[0]);
-        for(ii=1; ii<db->nDb; ii++){
-          if( db->aDb[ii].pBt ){
-            pPager = sqlite3BtreePager(db->aDb[ii].pBt);
-            sqlite3PagerJournalMode(pPager, eMode);
-          }
-        }
         db->dfltJournalMode = (u8)eMode;
       }
-      pPager = sqlite3BtreePager(pDb->pBt);
-      eMode = sqlite3PagerJournalMode(pPager, eMode);
+
+      for(ii=db->nDb-1; ii>=0; ii--){
+        if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
+          sqlite3VdbeUsesBtree(v, ii);
+          sqlite3VdbeAddOp3(v, OP_JournalMode, ii, 1, eMode);
+        }
+      }
     }
-    assert( eMode==PAGER_JOURNALMODE_DELETE
-              || eMode==PAGER_JOURNALMODE_TRUNCATE
-              || eMode==PAGER_JOURNALMODE_PERSIST
-              || eMode==PAGER_JOURNALMODE_OFF
-              || eMode==PAGER_JOURNALMODE_MEMORY );
-    sqlite3VdbeSetNumCols(v, 1);
-    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "journal_mode", SQLITE_STATIC);
-    sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, 
-           azModeName[eMode], P4_STATIC);
+
     sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
   }else
 
@@ -78279,6 +84175,56 @@
   }else
 #endif /* SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS */
 
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  /*
+  **   PRAGMA compile_options
+  **
+  ** Return the names of all compile-time options used in this build,
+  ** one option per row.
+  */
+  if( sqlite3StrICmp(zLeft, "compile_options")==0 ){
+    int i = 0;
+    const char *zOpt;
+    sqlite3VdbeSetNumCols(v, 1);
+    pParse->nMem = 1;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "compile_option", SQLITE_STATIC);
+    while( (zOpt = sqlite3_compileoption_get(i++))!=0 ){
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, zOpt, 0);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    }
+  }else
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+#ifndef SQLITE_OMIT_WAL
+  /*
+  **   PRAGMA [database.]wal_checkpoint
+  **
+  ** Checkpoint the database.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_checkpoint")==0 ){
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3VdbeAddOp3(v, OP_Checkpoint, pId2->z?iDb:SQLITE_MAX_ATTACHED, 0, 0);
+  }else
+
+  /*
+  **   PRAGMA wal_autocheckpoint
+  **   PRAGMA wal_autocheckpoint = N
+  **
+  ** Configure a database connection to automatically checkpoint a database
+  ** after accumulating N frames in the log. Or query for the current value
+  ** of N.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_autocheckpoint")==0 ){
+    if( zRight ){
+      int nAuto = atoi(zRight);
+      sqlite3_wal_autocheckpoint(db, nAuto);
+    }
+    returnSingleInt(pParse, "wal_autocheckpoint", 
+       db->xWalCallback==sqlite3WalDefaultHook ? 
+           SQLITE_PTR_TO_INT(db->pWalArg) : 0);
+  }else
+#endif
+
 #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
   /*
   ** Report the current state of file logs for all databases
@@ -78313,7 +84259,7 @@
   }else
 #endif
 
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
   if( sqlite3StrICmp(zLeft, "key")==0 && zRight ){
     sqlite3_key(db, zRight, sqlite3Strlen30(zRight));
   }else
@@ -78336,17 +84282,15 @@
     }
   }else
 #endif
-#if SQLITE_HAS_CODEC || defined(SQLITE_ENABLE_CEROD)
+#if defined(SQLITE_HAS_CODEC) || defined(SQLITE_ENABLE_CEROD)
   if( sqlite3StrICmp(zLeft, "activate_extensions")==0 ){
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
     if( sqlite3StrNICmp(zRight, "see-", 4)==0 ){
-      extern void sqlite3_activate_see(const char*);
       sqlite3_activate_see(&zRight[4]);
     }
 #endif
 #ifdef SQLITE_ENABLE_CEROD
     if( sqlite3StrNICmp(zRight, "cerod-", 6)==0 ){
-      extern void sqlite3_activate_cerod(const char*);
       sqlite3_activate_cerod(&zRight[6]);
     }
 #endif
@@ -78449,15 +84393,15 @@
     ** or executed.  All the parser does is build the internal data
     ** structures that describe the table, index, or view.
     */
-    char *zErr;
     int rc;
+    sqlite3_stmt *pStmt;
+
     assert( db->init.busy );
     db->init.iDb = iDb;
     db->init.newTnum = atoi(argv[1]);
     db->init.orphanTrigger = 0;
-    rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
+    rc = sqlite3_prepare(db, argv[2], -1, &pStmt, 0);
     db->init.iDb = 0;
-    assert( rc!=SQLITE_OK || zErr==0 );
     if( SQLITE_OK!=rc ){
       if( db->init.orphanTrigger ){
         assert( iDb==1 );
@@ -78466,11 +84410,11 @@
         if( rc==SQLITE_NOMEM ){
           db->mallocFailed = 1;
         }else if( rc!=SQLITE_INTERRUPT && rc!=SQLITE_LOCKED ){
-          corruptSchema(pData, argv[0], zErr);
+          corruptSchema(pData, argv[0], sqlite3_errmsg(db));
         }
       }
-      sqlite3DbFree(db, zErr);
     }
+    sqlite3_finalize(pStmt);
   }else if( argv[0]==0 ){
     corruptSchema(pData, 0, 0);
   }else{
@@ -78689,7 +84633,7 @@
   {
     char *zSql;
     zSql = sqlite3MPrintf(db, 
-        "SELECT name, rootpage, sql FROM '%q'.%s",
+        "SELECT name, rootpage, sql FROM '%q'.%s ORDER BY rowid",
         db->aDb[iDb].zName, zMasterName);
 #ifndef SQLITE_OMIT_AUTHORIZATION
     {
@@ -78955,6 +84899,7 @@
   sqlite3VtabUnlockList(db);
 
   pParse->db = db;
+  pParse->nQueryLoop = (double)1;
   if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
     char *zSqlCopy;
     int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
@@ -78976,6 +84921,7 @@
   }else{
     sqlite3RunParser(pParse, zSql, &zErrMsg);
   }
+  assert( 1==(int)pParse->nQueryLoop );
 
   if( db->mallocFailed ){
     pParse->rc = SQLITE_NOMEM;
@@ -79176,7 +85122,7 @@
     return SQLITE_MISUSE_BKPT;
   }
   sqlite3_mutex_enter(db->mutex);
-  zSql8 = sqlite3Utf16to8(db, zSql, nBytes);
+  zSql8 = sqlite3Utf16to8(db, zSql, nBytes, SQLITE_UTF16NATIVE);
   if( zSql8 ){
     rc = sqlite3LockAndPrepare(db, zSql8, -1, saveSqlFlag, 0, ppStmt, &zTail8);
   }
@@ -81760,8 +87706,8 @@
 **  (14)  The subquery does not use OFFSET
 **
 **  (15)  The outer query is not part of a compound select or the
-**        subquery does not have both an ORDER BY and a LIMIT clause.
-**        (See ticket #2339)
+**        subquery does not have a LIMIT clause.
+**        (See ticket #2339 and ticket [02a8e81d44]).
 **
 **  (16)  The outer query is not an aggregate or the subquery does
 **        not contain ORDER BY.  (Ticket #2942)  This used to not matter
@@ -81844,7 +87790,7 @@
   ** and (14). */
   if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
   if( pSub->pOffset ) return 0;                          /* Restriction (14) */
-  if( p->pRightmost && pSub->pLimit && pSub->pOrderBy ){
+  if( p->pRightmost && pSub->pLimit ){
     return 0;                                            /* Restriction (15) */
   }
   if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
@@ -82561,18 +88507,19 @@
   struct SrcList_item *pFrom;
 
   assert( p->selFlags & SF_Resolved );
-  assert( (p->selFlags & SF_HasTypeInfo)==0 );
-  p->selFlags |= SF_HasTypeInfo;
-  pParse = pWalker->pParse;
-  pTabList = p->pSrc;
-  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
-    Table *pTab = pFrom->pTab;
-    if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
-      /* A sub-query in the FROM clause of a SELECT */
-      Select *pSel = pFrom->pSelect;
-      assert( pSel );
-      while( pSel->pPrior ) pSel = pSel->pPrior;
-      selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+  if( (p->selFlags & SF_HasTypeInfo)==0 ){
+    p->selFlags |= SF_HasTypeInfo;
+    pParse = pWalker->pParse;
+    pTabList = p->pSrc;
+    for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+      Table *pTab = pFrom->pTab;
+      if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
+        /* A sub-query in the FROM clause of a SELECT */
+        Select *pSel = pFrom->pSelect;
+        assert( pSel );
+        while( pSel->pPrior ) pSel = pSel->pPrior;
+        selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+      }
     }
   }
   return WRC_Continue;
@@ -82731,6 +88678,18 @@
       sqlite3ExprCacheClear(pParse);
     }
   }
+
+  /* Before populating the accumulator registers, clear the column cache.
+  ** Otherwise, if any of the required column values are already present 
+  ** in registers, sqlite3ExprCode() may use OP_SCopy to copy the value
+  ** to pC->iMem. But by the time the value is used, the original register
+  ** may have been used, invalidating the underlying buffer holding the
+  ** text or blob value. See ticket [883034dcb5].
+  **
+  ** Another solution would be to change the OP_SCopy used to copy cached
+  ** values to an OP_Copy.
+  */
+  sqlite3ExprCacheClear(pParse);
   for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
     sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
   }
@@ -82939,6 +88898,18 @@
     isDistinct = 0;
   }
 
+  /* If there is both a GROUP BY and an ORDER BY clause and they are
+  ** identical, then disable the ORDER BY clause since the GROUP BY
+  ** will cause elements to come out in the correct order.  This is
+  ** an optimization - the correct answer should result regardless.
+  ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
+  ** to disable this optimization for testing purposes.
+  */
+  if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy)==0
+         && (db->flags & SQLITE_GroupByOrder)==0 ){
+    pOrderBy = 0;
+  }
+
   /* If there is an ORDER BY clause, then this sorting
   ** index might end up being unused if the data can be 
   ** extracted in pre-sorted order.  If that is the case, then the
@@ -83844,7 +89815,8 @@
     goto trigger_cleanup;
   }
   pTab = sqlite3SrcListLookup(pParse, pTableName);
-  if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){
+  if( db->init.busy==0 && pName2->n==0 && pTab
+        && pTab->pSchema==db->aDb[1].pSchema ){
     iDb = 1;
   }
 
@@ -83972,12 +89944,12 @@
   TriggerStep *pStepList, /* The triggered program */
   Token *pAll             /* Token that describes the complete CREATE TRIGGER */
 ){
-  Trigger *pTrig = pParse->pNewTrigger;    /* Trigger being finished */
-  char *zName;                             /* Name of trigger */
-  sqlite3 *db = pParse->db;                /* The database */
-  DbFixer sFix;
-  int iDb;                                 /* Database containing the trigger */
-  Token nameToken;           /* Trigger name for error reporting */
+  Trigger *pTrig = pParse->pNewTrigger;   /* Trigger being finished */
+  char *zName;                            /* Name of trigger */
+  sqlite3 *db = pParse->db;               /* The database */
+  DbFixer sFix;                           /* Fixer object */
+  int iDb;                                /* Database containing the trigger */
+  Token nameToken;                        /* Trigger name for error reporting */
 
   pTrig = pParse->pNewTrigger;
   pParse->pNewTrigger = 0;
@@ -83996,7 +89968,7 @@
     goto triggerfinish_cleanup;
   }
 
-  /* if we are not initializing, and this trigger is not on a TEMP table, 
+  /* if we are not initializing,
   ** build the sqlite_master entry
   */
   if( !db->init.busy ){
@@ -84543,6 +90515,7 @@
   pSubParse->pToplevel = pTop;
   pSubParse->zAuthContext = pTrigger->zName;
   pSubParse->eTriggerOp = pTrigger->op;
+  pSubParse->nQueryLoop = pParse->nQueryLoop;
 
   v = sqlite3GetVdbe(pSubParse);
   if( v ){
@@ -84819,7 +90792,7 @@
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
-*************************************************************************
+sqlite*************************************************************************
 ** This file contains C code routines that are called by the parser
 ** to handle UPDATE statements.
 */
@@ -85206,8 +91179,7 @@
     );
     for(i=0; i<pTab->nCol; i++){
       if( aXRef[i]<0 || oldmask==0xffffffff || (oldmask & (1<<i)) ){
-        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regOld+i);
-        sqlite3ColumnDefault(v, pTab, i, regOld+i);
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOld+i);
       }else{
         sqlite3VdbeAddOp2(v, OP_Null, 0, regOld+i);
       }
@@ -85580,7 +91552,8 @@
   void (*saved_xTrace)(void*,const char*);  /* Saved db->xTrace */
   Db *pDb = 0;            /* Database to detach at end of vacuum */
   int isMemDb;            /* True if vacuuming a :memory: database */
-  int nRes;
+  int nRes;               /* Bytes of reserved space at the end of each page */
+  int nDb;                /* Number of attached databases */
 
   if( !db->autoCommit ){
     sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
@@ -85594,8 +91567,8 @@
   saved_nChange = db->nChange;
   saved_nTotalChange = db->nTotalChange;
   saved_xTrace = db->xTrace;
-  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
-  db->flags &= ~SQLITE_ForeignKeys;
+  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin;
+  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder);
   db->xTrace = 0;
 
   pMain = db->aDb[0].pBt;
@@ -85615,15 +91588,18 @@
   ** time to parse and run the PRAGMA to turn journalling off than it does
   ** to write the journal header file.
   */
+  nDb = db->nDb;
   if( sqlite3TempInMemory(db) ){
     zSql = "ATTACH ':memory:' AS vacuum_db;";
   }else{
     zSql = "ATTACH '' AS vacuum_db;";
   }
   rc = execSql(db, pzErrMsg, zSql);
+  if( db->nDb>nDb ){
+    pDb = &db->aDb[db->nDb-1];
+    assert( strcmp(pDb->zName,"vacuum_db")==0 );
+  }
   if( rc!=SQLITE_OK ) goto end_of_vacuum;
-  pDb = &db->aDb[db->nDb-1];
-  assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
   pTemp = db->aDb[db->nDb-1].pBt;
 
   /* The call to execSql() to attach the temp database has left the file
@@ -85645,6 +91621,12 @@
   }
 #endif
 
+  /* Do not attempt to change the page size for a WAL database */
+  if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+                                               ==PAGER_JOURNALMODE_WAL ){
+    db->nextPagesize = 0;
+  }
+
   if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
    || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
    || NEVER(db->mallocFailed)
@@ -85781,6 +91763,7 @@
   db->nChange = saved_nChange;
   db->nTotalChange = saved_nTotalChange;
   db->xTrace = saved_xTrace;
+  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
 
   /* Currently there is an SQL level transaction open on the vacuum
   ** database. No locks are held on any other files (since the main file
@@ -86463,6 +92446,7 @@
   }else{
     pParse->declareVtab = 1;
     pParse->db = db;
+    pParse->nQueryLoop = 1;
   
     if( SQLITE_OK==sqlite3RunParser(pParse, zCreateTable, &zErr) 
      && pParse->pNewTable
@@ -86983,6 +92967,7 @@
 #define WHERE_COLUMN_IN    0x00040000  /* x IN (...) */
 #define WHERE_COLUMN_NULL  0x00080000  /* x IS NULL */
 #define WHERE_INDEXED      0x000f0000  /* Anything that uses an index */
+#define WHERE_NOT_FULLSCAN 0x000f3000  /* Does not do a full table scan */
 #define WHERE_IN_ABLE      0x000f1000  /* Able to support an IN operator */
 #define WHERE_TOP_LIMIT    0x00100000  /* x<EXPR or x<=EXPR constraint */
 #define WHERE_BTM_LIMIT    0x00200000  /* x>EXPR or x>=EXPR constraint */
@@ -86992,6 +92977,7 @@
 #define WHERE_UNIQUE       0x04000000  /* Selects no more than one row */
 #define WHERE_VIRTUALTABLE 0x08000000  /* Use virtual-table processing */
 #define WHERE_MULTI_OR     0x10000000  /* OR using multiple indices */
+#define WHERE_TEMP_INDEX   0x20000000  /* Uses an ephemeral index */
 
 /*
 ** Initialize a preallocated WhereClause structure.
@@ -87401,7 +93387,7 @@
   }
   assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
   pColl = sqlite3ExprCollSeq(pParse, pLeft);
-  assert( pColl!=0 );  /* Every non-IPK column has a collating sequence */
+  if( pColl==0 ) return 0;  /* Happens when LHS has an undefined collation */
   if( (pColl->type!=SQLITE_COLL_BINARY || *pnoCase) &&
       (pColl->type!=SQLITE_COLL_NOCASE || !*pnoCase) ){
     /* IMP: R-09003-32046 For the GLOB operator, the column must use the
@@ -87844,7 +93830,7 @@
   Expr *pExpr;                     /* The expression to be analyzed */
   Bitmask prereqLeft;              /* Prerequesites of the pExpr->pLeft */
   Bitmask prereqAll;               /* Prerequesites of pExpr */
-  Bitmask extraRight = 0;          /* */
+  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
   Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
   int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
   int noCase = 0;                  /* LIKE/GLOB distinguishes case */
@@ -87916,7 +93902,8 @@
       pLeft = pDup->pLeft;
       pNew->leftCursor = pLeft->iTable;
       pNew->u.leftColumn = pLeft->iColumn;
-      pNew->prereqRight = prereqLeft;
+      testcase( (prereqLeft | extraRight) != prereqLeft );
+      pNew->prereqRight = prereqLeft | extraRight;
       pNew->prereqAll = prereqAll;
       pNew->eOperator = operatorMask(pDup->op);
     }
@@ -88320,6 +94307,11 @@
   WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm];        /* End of pWC->a[] */
   WhereTerm *pTerm;                 /* A single term of the WHERE clause */
 
+  /* No OR-clause optimization allowed if the NOT INDEXED clause is used */
+  if( pSrc->notIndexed ){
+    return;
+  }
+
   /* Search the WHERE clause terms for a usable WO_OR term. */
   for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
     if( pTerm->eOperator==WO_OR 
@@ -88362,8 +94354,9 @@
       /* If there is an ORDER BY clause, increase the scan cost to account 
       ** for the cost of the sort. */
       if( pOrderBy!=0 ){
+        WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
+                    rTotal, rTotal+nRow*estLog(nRow)));
         rTotal += nRow*estLog(nRow);
-        WHERETRACE(("... sorting increases OR cost to %.9g\n", rTotal));
       }
 
       /* If the cost of scanning using this OR term for optimization is
@@ -88382,6 +94375,247 @@
 #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
 }
 
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Return TRUE if the WHERE clause term pTerm is of a form where it
+** could be used with an index to access pSrc, assuming an appropriate
+** index existed.
+*/
+static int termCanDriveIndex(
+  WhereTerm *pTerm,              /* WHERE clause term to check */
+  struct SrcList_item *pSrc,     /* Table we are trying to access */
+  Bitmask notReady               /* Tables in outer loops of the join */
+){
+  char aff;
+  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
+  if( pTerm->eOperator!=WO_EQ ) return 0;
+  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
+  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
+  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  return 1;
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** If the query plan for pSrc specified in pCost is a full table scan
+** and indexing is allows (if there is no NOT INDEXED clause) and it
+** possible to construct a transient index that would perform better
+** than a full table scan even when the cost of constructing the index
+** is taken into account, then alter the query plan to use the
+** transient index.
+*/
+static void bestAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+  double nTableRow;           /* Rows in the input table */
+  double logN;                /* log(nTableRow) */
+  double costTempIdx;         /* per-query cost of the transient index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  Table *pTable;              /* Table tht might be indexed */
+
+  if( (pParse->db->flags & SQLITE_AutoIndex)==0 ){
+    /* Automatic indices are disabled at run-time */
+    return;
+  }
+  if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
+    /* We already have some kind of index in use for this query. */
+    return;
+  }
+  if( pSrc->notIndexed ){
+    /* The NOT INDEXED clause appears in the SQL. */
+    return;
+  }
+
+  assert( pParse->nQueryLoop >= (double)1 );
+  pTable = pSrc->pTab;
+  nTableRow = pTable->pIndex ? pTable->pIndex->aiRowEst[0] : 1000000;
+  logN = estLog(nTableRow);
+  costTempIdx = 2*logN*(nTableRow/pParse->nQueryLoop + 1);
+  if( costTempIdx>=pCost->rCost ){
+    /* The cost of creating the transient table would be greater than
+    ** doing the full table scan */
+    return;
+  }
+
+  /* Search for any equality comparison term */
+  pWCEnd = &pWC->a[pWC->nTerm];
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      WHERETRACE(("auto-index reduces cost from %.2f to %.2f\n",
+                    pCost->rCost, costTempIdx));
+      pCost->rCost = costTempIdx;
+      pCost->nRow = logN + 1;
+      pCost->plan.wsFlags = WHERE_TEMP_INDEX;
+      pCost->used = pTerm->prereqRight;
+      break;
+    }
+  }
+}
+#else
+# define bestAutomaticIndex(A,B,C,D,E)  /* no-op */
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Generate code to construct the Index object for an automatic index
+** and to set up the WhereLevel object pLevel so that the code generator
+** makes use of the automatic index.
+*/
+static void constructAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to get the next index */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereLevel *pLevel          /* Write new index here */
+){
+  int nColumn;                /* Number of columns in the constructed index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  int nByte;                  /* Byte of memory needed for pIdx */
+  Index *pIdx;                /* Object describing the transient index */
+  Vdbe *v;                    /* Prepared statement under construction */
+  int regIsInit;              /* Register set by initialization */
+  int addrInit;               /* Address of the initialization bypass jump */
+  Table *pTable;              /* The table being indexed */
+  KeyInfo *pKeyinfo;          /* Key information for the index */   
+  int addrTop;                /* Top of the index fill loop */
+  int regRecord;              /* Register holding an index record */
+  int n;                      /* Column counter */
+  int i;                      /* Loop counter */
+  int mxBitCol;               /* Maximum column in pSrc->colUsed */
+  CollSeq *pColl;             /* Collating sequence to on a column */
+  Bitmask idxCols;            /* Bitmap of columns used for indexing */
+  Bitmask extraCols;          /* Bitmap of additional columns */
+
+  /* Generate code to skip over the creation and initialization of the
+  ** transient index on 2nd and subsequent iterations of the loop. */
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  regIsInit = ++pParse->nMem;
+  addrInit = sqlite3VdbeAddOp1(v, OP_If, regIsInit);
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, regIsInit);
+
+  /* Count the number of columns that will be added to the index
+  ** and used to match WHERE clause constraints */
+  nColumn = 0;
+  pTable = pSrc->pTab;
+  pWCEnd = &pWC->a[pWC->nTerm];
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      if( (idxCols & cMask)==0 ){
+        nColumn++;
+        idxCols |= cMask;
+      }
+    }
+  }
+  assert( nColumn>0 );
+  pLevel->plan.nEq = nColumn;
+
+  /* Count the number of additional columns needed to create a
+  ** covering index.  A "covering index" is an index that contains all
+  ** columns that are needed by the query.  With a covering index, the
+  ** original table never needs to be accessed.  Automatic indices must
+  ** be a covering index because the index will not be updated if the
+  ** original table changes and the index and table cannot both be used
+  ** if they go out of sync.
+  */
+  extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
+  mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
+  testcase( pTable->nCol==BMS-1 );
+  testcase( pTable->nCol==BMS-2 );
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ) nColumn++;
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    nColumn += pTable->nCol - BMS + 1;
+  }
+  pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
+
+  /* Construct the Index object to describe this index */
+  nByte = sizeof(Index);
+  nByte += nColumn*sizeof(int);     /* Index.aiColumn */
+  nByte += nColumn*sizeof(char*);   /* Index.azColl */
+  nByte += nColumn;                 /* Index.aSortOrder */
+  pIdx = sqlite3DbMallocZero(pParse->db, nByte);
+  if( pIdx==0 ) return;
+  pLevel->plan.u.pIdx = pIdx;
+  pIdx->azColl = (char**)&pIdx[1];
+  pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
+  pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
+  pIdx->zName = "auto-index";
+  pIdx->nColumn = nColumn;
+  pIdx->pTable = pTable;
+  n = 0;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      if( (idxCols & cMask)==0 ){
+        Expr *pX = pTerm->pExpr;
+        idxCols |= cMask;
+        pIdx->aiColumn[n] = pTerm->u.leftColumn;
+        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+        pIdx->azColl[n] = pColl->zName;
+        n++;
+      }
+    }
+  }
+  assert( n==pLevel->plan.nEq );
+
+  /* Add additional columns needed to make the automatic index into
+  ** a covering index */
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    for(i=BMS-1; i<pTable->nCol; i++){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  assert( n==nColumn );
+
+  /* Create the automatic index */
+  pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
+  assert( pLevel->iIdxCur>=0 );
+  sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
+                    (char*)pKeyinfo, P4_KEYINFO_HANDOFF);
+  VdbeComment((v, "for %s", pTable->zName));
+
+  /* Fill the automatic index with content */
+  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
+  regRecord = sqlite3GetTempReg(pParse);
+  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
+  sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
+  sqlite3VdbeJumpHere(v, addrTop);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  
+  /* Jump here when skipping the initialization */
+  sqlite3VdbeJumpHere(v, addrInit);
+}
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 /*
 ** Allocate and populate an sqlite3_index_info structure. It is the 
@@ -88566,6 +94800,7 @@
   WhereTerm *pTerm;
   int i, j;
   int nOrderBy;
+  double rCost;
 
   /* Make sure wsFlags is initialized to some sane value. Otherwise, if the 
   ** malloc in allocateIndexInfo() fails and this function returns leaving
@@ -88652,6 +94887,15 @@
     }
   }
 
+  /* If there is an ORDER BY clause, and the selected virtual table index
+  ** does not satisfy it, increase the cost of the scan accordingly. This
+  ** matches the processing for non-virtual tables in bestBtreeIndex().
+  */
+  rCost = pIdxInfo->estimatedCost;
+  if( pOrderBy && pIdxInfo->orderByConsumed==0 ){
+    rCost += estLog(rCost)*rCost;
+  }
+
   /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
   ** inital value of lowestCost in this loop. If it is, then the
   ** (cost<lowestCost) test below will never be true.
@@ -88659,10 +94903,10 @@
   ** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT 
   ** is defined.
   */
-  if( (SQLITE_BIG_DBL/((double)2))<pIdxInfo->estimatedCost ){
+  if( (SQLITE_BIG_DBL/((double)2))<rCost ){
     pCost->rCost = (SQLITE_BIG_DBL/((double)2));
   }else{
-    pCost->rCost = pIdxInfo->estimatedCost;
+    pCost->rCost = rCost;
   }
   pCost->plan.u.pVtabIdx = pIdxInfo;
   if( pIdxInfo->orderByConsumed ){
@@ -89063,14 +95307,14 @@
     **    Set to true if there was at least one "x IN (SELECT ...)" term used 
     **    in determining the value of nInMul.
     **
-    **  nBound:
+    **  estBound:
     **    An estimate on the amount of the table that must be searched.  A
     **    value of 100 means the entire table is searched.  Range constraints
     **    might reduce this to a value less than 100 to indicate that only
     **    a fraction of the table needs searching.  In the absence of
     **    sqlite_stat2 ANALYZE data, a single inequality reduces the search
     **    space to 1/3rd its original size.  So an x>? constraint reduces
-    **    nBound to 33.  Two constraints (x>? AND x<?) reduce nBound to 11.
+    **    estBound to 33.  Two constraints (x>? AND x<?) reduce estBound to 11.
     **
     **  bSort:   
     **    Boolean. True if there is an ORDER BY clause that will require an 
@@ -89092,13 +95336,14 @@
     int nEq;
     int bInEst = 0;
     int nInMul = 1;
-    int nBound = 100;
+    int estBound = 100;
+    int nBound = 0;             /* Number of range constraints seen */
     int bSort = 0;
     int bLookup = 0;
+    WhereTerm *pTerm;           /* A single term of the WHERE clause */
 
     /* Determine the values of nEq and nInMul */
     for(nEq=0; nEq<pProbe->nColumn; nEq++){
-      WhereTerm *pTerm;           /* A single term of the WHERE clause */
       int j = pProbe->aiColumn[nEq];
       pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
       if( pTerm==0 ) break;
@@ -89118,18 +95363,20 @@
       used |= pTerm->prereqRight;
     }
 
-    /* Determine the value of nBound. */
+    /* Determine the value of estBound. */
     if( nEq<pProbe->nColumn ){
       int j = pProbe->aiColumn[nEq];
       if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
         WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
         WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
-        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &nBound);
+        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &estBound);
         if( pTop ){
+          nBound = 1;
           wsFlags |= WHERE_TOP_LIMIT;
           used |= pTop->prereqRight;
         }
         if( pBtm ){
+          nBound++;
           wsFlags |= WHERE_BTM_LIMIT;
           used |= pBtm->prereqRight;
         }
@@ -89160,7 +95407,7 @@
 
     /* If currently calculating the cost of using an index (not the IPK
     ** index), determine if all required column data may be obtained without 
-    ** seeking to entries in the main table (i.e. if the index is a covering
+    ** using the main table (i.e. if the index is a covering
     ** index for this query). If it is, set the WHERE_IDX_ONLY flag in
     ** wsFlags. Otherwise, set the bLookup variable to true.  */
     if( pIdx && wsFlags ){
@@ -89179,8 +95426,7 @@
       }
     }
 
-    /**** Begin adding up the cost of using this index (Needs improvements)
-    **
+    /*
     ** Estimate the number of rows of output.  For an IN operator,
     ** do not let the estimate exceed half the rows in the table.
     */
@@ -89199,8 +95445,8 @@
     /* Adjust the number of rows and the cost downward to reflect rows
     ** that are excluded by range constraints.
     */
-    nRow = (nRow * (double)nBound) / (double)100;
-    cost = (cost * (double)nBound) / (double)100;
+    nRow = (nRow * (double)estBound) / (double)100;
+    cost = (cost * (double)estBound) / (double)100;
 
     /* Add in the estimated cost of sorting the result
     */
@@ -89217,17 +95463,75 @@
     }
     /**** Cost of using this index has now been computed ****/
 
+    /* If there are additional constraints on this table that cannot
+    ** be used with the current index, but which might lower the number
+    ** of output rows, adjust the nRow value accordingly.  This only 
+    ** matters if the current index is the least costly, so do not bother
+    ** with this step if we already know this index will not be chosen.
+    ** Also, never reduce the output row count below 2 using this step.
+    **
+    ** Do not reduce the output row count if pSrc is the only table that
+    ** is notReady; if notReady is a power of two.  This will be the case
+    ** when the main sqlite3WhereBegin() loop is scanning for a table with
+    ** and "optimal" index, and on such a scan the output row count
+    ** reduction is not valid because it does not update the "pCost->used"
+    ** bitmap.  The notReady bitmap will also be a power of two when we
+    ** are scanning for the last table in a 64-way join.  We are willing
+    ** to bypass this optimization in that corner case.
+    */
+    if( nRow>2 && cost<=pCost->rCost && (notReady & (notReady-1))!=0 ){
+      int k;                       /* Loop counter */
+      int nSkipEq = nEq;           /* Number of == constraints to skip */
+      int nSkipRange = nBound;     /* Number of < constraints to skip */
+      Bitmask thisTab;             /* Bitmap for pSrc */
+
+      thisTab = getMask(pWC->pMaskSet, iCur);
+      for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
+        if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
+        if( (pTerm->prereqAll & notReady)!=thisTab ) continue;
+        if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
+          if( nSkipEq ){
+            /* Ignore the first nEq equality matches since the index
+            ** has already accounted for these */
+            nSkipEq--;
+          }else{
+            /* Assume each additional equality match reduces the result
+            ** set size by a factor of 10 */
+            nRow /= 10;
+          }
+        }else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
+          if( nSkipRange ){
+            /* Ignore the first nBound range constraints since the index
+            ** has already accounted for these */
+            nSkipRange--;
+          }else{
+            /* Assume each additional range constraint reduces the result
+            ** set size by a factor of 3 */
+            nRow /= 3;
+          }
+        }else{
+          /* Any other expression lowers the output row count by half */
+          nRow /= 2;
+        }
+      }
+      if( nRow<2 ) nRow = 2;
+    }
+
+
     WHERETRACE((
-      "tbl=%s idx=%s nEq=%d nInMul=%d nBound=%d bSort=%d bLookup=%d"
-      " wsFlags=%d   (nRow=%.2f cost=%.2f)\n",
+      "%s(%s): nEq=%d nInMul=%d estBound=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
+      "         notReady=0x%llx nRow=%.2f cost=%.2f used=0x%llx\n",
       pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"), 
-      nEq, nInMul, nBound, bSort, bLookup, wsFlags, nRow, cost
+      nEq, nInMul, estBound, bSort, bLookup, wsFlags,
+      notReady, nRow, cost, used
     ));
 
     /* If this index is the best we have seen so far, then record this
     ** index and its cost in the pCost structure.
     */
-    if( (!pIdx || wsFlags) && cost<pCost->rCost ){
+    if( (!pIdx || wsFlags)
+     && (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->nRow))
+    ){
       pCost->rCost = cost;
       pCost->nRow = nRow;
       pCost->used = used;
@@ -89262,10 +95566,12 @@
   );
 
   WHERETRACE(("best index is: %s\n", 
-    (pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
+    ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" : 
+         pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
   ));
   
   bestOrClauseIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
+  bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
   pCost->plan.wsFlags |= eqTermMask;
 }
 
@@ -89323,7 +95629,7 @@
 */
 static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
   if( pTerm
-      && ALWAYS((pTerm->wtFlags & TERM_CODED)==0)
+      && (pTerm->wtFlags & TERM_CODED)==0
       && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
   ){
     pTerm->wtFlags |= TERM_CODED;
@@ -89521,7 +95827,9 @@
     int k = pIdx->aiColumn[j];
     pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
     if( NEVER(pTerm==0) ) break;
-    assert( (pTerm->wtFlags & TERM_CODED)==0 );
+    /* The following true for indices with redundant columns. 
+    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
+    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
     r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
     if( r1!=regBase+j ){
       if( nReg==1 ){
@@ -89735,7 +96043,11 @@
     pLevel->op = bRev ? OP_Prev : OP_Next;
     pLevel->p1 = iCur;
     pLevel->p2 = start;
-    pLevel->p5 = (pStart==0 && pEnd==0) ?1:0;
+    if( pStart==0 && pEnd==0 ){
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }else{
+      assert( pLevel->p5==0 );
+    }
     if( testOp!=OP_Noop ){
       iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
       sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
@@ -89804,7 +96116,8 @@
     int iIdxCur;         /* The VDBE cursor for the index */
     int nExtraReg = 0;   /* Number of extra registers needed */
     int op;              /* Instruction opcode */
-    char *zAff;
+    char *zStartAff;             /* Affinity for start of range constraint */
+    char *zEndAff;               /* Affinity for end of range constraint */
 
     pIdx = pLevel->plan.u.pIdx;
     iIdxCur = pLevel->iIdxCur;
@@ -89845,8 +96158,9 @@
     ** starting at regBase.
     */
     regBase = codeAllEqualityTerms(
-        pParse, pLevel, pWC, notReady, nExtraReg, &zAff
+        pParse, pLevel, pWC, notReady, nExtraReg, &zStartAff
     );
+    zEndAff = sqlite3DbStrDup(pParse->db, zStartAff);
     addrNxt = pLevel->addrNxt;
 
     /* If we are doing a reverse order scan on an ascending index, or
@@ -89871,15 +96185,15 @@
       Expr *pRight = pRangeStart->pExpr->pRight;
       sqlite3ExprCode(pParse, pRight, regBase+nEq);
       sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE){
+      if( zStartAff ){
+        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
           /* Since the comparison is to be performed with no conversions
           ** applied to the operands, set the affinity to apply to pRight to 
           ** SQLITE_AFF_NONE.  */
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+          zStartAff[nEq] = SQLITE_AFF_NONE;
         }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[nConstraint]) ){
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
+          zStartAff[nEq] = SQLITE_AFF_NONE;
         }
       }  
       nConstraint++;
@@ -89889,7 +96203,7 @@
       startEq = 0;
       start_constraints = 1;
     }
-    codeApplyAffinity(pParse, regBase, nConstraint, zAff);
+    codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
     op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
     assert( op!=0 );
     testcase( op==OP_Rewind );
@@ -89909,21 +96223,22 @@
       sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
       sqlite3ExprCode(pParse, pRight, regBase+nEq);
       sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE){
+      if( zEndAff ){
+        if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
           /* Since the comparison is to be performed with no conversions
           ** applied to the operands, set the affinity to apply to pRight to 
           ** SQLITE_AFF_NONE.  */
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+          zEndAff[nEq] = SQLITE_AFF_NONE;
         }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[nConstraint]) ){
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
+          zEndAff[nEq] = SQLITE_AFF_NONE;
         }
       }  
-      codeApplyAffinity(pParse, regBase, nEq+1, zAff);
+      codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
       nConstraint++;
     }
-    sqlite3DbFree(pParse->db, zAff);
+    sqlite3DbFree(pParse->db, zStartAff);
+    sqlite3DbFree(pParse->db, zEndAff);
 
     /* Top of the loop body */
     pLevel->p2 = sqlite3VdbeCurrentAddr(v);
@@ -90193,7 +96508,7 @@
 ** Free a WhereInfo structure
 */
 static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
-  if( pWInfo ){
+  if( ALWAYS(pWInfo) ){
     int i;
     for(i=0; i<pWInfo->nLevel; i++){
       sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
@@ -90204,6 +96519,13 @@
         }
         sqlite3DbFree(db, pInfo);
       }
+      if( pWInfo->a[i].plan.wsFlags & WHERE_TEMP_INDEX ){
+        Index *pIdx = pWInfo->a[i].plan.u.pIdx;
+        if( pIdx ){
+          sqlite3DbFree(db, pIdx->zColAff);
+          sqlite3DbFree(db, pIdx);
+        }
+      }
     }
     whereClauseClear(pWInfo->pWC);
     sqlite3DbFree(db, pWInfo);
@@ -90323,6 +96645,7 @@
   /* The number of tables in the FROM clause is limited by the number of
   ** bits in a Bitmask 
   */
+  testcase( pTabList->nSrc==BMS );
   if( pTabList->nSrc>BMS ){
     sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
     return 0;
@@ -90350,6 +96673,8 @@
       sizeof(WhereMaskSet)
   );
   if( db->mallocFailed ){
+    sqlite3DbFree(db, pWInfo);
+    pWInfo = 0;
     goto whereBeginError;
   }
   pWInfo->nLevel = nTabList;
@@ -90358,6 +96683,7 @@
   pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
   pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
   pWInfo->wctrlFlags = wctrlFlags;
+  pWInfo->savedNQueryLoop = pParse->nQueryLoop;
   pMaskSet = (WhereMaskSet*)&pWC[1];
 
   /* Split the WHERE clause into separate subexpressions where each
@@ -90459,20 +96785,25 @@
     bestPlan.rCost = SQLITE_BIG_DBL;
 
     /* Loop through the remaining entries in the FROM clause to find the
-    ** next nested loop. The FROM clause entries may be iterated through
+    ** next nested loop. The loop tests all FROM clause entries
     ** either once or twice. 
     **
-    ** The first iteration, which is always performed, searches for the
-    ** FROM clause entry that permits the lowest-cost, "optimal" scan. In
+    ** The first test is always performed if there are two or more entries
+    ** remaining and never performed if there is only one FROM clause entry
+    ** to choose from.  The first test looks for an "optimal" scan.  In
     ** this context an optimal scan is one that uses the same strategy
     ** for the given FROM clause entry as would be selected if the entry
     ** were used as the innermost nested loop.  In other words, a table
     ** is chosen such that the cost of running that table cannot be reduced
-    ** by waiting for other tables to run first.
+    ** by waiting for other tables to run first.  This "optimal" test works
+    ** by first assuming that the FROM clause is on the inner loop and finding
+    ** its query plan, then checking to see if that query plan uses any
+    ** other FROM clause terms that are notReady.  If no notReady terms are
+    ** used then the "optimal" query plan works.
     **
-    ** The second iteration is only performed if no optimal scan strategies
-    ** were found by the first. This iteration is used to search for the
-    ** lowest cost scan overall.
+    ** The second loop iteration is only performed if no optimal scan
+    ** strategies were found by the first loop. This 2nd iteration is used to
+    ** search for the lowest cost scan overall.
     **
     ** Previous versions of SQLite performed only the second iteration -
     ** the next outermost loop was always that with the lowest overall
@@ -90490,9 +96821,8 @@
     ** algorithm may choose to use t2 for the outer loop, which is a much
     ** costlier approach.
     */
-    for(isOptimal=1; isOptimal>=0 && bestJ<0; isOptimal--){
-      Bitmask mask = (isOptimal ? 0 : notReady);
-      assert( (nTabList-iFrom)>1 || isOptimal );
+    for(isOptimal=(iFrom<nTabList-1); isOptimal>=0; isOptimal--){
+      Bitmask mask;  /* Mask of tables not yet ready */
       for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
         int doNotReorder;    /* True if this table should not be reordered */
         WhereCost sCost;     /* Cost information from best[Virtual]Index() */
@@ -90505,6 +96835,7 @@
           if( j==iFrom ) iFrom++;
           continue;
         }
+        mask = (isOptimal ? m : notReady);
         pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
   
         assert( pTabItem->pTab );
@@ -90520,8 +96851,11 @@
         assert( isOptimal || (sCost.used&notReady)==0 );
 
         if( (sCost.used&notReady)==0
-         && (j==iFrom || sCost.rCost<bestPlan.rCost) 
+         && (bestJ<0 || sCost.rCost<bestPlan.rCost
+             || (sCost.rCost<=bestPlan.rCost && sCost.nRow<bestPlan.nRow))
         ){
+          WHERETRACE(("... best so far with cost=%g and nRow=%g\n",
+                      sCost.rCost, sCost.nRow));
           bestPlan = sCost;
           bestJ = j;
         }
@@ -90537,13 +96871,16 @@
     }
     andFlags &= bestPlan.plan.wsFlags;
     pLevel->plan = bestPlan.plan;
-    if( bestPlan.plan.wsFlags & WHERE_INDEXED ){
+    testcase( bestPlan.plan.wsFlags & WHERE_INDEXED );
+    testcase( bestPlan.plan.wsFlags & WHERE_TEMP_INDEX );
+    if( bestPlan.plan.wsFlags & (WHERE_INDEXED|WHERE_TEMP_INDEX) ){
       pLevel->iIdxCur = pParse->nTab++;
     }else{
       pLevel->iIdxCur = -1;
     }
     notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
     pLevel->iFrom = (u8)bestJ;
+    if( bestPlan.nRow>=(double)1 ) pParse->nQueryLoop *= bestPlan.nRow;
 
     /* Check that if the table scanned by this loop iteration had an
     ** INDEXED BY clause attached to it, that the named index is being
@@ -90590,6 +96927,7 @@
   ** searching those tables.
   */
   sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
+  notReady = ~(Bitmask)0;
   for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
     Table *pTab;     /* Table to open */
     int iDb;         /* Index of database containing table/index */
@@ -90602,7 +96940,9 @@
       if( pItem->zAlias ){
         zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
       }
-      if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s WITH AUTOMATIC INDEX", zMsg);
+      }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
         zMsg = sqlite3MAppendf(db, zMsg, "%s WITH INDEX %s",
            zMsg, pLevel->plan.u.pIdx->zName);
       }else if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
@@ -90625,8 +96965,11 @@
 #endif /* SQLITE_OMIT_EXPLAIN */
     pTabItem = &pTabList->a[pLevel->iFrom];
     pTab = pTabItem->pTab;
+    pLevel->iTabCur = pTabItem->iCursor;
     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
-    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
+      /* Do nothing */
+    }else
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
       const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
@@ -90638,6 +96981,8 @@
          && (wctrlFlags & WHERE_OMIT_OPEN)==0 ){
       int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
       sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
+      testcase( pTab->nCol==BMS-1 );
+      testcase( pTab->nCol==BMS );
       if( !pWInfo->okOnePass && pTab->nCol<BMS ){
         Bitmask b = pTabItem->colUsed;
         int n = 0;
@@ -90649,7 +96994,11 @@
     }else{
       sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
     }
-    pLevel->iTabCur = pTabItem->iCursor;
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
+      constructAutomaticIndex(pParse, pWC, pTabItem, notReady, pLevel);
+    }else
+#endif
     if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
       Index *pIx = pLevel->plan.u.pIdx;
       KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
@@ -90661,8 +97010,10 @@
       VdbeComment((v, "%s", pIx->zName));
     }
     sqlite3CodeVerifySchema(pParse, iDb);
+    notReady &= ~getMask(pWC->pMaskSet, pTabItem->iCursor);
   }
   pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
+  if( db->mallocFailed ) goto whereBeginError;
 
   /* Generate the code to do the search.  Each iteration of the for
   ** loop below generates code for a single nested loop of the VM
@@ -90730,7 +97081,10 @@
 
   /* Jump here if malloc fails */
 whereBeginError:
-  whereInfoFree(db, pWInfo);
+  if( pWInfo ){
+    pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+    whereInfoFree(db, pWInfo);
+  }
   return 0;
 }
 
@@ -90800,12 +97154,15 @@
     struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
     Table *pTab = pTabItem->pTab;
     assert( pTab!=0 );
-    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
-    if( (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0 ){
-      if( !pWInfo->okOnePass && (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
+    if( (pTab->tabFlags & TF_Ephemeral)==0
+     && pTab->pSelect==0
+     && (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0
+    ){
+      int ws = pLevel->plan.wsFlags;
+      if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
         sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
       }
-      if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      if( (ws & WHERE_INDEXED)!=0 && (ws & WHERE_TEMP_INDEX)==0 ){
         sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
       }
     }
@@ -90853,6 +97210,7 @@
 
   /* Final cleanup
   */
+  pParse->nQueryLoop = pWInfo->savedNQueryLoop;
   whereInfoFree(db, pWInfo);
   return;
 }
@@ -91139,7 +97497,7 @@
 **                     shifting non-terminals after a reduce.
 **  yy_default[]       Default action for each state.
 */
-#define YY_ACTTAB_COUNT (1543)
+#define YY_ACTTAB_COUNT (1550)
 static const YYACTIONTYPE yy_action[] = {
  /*     0 */   313,   49,  556,   46,  147,  172,  628,  598,   55,   55,
  /*    10 */    55,   55,  302,   53,   53,   53,   53,   52,   52,   51,
@@ -91289,13 +97647,13 @@
  /*  1450 */   249,  389,  487,  486,  314,  164,  602,   79,  310,  240,
  /*  1460 */   414,  373,  480,  163,  262,  371,  414,  162,  369,  602,
  /*  1470 */    78,  212,  478,   26,  477,  602,    9,  161,  467,  363,
- /*  1480 */   141,  122,  339,  187,  119,  457,  348,  117,  347,  116,
- /*  1490 */   115,  114,  448,  112,  182,  320,   22,  433,   19,  432,
- /*  1500 */   431,   63,  428,  610,  193,  298,  597,  574,  572,  404,
- /*  1510 */   555,  552,  290,  281,  510,  499,  498,  497,  495,  380,
- /*  1520 */   356,  460,  256,  250,  345,  447,  306,    5,  570,  550,
- /*  1530 */   299,  211,  370,  401,  550,  508,  502,  501,  490,  527,
- /*  1540 */   525,  483,  238,
+ /*  1480 */   141,  122,  339,  187,  119,  457,  348,  347,  117,  116,
+ /*  1490 */   115,  112,  114,  448,  182,   22,  320,  433,  432,  431,
+ /*  1500 */    19,  428,  610,  597,  574,  193,  572,   63,  298,  404,
+ /*  1510 */   555,  552,  290,  281,  510,  460,  498,  499,  495,  447,
+ /*  1520 */   356,  497,  256,  380,  306,  570,    5,  250,  345,  238,
+ /*  1530 */   299,  550,  527,  490,  508,  525,  502,  401,  501,  963,
+ /*  1540 */   211,  963,  483,  963,  963,  963,  963,  963,  963,  370,
 };
 static const YYCODETYPE yy_lookahead[] = {
  /*     0 */    19,  222,  223,  224,  225,   24,    1,   26,   77,   78,
@@ -91446,18 +97804,18 @@
  /*  1450 */   107,  150,  176,  176,  111,  156,  174,  175,  179,  116,
  /*  1460 */   165,   18,  157,  156,  238,  157,  165,  156,   45,  174,
  /*  1470 */   175,  157,  157,  135,  239,  174,  175,  156,  189,  157,
- /*  1480 */    68,  189,  139,  219,   22,  199,  157,  192,   18,  192,
- /*  1490 */   192,  192,  199,  189,  219,  157,  243,   40,  243,  157,
- /*  1500 */   157,  246,   38,  153,  196,  198,  166,  233,  233,  228,
- /*  1510 */   177,  177,  209,  177,  182,  177,  166,  177,  166,  178,
- /*  1520 */   242,  199,  242,  209,  209,  199,  148,  196,  166,  208,
- /*  1530 */   195,  236,  237,  191,  208,  183,  183,  183,  186,  174,
- /*  1540 */   174,  186,   92,
+ /*  1480 */    68,  189,  139,  219,   22,  199,  157,   18,  192,  192,
+ /*  1490 */   192,  189,  192,  199,  219,  243,  157,   40,  157,  157,
+ /*  1500 */   243,   38,  153,  166,  233,  196,  233,  246,  198,  228,
+ /*  1510 */   177,  177,  209,  177,  182,  199,  166,  177,  166,  199,
+ /*  1520 */   242,  177,  242,  178,  148,  166,  196,  209,  209,   92,
+ /*  1530 */   195,  208,  174,  186,  183,  174,  183,  191,  183,  253,
+ /*  1540 */   236,  253,  186,  253,  253,  253,  253,  253,  253,  237,
 };
 #define YY_SHIFT_USE_DFLT (-90)
 #define YY_SHIFT_COUNT (418)
 #define YY_SHIFT_MIN   (-89)
-#define YY_SHIFT_MAX   (1470)
+#define YY_SHIFT_MAX   (1469)
 static const short yy_shift_ofst[] = {
  /*     0 */   993, 1114, 1343, 1114, 1213, 1213,   90,   90,    0,  -19,
  /*    10 */  1213, 1213, 1213, 1213, 1213,  352,  517,  721, 1091, 1213,
@@ -91472,7 +97830,7 @@
  /*   100 */  1017,  -69,  -69,  -69,  -69,   -1,   -1,   58,  138,  -44,
  /*   110 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
  /*   120 */   517,  517,  517,  517,  517,  517,  202,  579,  517,  517,
- /*   130 */   517,  517,  517,  382,  885, 1450,  -90,  -90,  -90, 1293,
+ /*   130 */   517,  517,  517,  382,  885, 1437,  -90,  -90,  -90, 1293,
  /*   140 */    73,  272,  272,  309,  311,  297,  282,  216,  602,  538,
  /*   150 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
  /*   160 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
@@ -91483,8 +97841,8 @@
  /*   210 */   149,  604,  516,  149,  149,  508,    3,  299,  677,  871,
  /*   220 */   613,  613,  879,  871,  879,  144,  382,  226,  382,  226,
  /*   230 */   564,  226,  613,  226,  226,  404,  625,  625,  382,  426,
- /*   240 */   -89,  801, 1464, 1244, 1244, 1457, 1457, 1244, 1462, 1412,
- /*   250 */  1188, 1470, 1470, 1470, 1470, 1244, 1188, 1462, 1412, 1412,
+ /*   240 */   -89,  801, 1463, 1244, 1244, 1457, 1457, 1244, 1462, 1412,
+ /*   250 */  1188, 1469, 1469, 1469, 1469, 1244, 1188, 1462, 1412, 1412,
  /*   260 */  1244, 1443, 1338, 1423, 1244, 1244, 1443, 1244, 1443, 1244,
  /*   270 */  1443, 1414, 1306, 1306, 1306, 1365, 1348, 1348, 1414, 1306,
  /*   280 */  1317, 1306, 1365, 1306, 1306, 1267, 1268, 1267, 1268, 1267,
@@ -91505,7 +97863,7 @@
 #define YY_REDUCE_USE_DFLT (-222)
 #define YY_REDUCE_COUNT (312)
 #define YY_REDUCE_MIN   (-221)
-#define YY_REDUCE_MAX   (1378)
+#define YY_REDUCE_MAX   (1376)
 static const short yy_reduce_ofst[] = {
  /*     0 */   310,  994, 1134,  221,  169,  157,   89,   18,   83,  301,
  /*    10 */   377,  316,  312,   16,  295,  238,  249,  391, 1301, 1295,
@@ -91526,13 +97884,13 @@
  /*   160 */  1084, 1066, 1049, 1011, 1010, 1006, 1002,  999,  998,  973,
  /*   170 */   972,  970,  966,  964,  895,  894,  892,  833,  822,  762,
  /*   180 */   761,  229,  811,  804,  803,  389,  688,  808,  807,  737,
- /*   190 */   460,  464,  572,  584, 1355, 1366, 1365, 1352, 1354, 1353,
- /*   200 */  1352, 1326, 1335, 1342, 1335, 1335, 1335, 1335, 1335, 1335,
- /*   210 */  1335, 1295, 1295, 1335, 1335, 1321, 1362, 1331, 1378, 1326,
- /*   220 */  1315, 1314, 1280, 1322, 1278, 1341, 1352, 1340, 1350, 1338,
- /*   230 */  1332, 1336, 1303, 1334, 1333, 1281, 1275, 1274, 1340, 1307,
- /*   240 */  1308, 1350, 1255, 1343, 1342, 1255, 1253, 1338, 1275, 1304,
- /*   250 */  1293, 1299, 1298, 1297, 1295, 1329, 1286, 1264, 1292, 1289,
+ /*   190 */   460,  464,  572,  584, 1356, 1361, 1358, 1347, 1355, 1353,
+ /*   200 */  1351, 1323, 1335, 1346, 1335, 1335, 1335, 1335, 1335, 1335,
+ /*   210 */  1335, 1312, 1304, 1335, 1335, 1323, 1359, 1330, 1376, 1320,
+ /*   220 */  1319, 1318, 1280, 1316, 1278, 1345, 1352, 1344, 1350, 1340,
+ /*   230 */  1332, 1336, 1303, 1334, 1333, 1281, 1273, 1271, 1337, 1310,
+ /*   240 */  1309, 1349, 1261, 1342, 1341, 1257, 1252, 1339, 1275, 1302,
+ /*   250 */  1294, 1300, 1298, 1297, 1296, 1329, 1286, 1264, 1292, 1289,
  /*   260 */  1322, 1321, 1235, 1226, 1315, 1314, 1311, 1308, 1307, 1305,
  /*   270 */  1299, 1279, 1277, 1276, 1270, 1258, 1211, 1209, 1250, 1259,
  /*   280 */  1255, 1242, 1243, 1241, 1201, 1200, 1184, 1186, 1182, 1178,
@@ -92952,7 +99310,7 @@
 {sqlite3BeginTransaction(pParse, yymsp[-1].minor.yy328);}
         break;
       case 13: /* transtype ::= */
-{yygotominor.yy328 = (pParse->db->flags&SQLITE_BeginImmediate) ? TK_IMMEDIATE : TK_DEFERRED;}/* Android Change */
+{yygotominor.yy328 = TK_DEFERRED;}
         break;
       case 14: /* transtype ::= DEFERRED */
       case 15: /* transtype ::= IMMEDIATE */ yytestcase(yyruleno==15);
@@ -95399,9 +101757,7 @@
 extern "C" {
 #endif  /* __cplusplus */
 
-// Begin Android Change
-SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs);
-// End Android Change
+SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs); // Android Change
 
 #if 0
 }  /* extern "C" */
@@ -95834,7 +102190,12 @@
     ** NULL.
     */
     case SQLITE_CONFIG_LOG: {
-      sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      /* MSVC is picky about pulling func ptrs from va lists.
+      ** http://support.microsoft.com/kb/47961
+      ** sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      */
+      typedef void(*LOGFUNC_t)(void*,int,const char*);
+      sqlite3GlobalConfig.xLog = va_arg(ap, LOGFUNC_t);
       sqlite3GlobalConfig.pLogArg = va_arg(ap, void*);
       break;
     }
@@ -96221,7 +102582,7 @@
     /* SQLITE_NOTFOUND    */ 0,
     /* SQLITE_FULL        */ "database or disk is full",
     /* SQLITE_CANTOPEN    */ "unable to open database file",
-    /* SQLITE_PROTOCOL    */ 0,
+    /* SQLITE_PROTOCOL    */ "locking protocol",
     /* SQLITE_EMPTY       */ "table contains no data",
     /* SQLITE_SCHEMA      */ "database schema has changed",
     /* SQLITE_TOOBIG      */ "string or blob too big",
@@ -96495,7 +102856,7 @@
   char *zFunc8;
   sqlite3_mutex_enter(db->mutex);
   assert( !db->mallocFailed );
-  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1);
+  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1, SQLITE_UTF16NATIVE);
   rc = sqlite3CreateFunc(db, zFunc8, nArg, eTextRep, p, xFunc, xStep, xFinal);
   sqlite3DbFree(db, zFunc8);
   rc = sqlite3ApiExit(db, rc);
@@ -96631,6 +102992,145 @@
   return pRet;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/*
+** The sqlite3_wal_hook() callback registered by sqlite3_wal_autocheckpoint().
+** Invoke sqlite3_wal_checkpoint if the number of frames in the log file
+** is greater than sqlite3.pWalArg cast to an integer (the value configured by
+** wal_autocheckpoint()).
+*/ 
+SQLITE_PRIVATE int sqlite3WalDefaultHook(
+  void *pClientData,     /* Argument */
+  sqlite3 *db,           /* Connection */
+  const char *zDb,       /* Database */
+  int nFrame             /* Size of WAL */
+){
+  if( nFrame>=SQLITE_PTR_TO_INT(pClientData) ){
+    sqlite3BeginBenignMalloc();
+    sqlite3_wal_checkpoint(db, zDb);
+    sqlite3EndBenignMalloc();
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** Configure an sqlite3_wal_hook() callback to automatically checkpoint
+** a database after committing a transaction if there are nFrame or
+** more frames in the log file. Passing zero or a negative value as the
+** nFrame parameter disables automatic checkpoints entirely.
+**
+** The callback registered by this function replaces any existing callback
+** registered using sqlite3_wal_hook(). Likewise, registering a callback
+** using sqlite3_wal_hook() disables the automatic checkpoint mechanism
+** configured by this function.
+*/
+SQLITE_API int sqlite3_wal_autocheckpoint(sqlite3 *db, int nFrame){
+#ifndef SQLITE_OMIT_WAL
+  if( nFrame>0 ){
+    sqlite3_wal_hook(db, sqlite3WalDefaultHook, SQLITE_INT_TO_PTR(nFrame));
+  }else{
+    sqlite3_wal_hook(db, 0, 0);
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is written
+** into the write-ahead-log by this database connection.
+*/
+SQLITE_API void *sqlite3_wal_hook(
+  sqlite3 *db,                    /* Attach the hook to this db handle */
+  int(*xCallback)(void *, sqlite3*, const char*, int),
+  void *pArg                      /* First argument passed to xCallback() */
+){
+#ifndef SQLITE_OMIT_WAL
+  void *pRet;
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pWalArg;
+  db->xWalCallback = xCallback;
+  db->pWalArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+#else
+  return 0;
+#endif
+}
+
+
+/*
+** Checkpoint database zDb. If zDb is NULL, or if the buffer zDb points
+** to contains a zero-length string, all attached databases are 
+** checkpointed.
+*/
+SQLITE_API int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb){
+#ifdef SQLITE_OMIT_WAL
+  return SQLITE_OK;
+#else
+  int rc;                         /* Return code */
+  int iDb = SQLITE_MAX_ATTACHED;  /* sqlite3.aDb[] index of db to checkpoint */
+
+  sqlite3_mutex_enter(db->mutex);
+  if( zDb && zDb[0] ){
+    iDb = sqlite3FindDbName(db, zDb);
+  }
+  if( iDb<0 ){
+    rc = SQLITE_ERROR;
+    sqlite3Error(db, SQLITE_ERROR, "unknown database: %s", zDb);
+  }else{
+    rc = sqlite3Checkpoint(db, iDb);
+    sqlite3Error(db, rc, 0);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+#endif
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on database iDb. This is a no-op if database iDb is
+** not currently open in WAL mode.
+**
+** If a transaction is open on the database being checkpointed, this 
+** function returns SQLITE_LOCKED and a checkpoint is not attempted. If 
+** an error occurs while running the checkpoint, an SQLite error code is 
+** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
+**
+** The mutex on database handle db should be held by the caller. The mutex
+** associated with the specific b-tree being checkpointed is taken by
+** this function while the checkpoint is running.
+**
+** If iDb is passed SQLITE_MAX_ATTACHED, then all attached databases are
+** checkpointed. If an error is encountered it is returned immediately -
+** no attempt is made to checkpoint any remaining databases.
+*/
+SQLITE_PRIVATE int sqlite3Checkpoint(sqlite3 *db, int iDb){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Used to iterate through attached dbs */
+
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
+    if( i==iDb || iDb==SQLITE_MAX_ATTACHED ){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        if( sqlite3BtreeIsInReadTrans(pBt) ){
+          rc = SQLITE_LOCKED;
+        }else{
+          sqlite3BtreeEnter(pBt);
+          rc = sqlite3PagerCheckpoint(sqlite3BtreePager(pBt));
+          sqlite3BtreeLeave(pBt);
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+#endif /* SQLITE_OMIT_WAL */
+
 /*
 ** This function returns true if main-memory should be used instead of
 ** a temporary file for transient pager files and statement journals.
@@ -97053,7 +103553,7 @@
   db->autoCommit = 1;
   db->nextAutovac = -1;
   db->nextPagesize = 0;
-  db->flags |= SQLITE_ShortColNames
+  db->flags |= SQLITE_ShortColNames | SQLITE_AutoIndex
 #if SQLITE_DEFAULT_FILE_FORMAT<4
                  | SQLITE_LegacyFileFmt
 #endif
@@ -97144,9 +103644,6 @@
   }
 
 #ifdef SQLITE_ENABLE_FTS1
-// Begin Android change
-#error "Do not enable FTS1 on Android as FTS3_BACKWARDS has been in use"
-// End Android add
   if( !db->mallocFailed ){
     extern int sqlite3Fts1Init(sqlite3*);
     rc = sqlite3Fts1Init(db);
@@ -97154,9 +103651,6 @@
 #endif
 
 #ifdef SQLITE_ENABLE_FTS2
-// Begin Android change
-#error "Do not enable FTS2 on Android as FTS3_BACKWARDS has been in use"
-// End Android add
   if( !db->mallocFailed && rc==SQLITE_OK ){
     extern int sqlite3Fts2Init(sqlite3*);
     rc = sqlite3Fts2Init(db);
@@ -97212,6 +103706,8 @@
   setupLookaside(db, 0, sqlite3GlobalConfig.szLookaside,
                         sqlite3GlobalConfig.nLookaside);
 
+  sqlite3_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);
+
 opendb_out:
   if( db ){
     assert( db->mutex!=0 || isThreadsafe==0 || sqlite3GlobalConfig.bFullMutex==0 );
@@ -97339,7 +103835,7 @@
   char *zName8;
   sqlite3_mutex_enter(db->mutex);
   assert( !db->mallocFailed );
-  zName8 = sqlite3Utf16to8(db, zName, -1);
+  zName8 = sqlite3Utf16to8(db, zName, -1, SQLITE_UTF16NATIVE);
   if( zName8 ){
     rc = createCollation(db, zName8, (u8)enc, SQLITE_COLL_USER, pCtx, xCompare, 0);
     sqlite3DbFree(db, zName8);
@@ -97706,9 +104202,13 @@
     ** dileterious behavior.
     */
     case SQLITE_TESTCTRL_PENDING_BYTE: {
-      unsigned int newVal = va_arg(ap, unsigned int);
-      rc = sqlite3PendingByte;
-      if( newVal ) sqlite3PendingByte = newVal;
+      rc = PENDING_BYTE;
+#ifndef SQLITE_OMIT_WSD
+      {
+        unsigned int newVal = va_arg(ap, unsigned int);
+        if( newVal ) sqlite3PendingByte = newVal;
+      }
+#endif
       break;
     }
 
@@ -97812,6 +104312,15 @@
     }
 #endif 
 
+    /* sqlite3_test_control(SQLITE_TESTCTRL_PGHDRSZ)
+    **
+    ** Return the size of a pcache header in bytes.
+    */
+    case SQLITE_TESTCTRL_PGHDRSZ: {
+      rc = sizeof(PgHdr);
+      break;
+    }
+
   }
   va_end(ap);
 #endif /* SQLITE_OMIT_BUILTIN_TEST */
@@ -97977,6 +104486,7 @@
 
   if( xNotify==0 ){
     removeFromBlockedList(db);
+    db->pBlockingConnection = 0;
     db->pUnlockConnection = 0;
     db->xUnlockNotify = 0;
     db->pUnlockArg = 0;
@@ -98177,9 +104687,6 @@
 **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
 */
 
-/* TODO(shess) Consider exporting this comment to an HTML file or the
-** wiki.
-*/
 /* The full-text index is stored in a series of b+tree (-like)
 ** structures called segments which map terms to doclists.  The
 ** structures are like b+trees in layout, but are constructed from the
@@ -98202,30 +104709,40 @@
 ** 21 bits - BBA
 ** and so on.
 **
-** This is identical to how sqlite encodes varints (see util.c).
+** This is similar in concept to how sqlite encodes "varints" but
+** the encoding is not the same.  SQLite varints are big-endian
+** are are limited to 9 bytes in length whereas FTS3 varints are
+** little-endian and can be up to 10 bytes in length (in theory).
+**
+** Example encodings:
+**
+**     1:    0x01
+**   127:    0x7f
+**   128:    0x81 0x00
 **
 **
 **** Document lists ****
 ** A doclist (document list) holds a docid-sorted list of hits for a
-** given term.  Doclists hold docids, and can optionally associate
-** token positions and offsets with docids.
+** given term.  Doclists hold docids and associated token positions.
+** A docid is the unique integer identifier for a single document.
+** A position is the index of a word within the document.  The first 
+** word of the document has a position of 0.
 **
-** A DL_POSITIONS_OFFSETS doclist is stored like this:
+** FTS3 used to optionally store character offsets using a compile-time
+** option.  But that functionality is no longer supported.
+**
+** A doclist is stored like this:
 **
 ** array {
 **   varint docid;
 **   array {                (position list for column 0)
-**     varint position;     (delta from previous position plus POS_BASE)
-**     varint startOffset;  (delta from previous startOffset)
-**     varint endOffset;    (delta from startOffset)
+**     varint position;     (2 more than the delta from previous position)
 **   }
 **   array {
 **     varint POS_COLUMN;   (marks start of position list for new column)
 **     varint column;       (index of new column)
 **     array {
-**       varint position;   (delta from previous position plus POS_BASE)
-**       varint startOffset;(delta from previous startOffset)
-**       varint endOffset;  (delta from startOffset)
+**       varint position;   (2 more than the delta from previous position)
 **     }
 **   }
 **   varint POS_END;        (marks end of positions for this document.
@@ -98233,19 +104750,32 @@
 **
 ** Here, array { X } means zero or more occurrences of X, adjacent in
 ** memory.  A "position" is an index of a token in the token stream
-** generated by the tokenizer, while an "offset" is a byte offset,
-** both based at 0.  Note that POS_END and POS_COLUMN occur in the
-** same logical place as the position element, and act as sentinals
-** ending a position list array.
+** generated by the tokenizer. Note that POS_END and POS_COLUMN occur 
+** in the same logical place as the position element, and act as sentinals
+** ending a position list array.  POS_END is 0.  POS_COLUMN is 1.
+** The positions numbers are not stored literally but rather as two more
+** than the difference from the prior position, or the just the position plus
+** 2 for the first position.  Example:
 **
-** A DL_POSITIONS doclist omits the startOffset and endOffset
-** information.  A DL_DOCIDS doclist omits both the position and
-** offset information, becoming an array of varint-encoded docids.
+**   label:       A B C D E  F  G H   I  J K
+**   value:     123 5 9 1 1 14 35 0 234 72 0
 **
-** On-disk data is stored as type DL_DEFAULT, so we don't serialize
-** the type.  Due to how deletion is implemented in the segmentation
-** system, on-disk doclists MUST store at least positions.
+** The 123 value is the first docid.  For column zero in this document
+** there are two matches at positions 3 and 10 (5-2 and 9-2+3).  The 1
+** at D signals the start of a new column; the 1 at E indicates that the
+** new column is column number 1.  There are two positions at 12 and 45
+** (14-2 and 35-2+12).  The 0 at H indicate the end-of-document.  The
+** 234 at I is the next docid.  It has one position 72 (72-2) and then
+** terminates with the 0 at K.
 **
+** A "position-list" is the list of positions for multiple columns for
+** a single docid.  A "column-list" is the set of positions for a single
+** column.  Hence, a position-list consists of one or more column-lists,
+** a document record consists of a docid followed by a position-list and
+** a doclist consists of one or more document records.
+**
+** A bare doclist omits the position information, becoming an 
+** array of varint-encoded docids.
 **
 **** Segment leaf nodes ****
 ** Segment leaf nodes store terms and doclists, ordered by term.  Leaf
@@ -98760,6 +105290,20 @@
 #define FTS3_VARINT_MAX 10
 
 /*
+** The testcase() macro is only used by the amalgamation.  If undefined,
+** make it a no-op.
+*/
+#ifndef testcase
+# define testcase(X)
+#endif
+
+/*
+** Terminator values for position-lists and column-lists.
+*/
+#define POS_COLUMN  (1)     /* Column-list terminator */
+#define POS_END     (0)     /* Position-list terminator */ 
+
+/*
 ** This section provides definitions to allow the
 ** FTS3 extension to be compiled outside of the 
 ** amalgamation.
@@ -98810,7 +105354,7 @@
   /* Precompiled statements used by the implementation. Each of these 
   ** statements is run and reset within a single virtual table API call. 
   */
-  sqlite3_stmt *aStmt[18];
+  sqlite3_stmt *aStmt[25];
 
   /* Pointer to string containing the SQL:
   **
@@ -98824,6 +105368,8 @@
   sqlite3_stmt **aLeavesStmt;     /* Array of prepared zSelectLeaves stmts */
 
   int nNodeSize;                  /* Soft limit for node size */
+  u8 bHasContent;                 /* True if %_content table exists */
+  u8 bHasDocsize;                 /* True if %_docsize table exists */
 
   /* The following hash table is used to buffer pending index updates during
   ** transactions. Variable nPendingData estimates the memory size of the 
@@ -98854,8 +105400,8 @@
   char *pNextId;                  /* Pointer into the body of aDoclist */
   char *aDoclist;                 /* List of docids for full-text queries */
   int nDoclist;                   /* Size of buffer at aDoclist */
-  int isMatchinfoOk;              /* True when aMatchinfo[] matches iPrevId */
-  u32 *aMatchinfo;
+  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
+  u32 *aMatchinfo;                /* Information about most recent match */
 };
 
 /*
@@ -98961,6 +105507,8 @@
 );
 SQLITE_PRIVATE int sqlite3Fts3ReadBlock(Fts3Table*, sqlite3_int64, char const**, int*);
 SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(Fts3Table*, sqlite3_stmt **);
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeLocal(Fts3Cursor*, u32*);
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeGlobal(Fts3Cursor*, u32*);
 
 /* Flags allowed as part of the 4th argument to SegmentReaderIterate() */
 #define FTS3_SEGMENT_REQUIRE_POS   0x00000001
@@ -98985,6 +105533,7 @@
 
 SQLITE_PRIVATE char *sqlite3Fts3FindPositions(Fts3Expr *, sqlite3_int64, int);
 SQLITE_PRIVATE int sqlite3Fts3ExprLoadDoclist(Fts3Table *, Fts3Expr *);
+SQLITE_PRIVATE int sqlite3Fts3ExprNearTrim(Fts3Expr *, Fts3Expr *, int);
 
 /* fts3_tokenizer.c */
 SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *, int *);
@@ -98995,10 +105544,7 @@
 
 /* fts3_snippet.c */
 SQLITE_PRIVATE void sqlite3Fts3Offsets(sqlite3_context*, Fts3Cursor*);
-SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context*, Fts3Cursor*, 
-  const char *, const char *, const char *
-);
-SQLITE_PRIVATE void sqlite3Fts3Snippet2(sqlite3_context *, Fts3Cursor *, const char *,
+SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context *, Fts3Cursor *, const char *,
   const char *, const char *, int, int
 );
 SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *, Fts3Cursor *);
@@ -99068,8 +105614,7 @@
 }
 
 /*
-** Return the number of bytes required to store the value passed as the
-** first argument in varint form.
+** Return the number of bytes required to encode v as a varint
 */
 SQLITE_PRIVATE int sqlite3Fts3VarintLen(sqlite3_uint64 v){
   int i = 0;
@@ -99118,12 +105663,23 @@
   }
 }
 
+/*
+** Read a single varint from the doclist at *pp and advance *pp to point
+** to the first byte past the end of the varint.  Add the value of the varint
+** to *pVal.
+*/
 static void fts3GetDeltaVarint(char **pp, sqlite3_int64 *pVal){
   sqlite3_int64 iVal;
   *pp += sqlite3Fts3GetVarint(*pp, &iVal);
   *pVal += iVal;
 }
 
+/*
+** As long as *pp has not reached its end (pEnd), then do the same
+** as fts3GetDeltaVarint(): read a single varint and add it to *pVal.
+** But if we have reached the end of the varint, just set *pp=0 and
+** leave *pVal unchanged.
+*/
 static void fts3GetDeltaVarint2(char **pp, char *pEnd, sqlite3_int64 *pVal){
   if( *pp>=pEnd ){
     *pp = 0;
@@ -99159,29 +105715,46 @@
 }
 
 /*
+** Construct one or more SQL statements from the format string given
+** and then evaluate those statements.  The success code is writting
+** into *pRc.
+**
+** If *pRc is initially non-zero then this routine is a no-op.
+*/
+static void fts3DbExec(
+  int *pRc,              /* Success code */
+  sqlite3 *db,           /* Database in which to run SQL */
+  const char *zFormat,   /* Format string for SQL */
+  ...                    /* Arguments to the format string */
+){
+  va_list ap;
+  char *zSql;
+  if( *pRc ) return;
+  va_start(ap, zFormat);
+  zSql = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  if( zSql==0 ){
+    *pRc = SQLITE_NOMEM;
+  }else{
+    *pRc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+}
+
+/*
 ** The xDestroy() virtual table method.
 */
 static int fts3DestroyMethod(sqlite3_vtab *pVtab){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;              /* Return code */
   Fts3Table *p = (Fts3Table *)pVtab;
+  sqlite3 *db = p->db;
 
-  /* Create a script to drop the underlying three storage tables. */
-  char *zSql = sqlite3_mprintf(
-      "DROP TABLE IF EXISTS %Q.'%q_content';"
-      "DROP TABLE IF EXISTS %Q.'%q_segments';"
-      "DROP TABLE IF EXISTS %Q.'%q_segdir';", 
-      p->zDb, p->zName, p->zDb, p->zName, p->zDb, p->zName
-  );
-
-  /* If malloc has failed, set rc to SQLITE_NOMEM. Otherwise, try to
-  ** execute the SQL script created above.
-  */
-  if( zSql ){
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
-    sqlite3_free(zSql);
-  }else{
-    rc = SQLITE_NOMEM;
-  }
+  /* Drop the shadow tables */
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_content'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segments'", p->zDb,p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segdir'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_docsize'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_stat'", p->zDb, p->zName);
 
   /* If everything has worked, invoke fts3DisconnectMethod() to free the
   ** memory associated with the Fts3Table structure and return SQLITE_OK.
@@ -99228,24 +105801,39 @@
 ** Create the backing store tables (%_content, %_segments and %_segdir)
 ** required by the FTS3 table passed as the only argument. This is done
 ** as part of the vtab xCreate() method.
+**
+** If the p->bHasDocsize boolean is true (indicating that this is an
+** FTS4 table, not an FTS3 table) then also create the %_docsize and
+** %_stat tables required by FTS4.
 */
 static int fts3CreateTables(Fts3Table *p){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;             /* Return code */
   int i;                          /* Iterator variable */
   char *zContentCols;             /* Columns of %_content table */
-  char *zSql;                     /* SQL script to create required tables */
+  sqlite3 *db = p->db;            /* The database connection */
 
   /* Create a list of user columns for the content table */
-  zContentCols = sqlite3_mprintf("docid INTEGER PRIMARY KEY");
-  for(i=0; zContentCols && i<p->nColumn; i++){
-    char *z = p->azColumn[i];
-    zContentCols = sqlite3_mprintf("%z, 'c%d%q'", zContentCols, i, z);
-  }
+  if( p->bHasContent ){
+    zContentCols = sqlite3_mprintf("docid INTEGER PRIMARY KEY");
+    for(i=0; zContentCols && i<p->nColumn; i++){
+      char *z = p->azColumn[i];
+      zContentCols = sqlite3_mprintf("%z, 'c%d%q'", zContentCols, i, z);
+    }
+    if( zContentCols==0 ) rc = SQLITE_NOMEM;
 
-  /* Create the whole SQL script */
-  zSql = sqlite3_mprintf(
-      "CREATE TABLE %Q.'%q_content'(%s);"
-      "CREATE TABLE %Q.'%q_segments'(blockid INTEGER PRIMARY KEY, block BLOB);"
+    /* Create the content table */
+    fts3DbExec(&rc, db, 
+       "CREATE TABLE %Q.'%q_content'(%s)",
+       p->zDb, p->zName, zContentCols
+    );
+    sqlite3_free(zContentCols);
+  }
+  /* Create other tables */
+  fts3DbExec(&rc, db, 
+      "CREATE TABLE %Q.'%q_segments'(blockid INTEGER PRIMARY KEY, block BLOB);",
+      p->zDb, p->zName
+  );
+  fts3DbExec(&rc, db, 
       "CREATE TABLE %Q.'%q_segdir'("
         "level INTEGER,"
         "idx INTEGER,"
@@ -99255,30 +105843,61 @@
         "root BLOB,"
         "PRIMARY KEY(level, idx)"
       ");",
-      p->zDb, p->zName, zContentCols, p->zDb, p->zName, p->zDb, p->zName
+      p->zDb, p->zName
   );
-
-  /* Unless a malloc() failure has occurred, execute the SQL script to 
-  ** create the tables used to store data for this FTS3 virtual table.
-  */
-  if( zContentCols==0 || zSql==0 ){
-    rc = SQLITE_NOMEM;
-  }else{
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db, 
+        "CREATE TABLE %Q.'%q_docsize'(docid INTEGER PRIMARY KEY, size BLOB);",
+        p->zDb, p->zName
+    );
+    fts3DbExec(&rc, db, 
+        "CREATE TABLE %Q.'%q_stat'(id INTEGER PRIMARY KEY, value BLOB);",
+        p->zDb, p->zName
+    );
   }
-
-  sqlite3_free(zSql);
-  sqlite3_free(zContentCols);
   return rc;
 }
 
 /*
+** An sqlite3_exec() callback for fts3TableExists.
+*/
+static int fts3TableExistsCallback(void *pArg, int n, char **pp1, char **pp2){
+  *(int*)pArg = 1;
+  return 1;
+}
+
+/*
+** Determine if a table currently exists in the database.
+*/
+static void fts3TableExists(
+  int *pRc,             /* Success code */
+  sqlite3 *db,          /* The database connection to test */
+  const char *zDb,      /* ATTACHed database within the connection */
+  const char *zName,    /* Name of the FTS3 table */
+  const char *zSuffix,  /* Shadow table extension */
+  u8 *pResult           /* Write results here */
+){
+  int rc = SQLITE_OK;
+  int res = 0;
+  char *zSql;
+  if( *pRc ) return;
+  zSql = sqlite3_mprintf(
+    "SELECT 1 FROM %Q.sqlite_master WHERE name='%q%s'",
+    zDb, zName, zSuffix
+  );    
+  rc = sqlite3_exec(db, zSql, fts3TableExistsCallback, &res, 0);
+  sqlite3_free(zSql);
+  *pResult = res & 0xff;
+  if( rc!=SQLITE_ABORT ) *pRc = rc;
+}
+
+/*
 ** This function is the implementation of both the xConnect and xCreate
 ** methods of the FTS3 virtual table.
 **
 ** The argv[] array contains the following:
 **
-**   argv[0]   -> module name
+**   argv[0]   -> module name  ("fts3" or "fts4")
 **   argv[1]   -> database name
 **   argv[2]   -> table name
 **   argv[...] -> "column name" and other module argument fields.
@@ -99297,12 +105916,12 @@
   int rc;                         /* Return code */
   int i;                          /* Iterator variable */
   int nByte;                      /* Size of allocation used for *p */
-  int iCol;
-  int nString = 0;
-  int nCol = 0;
-  char *zCsr;
-  int nDb;
-  int nName;
+  int iCol;                       /* Column index */
+  int nString = 0;                /* Bytes required to hold all column names */
+  int nCol = 0;                   /* Number of columns in the FTS table */
+  char *zCsr;                     /* Space for holding column names */
+  int nDb;                        /* Bytes required to hold database name */
+  int nName;                      /* Bytes required to hold table name */
 
   const char *zTokenizer = 0;               /* Name of tokenizer to use */
   sqlite3_tokenizer *pTokenizer = 0;        /* Tokenizer for this table */
@@ -99388,9 +106007,15 @@
   ** database. TODO: For xConnect(), it could verify that said tables exist.
   */
   if( isCreate ){
+    p->bHasContent = 1;
+    p->bHasDocsize = argv[0][3]=='4';
     rc = fts3CreateTables(p);
-    if( rc!=SQLITE_OK ) goto fts3_init_out;
+  }else{
+    rc = SQLITE_OK;
+    fts3TableExists(&rc, db, argv[1], argv[2], "_content", &p->bHasContent);
+    fts3TableExists(&rc, db, argv[1], argv[2], "_docsize", &p->bHasDocsize);
   }
+  if( rc!=SQLITE_OK ) goto fts3_init_out;
 
   rc = fts3DeclareVtab(p);
   if( rc!=SQLITE_OK ) goto fts3_init_out;
@@ -99512,12 +106137,6 @@
   return SQLITE_OK;
 }
 
-/****************************************************************/
-/****************************************************************/
-/****************************************************************/
-/****************************************************************/
-
-
 /*
 ** Close the cursor.  For additional information see the documentation
 ** on the xClose method of the virtual table interface.
@@ -99532,6 +106151,11 @@
   return SQLITE_OK;
 }
 
+/*
+** Position the pCsr->pStmt statement so that it is on the row
+** of the %_content table that contains the last match.  Return
+** SQLITE_OK on success.  
+*/
 static int fts3CursorSeek(sqlite3_context *pContext, Fts3Cursor *pCsr){
   if( pCsr->isRequireSeek ){
     pCsr->isRequireSeek = 0;
@@ -99558,6 +106182,17 @@
   }
 }
 
+/*
+** Advance the cursor to the next row in the %_content table that
+** matches the search criteria.  For a MATCH search, this will be
+** the next row that matches.  For a full-table scan, this will be
+** simply the next row in the %_content table.  For a docid lookup,
+** this routine simply sets the EOF flag.
+**
+** Return SQLITE_OK if nothing goes wrong.  SQLITE_OK is returned
+** even if we reach end-of-file.  The fts3EofMethod() will be called
+** subsequently to determine whether or not an EOF was hit.
+*/
 static int fts3NextMethod(sqlite3_vtab_cursor *pCursor){
   int rc = SQLITE_OK;             /* Return code */
   Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;
@@ -99573,7 +106208,7 @@
     sqlite3_reset(pCsr->pStmt);
     fts3GetDeltaVarint(&pCsr->pNextId, &pCsr->iPrevId);
     pCsr->isRequireSeek = 1;
-    pCsr->isMatchinfoOk = 1;
+    pCsr->isMatchinfoNeeded = 1;
   }
   return rc;
 }
@@ -99691,24 +106326,37 @@
 
 /*
 ** When this function is called, *ppPoslist is assumed to point to the 
-** start of a position-list.
+** start of a position-list. After it returns, *ppPoslist points to the
+** first byte after the position-list.
+**
+** A position list is list of positions (delta encoded) and columns for 
+** a single document record of a doclist.  So, in other words, this
+** routine advances *ppPoslist so that it points to the next docid in
+** the doclist, or to the first byte past the end of the doclist.
+**
+** If pp is not NULL, then the contents of the position list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.
 */
 static void fts3PoslistCopy(char **pp, char **ppPoslist){
   char *pEnd = *ppPoslist;
   char c = 0;
 
   /* The end of a position list is marked by a zero encoded as an FTS3 
-  ** varint. A single 0x00 byte. Except, if the 0x00 byte is preceded by
+  ** varint. A single POS_END (0) byte. Except, if the 0 byte is preceded by
   ** a byte with the 0x80 bit set, then it is not a varint 0, but the tail
   ** of some other, multi-byte, value.
   **
-  ** The following block moves pEnd to point to the first byte that is not 
+  ** The following while-loop moves pEnd to point to the first byte that is not 
   ** immediately preceded by a byte with the 0x80 bit set. Then increments
   ** pEnd once more so that it points to the byte immediately following the
   ** last byte in the position-list.
   */
-  while( *pEnd | c ) c = *pEnd++ & 0x80;
-  pEnd++;
+  while( *pEnd | c ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && (*pEnd)==0 );
+  }
+  pEnd++;  /* Advance past the POS_END terminator byte */
 
   if( pp ){
     int n = (int)(pEnd - *ppPoslist);
@@ -99720,12 +106368,34 @@
   *ppPoslist = pEnd;
 }
 
+/*
+** When this function is called, *ppPoslist is assumed to point to the 
+** start of a column-list. After it returns, *ppPoslist points to the
+** to the terminator (POS_COLUMN or POS_END) byte of the column-list.
+**
+** A column-list is list of delta-encoded positions for a single column
+** within a single document within a doclist.
+**
+** The column-list is terminated either by a POS_COLUMN varint (1) or
+** a POS_END varint (0).  This routine leaves *ppPoslist pointing to
+** the POS_COLUMN or POS_END that terminates the column-list.
+**
+** If pp is not NULL, then the contents of the column-list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.  The POS_COLUMN or POS_END terminator
+** is not copied into *pp.
+*/
 static void fts3ColumnlistCopy(char **pp, char **ppPoslist){
   char *pEnd = *ppPoslist;
   char c = 0;
 
-  /* A column-list is terminated by either a 0x01 or 0x00. */
-  while( 0xFE & (*pEnd | c) ) c = *pEnd++ & 0x80;
+  /* A column-list is terminated by either a 0x01 or 0x00 byte that is
+  ** not part of a multi-byte varint.
+  */
+  while( 0xFE & (*pEnd | c) ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && ((*pEnd)&0xfe)==0 );
+  }
   if( pp ){
     int n = (int)(pEnd - *ppPoslist);
     char *p = *pp;
@@ -99737,37 +106407,45 @@
 }
 
 /*
-** Value used to signify the end of an offset-list. This is safe because
+** Value used to signify the end of an position-list. This is safe because
 ** it is not possible to have a document with 2^31 terms.
 */
-#define OFFSET_LIST_END 0x7fffffff
+#define POSITION_LIST_END 0x7fffffff
 
 /*
-** This function is used to help parse offset-lists. When this function is
-** called, *pp may point to the start of the next varint in the offset-list
-** being parsed, or it may point to 1 byte past the end of the offset-list
-** (in which case **pp will be 0x00 or 0x01).
+** This function is used to help parse position-lists. When this function is
+** called, *pp may point to the start of the next varint in the position-list
+** being parsed, or it may point to 1 byte past the end of the position-list
+** (in which case **pp will be a terminator bytes POS_END (0) or
+** (1)).
 **
-** If *pp points past the end of the current offset list, set *pi to 
-** OFFSET_LIST_END and return. Otherwise, read the next varint from *pp,
+** If *pp points past the end of the current position-list, set *pi to 
+** POSITION_LIST_END and return. Otherwise, read the next varint from *pp,
 ** increment the current value of *pi by the value read, and set *pp to
 ** point to the next value before returning.
+**
+** Before calling this routine *pi must be initialized to the value of
+** the previous position, or zero if we are reading the first position
+** in the position-list.  Because positions are delta-encoded, the value
+** of the previous position is needed in order to compute the value of
+** the next position.
 */
 static void fts3ReadNextPos(
-  char **pp,                      /* IN/OUT: Pointer into offset-list buffer */
-  sqlite3_int64 *pi               /* IN/OUT: Value read from offset-list */
+  char **pp,                    /* IN/OUT: Pointer into position-list buffer */
+  sqlite3_int64 *pi             /* IN/OUT: Value read from position-list */
 ){
-  if( **pp&0xFE ){
+  if( (**pp)&0xFE ){
     fts3GetDeltaVarint(pp, pi);
     *pi -= 2;
   }else{
-    *pi = OFFSET_LIST_END;
+    *pi = POSITION_LIST_END;
   }
 }
 
 /*
-** If parameter iCol is not 0, write an 0x01 byte followed by the value of
-** iCol encoded as a varint to *pp. 
+** If parameter iCol is not 0, write an POS_COLUMN (1) byte followed by
+** the value of iCol encoded as a varint to *pp.   This will start a new
+** column list.
 **
 ** Set *pp to point to the byte just after the last byte written before 
 ** returning (do not modify it if iCol==0). Return the total number of bytes
@@ -99785,7 +106463,11 @@
 }
 
 /*
-**
+** Compute the union of two position lists.  The output written
+** into *pp contains all positions of both *pp1 and *pp2 in sorted
+** order and with any duplicates removed.  All pointers are
+** updated appropriately.   The caller is responsible for insuring
+** that there is enough space in *pp to hold the complete output.
 */
 static void fts3PoslistMerge(
   char **pp,                      /* Output buffer */
@@ -99797,32 +106479,33 @@
   char *p2 = *pp2;
 
   while( *p1 || *p2 ){
-    int iCol1;
-    int iCol2;
+    int iCol1;         /* The current column index in pp1 */
+    int iCol2;         /* The current column index in pp2 */
 
-    if( *p1==0x01 ) sqlite3Fts3GetVarint32(&p1[1], &iCol1);
-    else if( *p1==0x00 ) iCol1 = OFFSET_LIST_END;
+    if( *p1==POS_COLUMN ) sqlite3Fts3GetVarint32(&p1[1], &iCol1);
+    else if( *p1==POS_END ) iCol1 = POSITION_LIST_END;
     else iCol1 = 0;
 
-    if( *p2==0x01 ) sqlite3Fts3GetVarint32(&p2[1], &iCol2);
-    else if( *p2==0x00 ) iCol2 = OFFSET_LIST_END;
+    if( *p2==POS_COLUMN ) sqlite3Fts3GetVarint32(&p2[1], &iCol2);
+    else if( *p2==POS_END ) iCol2 = POSITION_LIST_END;
     else iCol2 = 0;
 
     if( iCol1==iCol2 ){
-      sqlite3_int64 i1 = 0;
-      sqlite3_int64 i2 = 0;
+      sqlite3_int64 i1 = 0;       /* Last position from pp1 */
+      sqlite3_int64 i2 = 0;       /* Last position from pp2 */
       sqlite3_int64 iPrev = 0;
       int n = fts3PutColNumber(&p, iCol1);
       p1 += n;
       p2 += n;
 
-      /* At this point, both p1 and p2 point to the start of offset-lists.
-      ** An offset-list is a list of non-negative delta-encoded varints, each 
-      ** incremented by 2 before being stored. Each list is terminated by a 0 
-      ** or 1 value (0x00 or 0x01). The following block merges the two lists
+      /* At this point, both p1 and p2 point to the start of column-lists
+      ** for the same column (the column with index iCol1 and iCol2).
+      ** A column-list is a list of non-negative delta-encoded varints, each 
+      ** incremented by 2 before being stored. Each list is terminated by a
+      ** POS_END (0) or POS_COLUMN (1). The following block merges the two lists
       ** and writes the results to buffer p. p is left pointing to the byte
-      ** after the list written. No terminator (0x00 or 0x01) is written to
-      ** the output.
+      ** after the list written. No terminator (POS_END or POS_COLUMN) is
+      ** written to the output.
       */
       fts3GetDeltaVarint(&p1, &i1);
       fts3GetDeltaVarint(&p2, &i2);
@@ -99837,7 +106520,7 @@
         }else{
           fts3ReadNextPos(&p2, &i2);
         }
-      }while( i1!=OFFSET_LIST_END || i2!=OFFSET_LIST_END );
+      }while( i1!=POSITION_LIST_END || i2!=POSITION_LIST_END );
     }else if( iCol1<iCol2 ){
       p1 += fts3PutColNumber(&p, iCol1);
       fts3ColumnlistCopy(&p, &p1);
@@ -99847,7 +106530,7 @@
     }
   }
 
-  *p++ = '\0';
+  *p++ = POS_END;
   *pp = p;
   *pp1 = p1 + 1;
   *pp2 = p2 + 1;
@@ -99870,11 +106553,11 @@
   int iCol1 = 0;
   int iCol2 = 0;
   assert( *p1!=0 && *p2!=0 );
-  if( *p1==0x01 ){ 
+  if( *p1==POS_COLUMN ){ 
     p1++;
     p1 += sqlite3Fts3GetVarint32(p1, &iCol1);
   }
-  if( *p2==0x01 ){ 
+  if( *p2==POS_COLUMN ){ 
     p2++;
     p2 += sqlite3Fts3GetVarint32(p2, &iCol2);
   }
@@ -99887,11 +106570,12 @@
       sqlite3_int64 iPos2 = 0;
 
       if( pp && iCol1 ){
-        *p++ = 0x01;
+        *p++ = POS_COLUMN;
         p += sqlite3Fts3PutVarint(p, iCol1);
       }
 
-      assert( *p1!=0x00 && *p2!=0x00 && *p1!=0x01 && *p2!=0x01 );
+      assert( *p1!=POS_END && *p1!=POS_COLUMN );
+      assert( *p2!=POS_END && *p2!=POS_COLUMN );
       fts3GetDeltaVarint(&p1, &iPos1); iPos1 -= 2;
       fts3GetDeltaVarint(&p2, &iPos2); iPos2 -= 2;
 
@@ -100143,6 +106827,7 @@
     default: assert( mergetype==MERGE_POS_NEAR || mergetype==MERGE_NEAR ); {
       char *aTmp = 0;
       char **ppPos = 0;
+
       if( mergetype==MERGE_POS_NEAR ){
         ppPos = &p;
         aTmp = sqlite3_malloc(2*(n1+n2+1));
@@ -100247,9 +106932,9 @@
 **
 ** The returned doclist may be in one of two formats, depending on the 
 ** value of parameter isReqPos. If isReqPos is zero, then the doclist is
-** a sorted list of delta-compressed docids. If isReqPos is non-zero, 
-** then the returned list is in the same format as is stored in the
-** database without the found length specifier at the start of on-disk
+** a sorted list of delta-compressed docids (a bare doclist). If isReqPos
+** is non-zero, then the returned list is in the same format as is stored 
+** in the database without the found length specifier at the start of on-disk
 ** doclists.
 */
 static int fts3TermSelect(
@@ -100439,9 +107124,79 @@
   return rc;
 }
 
+static int fts3NearMerge(
+  int mergetype,                  /* MERGE_POS_NEAR or MERGE_NEAR */
+  int nNear,                      /* Parameter to NEAR operator */
+  int nTokenLeft,                 /* Number of tokens in LHS phrase arg */
+  char *aLeft,                    /* Doclist for LHS (incl. positions) */
+  int nLeft,                      /* Size of LHS doclist in bytes */
+  int nTokenRight,                /* As nTokenLeft */
+  char *aRight,                   /* As aLeft */
+  int nRight,                     /* As nRight */
+  char **paOut,                   /* OUT: Results of merge (malloced) */
+  int *pnOut                      /* OUT: Sized of output buffer */
+){
+  char *aOut;
+  int rc;
+
+  assert( mergetype==MERGE_POS_NEAR || MERGE_NEAR );
+
+  aOut = sqlite3_malloc(nLeft+nRight+1);
+  if( aOut==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = fts3DoclistMerge(mergetype, nNear+nTokenRight, nNear+nTokenLeft, 
+      aOut, pnOut, aLeft, nLeft, aRight, nRight
+    );
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(aOut);
+      aOut = 0;
+    }
+  }
+
+  *paOut = aOut;
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3ExprNearTrim(Fts3Expr *pLeft, Fts3Expr *pRight, int nNear){
+  int rc;
+  if( pLeft->aDoclist==0 || pRight->aDoclist==0 ){
+    sqlite3_free(pLeft->aDoclist);
+    sqlite3_free(pRight->aDoclist);
+    pRight->aDoclist = 0;
+    pLeft->aDoclist = 0;
+    rc = SQLITE_OK;
+  }else{
+    char *aOut;
+    int nOut;
+
+    rc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
+        pLeft->pPhrase->nToken, pLeft->aDoclist, pLeft->nDoclist,
+        pRight->pPhrase->nToken, pRight->aDoclist, pRight->nDoclist,
+        &aOut, &nOut
+    );
+    if( rc!=SQLITE_OK ) return rc;
+    sqlite3_free(pRight->aDoclist);
+    pRight->aDoclist = aOut;
+    pRight->nDoclist = nOut;
+
+    rc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
+        pRight->pPhrase->nToken, pRight->aDoclist, pRight->nDoclist,
+        pLeft->pPhrase->nToken, pLeft->aDoclist, pLeft->nDoclist,
+        &aOut, &nOut
+    );
+    sqlite3_free(pLeft->aDoclist);
+    pLeft->aDoclist = aOut;
+    pLeft->nDoclist = nOut;
+  }
+  return rc;
+}
+
 /*
 ** Evaluate the full-text expression pExpr against fts3 table pTab. Store
-** the resulting doclist in *paOut and *pnOut.
+** the resulting doclist in *paOut and *pnOut.  This routine mallocs for
+** the space needed to store the output.  The caller is responsible for
+** freeing the space when it has finished.
 */
 static int evalFts3Expr(
   Fts3Table *p,                   /* Virtual table handle */
@@ -100483,9 +107238,6 @@
             Fts3Expr *pLeft;
             Fts3Expr *pRight;
             int mergetype = isReqPos ? MERGE_POS_NEAR : MERGE_NEAR;
-            int nParam1;
-            int nParam2;
-            char *aBuffer;
            
             if( pExpr->pParent && pExpr->pParent->eType==FTSQUERY_NEAR ){
               mergetype = MERGE_POS_NEAR;
@@ -100498,17 +107250,11 @@
             assert( pRight->eType==FTSQUERY_PHRASE );
             assert( pLeft->eType==FTSQUERY_PHRASE );
 
-            nParam1 = pExpr->nNear+1;
-            nParam2 = nParam1+pLeft->pPhrase->nToken+pRight->pPhrase->nToken-2;
-            aBuffer = sqlite3_malloc(nLeft+nRight+1);
-            rc = fts3DoclistMerge(mergetype, nParam1, nParam2, aBuffer,
-                pnOut, aLeft, nLeft, aRight, nRight
+            rc = fts3NearMerge(mergetype, pExpr->nNear, 
+                pLeft->pPhrase->nToken, aLeft, nLeft,
+                pRight->pPhrase->nToken, aRight, nRight,
+                paOut, pnOut
             );
-            if( rc!=SQLITE_OK ){
-              sqlite3_free(aBuffer);
-            }else{
-              *paOut = aBuffer;
-            }
             sqlite3_free(aLeft);
             break;
           }
@@ -100623,7 +107369,13 @@
     rc = sqlite3Fts3ExprParse(p->pTokenizer, p->azColumn, p->nColumn, 
         iCol, zQuery, -1, &pCsr->pExpr
     );
-    if( rc!=SQLITE_OK ) return rc;
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_ERROR ){
+        p->base.zErrMsg = sqlite3_mprintf("malformed MATCH expression: [%s]",
+                                          zQuery);
+      }
+      return rc;
+    }
 
     rc = evalFts3Expr(p, pCsr->pExpr, &pCsr->aDoclist, &pCsr->nDoclist, 0);
     pCsr->pNextId = pCsr->aDoclist;
@@ -100759,7 +107511,7 @@
 
 /*
 ** After ExprLoadDoclist() (see above) has been called, this function is
-** used to iterate through the position lists that make up the doclist
+** used to iterate/search through the position lists that make up the doclist
 ** stored in pExpr->aDoclist.
 */
 SQLITE_PRIVATE char *sqlite3Fts3FindPositions(
@@ -100776,7 +107528,9 @@
     while( pCsr<pEnd ){
       if( pExpr->iCurrent<iDocid ){
         fts3PoslistCopy(0, &pCsr);
-        fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
+        if( pCsr<pEnd ){
+          fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
+        }
         pExpr->pCurrent = pCsr;
       }else{
         if( pExpr->iCurrent==iDocid ){
@@ -100794,7 +107548,7 @@
             pCsr++;
             pCsr += sqlite3Fts3GetVarint32(pCsr, &iThis);
           }
-          if( iCol==iThis ) return pCsr;
+          if( iCol==iThis && (*pCsr&0xFE) ) return pCsr;
         }
         return 0;
       }
@@ -100846,45 +107600,8 @@
   const char *zStart = "<b>";
   const char *zEnd = "</b>";
   const char *zEllipsis = "<b>...</b>";
-
-  /* There must be at least one argument passed to this function (otherwise
-  ** the non-overloaded version would have been called instead of this one).
-  */
-  assert( nVal>=1 );
-
-  if( nVal>4 ){
-    sqlite3_result_error(pContext, 
-        "wrong number of arguments to function snippet()", -1);
-    return;
-  }
-  if( fts3FunctionArg(pContext, "snippet", apVal[0], &pCsr) ) return;
-
-  switch( nVal ){
-    case 4: zEllipsis = (const char*)sqlite3_value_text(apVal[3]);
-    case 3: zEnd = (const char*)sqlite3_value_text(apVal[2]);
-    case 2: zStart = (const char*)sqlite3_value_text(apVal[1]);
-  }
-  if( !zEllipsis || !zEnd || !zStart ){
-    sqlite3_result_error_nomem(pContext);
-  }else if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
-    sqlite3Fts3Snippet(pContext, pCsr, zStart, zEnd, zEllipsis);
-  }
-}
-
-/*
-** Implementation of the snippet2() function for FTS3
-*/
-static void fts3Snippet2Func(
-  sqlite3_context *pContext,      /* SQLite function call context */
-  int nVal,                       /* Size of apVal[] array */
-  sqlite3_value **apVal           /* Array of arguments */
-){
-  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
-  const char *zStart = "<b>";
-  const char *zEnd = "</b>";
-  const char *zEllipsis = "<b>...</b>";
   int iCol = -1;
-  int nToken = 10;
+  int nToken = 15;                /* Default number of tokens in snippet */
 
   /* There must be at least one argument passed to this function (otherwise
   ** the non-overloaded version would have been called instead of this one).
@@ -100908,7 +107625,7 @@
   if( !zEllipsis || !zEnd || !zStart ){
     sqlite3_result_error_nomem(pContext);
   }else if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
-    sqlite3Fts3Snippet2(pContext, pCsr, zStart, zEnd, zEllipsis, iCol, nToken);
+    sqlite3Fts3Snippet(pContext, pCsr, zStart, zEnd, zEllipsis, iCol, nToken);
   }
 }
 
@@ -101009,7 +107726,6 @@
     void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
   } aOverload[] = {
     { "snippet", fts3SnippetFunc },
-    { "snippet2", fts3Snippet2Func },
     { "offsets", fts3OffsetsFunc },
     { "optimize", fts3OptimizeFunc },
     { "matchinfo", fts3MatchinfoFunc },
@@ -101038,22 +107754,35 @@
   sqlite3_vtab *pVtab,            /* Virtual table handle */
   const char *zName               /* New name of table */
 ){
-  Fts3Table *p = (Fts3Table *)pVtab;     
-  int rc = SQLITE_NOMEM;          /* Return Code */
-  char *zSql;                     /* SQL script to run to rename tables */
+  Fts3Table *p = (Fts3Table *)pVtab;
+  sqlite3 *db;                    /* Database connection */
+  int rc;                         /* Return Code */
  
-  zSql = sqlite3_mprintf(
-    "ALTER TABLE %Q.'%q_content'  RENAME TO '%q_content';"
-    "ALTER TABLE %Q.'%q_segments' RENAME TO '%q_segments';"
-    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';"
-    , p->zDb, p->zName, zName 
-    , p->zDb, p->zName, zName 
-    , p->zDb, p->zName, zName
+  db = p->db;
+  rc = SQLITE_OK;
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_content'  RENAME TO '%q_content';",
+    p->zDb, p->zName, zName
   );
-  if( zSql ){
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
-    sqlite3_free(zSql);
+  if( rc==SQLITE_ERROR ) rc = SQLITE_OK;
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_docsize'  RENAME TO '%q_docsize';",
+      p->zDb, p->zName, zName
+    );
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_stat'  RENAME TO '%q_stat';",
+      p->zDb, p->zName, zName
+    );
   }
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segments' RENAME TO '%q_segments';",
+    p->zDb, p->zName, zName
+  );
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';",
+    p->zDb, p->zName, zName
+  );
   return rc;
 }
 
@@ -101112,10 +107841,7 @@
 ** SQLite. If fts3 is built as a dynamically loadable extension, this
 ** function is called by the sqlite3_extension_init() entry point.
 */
-// Begin Android change
-SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs){
-// End Android change
-
+SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs){ // Android change
   int rc = SQLITE_OK;
   Fts3Hash *pHash = 0;
   const sqlite3_tokenizer_module *pSimple = 0;
@@ -101162,17 +107888,22 @@
   if( SQLITE_OK==rc 
    && SQLITE_OK==(rc = sqlite3Fts3InitHashTable(db, pHash, "fts3_tokenizer"))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "snippet", -1))
-   && SQLITE_OK==(rc = sqlite3_overload_function(db, "snippet2", -1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "offsets", 1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "matchinfo", -1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "optimize", 1))
   ){
-    // Begin Android change
-    /* Also register as fts1 and fts2 */
-    return sqlite3_create_module_v2(
+    rc = sqlite3_create_module_v2(
+        // Begin Android change
+        // Also register as fts1 and fts2
         db, registerAs, &fts3Module, (void *)pHash, hashDestroy
-    // End Android change
+        // End Android change
     );
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_create_module_v2(
+          db, "fts4", &fts3Module, (void *)pHash, 0
+      );
+    }
+    return rc;
   }
 
   /* An error has occurred. Delete the hash table and return the error code. */
@@ -103102,9 +109833,11 @@
     if( c->iOffset>iStartOffset ){
       int n = c->iOffset-iStartOffset;
       if( n>c->nAllocated ){
+        char *pNew;
         c->nAllocated = n+20;
-        c->zToken = sqlite3_realloc(c->zToken, c->nAllocated);
-        if( c->zToken==NULL ) return SQLITE_NOMEM;
+        pNew = sqlite3_realloc(c->zToken, c->nAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->zToken = pNew;
       }
       porter_stemmer(&z[iStartOffset], n, c->zToken, pnBytes);
       *pzToken = c->zToken;
@@ -103815,9 +110548,11 @@
     if( c->iOffset>iStartOffset ){
       int i, n = c->iOffset-iStartOffset;
       if( n>c->nTokenAllocated ){
+        char *pNew;
         c->nTokenAllocated = n+20;
-        c->pToken = sqlite3_realloc(c->pToken, c->nTokenAllocated);
-        if( c->pToken==NULL ) return SQLITE_NOMEM;
+        pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->pToken = pNew;
       }
       for(i=0; i<n; i++){
         /* TODO(shess) This needs expansion to handle UTF-8
@@ -104001,19 +110736,26 @@
 #define SQL_DELETE_ALL_CONTENT         2 
 #define SQL_DELETE_ALL_SEGMENTS        3
 #define SQL_DELETE_ALL_SEGDIR          4
-#define SQL_SELECT_CONTENT_BY_ROWID    5
-#define SQL_NEXT_SEGMENT_INDEX         6
-#define SQL_INSERT_SEGMENTS            7
-#define SQL_NEXT_SEGMENTS_ID           8
-#define SQL_INSERT_SEGDIR              9
-#define SQL_SELECT_LEVEL              10
-#define SQL_SELECT_ALL_LEVEL          11
-#define SQL_SELECT_LEVEL_COUNT        12
-#define SQL_SELECT_SEGDIR_COUNT_MAX   13
-#define SQL_DELETE_SEGDIR_BY_LEVEL    14
-#define SQL_DELETE_SEGMENTS_RANGE     15
-#define SQL_CONTENT_INSERT            16
-#define SQL_GET_BLOCK                 17
+#define SQL_DELETE_ALL_DOCSIZE         5
+#define SQL_DELETE_ALL_STAT            6
+#define SQL_SELECT_CONTENT_BY_ROWID    7
+#define SQL_NEXT_SEGMENT_INDEX         8
+#define SQL_INSERT_SEGMENTS            9
+#define SQL_NEXT_SEGMENTS_ID          10
+#define SQL_INSERT_SEGDIR             11
+#define SQL_SELECT_LEVEL              12
+#define SQL_SELECT_ALL_LEVEL          13
+#define SQL_SELECT_LEVEL_COUNT        14
+#define SQL_SELECT_SEGDIR_COUNT_MAX   15
+#define SQL_DELETE_SEGDIR_BY_LEVEL    16
+#define SQL_DELETE_SEGMENTS_RANGE     17
+#define SQL_CONTENT_INSERT            18
+#define SQL_GET_BLOCK                 19
+#define SQL_DELETE_DOCSIZE            20
+#define SQL_REPLACE_DOCSIZE           21
+#define SQL_SELECT_DOCSIZE            22
+#define SQL_SELECT_DOCTOTAL           23
+#define SQL_REPLACE_DOCTOTAL          24
 
 /*
 ** This function is used to obtain an SQLite prepared statement handle
@@ -104038,25 +110780,32 @@
 /* 2  */  "DELETE FROM %Q.'%q_content'",
 /* 3  */  "DELETE FROM %Q.'%q_segments'",
 /* 4  */  "DELETE FROM %Q.'%q_segdir'",
-/* 5  */  "SELECT * FROM %Q.'%q_content' WHERE rowid=?",
-/* 6  */  "SELECT coalesce(max(idx)+1, 0) FROM %Q.'%q_segdir' WHERE level=?",
-/* 7  */  "INSERT INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
-/* 8  */  "SELECT coalesce(max(blockid)+1, 1) FROM %Q.'%q_segments'",
-/* 9  */  "INSERT INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
+/* 5  */  "DELETE FROM %Q.'%q_docsize'",
+/* 6  */  "DELETE FROM %Q.'%q_stat'",
+/* 7  */  "SELECT * FROM %Q.'%q_content' WHERE rowid=?",
+/* 8  */  "SELECT (SELECT max(idx) FROM %Q.'%q_segdir' WHERE level = ?) + 1",
+/* 9  */  "INSERT INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
+/* 10 */  "SELECT coalesce((SELECT max(blockid) FROM %Q.'%q_segments') + 1, 1)",
+/* 11 */  "INSERT INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
 
           /* Return segments in order from oldest to newest.*/ 
-/* 10 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+/* 12 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
             "FROM %Q.'%q_segdir' WHERE level = ? ORDER BY idx ASC",
-/* 11 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+/* 13 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
             "FROM %Q.'%q_segdir' ORDER BY level DESC, idx ASC",
 
-/* 12 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
-/* 13 */  "SELECT count(*), max(level) FROM %Q.'%q_segdir'",
+/* 14 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
+/* 15 */  "SELECT count(*), max(level) FROM %Q.'%q_segdir'",
 
-/* 14 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
-/* 15 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
-/* 16 */  "INSERT INTO %Q.'%q_content' VALUES(%z)",
-/* 17 */  "SELECT block FROM %Q.'%q_segments' WHERE blockid = ?",
+/* 16 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
+/* 17 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
+/* 18 */  "INSERT INTO %Q.'%q_content' VALUES(%z)",
+/* 19 */  "SELECT block FROM %Q.'%q_segments' WHERE blockid = ?",
+/* 20 */  "DELETE FROM %Q.'%q_docsize' WHERE docid = ?",
+/* 21 */  "REPLACE INTO %Q.'%q_docsize' VALUES(?,?)",
+/* 22 */  "SELECT size FROM %Q.'%q_docsize' WHERE docid=?",
+/* 23 */  "SELECT value FROM %Q.'%q_stat' WHERE id=0",
+/* 24 */  "REPLACE INTO %Q.'%q_stat' VALUES(0,?)",
   };
   int rc = SQLITE_OK;
   sqlite3_stmt *pStmt;
@@ -104113,14 +110862,21 @@
 ** Returns SQLITE_OK if the statement is successfully executed, or an
 ** SQLite error code otherwise.
 */
-static int fts3SqlExec(Fts3Table *p, int eStmt, sqlite3_value **apVal){
+static void fts3SqlExec(
+  int *pRC,                /* Result code */
+  Fts3Table *p,            /* The FTS3 table */
+  int eStmt,               /* Index of statement to evaluate */
+  sqlite3_value **apVal    /* Parameters to bind */
+){
   sqlite3_stmt *pStmt;
-  int rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
+  int rc;
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
   if( rc==SQLITE_OK ){
     sqlite3_step(pStmt);
     rc = sqlite3_reset(pStmt);
   }
-  return rc;
+  *pRC = rc;
 }
 
 
@@ -104300,11 +111056,17 @@
 **
 ** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
 */
-static int fts3PendingTermsAdd(Fts3Table *p, const char *zText, int iCol){
+static int fts3PendingTermsAdd(
+  Fts3Table *p,          /* FTS table into which text will be inserted */
+  const char *zText,     /* Text of document to be inseted */
+  int iCol,              /* Column number into which text is inserted */
+  u32 *pnWord            /* OUT: Number of tokens inserted */
+){
   int rc;
   int iStart;
   int iEnd;
   int iPos;
+  int nWord = 0;
 
   char const *zToken;
   int nToken;
@@ -104328,6 +111090,8 @@
       && SQLITE_OK==(rc = xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos))
   ){
     PendingList *pList;
+ 
+    if( iPos>=nWord ) nWord = iPos+1;
 
     /* Positions cannot be negative; we use -1 as a terminator internally.
     ** Tokens must have a non-zero length.
@@ -104357,6 +111121,7 @@
   }
 
   pModule->xClose(pCsr);
+  *pnWord = nWord;
   return (rc==SQLITE_DONE ? SQLITE_OK : rc);
 }
 
@@ -104397,12 +111162,12 @@
 ** Argument apVal is the same as the similarly named argument passed to
 ** fts3InsertData(). Parameter iDocid is the docid of the new row.
 */
-static int fts3InsertTerms(Fts3Table *p, sqlite3_value **apVal){
+static int fts3InsertTerms(Fts3Table *p, sqlite3_value **apVal, u32 *aSz){
   int i;                          /* Iterator variable */
   for(i=2; i<p->nColumn+2; i++){
     const char *zText = (const char *)sqlite3_value_text(apVal[i]);
     if( zText ){
-      int rc = fts3PendingTermsAdd(p, zText, i-2);
+      int rc = fts3PendingTermsAdd(p, zText, i-2, &aSz[i-2]);
       if( rc!=SQLITE_OK ){
         return rc;
       }
@@ -104483,18 +111248,18 @@
 ** pending terms.
 */
 static int fts3DeleteAll(Fts3Table *p){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;             /* Return code */
 
   /* Discard the contents of the pending-terms hash table. */
   sqlite3Fts3PendingTermsClear(p);
 
   /* Delete everything from the %_content, %_segments and %_segdir tables. */
-  rc = fts3SqlExec(p, SQL_DELETE_ALL_CONTENT, 0);
-  if( rc==SQLITE_OK ){
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGMENTS, 0);
-  }
-  if( rc==SQLITE_OK ){
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGDIR, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_CONTENT, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGMENTS, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
+  if( p->bHasDocsize ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_DOCSIZE, 0);
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_STAT, 0);
   }
   return rc;
 }
@@ -104504,20 +111269,27 @@
 ** (an integer) of a row about to be deleted. Remove all terms from the
 ** full-text index.
 */
-static int fts3DeleteTerms(Fts3Table *p, sqlite3_value **apVal){
+static void fts3DeleteTerms(
+  int *pRC,               /* Result code */
+  Fts3Table *p,           /* The FTS table to delete from */
+  sqlite3_value **apVal,  /* apVal[] contains the docid to be deleted */
+  u32 *aSz                /* Sizes of deleted document written here */
+){
   int rc;
   sqlite3_stmt *pSelect;
 
+  if( *pRC ) return;
   rc = fts3SqlStmt(p, SQL_SELECT_CONTENT_BY_ROWID, &pSelect, apVal);
   if( rc==SQLITE_OK ){
     if( SQLITE_ROW==sqlite3_step(pSelect) ){
       int i;
       for(i=1; i<=p->nColumn; i++){
         const char *zText = (const char *)sqlite3_column_text(pSelect, i);
-        rc = fts3PendingTermsAdd(p, zText, -1);
+        rc = fts3PendingTermsAdd(p, zText, -1, &aSz[i-1]);
         if( rc!=SQLITE_OK ){
           sqlite3_reset(pSelect);
-          return rc;
+          *pRC = rc;
+          return;
         }
       }
     }
@@ -104525,7 +111297,7 @@
   }else{
     sqlite3_reset(pSelect);
   }
-  return rc;
+  *pRC = rc;
 }
 
 /*
@@ -105645,7 +112417,7 @@
       rc = sqlite3_reset(pDelete);
     }
   }else{
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGDIR, 0);
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
   }
 
   return rc;
@@ -106074,6 +112846,211 @@
 }
 
 /*
+** Encode N integers as varints into a blob.
+*/
+static void fts3EncodeIntArray(
+  int N,             /* The number of integers to encode */
+  u32 *a,            /* The integer values */
+  char *zBuf,        /* Write the BLOB here */
+  int *pNBuf         /* Write number of bytes if zBuf[] used here */
+){
+  int i, j;
+  for(i=j=0; i<N; i++){
+    j += sqlite3Fts3PutVarint(&zBuf[j], (sqlite3_int64)a[i]);
+  }
+  *pNBuf = j;
+}
+
+/*
+** Decode a blob of varints into N integers
+*/
+static void fts3DecodeIntArray(
+  int N,             /* The number of integers to decode */
+  u32 *a,            /* Write the integer values */
+  const char *zBuf,  /* The BLOB containing the varints */
+  int nBuf           /* size of the BLOB */
+){
+  int i, j;
+  UNUSED_PARAMETER(nBuf);
+  for(i=j=0; i<N; i++){
+    sqlite3_int64 x;
+    j += sqlite3Fts3GetVarint(&zBuf[j], &x);
+    assert(j<=nBuf);
+    a[i] = (u32)(x & 0xffffffff);
+  }
+}
+
+/*
+** Fill in the document size auxiliary information for the matchinfo
+** structure.  The auxiliary information is:
+**
+**    N     Total number of documents in the full-text index
+**    a0    Average length of column 0 over the whole index
+**    n0    Length of column 0 on the matching row
+**    ...
+**    aM    Average length of column M over the whole index
+**    nM    Length of column M on the matching row
+**
+** The fts3MatchinfoDocsizeLocal() routine fills in the nX values.
+** The fts3MatchinfoDocsizeGlobal() routine fills in N and the aX values.
+*/
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeLocal(Fts3Cursor *pCur, u32 *a){
+  const char *pBlob;       /* The BLOB holding %_docsize info */
+  int nBlob;               /* Size of the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i, j;                /* Loop counters */
+  sqlite3_int64 x;         /* Varint value */
+  int rc;                  /* Result code from subfunctions */
+  Fts3Table *p;            /* The FTS table */
+
+  p = (Fts3Table*)pCur->base.pVtab;
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    return rc;
+  }
+  sqlite3_bind_int64(pStmt, 1, pCur->iPrevId);
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    nBlob = sqlite3_column_bytes(pStmt, 0);
+    pBlob = (const char*)sqlite3_column_blob(pStmt, 0);
+    for(i=j=0; i<p->nColumn && j<nBlob; i++){
+      j = sqlite3Fts3GetVarint(&pBlob[j], &x);
+      a[2+i*2] = (u32)(x & 0xffffffff);
+    }
+  }
+  sqlite3_reset(pStmt);
+  return SQLITE_OK; 
+}
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeGlobal(Fts3Cursor *pCur, u32 *a){
+  const char *pBlob;       /* The BLOB holding %_stat info */
+  int nBlob;               /* Size of the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i, j;                /* Loop counters */
+  sqlite3_int64 x;         /* Varint value */
+  int nDoc;                /* Number of documents */
+  int rc;                  /* Result code from subfunctions */
+  Fts3Table *p;            /* The FTS table */
+
+  p = (Fts3Table*)pCur->base.pVtab;
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    return rc;
+  }
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    nBlob = sqlite3_column_bytes(pStmt, 0);
+    pBlob = (const char*)sqlite3_column_blob(pStmt, 0);
+    j = sqlite3Fts3GetVarint(pBlob, &x);
+    a[0] = nDoc = (u32)(x & 0xffffffff);
+    for(i=0; i<p->nColumn && j<nBlob; i++){
+      j = sqlite3Fts3GetVarint(&pBlob[j], &x);
+      a[1+i*2] = ((u32)(x & 0xffffffff) + nDoc/2)/nDoc;
+    }
+  }
+  sqlite3_reset(pStmt);
+  return SQLITE_OK; 
+}
+
+/*
+** Insert the sizes (in tokens) for each column of the document
+** with docid equal to p->iPrevDocid.  The sizes are encoded as
+** a blob of varints.
+*/
+static void fts3InsertDocsize(
+  int *pRC,         /* Result code */
+  Fts3Table *p,     /* Table into which to insert */
+  u32 *aSz          /* Sizes of each column */
+){
+  char *pBlob;             /* The BLOB encoding of the document size */
+  int nBlob;               /* Number of bytes in the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement used to insert the encoding */
+  int rc;                  /* Result code from subfunctions */
+
+  if( *pRC ) return;
+  pBlob = sqlite3_malloc( 10*p->nColumn );
+  if( pBlob==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  fts3EncodeIntArray(p->nColumn, aSz, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(pBlob);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int64(pStmt, 1, p->iPrevDocid);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, sqlite3_free);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+}
+
+/*
+** Update the 0 record of the %_stat table so that it holds a blob
+** which contains the document count followed by the cumulative
+** document sizes for all columns.
+*/
+static void fts3UpdateDocTotals(
+  int *pRC,       /* The result code */
+  Fts3Table *p,   /* Table being updated */
+  u32 *aSzIns,    /* Size increases */
+  u32 *aSzDel,    /* Size decreases */
+  int nChng       /* Change in the number of documents */
+){
+  char *pBlob;             /* Storage for BLOB written into %_stat */
+  int nBlob;               /* Size of BLOB written into %_stat */
+  u32 *a;                  /* Array of integers that becomes the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subfunctions */
+
+  if( *pRC ) return;
+  a = sqlite3_malloc( (sizeof(u32)+10)*(p->nColumn+1) );
+  if( a==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  pBlob = (char*)&a[p->nColumn+1];
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    fts3DecodeIntArray(p->nColumn+1, a,
+         sqlite3_column_blob(pStmt, 0),
+         sqlite3_column_bytes(pStmt, 0));
+  }else{
+    memset(a, 0, sizeof(u32)*(p->nColumn+1) );
+  }
+  sqlite3_reset(pStmt);
+  if( nChng<0 && a[0]<(u32)(-nChng) ){
+    a[0] = 0;
+  }else{
+    a[0] += nChng;
+  }
+  for(i=0; i<p->nColumn; i++){
+    u32 x = a[i+1];
+    if( x+aSzIns[i] < aSzDel[i] ){
+      x = 0;
+    }else{
+      x = x + aSzIns[i] - aSzDel[i];
+    }
+    a[i+1] = x;
+  }
+  fts3EncodeIntArray(p->nColumn+1, a, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_blob(pStmt, 1, pBlob, nBlob, SQLITE_STATIC);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+  sqlite3_free(a);
+}
+
+/*
 ** Handle a 'special' INSERT of the form:
 **
 **   "INSERT INTO tbl(tbl) VALUES(<expr>)"
@@ -106124,8 +113101,17 @@
   int rc = SQLITE_OK;             /* Return Code */
   int isRemove = 0;               /* True for an UPDATE or DELETE */
   sqlite3_int64 iRemove = 0;      /* Rowid removed by UPDATE or DELETE */
+  u32 *aSzIns;                    /* Sizes of inserted documents */
+  u32 *aSzDel;                    /* Sizes of deleted documents */
+  int nChng = 0;                  /* Net change in number of documents */
 
 
+  /* Allocate space to hold the change in document sizes */
+  aSzIns = sqlite3_malloc( sizeof(aSzIns[0])*p->nColumn*2 );
+  if( aSzIns==0 ) return SQLITE_NOMEM;
+  aSzDel = &aSzIns[p->nColumn];
+  memset(aSzIns, 0, sizeof(aSzIns[0])*p->nColumn*2);
+
   /* If this is a DELETE or UPDATE operation, remove the old record. */
   if( sqlite3_value_type(apVal[0])!=SQLITE_NULL ){
     int isEmpty;
@@ -106141,15 +113127,16 @@
         isRemove = 1;
         iRemove = sqlite3_value_int64(apVal[0]);
         rc = fts3PendingTermsDocid(p, iRemove);
-        if( rc==SQLITE_OK ){
-          rc = fts3DeleteTerms(p, apVal);
-          if( rc==SQLITE_OK ){
-            rc = fts3SqlExec(p, SQL_DELETE_CONTENT, apVal);
-          }
+        fts3DeleteTerms(&rc, p, apVal, aSzDel);
+        fts3SqlExec(&rc, p, SQL_DELETE_CONTENT, apVal);
+        if( p->bHasDocsize ){
+          fts3SqlExec(&rc, p, SQL_DELETE_DOCSIZE, apVal);
+          nChng--;
         }
       }
     }
   }else if( sqlite3_value_type(apVal[p->nColumn+2])!=SQLITE_NULL ){
+    sqlite3_free(aSzIns);
     return fts3SpecialInsert(p, apVal[p->nColumn+2]);
   }
   
@@ -106160,10 +113147,19 @@
       rc = fts3PendingTermsDocid(p, *pRowid);
     }
     if( rc==SQLITE_OK ){
-      rc = fts3InsertTerms(p, apVal);
+      rc = fts3InsertTerms(p, apVal, aSzIns);
+    }
+    if( p->bHasDocsize ){
+      nChng++;
+      fts3InsertDocsize(&rc, p, aSzIns);
     }
   }
 
+  if( p->bHasDocsize ){
+    fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nChng);
+  }
+
+  sqlite3_free(aSzIns);
   return rc;
 }
 
@@ -106210,727 +113206,97 @@
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 
-typedef struct Snippet Snippet;
 
 /*
-** An instance of the following structure keeps track of generated
-** matching-word offset information and snippets.
+** Used as an fts3ExprIterate() context when loading phrase doclists to
+** Fts3Expr.aDoclist[]/nDoclist.
 */
-struct Snippet {
-  int nMatch;                     /* Total number of matches */
-  int nAlloc;                     /* Space allocated for aMatch[] */
-  struct snippetMatch {  /* One entry for each matching term */
-    char snStatus;       /* Status flag for use while constructing snippets */
-    short int nByte;     /* Number of bytes in the term */
-    short int iCol;      /* The column that contains the match */
-    short int iTerm;     /* The index in Query.pTerms[] of the matching term */
-    int iToken;          /* The index of the matching document token */
-    int iStart;          /* The offset to the first character of the term */
-  } *aMatch;                      /* Points to space obtained from malloc */
-  char *zOffset;                  /* Text rendering of aMatch[] */
-  int nOffset;                    /* strlen(zOffset) */
-  char *zSnippet;                 /* Snippet text */
-  int nSnippet;                   /* strlen(zSnippet) */
+typedef struct LoadDoclistCtx LoadDoclistCtx;
+struct LoadDoclistCtx {
+  Fts3Table *pTab;                /* FTS3 Table */
+  int nPhrase;                    /* Number of phrases seen so far */
+  int nToken;                     /* Number of tokens seen so far */
+};
+
+/*
+** The following types are used as part of the implementation of the 
+** fts3BestSnippet() routine.
+*/
+typedef struct SnippetIter SnippetIter;
+typedef struct SnippetPhrase SnippetPhrase;
+typedef struct SnippetFragment SnippetFragment;
+
+struct SnippetIter {
+  Fts3Cursor *pCsr;               /* Cursor snippet is being generated from */
+  int iCol;                       /* Extract snippet from this column */
+  int nSnippet;                   /* Requested snippet length (in tokens) */
+  int nPhrase;                    /* Number of phrases in query */
+  SnippetPhrase *aPhrase;         /* Array of size nPhrase */
+  int iCurrent;                   /* First token of current snippet */
+};
+
+struct SnippetPhrase {
+  int nToken;                     /* Number of tokens in phrase */
+  char *pList;                    /* Pointer to start of phrase position list */
+  int iHead;                      /* Next value in position list */
+  char *pHead;                    /* Position list data following iHead */
+  int iTail;                      /* Next value in trailing position list */
+  char *pTail;                    /* Position list data following iTail */
+};
+
+struct SnippetFragment {
+  int iCol;                       /* Column snippet is extracted from */
+  int iPos;                       /* Index of first token in snippet */
+  u64 covered;                    /* Mask of query phrases covered */
+  u64 hlmask;                     /* Mask of snippet terms to highlight */
+};
+
+/*
+** This type is used as an fts3ExprIterate() context object while 
+** accumulating the data returned by the matchinfo() function.
+*/
+typedef struct MatchInfo MatchInfo;
+struct MatchInfo {
+  Fts3Cursor *pCursor;            /* FTS3 Cursor */
+  int nCol;                       /* Number of columns in table */
+  u32 *aMatchinfo;                /* Pre-allocated buffer */
 };
 
 
-/* It is not safe to call isspace(), tolower(), or isalnum() on
-** hi-bit-set characters.  This is the same solution used in the
-** tokenizer.
+
+/*
+** The snippet() and offsets() functions both return text values. An instance
+** of the following structure is used to accumulate those values while the
+** functions are running. See fts3StringAppend() for details.
 */
-static int fts3snippetIsspace(char c){
-  return (c&0x80)==0 ? isspace(c) : 0;
-}
+typedef struct StrBuffer StrBuffer;
+struct StrBuffer {
+  char *z;                        /* Pointer to buffer containing string */
+  int n;                          /* Length of z in bytes (excl. nul-term) */
+  int nAlloc;                     /* Allocated size of buffer z in bytes */
+};
 
 
 /*
-** A StringBuffer object holds a zero-terminated string that grows
-** arbitrarily by appending.  Space to hold the string is obtained
-** from sqlite3_malloc().  After any memory allocation failure, 
-** StringBuffer.z is set to NULL and no further allocation is attempted.
-*/
-typedef struct StringBuffer {
-  char *z;         /* Text of the string.  Space from malloc. */
-  int nUsed;       /* Number bytes of z[] used, not counting \000 terminator */
-  int nAlloc;      /* Bytes allocated for z[] */
-} StringBuffer;
-
-
-/*
-** Initialize a new StringBuffer.
-*/
-static void fts3SnippetSbInit(StringBuffer *p){
-  p->nAlloc = 100;
-  p->nUsed = 0;
-  p->z = sqlite3_malloc( p->nAlloc );
-}
-
-/*
-** Append text to the string buffer.
-*/
-static void fts3SnippetAppend(StringBuffer *p, const char *zNew, int nNew){
-  if( p->z==0 ) return;
-  if( nNew<0 ) nNew = (int)strlen(zNew);
-  if( p->nUsed + nNew >= p->nAlloc ){
-    int nAlloc;
-    char *zNew;
-
-    nAlloc = p->nUsed + nNew + p->nAlloc;
-    zNew = sqlite3_realloc(p->z, nAlloc);
-    if( zNew==0 ){
-      sqlite3_free(p->z);
-      p->z = 0;
-      return;
-    }
-    p->z = zNew;
-    p->nAlloc = nAlloc;
-  }
-  memcpy(&p->z[p->nUsed], zNew, nNew);
-  p->nUsed += nNew;
-  p->z[p->nUsed] = 0;
-}
-
-/* If the StringBuffer ends in something other than white space, add a
-** single space character to the end.
-*/
-static void fts3SnippetAppendWhiteSpace(StringBuffer *p){
-  if( p->z && p->nUsed && !fts3snippetIsspace(p->z[p->nUsed-1]) ){
-    fts3SnippetAppend(p, " ", 1);
-  }
-}
-
-/* Remove white space from the end of the StringBuffer */
-static void fts3SnippetTrimWhiteSpace(StringBuffer *p){
-  if( p->z ){
-    while( p->nUsed && fts3snippetIsspace(p->z[p->nUsed-1]) ){
-      p->nUsed--;
-    }
-    p->z[p->nUsed] = 0;
-  }
-}
-
-/* 
-** Release all memory associated with the Snippet structure passed as
-** an argument.
-*/
-static void fts3SnippetFree(Snippet *p){
-  if( p ){
-    sqlite3_free(p->aMatch);
-    sqlite3_free(p->zOffset);
-    sqlite3_free(p->zSnippet);
-    sqlite3_free(p);
-  }
-}
-
-/*
-** Append a single entry to the p->aMatch[] log.
-*/
-static int snippetAppendMatch(
-  Snippet *p,               /* Append the entry to this snippet */
-  int iCol, int iTerm,      /* The column and query term */
-  int iToken,               /* Matching token in document */
-  int iStart, int nByte     /* Offset and size of the match */
-){
-  int i;
-  struct snippetMatch *pMatch;
-  if( p->nMatch+1>=p->nAlloc ){
-    struct snippetMatch *pNew;
-    p->nAlloc = p->nAlloc*2 + 10;
-    pNew = sqlite3_realloc(p->aMatch, p->nAlloc*sizeof(p->aMatch[0]) );
-    if( pNew==0 ){
-      p->aMatch = 0;
-      p->nMatch = 0;
-      p->nAlloc = 0;
-      return SQLITE_NOMEM;
-    }
-    p->aMatch = pNew;
-  }
-  i = p->nMatch++;
-  pMatch = &p->aMatch[i];
-  pMatch->iCol = (short)iCol;
-  pMatch->iTerm = (short)iTerm;
-  pMatch->iToken = iToken;
-  pMatch->iStart = iStart;
-  pMatch->nByte = (short)nByte;
-  return SQLITE_OK;
-}
-
-/*
-** Sizing information for the circular buffer used in snippetOffsetsOfColumn()
-*/
-#define FTS3_ROTOR_SZ   (32)
-#define FTS3_ROTOR_MASK (FTS3_ROTOR_SZ-1)
-
-/*
-** Function to iterate through the tokens of a compiled expression.
+** This function is used to help iterate through a position-list. A position
+** list is a list of unique integers, sorted from smallest to largest. Each
+** element of the list is represented by an FTS3 varint that takes the value
+** of the difference between the current element and the previous one plus
+** two. For example, to store the position-list:
 **
-** Except, skip all tokens on the right-hand side of a NOT operator.
-** This function is used to find tokens as part of snippet and offset
-** generation and we do nt want snippets and offsets to report matches
-** for tokens on the RHS of a NOT.
-*/
-static int fts3NextExprToken(Fts3Expr **ppExpr, int *piToken){
-  Fts3Expr *p = *ppExpr;
-  int iToken = *piToken;
-  if( iToken<0 ){
-    /* In this case the expression p is the root of an expression tree.
-    ** Move to the first token in the expression tree.
-    */
-    while( p->pLeft ){
-      p = p->pLeft;
-    }
-    iToken = 0;
-  }else{
-    assert(p && p->eType==FTSQUERY_PHRASE );
-    if( iToken<(p->pPhrase->nToken-1) ){
-      iToken++;
-    }else{
-      iToken = 0;
-      while( p->pParent && p->pParent->pLeft!=p ){
-        assert( p->pParent->pRight==p );
-        p = p->pParent;
-      }
-      p = p->pParent;
-      if( p ){
-        assert( p->pRight!=0 );
-        p = p->pRight;
-        while( p->pLeft ){
-          p = p->pLeft;
-        }
-      }
-    }
-  }
-
-  *ppExpr = p;
-  *piToken = iToken;
-  return p?1:0;
-}
-
-/*
-** Return TRUE if the expression node pExpr is located beneath the
-** RHS of a NOT operator.
-*/
-static int fts3ExprBeneathNot(Fts3Expr *p){
-  Fts3Expr *pParent;
-  while( p ){
-    pParent = p->pParent;
-    if( pParent && pParent->eType==FTSQUERY_NOT && pParent->pRight==p ){
-      return 1;
-    }
-    p = pParent;
-  }
-  return 0;
-}
-
-/*
-** Add entries to pSnippet->aMatch[] for every match that occurs against
-** document zDoc[0..nDoc-1] which is stored in column iColumn.
-*/
-static int snippetOffsetsOfColumn(
-  Fts3Cursor *pCur,         /* The fulltest search cursor */
-  Snippet *pSnippet,             /* The Snippet object to be filled in */
-  int iColumn,                   /* Index of fulltext table column */
-  const char *zDoc,              /* Text of the fulltext table column */
-  int nDoc                       /* Length of zDoc in bytes */
-){
-  const sqlite3_tokenizer_module *pTModule;  /* The tokenizer module */
-  sqlite3_tokenizer *pTokenizer;             /* The specific tokenizer */
-  sqlite3_tokenizer_cursor *pTCursor;        /* Tokenizer cursor */
-  Fts3Table *pVtab;                /* The full text index */
-  int nColumn;                         /* Number of columns in the index */
-  int i, j;                            /* Loop counters */
-  int rc;                              /* Return code */
-  unsigned int match, prevMatch;       /* Phrase search bitmasks */
-  const char *zToken;                  /* Next token from the tokenizer */
-  int nToken;                          /* Size of zToken */
-  int iBegin, iEnd, iPos;              /* Offsets of beginning and end */
-
-  /* The following variables keep a circular buffer of the last
-  ** few tokens */
-  unsigned int iRotor = 0;             /* Index of current token */
-  int iRotorBegin[FTS3_ROTOR_SZ];      /* Beginning offset of token */
-  int iRotorLen[FTS3_ROTOR_SZ];        /* Length of token */
-
-  pVtab =  (Fts3Table *)pCur->base.pVtab;
-  nColumn = pVtab->nColumn;
-  pTokenizer = pVtab->pTokenizer;
-  pTModule = pTokenizer->pModule;
-  rc = pTModule->xOpen(pTokenizer, zDoc, nDoc, &pTCursor);
-  if( rc ) return rc;
-  pTCursor->pTokenizer = pTokenizer;
-
-  prevMatch = 0;
-  while( (rc = pTModule->xNext(pTCursor, &zToken, &nToken,
-                               &iBegin, &iEnd, &iPos))==SQLITE_OK ){
-    Fts3Expr *pIter = pCur->pExpr;
-    int iIter = -1;
-    iRotorBegin[iRotor&FTS3_ROTOR_MASK] = iBegin;
-    iRotorLen[iRotor&FTS3_ROTOR_MASK] = iEnd-iBegin;
-    match = 0;
-    for(i=0; i<(FTS3_ROTOR_SZ-1) && fts3NextExprToken(&pIter, &iIter); i++){
-      int nPhrase;                    /* Number of tokens in current phrase */
-      struct PhraseToken *pToken;     /* Current token */
-      int iCol;                       /* Column index */
-
-      if( fts3ExprBeneathNot(pIter) ) continue;
-      nPhrase = pIter->pPhrase->nToken;
-      pToken = &pIter->pPhrase->aToken[iIter];
-      iCol = pIter->pPhrase->iColumn;
-      if( iCol>=0 && iCol<nColumn && iCol!=iColumn ) continue;
-      if( pToken->n>nToken ) continue;
-      if( !pToken->isPrefix && pToken->n<nToken ) continue;
-      assert( pToken->n<=nToken );
-      if( memcmp(pToken->z, zToken, pToken->n) ) continue;
-      if( iIter>0 && (prevMatch & (1<<i))==0 ) continue;
-      match |= 1<<i;
-      if( i==(FTS3_ROTOR_SZ-2) || nPhrase==iIter+1 ){
-        for(j=nPhrase-1; j>=0; j--){
-          int k = (iRotor-j) & FTS3_ROTOR_MASK;
-          rc = snippetAppendMatch(pSnippet, iColumn, i-j, iPos-j,
-                                  iRotorBegin[k], iRotorLen[k]);
-          if( rc ) goto end_offsets_of_column;
-        }
-      }
-    }
-    prevMatch = match<<1;
-    iRotor++;
-  }
-end_offsets_of_column:
-  pTModule->xClose(pTCursor);  
-  return rc==SQLITE_DONE ? SQLITE_OK : rc;
-}
-
-/*
-** Remove entries from the pSnippet structure to account for the NEAR
-** operator. When this is called, pSnippet contains the list of token 
-** offsets produced by treating all NEAR operators as AND operators.
-** This function removes any entries that should not be present after
-** accounting for the NEAR restriction. For example, if the queried
-** document is:
+**     4 9 113
 **
-**     "A B C D E A"
+** the three varints:
 **
-** and the query is:
-** 
-**     A NEAR/0 E
+**     6 7 106
 **
-** then when this function is called the Snippet contains token offsets
-** 0, 4 and 5. This function removes the "0" entry (because the first A
-** is not near enough to an E).
+** are encoded.
 **
-** When this function is called, the value pointed to by parameter piLeft is
-** the integer id of the left-most token in the expression tree headed by
-** pExpr. This function increments *piLeft by the total number of tokens
-** in the expression tree headed by pExpr.
-**
-** Return 1 if any trimming occurs.  Return 0 if no trimming is required.
+** When this function is called, *pp points to the start of an element of
+** the list. *piPos contains the value of the previous entry in the list.
+** After it returns, *piPos contains the value of the next element of the
+** list and *pp is advanced to the following varint.
 */
-static int trimSnippetOffsets(
-  Fts3Expr *pExpr,      /* The search expression */
-  Snippet *pSnippet,    /* The set of snippet offsets to be trimmed */
-  int *piLeft           /* Index of left-most token in pExpr */
-){
-  if( pExpr ){
-    if( trimSnippetOffsets(pExpr->pLeft, pSnippet, piLeft) ){
-      return 1;
-    }
-
-    switch( pExpr->eType ){
-      case FTSQUERY_PHRASE:
-        *piLeft += pExpr->pPhrase->nToken;
-        break;
-      case FTSQUERY_NEAR: {
-        /* The right-hand-side of a NEAR operator is always a phrase. The
-        ** left-hand-side is either a phrase or an expression tree that is 
-        ** itself headed by a NEAR operator. The following initializations
-        ** set local variable iLeft to the token number of the left-most
-        ** token in the right-hand phrase, and iRight to the right most
-        ** token in the same phrase. For example, if we had:
-        **
-        **     <col> MATCH '"abc def" NEAR/2 "ghi jkl"'
-        **
-        ** then iLeft will be set to 2 (token number of ghi) and nToken will
-        ** be set to 4.
-        */
-        Fts3Expr *pLeft = pExpr->pLeft;
-        Fts3Expr *pRight = pExpr->pRight;
-        int iLeft = *piLeft;
-        int nNear = pExpr->nNear;
-        int nToken = pRight->pPhrase->nToken;
-        int jj, ii;
-        if( pLeft->eType==FTSQUERY_NEAR ){
-          pLeft = pLeft->pRight;
-        }
-        assert( pRight->eType==FTSQUERY_PHRASE );
-        assert( pLeft->eType==FTSQUERY_PHRASE );
-        nToken += pLeft->pPhrase->nToken;
-
-        for(ii=0; ii<pSnippet->nMatch; ii++){
-          struct snippetMatch *p = &pSnippet->aMatch[ii];
-          if( p->iTerm==iLeft ){
-            int isOk = 0;
-            /* Snippet ii is an occurence of query term iLeft in the document.
-            ** It occurs at position (p->iToken) of the document. We now
-            ** search for an instance of token (iLeft-1) somewhere in the 
-            ** range (p->iToken - nNear)...(p->iToken + nNear + nToken) within 
-            ** the set of snippetMatch structures. If one is found, proceed. 
-            ** If one cannot be found, then remove snippets ii..(ii+N-1) 
-            ** from the matching snippets, where N is the number of tokens 
-            ** in phrase pRight->pPhrase.
-            */
-            for(jj=0; isOk==0 && jj<pSnippet->nMatch; jj++){
-              struct snippetMatch *p2 = &pSnippet->aMatch[jj];
-              if( p2->iTerm==(iLeft-1) ){
-                if( p2->iToken>=(p->iToken-nNear-1) 
-                 && p2->iToken<(p->iToken+nNear+nToken) 
-                ){
-                  isOk = 1;
-                }
-              }
-            }
-            if( !isOk ){
-              int kk;
-              for(kk=0; kk<pRight->pPhrase->nToken; kk++){
-                pSnippet->aMatch[kk+ii].iTerm = -2;
-              }
-              return 1;
-            }
-          }
-          if( p->iTerm==(iLeft-1) ){
-            int isOk = 0;
-            for(jj=0; isOk==0 && jj<pSnippet->nMatch; jj++){
-              struct snippetMatch *p2 = &pSnippet->aMatch[jj];
-              if( p2->iTerm==iLeft ){
-                if( p2->iToken<=(p->iToken+nNear+1) 
-                 && p2->iToken>(p->iToken-nNear-nToken) 
-                ){
-                  isOk = 1;
-                }
-              }
-            }
-            if( !isOk ){
-              int kk;
-              for(kk=0; kk<pLeft->pPhrase->nToken; kk++){
-                pSnippet->aMatch[ii-kk].iTerm = -2;
-              }
-              return 1;
-            }
-          }
-        }
-        break;
-      }
-    }
-
-    if( trimSnippetOffsets(pExpr->pRight, pSnippet, piLeft) ){
-      return 1;
-    }
-  }
-  return 0;
-}
-
-/*
-** Compute all offsets for the current row of the query.  
-** If the offsets have already been computed, this routine is a no-op.
-*/
-static int snippetAllOffsets(Fts3Cursor *pCsr, Snippet **ppSnippet){
-  Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;  /* The FTS3 virtual table */
-  int nColumn;           /* Number of columns.  Docid does count */
-  int iColumn;           /* Index of of a column */
-  int i;                 /* Loop index */
-  int iFirst;            /* First column to search */
-  int iLast;             /* Last coumn to search */
-  int iTerm = 0;
-  Snippet *pSnippet;
-  int rc = SQLITE_OK;
-
-  if( pCsr->pExpr==0 ){
-    return SQLITE_OK;
-  }
-
-  pSnippet = (Snippet *)sqlite3_malloc(sizeof(Snippet));
-  *ppSnippet = pSnippet;
-  if( !pSnippet ){
-    return SQLITE_NOMEM;
-  }
-  memset(pSnippet, 0, sizeof(Snippet));
-
-  nColumn = p->nColumn;
-  iColumn = (pCsr->eSearch - 2);
-  if( iColumn<0 || iColumn>=nColumn ){
-    /* Look for matches over all columns of the full-text index */
-    iFirst = 0;
-    iLast = nColumn-1;
-  }else{
-    /* Look for matches in the iColumn-th column of the index only */
-    iFirst = iColumn;
-    iLast = iColumn;
-  }
-  for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
-    const char *zDoc;
-    int nDoc;
-    zDoc = (const char*)sqlite3_column_text(pCsr->pStmt, i+1);
-    nDoc = sqlite3_column_bytes(pCsr->pStmt, i+1);
-    if( zDoc==0 && sqlite3_column_type(pCsr->pStmt, i+1)!=SQLITE_NULL ){
-      rc = SQLITE_NOMEM;
-    }else{
-      rc = snippetOffsetsOfColumn(pCsr, pSnippet, i, zDoc, nDoc);
-    }
-  }
-
-  while( trimSnippetOffsets(pCsr->pExpr, pSnippet, &iTerm) ){
-    iTerm = 0;
-  }
-
-  return rc;
-}
-
-/*
-** Convert the information in the aMatch[] array of the snippet
-** into the string zOffset[0..nOffset-1]. This string is used as
-** the return of the SQL offsets() function.
-*/
-static void snippetOffsetText(Snippet *p){
-  int i;
-  int cnt = 0;
-  StringBuffer sb;
-  char zBuf[200];
-  if( p->zOffset ) return;
-  fts3SnippetSbInit(&sb);
-  for(i=0; i<p->nMatch; i++){
-    struct snippetMatch *pMatch = &p->aMatch[i];
-    if( pMatch->iTerm>=0 ){
-      /* If snippetMatch.iTerm is less than 0, then the match was 
-      ** discarded as part of processing the NEAR operator (see the 
-      ** trimSnippetOffsetsForNear() function for details). Ignore 
-      ** it in this case
-      */
-      zBuf[0] = ' ';
-      sqlite3_snprintf(sizeof(zBuf)-1, &zBuf[cnt>0], "%d %d %d %d",
-          pMatch->iCol, pMatch->iTerm, pMatch->iStart, pMatch->nByte);
-      fts3SnippetAppend(&sb, zBuf, -1);
-      cnt++;
-    }
-  }
-  p->zOffset = sb.z;
-  p->nOffset = sb.z ? sb.nUsed : 0;
-}
-
-/*
-** zDoc[0..nDoc-1] is phrase of text.  aMatch[0..nMatch-1] are a set
-** of matching words some of which might be in zDoc.  zDoc is column
-** number iCol.
-**
-** iBreak is suggested spot in zDoc where we could begin or end an
-** excerpt.  Return a value similar to iBreak but possibly adjusted
-** to be a little left or right so that the break point is better.
-*/
-static int wordBoundary(
-  int iBreak,                   /* The suggested break point */
-  const char *zDoc,             /* Document text */
-  int nDoc,                     /* Number of bytes in zDoc[] */
-  struct snippetMatch *aMatch,  /* Matching words */
-  int nMatch,                   /* Number of entries in aMatch[] */
-  int iCol                      /* The column number for zDoc[] */
-){
-  int i;
-  if( iBreak<=10 ){
-    return 0;
-  }
-  if( iBreak>=nDoc-10 ){
-    return nDoc;
-  }
-  for(i=0; ALWAYS(i<nMatch) && aMatch[i].iCol<iCol; i++){}
-  while( i<nMatch && aMatch[i].iStart+aMatch[i].nByte<iBreak ){ i++; }
-  if( i<nMatch ){
-    if( aMatch[i].iStart<iBreak+10 ){
-      return aMatch[i].iStart;
-    }
-    if( i>0 && aMatch[i-1].iStart+aMatch[i-1].nByte>=iBreak ){
-      return aMatch[i-1].iStart;
-    }
-  }
-  for(i=1; i<=10; i++){
-    if( fts3snippetIsspace(zDoc[iBreak-i]) ){
-      return iBreak - i + 1;
-    }
-    if( fts3snippetIsspace(zDoc[iBreak+i]) ){
-      return iBreak + i + 1;
-    }
-  }
-  return iBreak;
-}
-
-
-
-/*
-** Allowed values for Snippet.aMatch[].snStatus
-*/
-#define SNIPPET_IGNORE  0   /* It is ok to omit this match from the snippet */
-#define SNIPPET_DESIRED 1   /* We want to include this match in the snippet */
-
-/*
-** Generate the text of a snippet.
-*/
-static void snippetText(
-  Fts3Cursor *pCursor,   /* The cursor we need the snippet for */
-  Snippet *pSnippet,
-  const char *zStartMark,     /* Markup to appear before each match */
-  const char *zEndMark,       /* Markup to appear after each match */
-  const char *zEllipsis       /* Ellipsis mark */
-){
-  int i, j;
-  struct snippetMatch *aMatch;
-  int nMatch;
-  int nDesired;
-  StringBuffer sb;
-  int tailCol;
-  int tailOffset;
-  int iCol;
-  int nDoc;
-  const char *zDoc;
-  int iStart, iEnd;
-  int tailEllipsis = 0;
-  int iMatch;
-  
-
-  sqlite3_free(pSnippet->zSnippet);
-  pSnippet->zSnippet = 0;
-  aMatch = pSnippet->aMatch;
-  nMatch = pSnippet->nMatch;
-  fts3SnippetSbInit(&sb);
-
-  for(i=0; i<nMatch; i++){
-    aMatch[i].snStatus = SNIPPET_IGNORE;
-  }
-  nDesired = 0;
-  for(i=0; i<FTS3_ROTOR_SZ; i++){
-    for(j=0; j<nMatch; j++){
-      if( aMatch[j].iTerm==i ){
-        aMatch[j].snStatus = SNIPPET_DESIRED;
-        nDesired++;
-        break;
-      }
-    }
-  }
-
-  iMatch = 0;
-  tailCol = -1;
-  tailOffset = 0;
-  for(i=0; i<nMatch && nDesired>0; i++){
-    if( aMatch[i].snStatus!=SNIPPET_DESIRED ) continue;
-    nDesired--;
-    iCol = aMatch[i].iCol;
-    zDoc = (const char*)sqlite3_column_text(pCursor->pStmt, iCol+1);
-    nDoc = sqlite3_column_bytes(pCursor->pStmt, iCol+1);
-    iStart = aMatch[i].iStart - 40;
-    iStart = wordBoundary(iStart, zDoc, nDoc, aMatch, nMatch, iCol);
-    if( iStart<=10 ){
-      iStart = 0;
-    }
-    if( iCol==tailCol && iStart<=tailOffset+20 ){
-      iStart = tailOffset;
-    }
-    if( (iCol!=tailCol && tailCol>=0) || iStart!=tailOffset ){
-      fts3SnippetTrimWhiteSpace(&sb);
-      fts3SnippetAppendWhiteSpace(&sb);
-      fts3SnippetAppend(&sb, zEllipsis, -1);
-      fts3SnippetAppendWhiteSpace(&sb);
-    }
-    iEnd = aMatch[i].iStart + aMatch[i].nByte + 40;
-    iEnd = wordBoundary(iEnd, zDoc, nDoc, aMatch, nMatch, iCol);
-    if( iEnd>=nDoc-10 ){
-      iEnd = nDoc;
-      tailEllipsis = 0;
-    }else{
-      tailEllipsis = 1;
-    }
-    while( iMatch<nMatch && aMatch[iMatch].iCol<iCol ){ iMatch++; }
-    while( iStart<iEnd ){
-      while( iMatch<nMatch && aMatch[iMatch].iStart<iStart
-             && aMatch[iMatch].iCol<=iCol ){
-        iMatch++;
-      }
-      if( iMatch<nMatch && aMatch[iMatch].iStart<iEnd
-             && aMatch[iMatch].iCol==iCol ){
-        fts3SnippetAppend(&sb, &zDoc[iStart], aMatch[iMatch].iStart - iStart);
-        iStart = aMatch[iMatch].iStart;
-        fts3SnippetAppend(&sb, zStartMark, -1);
-        fts3SnippetAppend(&sb, &zDoc[iStart], aMatch[iMatch].nByte);
-        fts3SnippetAppend(&sb, zEndMark, -1);
-        iStart += aMatch[iMatch].nByte;
-        for(j=iMatch+1; j<nMatch; j++){
-          if( aMatch[j].iTerm==aMatch[iMatch].iTerm
-              && aMatch[j].snStatus==SNIPPET_DESIRED ){
-            nDesired--;
-            aMatch[j].snStatus = SNIPPET_IGNORE;
-          }
-        }
-      }else{
-        fts3SnippetAppend(&sb, &zDoc[iStart], iEnd - iStart);
-        iStart = iEnd;
-      }
-    }
-    tailCol = iCol;
-    tailOffset = iEnd;
-  }
-  fts3SnippetTrimWhiteSpace(&sb);
-  if( tailEllipsis ){
-    fts3SnippetAppendWhiteSpace(&sb);
-    fts3SnippetAppend(&sb, zEllipsis, -1);
-  }
-  pSnippet->zSnippet = sb.z;
-  pSnippet->nSnippet = sb.z ? sb.nUsed : 0;
-}
-
-SQLITE_PRIVATE void sqlite3Fts3Offsets(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr                /* Cursor object */
-){
-  Snippet *p;                     /* Snippet structure */
-  int rc = snippetAllOffsets(pCsr, &p);
-  if( rc==SQLITE_OK ){
-    snippetOffsetText(p);
-    if( p->zOffset ){
-      sqlite3_result_text(pCtx, p->zOffset, p->nOffset, SQLITE_TRANSIENT);
-    }else{
-      sqlite3_result_error_nomem(pCtx);
-    }
-  }else{
-    sqlite3_result_error_nomem(pCtx);
-  }
-  fts3SnippetFree(p);
-}
-
-SQLITE_PRIVATE void sqlite3Fts3Snippet(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr,               /* Cursor object */
-  const char *zStart,             /* Snippet start text - "<b>" */
-  const char *zEnd,               /* Snippet end text - "</b>" */
-  const char *zEllipsis           /* Snippet ellipsis text - "<b>...</b>" */
-){
-  Snippet *p;                     /* Snippet structure */
-  int rc = snippetAllOffsets(pCsr, &p);
-  if( rc==SQLITE_OK ){
-    snippetText(pCsr, p, zStart, zEnd, zEllipsis);
-    if( p->zSnippet ){
-      sqlite3_result_text(pCtx, p->zSnippet, p->nSnippet, SQLITE_TRANSIENT);
-    }else{
-      sqlite3_result_error_nomem(pCtx);
-    }
-  }else{
-    sqlite3_result_error_nomem(pCtx);
-  }
-  fts3SnippetFree(p);
-}
-
-/*************************************************************************
-** Below this point is the alternative, experimental snippet() implementation.
-*/
-
-#define SNIPPET_BUFFER_CHUNK  64
-#define SNIPPET_BUFFER_SIZE   SNIPPET_BUFFER_CHUNK*4
-#define SNIPPET_BUFFER_MASK   (SNIPPET_BUFFER_SIZE-1)
-
 static void fts3GetDeltaPosition(char **pp, int *piPos){
   int iVal;
   *pp += sqlite3Fts3GetVarint32(*pp, &iVal);
@@ -106938,6 +113304,31 @@
 }
 
 /*
+** Helper function for fts3ExprIterate() (see below).
+*/
+static int fts3ExprIterate2(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int *piPhrase,                  /* Pointer to phrase counter */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
+){
+  int rc;                         /* Return code */
+  int eType = pExpr->eType;       /* Type of expression node pExpr */
+
+  if( eType!=FTSQUERY_PHRASE ){
+    assert( pExpr->pLeft && pExpr->pRight );
+    rc = fts3ExprIterate2(pExpr->pLeft, piPhrase, x, pCtx);
+    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
+      rc = fts3ExprIterate2(pExpr->pRight, piPhrase, x, pCtx);
+    }
+  }else{
+    rc = x(pExpr, *piPhrase, pCtx);
+    (*piPhrase)++;
+  }
+  return rc;
+}
+
+/*
 ** Iterate through all phrase nodes in an FTS3 query, except those that
 ** are part of a sub-tree that is the right-hand-side of a NOT operator.
 ** For each phrase node found, the supplied callback function is invoked.
@@ -106949,285 +113340,387 @@
 */
 static int fts3ExprIterate(
   Fts3Expr *pExpr,                /* Expression to iterate phrases of */
-  int (*x)(Fts3Expr *, void *),   /* Callback function to invoke for phrases */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
   void *pCtx                      /* Second argument to pass to callback */
 ){
-  int rc;
-  int eType = pExpr->eType;
-  if( eType==FTSQUERY_NOT ){
-    rc = SQLITE_OK;
-  }else if( eType!=FTSQUERY_PHRASE ){
-    assert( pExpr->pLeft && pExpr->pRight );
-    rc = fts3ExprIterate(pExpr->pLeft, x, pCtx);
-    if( rc==SQLITE_OK ){
-      rc = fts3ExprIterate(pExpr->pRight, x, pCtx);
-    }
-  }else{
-    rc = x(pExpr, pCtx);
-  }
-  return rc;
+  int iPhrase = 0;                /* Variable used as the phrase counter */
+  return fts3ExprIterate2(pExpr, &iPhrase, x, pCtx);
 }
 
-typedef struct LoadDoclistCtx LoadDoclistCtx;
-struct LoadDoclistCtx {
-  Fts3Table *pTab;                /* FTS3 Table */
-  int nPhrase;                    /* Number of phrases so far */
-};
-
-static int fts3ExprLoadDoclistsCb(Fts3Expr *pExpr, void *ctx){
+/*
+** The argument to this function is always a phrase node. Its doclist 
+** (Fts3Expr.aDoclist[]) and the doclists associated with all phrase nodes
+** to the left of this one in the query tree have already been loaded.
+**
+** If this phrase node is part of a series of phrase nodes joined by 
+** NEAR operators (and is not the left-most of said series), then elements are
+** removed from the phrases doclist consistent with the NEAR restriction. If
+** required, elements may be removed from the doclists of phrases to the
+** left of this one that are part of the same series of NEAR operator 
+** connected phrases.
+**
+** If an OOM error occurs, SQLITE_NOMEM is returned. Otherwise, SQLITE_OK.
+*/
+static int fts3ExprNearTrim(Fts3Expr *pExpr){
   int rc = SQLITE_OK;
-  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
-  p->nPhrase++;
-  if( pExpr->isLoaded==0 ){
-    rc = sqlite3Fts3ExprLoadDoclist(p->pTab, pExpr);
-    pExpr->isLoaded = 1;
-    if( rc==SQLITE_OK && pExpr->aDoclist ){
-      pExpr->pCurrent = pExpr->aDoclist;
-      pExpr->pCurrent += sqlite3Fts3GetVarint(pExpr->pCurrent,&pExpr->iCurrent);
-    }
-  }
-  return rc;
-}
+  Fts3Expr *pParent = pExpr->pParent;
 
-static int fts3ExprLoadDoclists(Fts3Cursor *pCsr, int *pnPhrase){
-  int rc;
-  LoadDoclistCtx sCtx = {0, 0};
-  sCtx.pTab = (Fts3Table *)pCsr->base.pVtab;
-  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb, (void *)&sCtx);
-  *pnPhrase = sCtx.nPhrase;
+  assert( pExpr->eType==FTSQUERY_PHRASE );
+  while( rc==SQLITE_OK
+   && pParent 
+   && pParent->eType==FTSQUERY_NEAR 
+   && pParent->pRight==pExpr 
+  ){
+    /* This expression (pExpr) is the right-hand-side of a NEAR operator. 
+    ** Find the expression to the left of the same operator.
+    */
+    int nNear = pParent->nNear;
+    Fts3Expr *pLeft = pParent->pLeft;
+
+    if( pLeft->eType!=FTSQUERY_PHRASE ){
+      assert( pLeft->eType==FTSQUERY_NEAR );
+      assert( pLeft->pRight->eType==FTSQUERY_PHRASE );
+      pLeft = pLeft->pRight;
+    }
+
+    rc = sqlite3Fts3ExprNearTrim(pLeft, pExpr, nNear);
+
+    pExpr = pLeft;
+    pParent = pExpr->pParent;
+  }
+
   return rc;
 }
 
 /*
-** Each call to this function populates a chunk of a snippet-buffer 
-** SNIPPET_BUFFER_CHUNK bytes in size.
-**
-** Return true if the end of the data has been reached (and all subsequent
-** calls to fts3LoadSnippetBuffer() with the same arguments will be no-ops), 
-** or false otherwise.
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
 */
-static int fts3LoadSnippetBuffer(
-  int iPos,                       /* Document token offset to load data for */
-  u8 *aBuffer,                    /* Circular snippet buffer to populate */
-  int nList,                      /* Number of position lists in appList */
-  char **apList,                  /* IN/OUT: nList position list pointers */
-  int *aiPrev                     /* IN/OUT: Previous positions read */
-){
-  int i;
-  int nFin = 0;
+static int fts3ExprLoadDoclistsCb1(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  int rc = SQLITE_OK;
+  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
 
-  assert( (iPos&(SNIPPET_BUFFER_CHUNK-1))==0 );
+  UNUSED_PARAMETER(iPhrase);
 
-  memset(&aBuffer[iPos&SNIPPET_BUFFER_MASK], 0, SNIPPET_BUFFER_CHUNK);
+  p->nPhrase++;
+  p->nToken += pExpr->pPhrase->nToken;
 
-  for(i=0; i<nList; i++){
-    int iPrev = aiPrev[i];
-    char *pList = apList[i];
-
-    if( !pList ){
-      nFin++;
-      continue;
+  if( pExpr->isLoaded==0 ){
+    rc = sqlite3Fts3ExprLoadDoclist(p->pTab, pExpr);
+    pExpr->isLoaded = 1;
+    if( rc==SQLITE_OK ){
+      rc = fts3ExprNearTrim(pExpr);
     }
-
-    while( iPrev<(iPos+SNIPPET_BUFFER_CHUNK) ){
-      if( iPrev>=iPos ){
-        aBuffer[iPrev&SNIPPET_BUFFER_MASK] = (u8)(i+1);
-      }
-      if( 0==((*pList)&0xFE) ){
-        nFin++;
-        break;
-      }
-      fts3GetDeltaPosition(&pList, &iPrev); 
-    }
-
-    aiPrev[i] = iPrev;
-    apList[i] = pList;
   }
 
-  return (nFin==nList);
+  return rc;
 }
 
-typedef struct SnippetCtx SnippetCtx;
-struct SnippetCtx {
-  Fts3Cursor *pCsr;
-  int iCol;
-  int iPhrase;
-  int *aiPrev;
-  int *anToken;
-  char **apList;
-};
-
-static int fts3SnippetFindPositions(Fts3Expr *pExpr, void *ctx){
-  SnippetCtx *p = (SnippetCtx *)ctx;
-  int iPhrase = p->iPhrase++;
-  char *pCsr;
-
-  p->anToken[iPhrase] = pExpr->pPhrase->nToken;
-  pCsr = sqlite3Fts3FindPositions(pExpr, p->pCsr->iPrevId, p->iCol);
-
-  if( pCsr ){
-    int iVal;
-    pCsr += sqlite3Fts3GetVarint32(pCsr, &iVal);
-    p->apList[iPhrase] = pCsr;
-    p->aiPrev[iPhrase] = iVal-2;
+/*
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
+*/
+static int fts3ExprLoadDoclistsCb2(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  UNUSED_PARAMETER(iPhrase);
+  UNUSED_PARAMETER(ctx);
+  if( pExpr->aDoclist ){
+    pExpr->pCurrent = pExpr->aDoclist;
+    pExpr->iCurrent = 0;
+    pExpr->pCurrent += sqlite3Fts3GetVarint(pExpr->pCurrent, &pExpr->iCurrent);
   }
   return SQLITE_OK;
 }
 
-static void fts3SnippetCnt(
-  int iIdx, 
-  int nSnippet, 
-  int *anCnt, 
-  u8 *aBuffer,
-  int *anToken,
-  u64 *pHlmask
+/*
+** Load the doclists for each phrase in the query associated with FTS3 cursor
+** pCsr. 
+**
+** If pnPhrase is not NULL, then *pnPhrase is set to the number of matchable 
+** phrases in the expression (all phrases except those directly or 
+** indirectly descended from the right-hand-side of a NOT operator). If 
+** pnToken is not NULL, then it is set to the number of tokens in all
+** matchable phrases of the expression.
+*/
+static int fts3ExprLoadDoclists(
+  Fts3Cursor *pCsr,               /* Fts3 cursor for current query */
+  int *pnPhrase,                  /* OUT: Number of phrases in query */
+  int *pnToken                    /* OUT: Number of tokens in query */
 ){
-  int iSub =  (iIdx-1)&SNIPPET_BUFFER_MASK;
-  int iAdd =  (iIdx+nSnippet-1)&SNIPPET_BUFFER_MASK;
-  int iSub2 = (iIdx+(nSnippet/3)-1)&SNIPPET_BUFFER_MASK;
-  int iAdd2 = (iIdx+(nSnippet*2/3)-1)&SNIPPET_BUFFER_MASK;
+  int rc;                         /* Return Code */
+  LoadDoclistCtx sCtx = {0,0,0};  /* Context for fts3ExprIterate() */
+  sCtx.pTab = (Fts3Table *)pCsr->base.pVtab;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb1, (void *)&sCtx);
+  if( rc==SQLITE_OK ){
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb2, 0);
+  }
+  if( pnPhrase ) *pnPhrase = sCtx.nPhrase;
+  if( pnToken ) *pnToken = sCtx.nToken;
+  return rc;
+}
 
-  u64 h = *pHlmask;
+/*
+** Advance the position list iterator specified by the first two 
+** arguments so that it points to the first element with a value greater
+** than or equal to parameter iNext.
+*/
+static void fts3SnippetAdvance(char **ppIter, int *piIter, int iNext){
+  char *pIter = *ppIter;
+  if( pIter ){
+    int iIter = *piIter;
 
-  anCnt[ aBuffer[iSub]  ]--;
-  anCnt[ aBuffer[iSub2] ]--;
-  anCnt[ aBuffer[iAdd]  ]++;
-  anCnt[ aBuffer[iAdd2] ]++;
+    while( iIter<iNext ){
+      if( 0==(*pIter & 0xFE) ){
+        iIter = -1;
+        pIter = 0;
+        break;
+      }
+      fts3GetDeltaPosition(&pIter, &iIter);
+    }
 
-  h = h >> 1;
-  if( aBuffer[iAdd] ){
-    int j;
-    for(j=anToken[aBuffer[iAdd]-1]; j>=1; j--){
-      h |= (u64)1 << (nSnippet-j);
+    *piIter = iIter;
+    *ppIter = pIter;
+  }
+}
+
+/*
+** Advance the snippet iterator to the next candidate snippet.
+*/
+static int fts3SnippetNextCandidate(SnippetIter *pIter){
+  int i;                          /* Loop counter */
+
+  if( pIter->iCurrent<0 ){
+    /* The SnippetIter object has just been initialized. The first snippet
+    ** candidate always starts at offset 0 (even if this candidate has a
+    ** score of 0.0).
+    */
+    pIter->iCurrent = 0;
+
+    /* Advance the 'head' iterator of each phrase to the first offset that
+    ** is greater than or equal to (iNext+nSnippet).
+    */
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, pIter->nSnippet);
+    }
+  }else{
+    int iStart;
+    int iEnd = 0x7FFFFFFF;
+
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      if( pPhrase->pHead && pPhrase->iHead<iEnd ){
+        iEnd = pPhrase->iHead;
+      }
+    }
+    if( iEnd==0x7FFFFFFF ){
+      return 1;
+    }
+
+    pIter->iCurrent = iStart = iEnd - pIter->nSnippet + 1;
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, iEnd+1);
+      fts3SnippetAdvance(&pPhrase->pTail, &pPhrase->iTail, iStart);
     }
   }
-  *pHlmask = h;
+
+  return 0;
 }
 
-static int fts3SnippetScore(int n, int *anCnt){
-  int j;
-  int iScore = 0;
-  for(j=1; j<=n; j++){
-    int nCnt = anCnt[j];
-    iScore += nCnt + (nCnt ? 1000 : 0);
+/*
+** Retrieve information about the current candidate snippet of snippet 
+** iterator pIter.
+*/
+static void fts3SnippetDetails(
+  SnippetIter *pIter,             /* Snippet iterator */
+  u64 mCovered,                   /* Bitmask of phrases already covered */
+  int *piToken,                   /* OUT: First token of proposed snippet */
+  int *piScore,                   /* OUT: "Score" for this snippet */
+  u64 *pmCover,                   /* OUT: Bitmask of phrases covered */
+  u64 *pmHighlight                /* OUT: Bitmask of terms to highlight */
+){
+  int iStart = pIter->iCurrent;   /* First token of snippet */
+  int iScore = 0;                 /* Score of this snippet */
+  int i;                          /* Loop counter */
+  u64 mCover = 0;                 /* Mask of phrases covered by this snippet */
+  u64 mHighlight = 0;             /* Mask of tokens to highlight in snippet */
+
+  for(i=0; i<pIter->nPhrase; i++){
+    SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+    if( pPhrase->pTail ){
+      char *pCsr = pPhrase->pTail;
+      int iCsr = pPhrase->iTail;
+
+      while( iCsr<(iStart+pIter->nSnippet) ){
+        int j;
+        u64 mPhrase = (u64)1 << i;
+        u64 mPos = (u64)1 << (iCsr - iStart);
+        assert( iCsr>=iStart );
+        if( (mCover|mCovered)&mPhrase ){
+          iScore++;
+        }else{
+          iScore += 1000;
+        }
+        mCover |= mPhrase;
+
+        for(j=0; j<pPhrase->nToken; j++){
+          mHighlight |= (mPos>>j);
+        }
+
+        if( 0==(*pCsr & 0x0FE) ) break;
+        fts3GetDeltaPosition(&pCsr, &iCsr);
+      }
+    }
   }
-  return iScore;
+
+  /* Set the output variables before returning. */
+  *piToken = iStart;
+  *piScore = iScore;
+  *pmCover = mCover;
+  *pmHighlight = mHighlight;
 }
 
+/*
+** This function is an fts3ExprIterate() callback used by fts3BestSnippet().
+** Each invocation populates an element of the SnippetIter.aPhrase[] array.
+*/
+static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  SnippetIter *p = (SnippetIter *)ctx;
+  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
+  char *pCsr;
+
+  pPhrase->nToken = pExpr->pPhrase->nToken;
+
+  pCsr = sqlite3Fts3FindPositions(pExpr, p->pCsr->iPrevId, p->iCol);
+  if( pCsr ){
+    int iFirst = 0;
+    pPhrase->pList = pCsr;
+    fts3GetDeltaPosition(&pCsr, &iFirst);
+    pPhrase->pHead = pCsr;
+    pPhrase->pTail = pCsr;
+    pPhrase->iHead = iFirst;
+    pPhrase->iTail = iFirst;
+  }else{
+    assert( pPhrase->pList==0 && pPhrase->pHead==0 && pPhrase->pTail==0 );
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Select the fragment of text consisting of nFragment contiguous tokens 
+** from column iCol that represent the "best" snippet. The best snippet
+** is the snippet with the highest score, where scores are calculated
+** by adding:
+**
+**   (a) +1 point for each occurence of a matchable phrase in the snippet.
+**
+**   (b) +1000 points for the first occurence of each matchable phrase in 
+**       the snippet for which the corresponding mCovered bit is not set.
+**
+** The selected snippet parameters are stored in structure *pFragment before
+** returning. The score of the selected snippet is stored in *piScore
+** before returning.
+*/
 static int fts3BestSnippet(
   int nSnippet,                   /* Desired snippet length */
   Fts3Cursor *pCsr,               /* Cursor to create snippet for */
   int iCol,                       /* Index of column to create snippet from */
-  int *piPos,                     /* OUT: Starting token for best snippet */
-  u64 *pHlmask                    /* OUT: Highlight mask for best snippet */
+  u64 mCovered,                   /* Mask of phrases already covered */
+  u64 *pmSeen,                    /* IN/OUT: Mask of phrases seen */
+  SnippetFragment *pFragment,     /* OUT: Best snippet found */
+  int *piScore                    /* OUT: Score of snippet pFragment */
 ){
   int rc;                         /* Return Code */
-  u8 aBuffer[SNIPPET_BUFFER_SIZE];/* Circular snippet buffer */
-  int *aiPrev;                    /* Used by fts3LoadSnippetBuffer() */
-  int *anToken;                   /* Number of tokens in each phrase */
-  char **apList;                  /* Array of position lists */
-  int *anCnt;                     /* Running totals of phrase occurences */
-  int nList;
+  int nList;                      /* Number of phrases in expression */
+  SnippetIter sIter;              /* Iterates through snippet candidates */
+  int nByte;                      /* Number of bytes of space to allocate */
+  int iBestScore = -1;            /* Best snippet score found so far */
+  int i;                          /* Loop counter */
 
-  int i;
-
-  u64 hlmask = 0;                 /* Current mask of highlighted terms */
-  u64 besthlmask = 0;             /* Mask of highlighted terms for iBestPos */
-  int iBestPos = 0;               /* Starting position of 'best' snippet */
-  int iBestScore = 0;             /* Score of best snippet higher->better */
-  SnippetCtx sCtx;
+  memset(&sIter, 0, sizeof(sIter));
 
   /* Iterate through the phrases in the expression to count them. The same
   ** callback makes sure the doclists are loaded for each phrase.
   */
-  rc = fts3ExprLoadDoclists(pCsr, &nList);
+  rc = fts3ExprLoadDoclists(pCsr, &nList, 0);
   if( rc!=SQLITE_OK ){
     return rc;
   }
 
   /* Now that it is known how many phrases there are, allocate and zero
-  ** the required arrays using malloc().
+  ** the required space using malloc().
   */
-  apList = sqlite3_malloc(
-      sizeof(u8*)*nList +         /* apList */
-      sizeof(int)*(nList) +       /* anToken */
-      sizeof(int)*nList +         /* aiPrev */
-      sizeof(int)*(nList+1)       /* anCnt */
-  );
-  if( !apList ){
+  nByte = sizeof(SnippetPhrase) * nList;
+  sIter.aPhrase = (SnippetPhrase *)sqlite3_malloc(nByte);
+  if( !sIter.aPhrase ){
     return SQLITE_NOMEM;
   }
-  memset(apList, 0, sizeof(u8*)*nList+sizeof(int)*nList+sizeof(int)*nList);
-  anToken = (int *)&apList[nList];
-  aiPrev = &anToken[nList];
-  anCnt = &aiPrev[nList];
+  memset(sIter.aPhrase, 0, nByte);
 
-  /* Initialize the contents of the aiPrev and aiList arrays. */
-  sCtx.pCsr = pCsr;
-  sCtx.iCol = iCol;
-  sCtx.apList = apList;
-  sCtx.aiPrev = aiPrev;
-  sCtx.anToken = anToken;
-  sCtx.iPhrase = 0;
-  (void)fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void *)&sCtx);
+  /* Initialize the contents of the SnippetIter object. Then iterate through
+  ** the set of phrases in the expression to populate the aPhrase[] array.
+  */
+  sIter.pCsr = pCsr;
+  sIter.iCol = iCol;
+  sIter.nSnippet = nSnippet;
+  sIter.nPhrase = nList;
+  sIter.iCurrent = -1;
+  (void)fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void *)&sIter);
 
-  /* Load the first two chunks of data into the buffer. */
-  memset(aBuffer, 0, SNIPPET_BUFFER_SIZE);
-  fts3LoadSnippetBuffer(0, aBuffer, nList, apList, aiPrev);
-  fts3LoadSnippetBuffer(SNIPPET_BUFFER_CHUNK, aBuffer, nList, apList, aiPrev);
-
-  /* Set the initial contents of the highlight-mask and anCnt[] array. */
-  for(i=1-nSnippet; i<=0; i++){
-    fts3SnippetCnt(i, nSnippet, anCnt, aBuffer, anToken, &hlmask);
+  /* Set the *pmSeen output variable. */
+  for(i=0; i<nList; i++){
+    if( sIter.aPhrase[i].pHead ){
+      *pmSeen |= (u64)1 << i;
+    }
   }
-  iBestScore = fts3SnippetScore(nList, anCnt);
-  besthlmask = hlmask;
-  iBestPos = 0;
 
-  for(i=1; 1; i++){
+  /* Loop through all candidate snippets. Store the best snippet in 
+  ** *pFragment. Store its associated 'score' in iBestScore.
+  */
+  pFragment->iCol = iCol;
+  while( !fts3SnippetNextCandidate(&sIter) ){
+    int iPos;
     int iScore;
-
-    if( 0==(i&(SNIPPET_BUFFER_CHUNK-1)) ){
-      int iLoad = i + SNIPPET_BUFFER_CHUNK;
-      if( fts3LoadSnippetBuffer(iLoad, aBuffer, nList, apList, aiPrev) ) break;
-    }
-
-    /* Figure out how highly a snippet starting at token offset i scores
-    ** according to fts3SnippetScore(). If it is higher than any previously
-    ** considered position, save the current position, score and hlmask as 
-    ** the best snippet candidate found so far.
-    */
-    fts3SnippetCnt(i, nSnippet, anCnt, aBuffer, anToken, &hlmask);
-    iScore = fts3SnippetScore(nList, anCnt);
+    u64 mCover;
+    u64 mHighlight;
+    fts3SnippetDetails(&sIter, mCovered, &iPos, &iScore, &mCover, &mHighlight);
+    assert( iScore>=0 );
     if( iScore>iBestScore ){
-      iBestPos = i;
+      pFragment->iPos = iPos;
+      pFragment->hlmask = mHighlight;
+      pFragment->covered = mCover;
       iBestScore = iScore;
-      besthlmask = hlmask;
     }
   }
 
-  sqlite3_free(apList);
-  *piPos = iBestPos;
-  *pHlmask = besthlmask;
+  sqlite3_free(sIter.aPhrase);
+  *piScore = iBestScore;
   return SQLITE_OK;
 }
 
-typedef struct StrBuffer StrBuffer;
-struct StrBuffer {
-  char *z;
-  int n;
-  int nAlloc;
-};
 
+/*
+** Append a string to the string-buffer passed as the first argument.
+**
+** If nAppend is negative, then the length of the string zAppend is
+** determined using strlen().
+*/
 static int fts3StringAppend(
-  StrBuffer *pStr, 
-  const char *zAppend, 
-  int nAppend
+  StrBuffer *pStr,                /* Buffer to append to */
+  const char *zAppend,            /* Pointer to data to append to buffer */
+  int nAppend                     /* Size of zAppend in bytes (or -1) */
 ){
   if( nAppend<0 ){
     nAppend = (int)strlen(zAppend);
   }
 
+  /* If there is insufficient space allocated at StrBuffer.z, use realloc()
+  ** to grow the buffer until so that it is big enough to accomadate the
+  ** appended data.
+  */
   if( pStr->n+nAppend+1>=pStr->nAlloc ){
     int nAlloc = pStr->nAlloc+nAppend+100;
     char *zNew = sqlite3_realloc(pStr->z, nAlloc);
@@ -107238,6 +113731,7 @@
     pStr->nAlloc = nAlloc;
   }
 
+  /* Append the data to the string buffer. */
   memcpy(&pStr->z[pStr->n], zAppend, nAppend);
   pStr->n += nAppend;
   pStr->z[pStr->n] = '\0';
@@ -107245,126 +113739,201 @@
   return SQLITE_OK;
 }
 
+/*
+** The fts3BestSnippet() function often selects snippets that end with a
+** query term. That is, the final term of the snippet is always a term
+** that requires highlighting. For example, if 'X' is a highlighted term
+** and '.' is a non-highlighted term, BestSnippet() may select:
+**
+**     ........X.....X
+**
+** This function "shifts" the beginning of the snippet forward in the 
+** document so that there are approximately the same number of 
+** non-highlighted terms to the right of the final highlighted term as there
+** are to the left of the first highlighted term. For example, to this:
+**
+**     ....X.....X....
+**
+** This is done as part of extracting the snippet text, not when selecting
+** the snippet. Snippet selection is done based on doclists only, so there
+** is no way for fts3BestSnippet() to know whether or not the document 
+** actually contains terms that follow the final highlighted term. 
+*/
+static int fts3SnippetShift(
+  Fts3Table *pTab,                /* FTS3 table snippet comes from */
+  int nSnippet,                   /* Number of tokens desired for snippet */
+  const char *zDoc,               /* Document text to extract snippet from */
+  int nDoc,                       /* Size of buffer zDoc in bytes */
+  int *piPos,                     /* IN/OUT: First token of snippet */
+  u64 *pHlmask                    /* IN/OUT: Mask of tokens to highlight */
+){
+  u64 hlmask = *pHlmask;          /* Local copy of initial highlight-mask */
+
+  if( hlmask ){
+    int nLeft;                    /* Tokens to the left of first highlight */
+    int nRight;                   /* Tokens to the right of last highlight */
+    int nDesired;                 /* Ideal number of tokens to shift forward */
+
+    for(nLeft=0; !(hlmask & ((u64)1 << nLeft)); nLeft++);
+    for(nRight=0; !(hlmask & ((u64)1 << (nSnippet-1-nRight))); nRight++);
+    nDesired = (nLeft-nRight)/2;
+
+    /* Ideally, the start of the snippet should be pushed forward in the
+    ** document nDesired tokens. This block checks if there are actually
+    ** nDesired tokens to the right of the snippet. If so, *piPos and
+    ** *pHlMask are updated to shift the snippet nDesired tokens to the
+    ** right. Otherwise, the snippet is shifted by the number of tokens
+    ** available.
+    */
+    if( nDesired>0 ){
+      int nShift;                 /* Number of tokens to shift snippet by */
+      int iCurrent = 0;           /* Token counter */
+      int rc;                     /* Return Code */
+      sqlite3_tokenizer_module *pMod;
+      sqlite3_tokenizer_cursor *pC;
+      pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+
+      /* Open a cursor on zDoc/nDoc. Check if there are (nSnippet+nDesired)
+      ** or more tokens in zDoc/nDoc.
+      */
+      rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      pC->pTokenizer = pTab->pTokenizer;
+      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
+        const char *ZDUMMY; int DUMMY1, DUMMY2, DUMMY3;
+        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
+      }
+      pMod->xClose(pC);
+      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }
+
+      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
+      assert( nShift<=nDesired );
+      if( nShift>0 ){
+        *piPos += nShift;
+        *pHlmask = hlmask >> nShift;
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Extract the snippet text for fragment pFragment from cursor pCsr and
+** append it to string buffer pOut.
+*/
 static int fts3SnippetText(
   Fts3Cursor *pCsr,               /* FTS3 Cursor */
-  const char *zDoc,               /* Document to extract snippet from */
-  int nDoc,                       /* Size of zDoc in bytes */
+  SnippetFragment *pFragment,     /* Snippet to extract */
+  int iFragment,                  /* Fragment number */
+  int isLast,                     /* True for final fragment in snippet */
   int nSnippet,                   /* Number of tokens in extracted snippet */
-  int iPos,                       /* Index of first document token in snippet */
-  u64 hlmask,                     /* Bitmask of terms to highlight in snippet */
   const char *zOpen,              /* String inserted before highlighted term */
   const char *zClose,             /* String inserted after highlighted term */
-  const char *zEllipsis,
-  char **pzSnippet                /* OUT: Snippet text */
+  const char *zEllipsis,          /* String inserted between snippets */
+  StrBuffer *pOut                 /* Write output here */
 ){
   Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
   int rc;                         /* Return code */
-  int iCurrent = 0;
-  int iStart = 0;
-  int iEnd;
-
+  const char *zDoc;               /* Document text to extract snippet from */
+  int nDoc;                       /* Size of zDoc in bytes */
+  int iCurrent = 0;               /* Current token number of document */
+  int iEnd = 0;                   /* Byte offset of end of current token */
+  int isShiftDone = 0;            /* True after snippet is shifted */
+  int iPos = pFragment->iPos;     /* First token of snippet */
+  u64 hlmask = pFragment->hlmask; /* Highlight-mask for snippet */
+  int iCol = pFragment->iCol+1;   /* Query column to extract text from */
   sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
   sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
-  const char *ZDUMMY;             /* Dummy arguments used with tokenizer */
-  int DUMMY1, DUMMY2, DUMMY3;     /* Dummy arguments used with tokenizer */
+  const char *ZDUMMY;             /* Dummy argument used with tokenizer */
+  int DUMMY1;                     /* Dummy argument used with tokenizer */
+  
+  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol);
+  if( zDoc==0 ){
+    if( sqlite3_column_type(pCsr->pStmt, iCol)!=SQLITE_NULL ){
+      return SQLITE_NOMEM;
+    }
+    return SQLITE_OK;
+  }
+  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol);
 
-  StrBuffer res = {0, 0, 0};   /* Result string */
-
-  /* Open a token cursor on the document. Read all tokens up to and 
-  ** including token iPos (the first token of the snippet). Set variable
-  ** iStart to the byte offset in zDoc of the start of token iPos.
-  */
+  /* Open a token cursor on the document. */
   pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
   rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
-  while( rc==SQLITE_OK && iCurrent<iPos ){
-    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iStart, &DUMMY2, &iCurrent);
+  if( rc!=SQLITE_OK ){
+    return rc;
   }
-  iEnd = iStart;
-
-  if( rc==SQLITE_OK && iStart>0 ){
-    rc = fts3StringAppend(&res, zEllipsis, -1);
-  }
+  pC->pTokenizer = pTab->pTokenizer;
 
   while( rc==SQLITE_OK ){
-    int iBegin;
-    int iFin;
-    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    int iBegin;                   /* Offset in zDoc of start of token */
+    int iFin;                     /* Offset in zDoc of end of token */
+    int isHighlight;              /* True for highlighted terms */
 
-    if( rc==SQLITE_OK ){
-      if( iCurrent>=(iPos+nSnippet) ){
-        rc = SQLITE_DONE;
-      }else{
-        iEnd = iFin;
-        if( hlmask & ((u64)1 << (iCurrent-iPos)) ){
-          if( fts3StringAppend(&res, &zDoc[iStart], iBegin-iStart)
-           || fts3StringAppend(&res, zOpen, -1)
-           || fts3StringAppend(&res, &zDoc[iBegin], iEnd-iBegin)
-           || fts3StringAppend(&res, zClose, -1)
-          ){
-            rc = SQLITE_NOMEM;
-          }
-          iStart = iEnd;
-        }
+    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        /* Special case - the last token of the snippet is also the last token
+        ** of the column. Append any punctuation that occurred between the end
+        ** of the previous token and the end of the document to the output. 
+        ** Then break out of the loop. */
+        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);
       }
+      break;
     }
-  }
-  assert( rc!=SQLITE_OK );
-  if( rc==SQLITE_DONE ){
-    rc = fts3StringAppend(&res, &zDoc[iStart], iEnd-iStart);
-    if( rc==SQLITE_OK ){
-      rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
-      if( rc==SQLITE_OK ){
-        rc = fts3StringAppend(&res, zEllipsis, -1);
-      }else if( rc==SQLITE_DONE ){
-        rc = fts3StringAppend(&res, &zDoc[iEnd], -1);
+    if( iCurrent<iPos ){ continue; }
+
+    if( !isShiftDone ){
+      int n = nDoc - iBegin;
+      rc = fts3SnippetShift(pTab, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask);
+      isShiftDone = 1;
+
+      /* Now that the shift has been done, check if the initial "..." are
+      ** required. They are required if (a) this is not the first fragment,
+      ** or (b) this fragment does not begin at position 0 of its column. 
+      */
+      if( rc==SQLITE_OK && (iPos>0 || iFragment>0) ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
       }
+      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
     }
+
+    if( iCurrent>=(iPos+nSnippet) ){
+      if( isLast ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
+      }
+      break;
+    }
+
+    /* Set isHighlight to true if this term should be highlighted. */
+    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;
+
+    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
+    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);
+
+    iEnd = iFin;
   }
 
   pMod->xClose(pC);
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(res.z);
-  }else{
-    *pzSnippet = res.z;
-  }
   return rc;
 }
 
 
 /*
-** An instance of this structure is used to collect the 'global' part of
-** the matchinfo statistics. The 'global' part consists of the following:
+** This function is used to count the entries in a column-list (a 
+** delta-encoded list of term offsets within a single column of a single 
+** row). When this function is called, *ppCollist should point to the
+** beginning of the first varint in the column-list (the varint that
+** contains the position of the first matching term in the column data).
+** Before returning, *ppCollist is set to point to the first byte after
+** the last varint in the column-list (either the 0x00 signifying the end
+** of the position-list, or the 0x01 that precedes the column number of
+** the next column in the position-list).
 **
-**   1. The number of phrases in the query (nPhrase).
-**
-**   2. The number of columns in the FTS3 table (nCol).
-**
-**   3. A matrix of (nPhrase*nCol) integers containing the sum of the
-**      number of hits for each phrase in each column across all rows
-**      of the table.
-**
-** The total size of the global matchinfo array, assuming the number of
-** columns is N and the number of phrases is P is:
-**
-**   2 + P*(N+1)
-**
-** The number of hits for the 3rd phrase in the second column is found
-** using the expression:
-**
-**   aGlobal[2 + P*(1+2) + 1]
-*/
-typedef struct MatchInfo MatchInfo;
-struct MatchInfo {
-  Fts3Table *pTab;                /* FTS3 Table */
-  Fts3Cursor *pCursor;            /* FTS3 Cursor */
-  int iPhrase;                    /* Number of phrases so far */
-  int nCol;                       /* Number of columns in table */
-  u32 *aGlobal;                   /* Pre-allocated buffer */
-};
-
-/*
-** This function is used to count the entries in a column-list (delta-encoded
-** list of term offsets within a single column of a single row).
+** The number of elements in the column-list is returned.
 */
 static int fts3ColumnlistCount(char **ppCollist){
   char *pEnd = *ppCollist;
@@ -107381,15 +113950,21 @@
   return nEntry;
 }
 
-static void fts3LoadColumnlistCounts(char **pp, u32 *aOut){
+static void fts3LoadColumnlistCounts(char **pp, u32 *aOut, int isGlobal){
   char *pCsr = *pp;
   while( *pCsr ){
+    int nHit;
     sqlite3_int64 iCol = 0;
     if( *pCsr==0x01 ){
       pCsr++;
       pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
     }
-    aOut[iCol] += fts3ColumnlistCount(&pCsr);
+    nHit = fts3ColumnlistCount(&pCsr);
+    assert( nHit>0 );
+    if( isGlobal ){
+      aOut[iCol*3+1]++;
+    }
+    aOut[iCol*3] += nHit;
   }
   pCsr++;
   *pp = pCsr;
@@ -107397,16 +113972,18 @@
 
 /*
 ** fts3ExprIterate() callback used to collect the "global" matchinfo stats
-** for a single query.
+** for a single query. The "global" stats are those elements of the matchinfo
+** array that are constant for all rows returned by the current query.
 */
 static int fts3ExprGlobalMatchinfoCb(
   Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
   void *pCtx                      /* Pointer to MatchInfo structure */
 ){
   MatchInfo *p = (MatchInfo *)pCtx;
   char *pCsr;
   char *pEnd;
-  const int iStart = 2 + p->nCol*p->iPhrase;
+  const int iStart = 2 + (iPhrase * p->nCol * 3) + 1;
 
   assert( pExpr->isLoaded );
 
@@ -107414,84 +113991,108 @@
   pCsr = pExpr->aDoclist;
   pEnd = &pExpr->aDoclist[pExpr->nDoclist];
   while( pCsr<pEnd ){
-    while( *pCsr++ & 0x80 );
-    fts3LoadColumnlistCounts(&pCsr, &p->aGlobal[iStart]);
-  }
-
-  p->iPhrase++;
-  return SQLITE_OK;
-}
-
-static int fts3ExprLocalMatchinfoCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  void *pCtx                      /* Pointer to MatchInfo structure */
-){
-  MatchInfo *p = (MatchInfo *)pCtx;
-  int iPhrase = p->iPhrase++;
-
-  if( pExpr->aDoclist ){
-    char *pCsr;
-    int iOffset = 2 + p->nCol*(p->aGlobal[0]+iPhrase);
-
-    memset(&p->aGlobal[iOffset], 0, p->nCol*sizeof(u32));
-    pCsr = sqlite3Fts3FindPositions(pExpr, p->pCursor->iPrevId, -1);
-    if( pCsr ) fts3LoadColumnlistCounts(&pCsr, &p->aGlobal[iOffset]);
+    while( *pCsr++ & 0x80 );      /* Skip past docid. */
+    fts3LoadColumnlistCounts(&pCsr, &p->aMatchinfo[iStart], 1);
   }
 
   return SQLITE_OK;
 }
 
 /*
-** Populate pCsr->aMatchinfo[] with data for the current row. The 'matchinfo'
-** data is an array of 32-bit unsigned integers (C type u32).
+** fts3ExprIterate() callback used to collect the "local" matchinfo stats
+** for a single query. The "local" stats are those elements of the matchinfo
+** array that are different for each row returned by the query.
 */
-static int fts3GetMatchinfo(Fts3Cursor *pCsr){
-  MatchInfo g;
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  if( pCsr->aMatchinfo==0 ){
-    int rc;
-    int nPhrase;
-    int nMatchinfo;
+static int fts3ExprLocalMatchinfoCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  MatchInfo *p = (MatchInfo *)pCtx;
 
-    g.pTab = pTab;
-    g.nCol = pTab->nColumn;
-    g.iPhrase = 0;
-    rc = fts3ExprLoadDoclists(pCsr, &nPhrase);
-    if( rc!=SQLITE_OK ){
-      return rc;
+  if( pExpr->aDoclist ){
+    char *pCsr;
+    int iStart = 2 + (iPhrase * p->nCol * 3);
+    int i;
+
+    for(i=0; i<p->nCol; i++) p->aMatchinfo[iStart+i*3] = 0;
+
+    pCsr = sqlite3Fts3FindPositions(pExpr, p->pCursor->iPrevId, -1);
+    if( pCsr ){
+      fts3LoadColumnlistCounts(&pCsr, &p->aMatchinfo[iStart], 0);
     }
-
-    nMatchinfo = 2 + 2*g.nCol*nPhrase;
-
-    g.iPhrase = 0;
-    g.aGlobal = (u32 *)sqlite3_malloc(sizeof(u32)*nMatchinfo);
-    if( !g.aGlobal ){ 
-      return SQLITE_NOMEM;
-    }
-    memset(g.aGlobal, 0, sizeof(u32)*nMatchinfo);
-
-    g.aGlobal[0] = nPhrase;
-    g.aGlobal[1] = g.nCol;
-    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprGlobalMatchinfoCb, (void *)&g);
-
-    pCsr->aMatchinfo = g.aGlobal;
-  }
-
-  g.pTab = pTab;
-  g.pCursor = pCsr;
-  g.nCol = pTab->nColumn;
-  g.iPhrase = 0;
-  g.aGlobal = pCsr->aMatchinfo;
-
-  if( pCsr->isMatchinfoOk ){
-    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLocalMatchinfoCb, (void *)&g);
-    pCsr->isMatchinfoOk = 0;
   }
 
   return SQLITE_OK;
 }
 
-SQLITE_PRIVATE void sqlite3Fts3Snippet2(
+/*
+** Populate pCsr->aMatchinfo[] with data for the current row. The 
+** 'matchinfo' data is an array of 32-bit unsigned integers (C type u32).
+*/
+static int fts3GetMatchinfo(Fts3Cursor *pCsr){
+  MatchInfo sInfo;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+
+  sInfo.pCursor = pCsr;
+  sInfo.nCol = pTab->nColumn;
+
+  if( pCsr->aMatchinfo==0 ){
+    /* If Fts3Cursor.aMatchinfo[] is NULL, then this is the first time the
+    ** matchinfo function has been called for this query. In this case 
+    ** allocate the array used to accumulate the matchinfo data and
+    ** initialize those elements that are constant for every row.
+    */
+    int nPhrase;                  /* Number of phrases */
+    int nMatchinfo;               /* Number of u32 elements in match-info */
+
+    /* Load doclists for each phrase in the query. */
+    rc = fts3ExprLoadDoclists(pCsr, &nPhrase, 0);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    nMatchinfo = 2 + 3*sInfo.nCol*nPhrase;
+    if( pTab->bHasDocsize ){
+      nMatchinfo += 1 + 2*pTab->nColumn;
+    }
+
+    sInfo.aMatchinfo = (u32 *)sqlite3_malloc(sizeof(u32)*nMatchinfo);
+    if( !sInfo.aMatchinfo ){ 
+      return SQLITE_NOMEM;
+    }
+    memset(sInfo.aMatchinfo, 0, sizeof(u32)*nMatchinfo);
+
+
+    /* First element of match-info is the number of phrases in the query */
+    sInfo.aMatchinfo[0] = nPhrase;
+    sInfo.aMatchinfo[1] = sInfo.nCol;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprGlobalMatchinfoCb,(void*)&sInfo);
+    if( pTab->bHasDocsize ){
+      int ofst = 2 + 3*sInfo.aMatchinfo[0]*sInfo.aMatchinfo[1];
+      rc = sqlite3Fts3MatchinfoDocsizeGlobal(pCsr, &sInfo.aMatchinfo[ofst]);
+    }
+    pCsr->aMatchinfo = sInfo.aMatchinfo;
+    pCsr->isMatchinfoNeeded = 1;
+  }
+
+  sInfo.aMatchinfo = pCsr->aMatchinfo;
+  if( rc==SQLITE_OK && pCsr->isMatchinfoNeeded ){
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLocalMatchinfoCb, (void*)&sInfo);
+    if( pTab->bHasDocsize ){
+      int ofst = 2 + 3*sInfo.aMatchinfo[0]*sInfo.aMatchinfo[1];
+      rc = sqlite3Fts3MatchinfoDocsizeLocal(pCsr, &sInfo.aMatchinfo[ofst]);
+    }
+    pCsr->isMatchinfoNeeded = 0;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of snippet() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Snippet(
   sqlite3_context *pCtx,          /* SQLite function call context */
   Fts3Cursor *pCsr,               /* Cursor object */
   const char *zStart,             /* Snippet start text - "<b>" */
@@ -107500,35 +114101,292 @@
   int iCol,                       /* Extract snippet from this column */
   int nToken                      /* Approximate number of tokens in snippet */
 ){
-  int rc;
-  int iPos = 0;
-  u64 hlmask = 0;
-  char *z = 0;
-  int nDoc;
-  const char *zDoc;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int i;
+  StrBuffer res = {0, 0, 0};
 
-  rc = fts3BestSnippet(nToken, pCsr, iCol, &iPos, &hlmask);
+  /* The returned text includes up to four fragments of text extracted from
+  ** the data in the current row. The first iteration of the for(...) loop
+  ** below attempts to locate a single fragment of text nToken tokens in 
+  ** size that contains at least one instance of all phrases in the query
+  ** expression that appear in the current row. If such a fragment of text
+  ** cannot be found, the second iteration of the loop attempts to locate
+  ** a pair of fragments, and so on.
+  */
+  int nSnippet = 0;               /* Number of fragments in this snippet */
+  SnippetFragment aSnippet[4];    /* Maximum of 4 fragments per snippet */
+  int nFToken = -1;               /* Number of tokens in each fragment */
 
-  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
-  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
-
-  if( rc==SQLITE_OK ){
-    rc = fts3SnippetText(
-        pCsr, zDoc, nDoc, nToken, iPos, hlmask, zStart, zEnd, zEllipsis, &z);
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
   }
+
+  for(nSnippet=1; 1; nSnippet++){
+
+    int iSnip;                    /* Loop counter 0..nSnippet-1 */
+    u64 mCovered = 0;             /* Bitmask of phrases covered by snippet */
+    u64 mSeen = 0;                /* Bitmask of phrases seen by BestSnippet() */
+
+    if( nToken>=0 ){
+      nFToken = (nToken+nSnippet-1) / nSnippet;
+    }else{
+      nFToken = -1 * nToken;
+    }
+
+    for(iSnip=0; iSnip<nSnippet; iSnip++){
+      int iBestScore = -1;        /* Best score of columns checked so far */
+      int iRead;                  /* Used to iterate through columns */
+      SnippetFragment *pFragment = &aSnippet[iSnip];
+
+      memset(pFragment, 0, sizeof(*pFragment));
+
+      /* Loop through all columns of the table being considered for snippets.
+      ** If the iCol argument to this function was negative, this means all
+      ** columns of the FTS3 table. Otherwise, only column iCol is considered.
+      */
+      for(iRead=0; iRead<pTab->nColumn; iRead++){
+        SnippetFragment sF;
+        int iS;
+        if( iCol>=0 && iRead!=iCol ) continue;
+
+        /* Find the best snippet of nFToken tokens in column iRead. */
+        rc = fts3BestSnippet(nFToken, pCsr, iRead, mCovered, &mSeen, &sF, &iS);
+        if( rc!=SQLITE_OK ){
+          goto snippet_out;
+        }
+        if( iS>iBestScore ){
+          *pFragment = sF;
+          iBestScore = iS;
+        }
+      }
+
+      mCovered |= pFragment->covered;
+    }
+
+    /* If all query phrases seen by fts3BestSnippet() are present in at least
+    ** one of the nSnippet snippet fragments, break out of the loop.
+    */
+    assert( (mCovered&mSeen)==mCovered );
+    if( mSeen==mCovered || nSnippet==SizeofArray(aSnippet) ) break;
+  }
+
+  assert( nFToken>0 );
+
+  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
+    rc = fts3SnippetText(pCsr, &aSnippet[i], 
+        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
+    );
+  }
+
+ snippet_out:
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pCtx, rc);
+    sqlite3_free(res.z);
   }else{
-    sqlite3_result_text(pCtx, z, -1, sqlite3_free);
+    sqlite3_result_text(pCtx, res.z, -1, sqlite3_free);
   }
 }
 
+
+typedef struct TermOffset TermOffset;
+typedef struct TermOffsetCtx TermOffsetCtx;
+
+struct TermOffset {
+  char *pList;                    /* Position-list */
+  int iPos;                       /* Position just read from pList */
+  int iOff;                       /* Offset of this term from read positions */
+};
+
+struct TermOffsetCtx {
+  int iCol;                       /* Column of table to populate aTerm for */
+  int iTerm;
+  sqlite3_int64 iDocid;
+  TermOffset *aTerm;
+};
+
+/*
+** This function is an fts3ExprIterate() callback used by sqlite3Fts3Offsets().
+*/
+static int fts3ExprTermOffsetInit(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
+  int nTerm;                      /* Number of tokens in phrase */
+  int iTerm;                      /* For looping through nTerm phrase terms */
+  char *pList;                    /* Pointer to position list for phrase */
+  int iPos = 0;                   /* First position in position-list */
+
+  UNUSED_PARAMETER(iPhrase);
+  pList = sqlite3Fts3FindPositions(pExpr, p->iDocid, p->iCol);
+  nTerm = pExpr->pPhrase->nToken;
+  if( pList ){
+    fts3GetDeltaPosition(&pList, &iPos);
+    assert( iPos>=0 );
+  }
+
+  for(iTerm=0; iTerm<nTerm; iTerm++){
+    TermOffset *pT = &p->aTerm[p->iTerm++];
+    pT->iOff = nTerm-iTerm-1;
+    pT->pList = pList;
+    pT->iPos = iPos;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of offsets() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Offsets(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr                /* Cursor object */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_tokenizer_module const *pMod = pTab->pTokenizer->pModule;
+  const char *ZDUMMY;             /* Dummy argument used with xNext() */
+  int NDUMMY;                     /* Dummy argument used with xNext() */
+  int rc;                         /* Return Code */
+  int nToken;                     /* Number of tokens in query */
+  int iCol;                       /* Column currently being processed */
+  StrBuffer res = {0, 0, 0};      /* Result string */
+  TermOffsetCtx sCtx;             /* Context for fts3ExprTermOffsetInit() */
+
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  memset(&sCtx, 0, sizeof(sCtx));
+  assert( pCsr->isRequireSeek==0 );
+
+  /* Count the number of terms in the query */
+  rc = fts3ExprLoadDoclists(pCsr, 0, &nToken);
+  if( rc!=SQLITE_OK ) goto offsets_out;
+
+  /* Allocate the array of TermOffset iterators. */
+  sCtx.aTerm = (TermOffset *)sqlite3_malloc(sizeof(TermOffset)*nToken);
+  if( 0==sCtx.aTerm ){
+    rc = SQLITE_NOMEM;
+    goto offsets_out;
+  }
+  sCtx.iDocid = pCsr->iPrevId;
+
+  /* Loop through the table columns, appending offset information to 
+  ** string-buffer res for each column.
+  */
+  for(iCol=0; iCol<pTab->nColumn; iCol++){
+    sqlite3_tokenizer_cursor *pC; /* Tokenizer cursor */
+    int iStart;
+    int iEnd;
+    int iCurrent;
+    const char *zDoc;
+    int nDoc;
+
+    /* Initialize the contents of sCtx.aTerm[] for column iCol. There is 
+    ** no way that this operation can fail, so the return code from
+    ** fts3ExprIterate() can be discarded.
+    */
+    sCtx.iCol = iCol;
+    sCtx.iTerm = 0;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprTermOffsetInit, (void *)&sCtx);
+
+    /* Retreive the text stored in column iCol. If an SQL NULL is stored 
+    ** in column iCol, jump immediately to the next iteration of the loop.
+    ** If an OOM occurs while retrieving the data (this can happen if SQLite
+    ** needs to transform the data from utf-16 to utf-8), return SQLITE_NOMEM 
+    ** to the caller. 
+    */
+    zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
+    nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
+    if( zDoc==0 ){
+      if( sqlite3_column_type(pCsr->pStmt, iCol+1)==SQLITE_NULL ){
+        continue;
+      }
+      rc = SQLITE_NOMEM;
+      goto offsets_out;
+    }
+
+    /* Initialize a tokenizer iterator to iterate through column iCol. */
+    rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
+    pC->pTokenizer = pTab->pTokenizer;
+
+    rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+    while( rc==SQLITE_OK ){
+      int i;                      /* Used to loop through terms */
+      int iMinPos = 0x7FFFFFFF;   /* Position of next token */
+      TermOffset *pTerm = 0;      /* TermOffset associated with next token */
+
+      for(i=0; i<nToken; i++){
+        TermOffset *pT = &sCtx.aTerm[i];
+        if( pT->pList && (pT->iPos-pT->iOff)<iMinPos ){
+          iMinPos = pT->iPos-pT->iOff;
+          pTerm = pT;
+        }
+      }
+
+      if( !pTerm ){
+        /* All offsets for this column have been gathered. */
+        break;
+      }else{
+        assert( iCurrent<=iMinPos );
+        if( 0==(0xFE&*pTerm->pList) ){
+          pTerm->pList = 0;
+        }else{
+          fts3GetDeltaPosition(&pTerm->pList, &pTerm->iPos);
+        }
+        while( rc==SQLITE_OK && iCurrent<iMinPos ){
+          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+        }
+        if( rc==SQLITE_OK ){
+          char aBuffer[64];
+          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
+              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
+          );
+          rc = fts3StringAppend(&res, aBuffer, -1);
+        }else if( rc==SQLITE_DONE ){
+          rc = SQLITE_CORRUPT;
+        }
+      }
+    }
+    if( rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
+    }
+
+    pMod->xClose(pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
+  }
+
+ offsets_out:
+  sqlite3_free(sCtx.aTerm);
+  assert( rc!=SQLITE_DONE );
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx,  rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, res.n-1, sqlite3_free);
+  }
+  return;
+}
+
+/*
+** Implementation of matchinfo() function.
+*/
 SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *pContext, Fts3Cursor *pCsr){
-  int rc = fts3GetMatchinfo(pCsr);
+  int rc;
+  if( !pCsr->pExpr ){
+    sqlite3_result_blob(pContext, "", 0, SQLITE_STATIC);
+    return;
+  }
+  rc = fts3GetMatchinfo(pCsr);
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pContext, rc);
   }else{
-    int n = sizeof(u32)*(2+pCsr->aMatchinfo[0]*pCsr->aMatchinfo[1]*2);
+    Fts3Table *pTab = (Fts3Table*)pCsr->base.pVtab;
+    int n = sizeof(u32)*(2+pCsr->aMatchinfo[0]*pCsr->aMatchinfo[1]*3);
+    if( pTab->bHasDocsize ){
+      n += sizeof(u32)*(1 + 2*pTab->nColumn);
+    }
     sqlite3_result_blob(pContext, pCsr->aMatchinfo, n, SQLITE_TRANSIENT);
   }
 }
@@ -107958,6 +114816,7 @@
   rc = sqlite3_step(pRtree->pReadNode);
   if( rc==SQLITE_ROW ){
     const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);
+    assert( sqlite3_column_bytes(pRtree->pReadNode, 0)==pRtree->iNodeSize );
     memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
     nodeReference(pParent);
   }else{
@@ -110017,6 +116876,7 @@
       }
       rc = sqlite3_reset(pRtree->pReadRowid);
     }
+    *pRowid = cell.iRowid;
 
     if( rc==SQLITE_OK ){
       rc = ChooseLeaf(pRtree, &cell, 0, &pLeaf);
@@ -110154,31 +117014,69 @@
 }
 
 /*
-** This routine queries database handle db for the page-size used by
-** database zDb. If successful, the page-size in bytes is written to
-** *piPageSize and SQLITE_OK returned. Otherwise, and an SQLite error 
-** code is returned.
+** The second argument to this function contains the text of an SQL statement
+** that returns a single integer value. The statement is compiled and executed
+** using database connection db. If successful, the integer value returned
+** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
+** code is returned and the value of *piVal after returning is not defined.
 */
-static int getPageSize(sqlite3 *db, const char *zDb, int *piPageSize){
+static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
   int rc = SQLITE_NOMEM;
+  if( zSql ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *piVal = sqlite3_column_int(pStmt, 0);
+      }
+      rc = sqlite3_finalize(pStmt);
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is called from within the xConnect() or xCreate() method to
+** determine the node-size used by the rtree table being created or connected
+** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned.
+**
+** If this function is being called as part of an xConnect(), then the rtree
+** table already exists. In this case the node-size is determined by inspecting
+** the root node of the tree.
+**
+** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
+** This ensures that each node is stored on a single database page. If the 
+** database page-size is so large that more than RTREE_MAXCELLS entries 
+** would fit in a single node, use a smaller node-size.
+*/
+static int getNodeSize(
+  sqlite3 *db,                    /* Database handle */
+  Rtree *pRtree,                  /* Rtree handle */
+  int isCreate                    /* True for xCreate, false for xConnect */
+){
+  int rc;
   char *zSql;
-  sqlite3_stmt *pStmt = 0;
-
-  zSql = sqlite3_mprintf("PRAGMA %Q.page_size", zDb);
-  if( !zSql ){
-    return SQLITE_NOMEM;
+  if( isCreate ){
+    int iPageSize;
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
+    rc = getIntFromStmt(db, zSql, &iPageSize);
+    if( rc==SQLITE_OK ){
+      pRtree->iNodeSize = iPageSize-64;
+      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
+        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
+      }
+    }
+  }else{
+    zSql = sqlite3_mprintf(
+        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
+        pRtree->zDb, pRtree->zName
+    );
+    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
   }
 
-  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
   sqlite3_free(zSql);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    *piPageSize = sqlite3_column_int(pStmt, 0);
-  }
-  return sqlite3_finalize(pStmt);
+  return rc;
 }
 
 /* 
@@ -110199,7 +117097,6 @@
   int isCreate                        /* True for xCreate, false for xConnect */
 ){
   int rc = SQLITE_OK;
-  int iPageSize = 0;
   Rtree *pRtree;
   int nDb;              /* Length of string argv[1] */
   int nName;            /* Length of string argv[2] */
@@ -110218,11 +117115,6 @@
     return SQLITE_ERROR;
   }
 
-  rc = getPageSize(db, argv[1], &iPageSize);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
   /* Allocate the sqlite3_vtab structure */
   nDb = strlen(argv[1]);
   nName = strlen(argv[2]);
@@ -110241,44 +117133,37 @@
   memcpy(pRtree->zDb, argv[1], nDb);
   memcpy(pRtree->zName, argv[2], nName);
 
-  /* Figure out the node size to use. By default, use 64 bytes less than
-  ** the database page-size. This ensures that each node is stored on
-  ** a single database page.
-  **
-  ** If the databasd page-size is so large that more than RTREE_MAXCELLS
-  ** entries would fit in a single node, use a smaller node-size.
-  */
-  pRtree->iNodeSize = iPageSize-64;
-  if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
-    pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
-  }
+  /* Figure out the node size to use. */
+  rc = getNodeSize(db, pRtree, isCreate);
 
   /* Create/Connect to the underlying relational database schema. If
   ** that is successful, call sqlite3_declare_vtab() to configure
   ** the r-tree table schema.
   */
-  if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
-    *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
-  }else{
-    char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
-    char *zTmp;
-    int ii;
-    for(ii=4; zSql && ii<argc; ii++){
-      zTmp = zSql;
-      zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
-      sqlite3_free(zTmp);
-    }
-    if( zSql ){
-      zTmp = zSql;
-      zSql = sqlite3_mprintf("%s);", zTmp);
-      sqlite3_free(zTmp);
-    }
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-    }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+  if( rc==SQLITE_OK ){
+    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
       *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }else{
+      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
+      char *zTmp;
+      int ii;
+      for(ii=4; zSql && ii<argc; ii++){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
+        sqlite3_free(zTmp);
+      }
+      if( zSql ){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s);", zTmp);
+        sqlite3_free(zTmp);
+      }
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+      }
+      sqlite3_free(zSql);
     }
-    sqlite3_free(zSql);
   }
 
   if( rc==SQLITE_OK ){
@@ -111154,18 +118039,3 @@
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
 /************** End of fts3_icu.c ********************************************/
-// Begin Android Add
-/*
-** Change the default behavior of BEGIN to IMMEDIATE instead of DEFERRED.
-*/
-SQLITE_API int sqlite3_set_transaction_default_immediate(sqlite3* db, int immediate){
-  sqlite3_mutex_enter(db->mutex);
-    if( immediate ){
-      db->flags|=SQLITE_BeginImmediate;
-    }else{
-      db->flags&=~SQLITE_BeginImmediate;
-    }
-    sqlite3_mutex_leave(db->mutex);
-    return SQLITE_OK;
-}
-// End Android Add
diff --git a/dist/sqlite3.c.orig b/dist/sqlite3.c.orig
index f84e675..38a1af8 100644
--- a/dist/sqlite3.c.orig
+++ b/dist/sqlite3.c.orig
@@ -1,6 +1,6 @@
 /******************************************************************************
 ** This file is an amalgamation of many separate C source files from SQLite
-** version 3.6.22.  By combining all the individual C code files into this 
+** version 3.7.0.  By combining all the individual C code files into this 
 ** single large file, the entire code can be compiled as a one translation
 ** unit.  This allows many compilers to do optimizations that would not be
 ** possible if the files were compiled separately.  Performance improvements
@@ -191,6 +191,14 @@
 #endif
 
 /*
+** The default number of frames to accumulate in the log file before
+** checkpointing the database in WAL mode.
+*/
+#ifndef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
+# define SQLITE_DEFAULT_WAL_AUTOCHECKPOINT  1000
+#endif
+
+/*
 ** The maximum number of attached databases.  This must be between 0
 ** and 30.  The upper bound on 30 is because a 32-bit integer bitmap
 ** is used internally to track attached databases.
@@ -307,41 +315,43 @@
 #include <inttypes.h>
 #endif
 
+/*
+** The number of samples of an index that SQLite takes in order to 
+** construct a histogram of the table content when running ANALYZE
+** and with SQLITE_ENABLE_STAT2
+*/
 #define SQLITE_INDEX_SAMPLES 10
 
 /*
-** This macro is used to "hide" some ugliness in casting an int
-** value to a ptr value under the MSVC 64-bit compiler.   Casting
-** non 64-bit values to ptr types results in a "hard" error with 
-** the MSVC 64-bit compiler which this attempts to avoid.  
+** The following macros are used to cast pointers to integers and
+** integers to pointers.  The way you do this varies from one compiler
+** to the next, so we have developed the following set of #if statements
+** to generate appropriate macros for a wide range of compilers.
 **
-** A simple compiler pragma or casting sequence could not be found
-** to correct this in all situations, so this macro was introduced.
-**
-** It could be argued that the intptr_t type could be used in this
-** case, but that type is not available on all compilers, or 
-** requires the #include of specific headers which differs between
-** platforms.
+** The correct "ANSI" way to do this is to use the intptr_t type. 
+** Unfortunately, that typedef is not available on all compilers, or
+** if it is available, it requires an #include of specific headers
+** that vary from one machine to the next.
 **
 ** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
 ** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
 ** So we have to define the macros in different ways depending on the
 ** compiler.
 */
-#if defined(__GNUC__)
-# if defined(HAVE_STDINT_H)
-#   define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
-#   define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
-# else
-#   define SQLITE_INT_TO_PTR(X)  ((void*)(X))
-#   define SQLITE_PTR_TO_INT(X)  ((int)(X))
-# endif
-#else
-# define SQLITE_INT_TO_PTR(X)   ((void*)&((char*)0)[X])
-# define SQLITE_PTR_TO_INT(X)   ((int)(((char*)X)-(char*)0))
+#if defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
+#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
+# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
+# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
+#elif defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
+#else                          /* Generates a warning - but it always works */
+# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
+# define SQLITE_PTR_TO_INT(X)  ((int)(X))
 #endif
 
-
 /*
 ** The SQLITE_THREADSAFE macro must be defined as either 0 or 1.
 ** Older versions of SQLite used an optional THREADSAFE macro.
@@ -371,23 +381,18 @@
 **
 **     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
 **     SQLITE_MEMDEBUG               // Debugging version of system malloc()
-**     SQLITE_MEMORY_SIZE            // internal allocator #1
-**     SQLITE_MMAP_HEAP_SIZE         // internal mmap() allocator
-**     SQLITE_POW2_MEMORY_SIZE       // internal power-of-two allocator
+**
+** (Historical note:  There used to be several other options, but we've
+** pared it down to just these two.)
 **
 ** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
 ** the default.
 */
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)>1
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)>1
 # error "At most one of the following compile-time configuration options\
- is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG, SQLITE_MEMORY_SIZE,\
- SQLITE_MMAP_HEAP_SIZE, SQLITE_POW2_MEMORY_SIZE"
+ is allows: SQLITE_SYSTEM_MALLOC, SQLITE_MEMDEBUG"
 #endif
-#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)+\
-    defined(SQLITE_MEMORY_SIZE)+defined(SQLITE_MMAP_HEAP_SIZE)+\
-    defined(SQLITE_POW2_MEMORY_SIZE)==0
+#if defined(SQLITE_SYSTEM_MALLOC)+defined(SQLITE_MEMDEBUG)==0
 # define SQLITE_SYSTEM_MALLOC 1
 #endif
 
@@ -631,13 +636,13 @@
 ** [sqlite3_libversion_number()], [sqlite3_sourceid()],
 ** [sqlite_version()] and [sqlite_source_id()].
 */
-#define SQLITE_VERSION        "3.6.22"
-#define SQLITE_VERSION_NUMBER 3006022
-#define SQLITE_SOURCE_ID      "2010-03-22 23:55:10 82dd61fccff3e4c77e060e5734cd4b4e2eeb7c32"
+#define SQLITE_VERSION        "3.7.0"
+#define SQLITE_VERSION_NUMBER 3007000
+#define SQLITE_SOURCE_ID      "2010-06-19 15:10:10 2241788bc85fbc48e9cfecb95fe0a858338e37cb"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
-** KEYWORDS: sqlite3_version
+** KEYWORDS: sqlite3_version, sqlite3_sourceid
 **
 ** These interfaces provide the same information as the [SQLITE_VERSION],
 ** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
@@ -659,9 +664,9 @@
 ** function is provided for use in DLLs since DLL users usually do not have
 ** direct access to string constants within the DLL.  ^The
 ** sqlite3_libversion_number() function returns an integer equal to
-** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function a pointer
-** to a string constant whose value is the same as the [SQLITE_SOURCE_ID]
-** C preprocessor macro.
+** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function returns 
+** a pointer to a string constant whose value is the same as the 
+** [SQLITE_SOURCE_ID] C preprocessor macro.
 **
 ** See also: [sqlite_version()] and [sqlite_source_id()].
 */
@@ -671,6 +676,33 @@
 SQLITE_API int sqlite3_libversion_number(void);
 
 /*
+** CAPI3REF: Run-Time Library Compilation Options Diagnostics
+**
+** ^The sqlite3_compileoption_used() function returns 0 or 1 
+** indicating whether the specified option was defined at 
+** compile time.  ^The SQLITE_ prefix may be omitted from the 
+** option name passed to sqlite3_compileoption_used().  
+**
+** ^The sqlite3_compileoption_get() function allows interating
+** over the list of options that were defined at compile time by
+** returning the N-th compile time option string.  ^If N is out of range,
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_ 
+** prefix is omitted from any strings returned by 
+** sqlite3_compileoption_get().
+**
+** ^Support for the diagnostic functions sqlite3_compileoption_used()
+** and sqlite3_compileoption_get() may be omitted by specifing the 
+** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
+**
+** See also: SQL functions [sqlite_compileoption_used()] and
+** [sqlite_compileoption_get()] and the [compile_options pragma].
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+SQLITE_API int sqlite3_compileoption_used(const char *zOptName);
+SQLITE_API const char *sqlite3_compileoption_get(int N);
+#endif
+
+/*
 ** CAPI3REF: Test To See If The Library Is Threadsafe
 **
 ** ^The sqlite3_threadsafe() function returns zero if and only if
@@ -890,7 +922,7 @@
 #define SQLITE_NOTFOUND    12   /* NOT USED. Table or record not found */
 #define SQLITE_FULL        13   /* Insertion failed because database is full */
 #define SQLITE_CANTOPEN    14   /* Unable to open the database file */
-#define SQLITE_PROTOCOL    15   /* NOT USED. Database lock protocol error */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
 #define SQLITE_EMPTY       16   /* Database is empty */
 #define SQLITE_SCHEMA      17   /* The database schema changed */
 #define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
@@ -946,7 +978,12 @@
 #define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
 #define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
 #define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
-#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED | (1<<8) )
+#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
+#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
+#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
+#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
+#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
+#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
 
 /*
 ** CAPI3REF: Flags For File Open Operations
@@ -961,6 +998,7 @@
 #define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
 #define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
 #define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
+#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
 #define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
 #define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
 #define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
@@ -1154,6 +1192,13 @@
   int (*xFileControl)(sqlite3_file*, int op, void *pArg);
   int (*xSectorSize)(sqlite3_file*);
   int (*xDeviceCharacteristics)(sqlite3_file*);
+  /* Methods above are valid for version 1 */
+  int (*xShmOpen)(sqlite3_file*);
+  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
+  int (*xShmMap)(sqlite3_file*, int iPage, int pgsz, int, void volatile**);
+  void (*xShmBarrier)(sqlite3_file*);
+  int (*xShmClose)(sqlite3_file*, int deleteFlag);
+  /* Methods above are valid for version 2 */
   /* Additional methods may be added in future releases */
 };
 
@@ -1171,11 +1216,19 @@
 ** into an integer that the pArg argument points to. This capability
 ** is used during testing and only needs to be supported when SQLITE_TEST
 ** is defined.
+**
+** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
+** layer a hint of how large the database file will grow to be during the
+** current transaction.  This hint is not guaranteed to be accurate but it
+** is often close.  The underlying VFS might choose to preallocate database
+** file space based on this hint in order to help writes to the database
+** file run faster.
 */
 #define SQLITE_FCNTL_LOCKSTATE        1
 #define SQLITE_GET_LOCKPROXYFILE      2
 #define SQLITE_SET_LOCKPROXYFILE      3
 #define SQLITE_LAST_ERRNO             4
+#define SQLITE_FCNTL_SIZE_HINT        5
 
 /*
 ** CAPI3REF: Mutex Handle
@@ -1320,7 +1373,7 @@
 */
 typedef struct sqlite3_vfs sqlite3_vfs;
 struct sqlite3_vfs {
-  int iVersion;            /* Structure version number */
+  int iVersion;            /* Structure version number (currently 2) */
   int szOsFile;            /* Size of subclassed sqlite3_file */
   int mxPathname;          /* Maximum file pathname length */
   sqlite3_vfs *pNext;      /* Next registered VFS */
@@ -1339,8 +1392,17 @@
   int (*xSleep)(sqlite3_vfs*, int microseconds);
   int (*xCurrentTime)(sqlite3_vfs*, double*);
   int (*xGetLastError)(sqlite3_vfs*, int, char *);
-  /* New fields may be appended in figure versions.  The iVersion
-  ** value will increment whenever this happens. */
+  /*
+  ** The methods above are in version 1 of the sqlite_vfs object
+  ** definition.  Those that follow are added in version 2 or later
+  */
+  int (*xRename)(sqlite3_vfs*, const char *zOld, const char *zNew, int dirSync);
+  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
+  /*
+  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
+  ** New fields may be appended in figure versions.  The iVersion
+  ** value will increment whenever this happens. 
+  */
 };
 
 /*
@@ -1361,6 +1423,44 @@
 #define SQLITE_ACCESS_READ      2
 
 /*
+** CAPI3REF: Flags for the xShmLock VFS method
+**
+** These integer constants define the various locking operations
+** allowed by the xShmLock method of [sqlite3_io_methods].  The
+** following are the only legal combinations of flags to the
+** xShmLock method:
+**
+** <ul>
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
+** </ul>
+**
+** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
+** was given no the corresponding lock.  
+**
+** The xShmLock method can transition between unlocked and SHARED or
+** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
+** and EXCLUSIVE.
+*/
+#define SQLITE_SHM_UNLOCK       1
+#define SQLITE_SHM_LOCK         2
+#define SQLITE_SHM_SHARED       4
+#define SQLITE_SHM_EXCLUSIVE    8
+
+/*
+** CAPI3REF: Maximum xShmLock index
+**
+** The xShmLock method on [sqlite3_io_methods] may use values
+** between 0 and this upper bound as its "offset" argument.
+** The SQLite core will never attempt to acquire or release a
+** lock outside of this range
+*/
+#define SQLITE_SHM_NLOCK        8
+
+
+/*
 ** CAPI3REF: Initialize The SQLite Library
 **
 ** ^The sqlite3_initialize() routine initializes the
@@ -1469,11 +1569,10 @@
 ** ^If the option is unknown or SQLite is unable to set the option
 ** then this routine returns a non-zero [error code].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_config(int, ...);
+SQLITE_API int sqlite3_config(int, ...);
 
 /*
 ** CAPI3REF: Configure database connections
-** EXPERIMENTAL
 **
 ** The sqlite3_db_config() interface is used to make configuration
 ** changes to a [database connection].  The interface is similar to
@@ -1493,11 +1592,10 @@
 ** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
 ** the call is considered successful.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_config(sqlite3*, int op, ...);
+SQLITE_API int sqlite3_db_config(sqlite3*, int op, ...);
 
 /*
 ** CAPI3REF: Memory Allocation Routines
-** EXPERIMENTAL
 **
 ** An instance of this object defines the interface between SQLite
 ** and low-level memory allocation routines.
@@ -1579,7 +1677,6 @@
 
 /*
 ** CAPI3REF: Configuration Options
-** EXPERIMENTAL
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the first argument to the [sqlite3_config()] interface.
@@ -1765,6 +1862,24 @@
 ** [sqlite3_pcache_methods] object.  SQLite copies of the current
 ** page cache implementation into that object.)^ </dd>
 **
+** <dt>SQLITE_CONFIG_LOG</dt>
+** <dd> ^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
+** function with a call signature of void(*)(void*,int,const char*), 
+** and a pointer to void. ^If the function pointer is not NULL, it is
+** invoked by [sqlite3_log()] to process each logging event.  ^If the
+** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
+** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
+** passed through as the first parameter to the application-defined logger
+** function whenever that function is invoked.  ^The second parameter to
+** the logger function is a copy of the first parameter to the corresponding
+** [sqlite3_log()] call and is intended to be a [result code] or an
+** [extended result code].  ^The third parameter passed to the logger is
+** log message after formatting via [sqlite3_snprintf()].
+** The SQLite logging interface is not reentrant; the logger function
+** supplied by the application must not invoke any SQLite interface.
+** In a multi-threaded application, the application-defined logger
+** function must be threadsafe. </dd>
+**
 ** </dl>
 */
 #define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
@@ -1785,8 +1900,7 @@
 #define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
 
 /*
-** CAPI3REF: Configuration Options
-** EXPERIMENTAL
+** CAPI3REF: Database Connection Configuration Options
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the second argument to the [sqlite3_db_config()] interface.
@@ -2562,7 +2676,6 @@
 
 /*
 ** CAPI3REF: Tracing And Profiling Functions
-** EXPERIMENTAL
 **
 ** These routines register callback functions that can be used for
 ** tracing and profiling the execution of SQL statements.
@@ -2580,7 +2693,7 @@
 ** the original statement text and an estimate of wall-clock time
 ** of how long that statement took to run.
 */
-SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
+SQLITE_API void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
 SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_profile(sqlite3*,
    void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
 
@@ -3373,6 +3486,14 @@
 ** be the case that the same database connection is being used by two or
 ** more threads at the same moment in time.
 **
+** For all versions of SQLite up to and including 3.6.23.1, it was required
+** after sqlite3_step() returned anything other than [SQLITE_ROW] that
+** [sqlite3_reset()] be called before any subsequent invocation of
+** sqlite3_step().  Failure to invoke [sqlite3_reset()] in this way would
+** result in an [SQLITE_MISUSE] return from sqlite3_step().  But after
+** version 3.6.23.1, sqlite3_step() began calling [sqlite3_reset()] 
+** automatically in this circumstance rather than returning [SQLITE_MISUSE].  
+**
 ** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
 ** API always returns a generic error code, [SQLITE_ERROR], following any
 ** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
@@ -4185,6 +4306,7 @@
   void(*)(void*,sqlite3*,int eTextRep,const void*)
 );
 
+#ifdef SQLITE_HAS_CODEC
 /*
 ** Specify the key for an encrypted database.  This routine should be
 ** called right after sqlite3_open().
@@ -4211,6 +4333,25 @@
 );
 
 /*
+** Specify the activation key for a SEE database.  Unless 
+** activated, none of the SEE routines will work.
+*/
+SQLITE_API void sqlite3_activate_see(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+#ifdef SQLITE_ENABLE_CEROD
+/*
+** Specify the activation key for a CEROD database.  Unless 
+** activated, none of the CEROD routines will work.
+*/
+SQLITE_API void sqlite3_activate_cerod(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+/*
 ** CAPI3REF: Suspend Execution For A Short Time
 **
 ** ^The sqlite3_sleep() function causes the current thread to suspend execution
@@ -4348,8 +4489,6 @@
 ** an error or constraint causes an implicit rollback to occur.
 ** ^The rollback callback is not invoked if a transaction is
 ** automatically rolled back because the database connection is closed.
-** ^The rollback callback is not invoked if a transaction is
-** rolled back because a commit callback returned non-zero.
 **
 ** See also the [sqlite3_update_hook()] interface.
 */
@@ -4635,8 +4774,6 @@
 SQLITE_API void sqlite3_reset_auto_extension(void);
 
 /*
-****** EXPERIMENTAL - subject to change without notice **************
-**
 ** The interface to the virtual-table mechanism is currently considered
 ** to be experimental.  The interface might change in incompatible ways.
 ** If this is a problem for you, do not use the interface at this time.
@@ -4656,7 +4793,6 @@
 /*
 ** CAPI3REF: Virtual Table Object
 ** KEYWORDS: sqlite3_module {virtual table module}
-** EXPERIMENTAL
 **
 ** This structure, sometimes called a a "virtual table module", 
 ** defines the implementation of a [virtual tables].  
@@ -4703,7 +4839,6 @@
 /*
 ** CAPI3REF: Virtual Table Indexing Information
 ** KEYWORDS: sqlite3_index_info
-** EXPERIMENTAL
 **
 ** The sqlite3_index_info structure and its substructures is used to
 ** pass information into and receive the reply from the [xBestIndex]
@@ -4785,7 +4920,6 @@
 
 /*
 ** CAPI3REF: Register A Virtual Table Implementation
-** EXPERIMENTAL
 **
 ** ^These routines are used to register a new [virtual table module] name.
 ** ^Module names must be registered before
@@ -4807,13 +4941,13 @@
 ** interface is equivalent to sqlite3_create_module_v2() with a NULL
 ** destructor.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module(
+SQLITE_API int sqlite3_create_module(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
   void *pClientData          /* Client data for xCreate/xConnect */
 );
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module_v2(
+SQLITE_API int sqlite3_create_module_v2(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
@@ -4824,7 +4958,6 @@
 /*
 ** CAPI3REF: Virtual Table Instance Object
 ** KEYWORDS: sqlite3_vtab
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass
 ** of this object to describe a particular instance
@@ -4850,7 +4983,6 @@
 /*
 ** CAPI3REF: Virtual Table Cursor Object
 ** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass of the
 ** following structure to describe cursors that point into the
@@ -4872,18 +5004,16 @@
 
 /*
 ** CAPI3REF: Declare The Schema Of A Virtual Table
-** EXPERIMENTAL
 **
 ** ^The [xCreate] and [xConnect] methods of a
 ** [virtual table module] call this interface
 ** to declare the format (the names and datatypes of the columns) of
 ** the virtual tables they implement.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
+SQLITE_API int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
 
 /*
 ** CAPI3REF: Overload A Function For A Virtual Table
-** EXPERIMENTAL
 **
 ** ^(Virtual tables can provide alternative implementations of functions
 ** using the [xFindFunction] method of the [virtual table module].  
@@ -4898,7 +5028,7 @@
 ** purpose is to be a placeholder function that can be overloaded
 ** by a [virtual table].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
+SQLITE_API int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
 
 /*
 ** The interface to the virtual-table mechanism defined above (back up
@@ -4908,8 +5038,6 @@
 **
 ** When the virtual-table mechanism stabilizes, we will declare the
 ** interface fixed, support it indefinitely, and remove this comment.
-**
-****** EXPERIMENTAL - subject to change without notice **************
 */
 
 /*
@@ -5252,7 +5380,6 @@
 
 /*
 ** CAPI3REF: Mutex Methods Object
-** EXPERIMENTAL
 **
 ** An instance of this structure defines the low-level routines
 ** used to allocate and use mutexes.
@@ -5465,11 +5592,11 @@
 #define SQLITE_TESTCTRL_RESERVE                 14
 #define SQLITE_TESTCTRL_OPTIMIZATIONS           15
 #define SQLITE_TESTCTRL_ISKEYWORD               16
-#define SQLITE_TESTCTRL_LAST                    16
+#define SQLITE_TESTCTRL_PGHDRSZ                 17
+#define SQLITE_TESTCTRL_LAST                    17
 
 /*
 ** CAPI3REF: SQLite Runtime Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information
 ** about the preformance of SQLite, and optionally to reset various
@@ -5497,12 +5624,11 @@
 **
 ** See also: [sqlite3_db_status()]
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+SQLITE_API int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
 
 
 /*
 ** CAPI3REF: Status Parameters
-** EXPERIMENTAL
 **
 ** These integer constants designate various run-time status parameters
 ** that can be returned by [sqlite3_status()].
@@ -5589,14 +5715,15 @@
 
 /*
 ** CAPI3REF: Database Connection Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information 
 ** about a single [database connection].  ^The first argument is the
 ** database connection object to be interrogated.  ^The second argument
-** is the parameter to interrogate.  ^Currently, the only allowed value
-** for the second parameter is [SQLITE_DBSTATUS_LOOKASIDE_USED].
-** Additional options will likely appear in future releases of SQLite.
+** is an integer constant, taken from the set of
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros, that
+** determiness the parameter to interrogate.  The set of 
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros is likely
+** to grow in future releases of SQLite.
 **
 ** ^The current value of the requested parameter is written into *pCur
 ** and the highest instantaneous value is written into *pHiwtr.  ^If
@@ -5605,11 +5732,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+SQLITE_API int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for database connections
-** EXPERIMENTAL
 **
 ** These constants are the available integer "verbs" that can be passed as
 ** the second argument to the [sqlite3_db_status()] interface.
@@ -5624,14 +5750,21 @@
 ** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
 ** <dd>This parameter returns the number of lookaside memory slots currently
 ** checked out.</dd>)^
+**
+** <dt>SQLITE_DBSTATUS_CACHE_USED</dt>
+** <dd>^This parameter returns the approximate number of of bytes of heap
+** memory used by all pager caches associated with the database connection.
+** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
+** checked out.</dd>)^
 ** </dl>
 */
 #define SQLITE_DBSTATUS_LOOKASIDE_USED     0
+#define SQLITE_DBSTATUS_CACHE_USED         1
+#define SQLITE_DBSTATUS_MAX                1   /* Largest defined DBSTATUS */
 
 
 /*
 ** CAPI3REF: Prepared Statement Status
-** EXPERIMENTAL
 **
 ** ^(Each prepared statement maintains various
 ** [SQLITE_STMTSTATUS_SORT | counters] that measure the number
@@ -5653,11 +5786,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_db_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+SQLITE_API int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for prepared statements
-** EXPERIMENTAL
 **
 ** These preprocessor macros define integer codes that name counter
 ** values associated with the [sqlite3_stmt_status()] interface.
@@ -5675,14 +5807,21 @@
 ** A non-zero value in this counter may indicate an opportunity to
 ** improvement performance through careful use of indices.</dd>
 **
+** <dt>SQLITE_STMTSTATUS_AUTOINDEX</dt>
+** <dd>^This is the number of rows inserted into transient indices that
+** were created automatically in order to help joins run faster.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance by adding permanent indices that do not
+** need to be reinitialized each time the statement is run.</dd>
+**
 ** </dl>
 */
 #define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
 #define SQLITE_STMTSTATUS_SORT              2
+#define SQLITE_STMTSTATUS_AUTOINDEX         3
 
 /*
 ** CAPI3REF: Custom Page Cache Object
-** EXPERIMENTAL
 **
 ** The sqlite3_pcache type is opaque.  It is implemented by
 ** the pluggable module.  The SQLite core has no knowledge of
@@ -5697,7 +5836,6 @@
 /*
 ** CAPI3REF: Application Defined Page Cache.
 ** KEYWORDS: {page cache}
-** EXPERIMENTAL
 **
 ** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
 ** register an alternative page cache implementation by passing in an 
@@ -5839,7 +5977,6 @@
 
 /*
 ** CAPI3REF: Online Backup Object
-** EXPERIMENTAL
 **
 ** The sqlite3_backup object records state information about an ongoing
 ** online backup operation.  ^The sqlite3_backup object is created by
@@ -5852,7 +5989,6 @@
 
 /*
 ** CAPI3REF: Online Backup API.
-** EXPERIMENTAL
 **
 ** The backup API copies the content of one database into another.
 ** It is useful either for creating backups of databases or
@@ -5921,10 +6057,14 @@
 ** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
 ** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
 **
-** ^The sqlite3_backup_step() might return [SQLITE_READONLY] if the destination
-** database was opened read-only or if
-** the destination is an in-memory database with a different page size
-** from the source database.
+** ^(The sqlite3_backup_step() might return [SQLITE_READONLY] if
+** <ol>
+** <li> the destination database was opened read-only, or
+** <li> the destination database is using write-ahead-log journaling
+** and the destination and source page sizes differ, or
+** <li> The destination database is an in-memory database and the
+** destination and source page sizes differ.
+** </ol>)^
 **
 ** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
 ** the [sqlite3_busy_handler | busy-handler function]
@@ -6040,7 +6180,6 @@
 
 /*
 ** CAPI3REF: Unlock Notification
-** EXPERIMENTAL
 **
 ** ^When running in shared-cache mode, a database operation may fail with
 ** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
@@ -6162,7 +6301,6 @@
 
 /*
 ** CAPI3REF: String Comparison
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_strnicmp()] API allows applications and extensions to
 ** compare the contents of two buffers containing UTF-8 strings in a
@@ -6173,16 +6311,19 @@
 
 /*
 ** CAPI3REF: Error Logging Interface
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_log()] interface writes a message into the error log
-** established by the [SQLITE_CONFIG_ERRORLOG] option to [sqlite3_config()].
+** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
+** ^If logging is enabled, the zFormat string and subsequent arguments are
+** used with [sqlite3_snprintf()] to generate the final output string.
 **
 ** The sqlite3_log() interface is intended for use by extensions such as
 ** virtual tables, collating functions, and SQL functions.  While there is
 ** nothing to prevent an application from calling sqlite3_log(), doing so
 ** is considered bad form.
 **
+** The zFormat string must not be NULL.
+**
 ** To avoid deadlocks and other threading problems, the sqlite3_log() routine
 ** will not use dynamically allocated memory.  The log message is stored in
 ** a fixed-length buffer on the stack.  If the log message is longer than
@@ -6192,6 +6333,89 @@
 SQLITE_API void sqlite3_log(int iErrCode, const char *zFormat, ...);
 
 /*
+** CAPI3REF: Write-Ahead Log Commit Hook
+**
+** ^The [sqlite3_wal_hook()] function is used to register a callback that
+** will be invoked each time a database connection commits data to a
+** [write-ahead log] (i.e. whenever a transaction is committed in
+** [journal_mode | journal_mode=WAL mode]). 
+**
+** ^The callback is invoked by SQLite after the commit has taken place and 
+** the associated write-lock on the database released, so the implementation 
+** may read, write or [checkpoint] the database as required.
+**
+** ^The first parameter passed to the callback function when it is invoked
+** is a copy of the third parameter passed to sqlite3_wal_hook() when
+** registering the callback. ^The second is a copy of the database handle.
+** ^The third parameter is the name of the database that was written to -
+** either "main" or the name of an [ATTACH]-ed database. ^The fourth parameter
+** is the number of pages currently in the write-ahead log file,
+** including those that were just committed.
+**
+** The callback function should normally return [SQLITE_OK].  ^If an error
+** code is returned, that error will propagate back up through the
+** SQLite code base to cause the statement that provoked the callback
+** to report an error, though the commit will have still occurred. If the
+** callback returns [SQLITE_ROW] or [SQLITE_DONE], or if it returns a value
+** that does not correspond to any valid SQLite error code, the results
+** are undefined.
+**
+** A single database handle may have at most a single write-ahead log callback 
+** registered at one time. ^Calling [sqlite3_wal_hook()] replaces any
+** previously registered write-ahead log callback. ^Note that the
+** [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] both invoke [sqlite3_wal_hook()] and will
+** those overwrite any prior [sqlite3_wal_hook()] settings.
+*/
+SQLITE_API void *sqlite3_wal_hook(
+  sqlite3*, 
+  int(*)(void *,sqlite3*,const char*,int),
+  void*
+);
+
+/*
+** CAPI3REF: Configure an auto-checkpoint
+**
+** ^The [sqlite3_wal_autocheckpoint(D,N)] is a wrapper around
+** [sqlite3_wal_hook()] that causes any database on [database connection] D
+** to automatically [checkpoint]
+** after committing a transaction if there are N or
+** more frames in the [write-ahead log] file.  ^Passing zero or 
+** a negative value as the nFrame parameter disables automatic
+** checkpoints entirely.
+**
+** ^The callback registered by this function replaces any existing callback
+** registered using [sqlite3_wal_hook()].  ^Likewise, registering a callback
+** using [sqlite3_wal_hook()] disables the automatic checkpoint mechanism
+** configured by this function.
+**
+** ^The [wal_autocheckpoint pragma] can be used to invoke this interface
+** from SQL.
+**
+** ^Every new [database connection] defaults to having the auto-checkpoint
+** enabled with a threshold of 1000 pages.  The use of this interface
+** is only necessary if the default setting is found to be suboptimal
+** for a particular application.
+*/
+SQLITE_API int sqlite3_wal_autocheckpoint(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Checkpoint a database
+**
+** ^The [sqlite3_wal_checkpoint(D,X)] interface causes database named X
+** on [database connection] D to be [checkpointed].  ^If X is NULL or an
+** empty string, then a checkpoint is run on all databases of
+** connection D.  ^If the database connection D is not in
+** [WAL | write-ahead log mode] then this interface is a harmless no-op.
+**
+** ^The [wal_checkpoint pragma] can be used to invoke this interface
+** from SQL.  ^The [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] can be used to cause this interface to be
+** run whenever the WAL reaches a certain size threshold.
+*/
+SQLITE_API int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);
+
+/*
 ** Undo the hack that converts floating point types to integer for
 ** builds on processors without floating point support.
 */
@@ -6482,6 +6706,7 @@
 */
 #ifdef SQLITE_OMIT_FLOATING_POINT
 # define double sqlite_int64
+# define float sqlite_int64
 # define LONGDOUBLE_TYPE sqlite_int64
 # ifndef SQLITE_BIG_DBL
 #   define SQLITE_BIG_DBL (((sqlite3_int64)1)<<50)
@@ -6507,20 +6732,6 @@
 #endif
 
 /*
-** If the following macro is set to 1, then NULL values are considered
-** distinct when determining whether or not two entries are the same
-** in a UNIQUE index.  This is the way PostgreSQL, Oracle, DB2, MySQL,
-** OCELOT, and Firebird all work.  The SQL92 spec explicitly says this
-** is the way things are suppose to work.
-**
-** If the following macro is set to 0, the NULLs are indistinct for
-** a UNIQUE index.  In this mode, you can only have a single NULL entry
-** for a column declared UNIQUE.  This is the way Informix and SQL Server
-** work.
-*/
-#define NULL_DISTINCT_FOR_UNIQUE 1
-
-/*
 ** The "file format" number is an integer that is incremented whenever
 ** the VDBE-level file format changes.  The following macros define the
 ** the default file format for new databases and the maximum file format
@@ -6531,6 +6742,10 @@
 # define SQLITE_DEFAULT_FILE_FORMAT 1
 #endif
 
+/*
+** Determine whether triggers are recursive by default.  This can be
+** changed at run-time using a pragma.
+*/
 #ifndef SQLITE_DEFAULT_RECURSIVE_TRIGGERS
 # define SQLITE_DEFAULT_RECURSIVE_TRIGGERS 0
 #endif
@@ -6775,7 +6990,6 @@
 typedef struct AuthContext AuthContext;
 typedef struct AutoincInfo AutoincInfo;
 typedef struct Bitvec Bitvec;
-typedef struct RowSet RowSet;
 typedef struct CollSeq CollSeq;
 typedef struct Column Column;
 typedef struct Db Db;
@@ -6796,6 +7010,7 @@
 typedef struct Module Module;
 typedef struct NameContext NameContext;
 typedef struct Parse Parse;
+typedef struct RowSet RowSet;
 typedef struct Savepoint Savepoint;
 typedef struct Select Select;
 typedef struct SrcList SrcList;
@@ -6803,9 +7018,9 @@
 typedef struct Table Table;
 typedef struct TableLock TableLock;
 typedef struct Token Token;
+typedef struct Trigger Trigger;
 typedef struct TriggerPrg TriggerPrg;
 typedef struct TriggerStep TriggerStep;
-typedef struct Trigger Trigger;
 typedef struct UnpackedRecord UnpackedRecord;
 typedef struct VTable VTable;
 typedef struct Walker Walker;
@@ -6903,6 +7118,8 @@
 SQLITE_PRIVATE int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
 SQLITE_PRIVATE int sqlite3BtreeGetPageSize(Btree*);
 SQLITE_PRIVATE int sqlite3BtreeMaxPageCount(Btree*,int);
+SQLITE_PRIVATE u32 sqlite3BtreeLastPage(Btree*);
+SQLITE_PRIVATE int sqlite3BtreeSecureDelete(Btree*,int);
 SQLITE_PRIVATE int sqlite3BtreeGetReserve(Btree*);
 SQLITE_PRIVATE int sqlite3BtreeSetAutoVacuum(Btree *, int);
 SQLITE_PRIVATE int sqlite3BtreeGetAutoVacuum(Btree *);
@@ -7006,6 +7223,8 @@
 SQLITE_PRIVATE void sqlite3BtreeCacheOverflow(BtCursor *);
 SQLITE_PRIVATE void sqlite3BtreeClearCursor(BtCursor *);
 
+SQLITE_PRIVATE int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
+
 #ifndef NDEBUG
 SQLITE_PRIVATE int sqlite3BtreeCursorIsValid(BtCursor*);
 #endif
@@ -7296,83 +7515,83 @@
 #define OP_VerifyCookie                        37
 #define OP_OpenRead                            38
 #define OP_OpenWrite                           39
-#define OP_OpenEphemeral                       40
-#define OP_OpenPseudo                          41
-#define OP_Close                               42
-#define OP_SeekLt                              43
-#define OP_SeekLe                              44
-#define OP_SeekGe                              45
-#define OP_SeekGt                              46
-#define OP_Seek                                47
-#define OP_NotFound                            48
-#define OP_Found                               49
-#define OP_IsUnique                            50
-#define OP_NotExists                           51
-#define OP_Sequence                            52
-#define OP_NewRowid                            53
-#define OP_Insert                              54
-#define OP_InsertInt                           55
-#define OP_Delete                              56
-#define OP_ResetCount                          57
-#define OP_RowKey                              58
-#define OP_RowData                             59
-#define OP_Rowid                               60
-#define OP_NullRow                             61
-#define OP_Last                                62
-#define OP_Sort                                63
-#define OP_Rewind                              64
-#define OP_Prev                                65
-#define OP_Next                                66
-#define OP_IdxInsert                           67
-#define OP_IdxDelete                           70
-#define OP_IdxRowid                            71
-#define OP_IdxLT                               72
-#define OP_IdxGE                               81
-#define OP_Destroy                             92
-#define OP_Clear                               95
-#define OP_CreateIndex                         96
-#define OP_CreateTable                         97
-#define OP_ParseSchema                         98
-#define OP_LoadAnalysis                        99
-#define OP_DropTable                          100
-#define OP_DropIndex                          101
-#define OP_DropTrigger                        102
-#define OP_IntegrityCk                        103
-#define OP_RowSetAdd                          104
-#define OP_RowSetRead                         105
-#define OP_RowSetTest                         106
-#define OP_Program                            107
-#define OP_Param                              108
-#define OP_FkCounter                          109
-#define OP_FkIfZero                           110
-#define OP_MemMax                             111
-#define OP_IfPos                              112
-#define OP_IfNeg                              113
-#define OP_IfZero                             114
-#define OP_AggStep                            115
-#define OP_AggFinal                           116
-#define OP_Vacuum                             117
-#define OP_IncrVacuum                         118
-#define OP_Expire                             119
-#define OP_TableLock                          120
-#define OP_VBegin                             121
-#define OP_VCreate                            122
-#define OP_VDestroy                           123
-#define OP_VOpen                              124
-#define OP_VFilter                            125
-#define OP_VColumn                            126
-#define OP_VNext                              127
-#define OP_VRename                            128
-#define OP_VUpdate                            129
-#define OP_Pagecount                          131
-#define OP_Trace                              132
-#define OP_Noop                               133
-#define OP_Explain                            134
+#define OP_OpenAutoindex                       40
+#define OP_OpenEphemeral                       41
+#define OP_OpenPseudo                          42
+#define OP_Close                               43
+#define OP_SeekLt                              44
+#define OP_SeekLe                              45
+#define OP_SeekGe                              46
+#define OP_SeekGt                              47
+#define OP_Seek                                48
+#define OP_NotFound                            49
+#define OP_Found                               50
+#define OP_IsUnique                            51
+#define OP_NotExists                           52
+#define OP_Sequence                            53
+#define OP_NewRowid                            54
+#define OP_Insert                              55
+#define OP_InsertInt                           56
+#define OP_Delete                              57
+#define OP_ResetCount                          58
+#define OP_RowKey                              59
+#define OP_RowData                             60
+#define OP_Rowid                               61
+#define OP_NullRow                             62
+#define OP_Last                                63
+#define OP_Sort                                64
+#define OP_Rewind                              65
+#define OP_Prev                                66
+#define OP_Next                                67
+#define OP_IdxInsert                           70
+#define OP_IdxDelete                           71
+#define OP_IdxRowid                            72
+#define OP_IdxLT                               81
+#define OP_IdxGE                               92
+#define OP_Destroy                             95
+#define OP_Clear                               96
+#define OP_CreateIndex                         97
+#define OP_CreateTable                         98
+#define OP_ParseSchema                         99
+#define OP_LoadAnalysis                       100
+#define OP_DropTable                          101
+#define OP_DropIndex                          102
+#define OP_DropTrigger                        103
+#define OP_IntegrityCk                        104
+#define OP_RowSetAdd                          105
+#define OP_RowSetRead                         106
+#define OP_RowSetTest                         107
+#define OP_Program                            108
+#define OP_Param                              109
+#define OP_FkCounter                          110
+#define OP_FkIfZero                           111
+#define OP_MemMax                             112
+#define OP_IfPos                              113
+#define OP_IfNeg                              114
+#define OP_IfZero                             115
+#define OP_AggStep                            116
+#define OP_AggFinal                           117
+#define OP_Checkpoint                         118
+#define OP_JournalMode                        119
+#define OP_Vacuum                             120
+#define OP_IncrVacuum                         121
+#define OP_Expire                             122
+#define OP_TableLock                          123
+#define OP_VBegin                             124
+#define OP_VCreate                            125
+#define OP_VDestroy                           126
+#define OP_VOpen                              127
+#define OP_VFilter                            128
+#define OP_VColumn                            129
+#define OP_VNext                              131
+#define OP_VRename                            132
+#define OP_VUpdate                            133
+#define OP_Pagecount                          134
+#define OP_Trace                              135
+#define OP_Noop                               136
+#define OP_Explain                            137
 
 /* The following opcode values are never used */
-#define OP_NotUsed_135                        135
-#define OP_NotUsed_136                        136
-#define OP_NotUsed_137                        137
 #define OP_NotUsed_138                        138
 #define OP_NotUsed_139                        139
 #define OP_NotUsed_140                        140
@@ -7391,22 +7610,22 @@
 #define OPFLG_OUT3            0x0040  /* out3:  P3 is an output */
 #define OPFLG_INITIALIZER {\
 /*   0 */ 0x00, 0x01, 0x05, 0x04, 0x04, 0x10, 0x00, 0x02,\
-/*   8 */ 0x02, 0x02, 0x02, 0x02, 0x00, 0x00, 0x24, 0x24,\
+/*   8 */ 0x02, 0x02, 0x02, 0x02, 0x02, 0x00, 0x24, 0x24,\
 /*  16 */ 0x00, 0x00, 0x00, 0x24, 0x04, 0x05, 0x04, 0x00,\
 /*  24 */ 0x00, 0x01, 0x05, 0x05, 0x00, 0x00, 0x00, 0x02,\
 /*  32 */ 0x00, 0x00, 0x00, 0x02, 0x10, 0x00, 0x00, 0x00,\
-/*  40 */ 0x00, 0x00, 0x00, 0x11, 0x11, 0x11, 0x11, 0x08,\
-/*  48 */ 0x11, 0x11, 0x11, 0x11, 0x02, 0x02, 0x00, 0x00,\
-/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x01, 0x01,\
-/*  64 */ 0x01, 0x01, 0x01, 0x08, 0x4c, 0x4c, 0x00, 0x02,\
-/*  72 */ 0x01, 0x05, 0x05, 0x15, 0x15, 0x15, 0x15, 0x15,\
+/*  40 */ 0x00, 0x00, 0x00, 0x00, 0x11, 0x11, 0x11, 0x11,\
+/*  48 */ 0x08, 0x11, 0x11, 0x11, 0x11, 0x02, 0x02, 0x00,\
+/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x01,\
+/*  64 */ 0x01, 0x01, 0x01, 0x01, 0x4c, 0x4c, 0x08, 0x00,\
+/*  72 */ 0x02, 0x05, 0x05, 0x15, 0x15, 0x15, 0x15, 0x15,\
 /*  80 */ 0x15, 0x01, 0x4c, 0x4c, 0x4c, 0x4c, 0x4c, 0x4c,\
-/*  88 */ 0x4c, 0x4c, 0x4c, 0x4c, 0x02, 0x24, 0x02, 0x00,\
-/*  96 */ 0x02, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
-/* 104 */ 0x0c, 0x45, 0x15, 0x01, 0x02, 0x00, 0x01, 0x08,\
-/* 112 */ 0x05, 0x05, 0x05, 0x00, 0x00, 0x00, 0x01, 0x00,\
-/* 120 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01,\
-/* 128 */ 0x00, 0x00, 0x02, 0x02, 0x00, 0x00, 0x00, 0x00,\
+/*  88 */ 0x4c, 0x4c, 0x4c, 0x4c, 0x01, 0x24, 0x02, 0x02,\
+/*  96 */ 0x00, 0x02, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 104 */ 0x00, 0x0c, 0x45, 0x15, 0x01, 0x02, 0x00, 0x01,\
+/* 112 */ 0x08, 0x05, 0x05, 0x05, 0x00, 0x00, 0x00, 0x02,\
+/* 120 */ 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 128 */ 0x01, 0x00, 0x02, 0x01, 0x00, 0x00, 0x02, 0x00,\
 /* 136 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x04,\
 /* 144 */ 0x04, 0x04,}
 
@@ -7552,14 +7771,15 @@
 #define PAGER_LOCKINGMODE_EXCLUSIVE   1
 
 /*
-** Valid values for the second argument to sqlite3PagerJournalMode().
+** Numeric constants that encode the journalmode.  
 */
-#define PAGER_JOURNALMODE_QUERY      -1
+#define PAGER_JOURNALMODE_QUERY     (-1)  /* Query the value of journalmode */
 #define PAGER_JOURNALMODE_DELETE      0   /* Commit by deleting journal file */
 #define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
 #define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */
 #define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
 #define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
+#define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
 
 /*
 ** The remainder of this file contains the declarations of the functions
@@ -7587,7 +7807,9 @@
 SQLITE_PRIVATE void sqlite3PagerSetCachesize(Pager*, int);
 SQLITE_PRIVATE void sqlite3PagerSetSafetyLevel(Pager*,int,int);
 SQLITE_PRIVATE int sqlite3PagerLockingMode(Pager *, int);
-SQLITE_PRIVATE int sqlite3PagerJournalMode(Pager *, int);
+SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *, int);
+SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager*);
+SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager*);
 SQLITE_PRIVATE i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
 SQLITE_PRIVATE sqlite3_backup **sqlite3PagerBackupPtr(Pager*);
 
@@ -7617,9 +7839,16 @@
 SQLITE_PRIVATE int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
 SQLITE_PRIVATE int sqlite3PagerSharedLock(Pager *pPager);
 
+SQLITE_PRIVATE int sqlite3PagerCheckpoint(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerWalSupported(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerWalCallback(Pager *pPager);
+SQLITE_PRIVATE int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
+SQLITE_PRIVATE int sqlite3PagerCloseWal(Pager *pPager);
+
 /* Functions used to query pager state and configuration. */
 SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager*);
 SQLITE_PRIVATE int sqlite3PagerRefcount(Pager*);
+SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager*);
 SQLITE_PRIVATE const char *sqlite3PagerFilename(Pager*);
 SQLITE_PRIVATE const sqlite3_vfs *sqlite3PagerVfs(Pager*);
 SQLITE_PRIVATE sqlite3_file *sqlite3PagerFile(Pager*);
@@ -8032,7 +8261,11 @@
 ** 1GB boundary.
 **
 */
-#define PENDING_BYTE      sqlite3PendingByte
+#ifdef SQLITE_OMIT_WSD
+# define PENDING_BYTE     (0x40000000)
+#else
+# define PENDING_BYTE      sqlite3PendingByte
+#endif
 #define RESERVED_BYTE     (PENDING_BYTE+1)
 #define SHARED_FIRST      (PENDING_BYTE+2)
 #define SHARED_SIZE       510
@@ -8058,6 +8291,11 @@
 #define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
 SQLITE_PRIVATE int sqlite3OsSectorSize(sqlite3_file *id);
 SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmOpen(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
+SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id);
+SQLITE_PRIVATE int sqlite3OsShmClose(sqlite3_file *id, int);
+SQLITE_PRIVATE int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
 
 /* 
 ** Functions for accessing sqlite3_vfs methods 
@@ -8074,7 +8312,7 @@
 #endif /* SQLITE_OMIT_LOAD_EXTENSION */
 SQLITE_PRIVATE int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
 SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *, int);
-SQLITE_PRIVATE int sqlite3OsCurrentTime(sqlite3_vfs *, double*);
+SQLITE_PRIVATE int sqlite3OsCurrentTimeInt64(sqlite3_vfs *, sqlite3_int64*);
 
 /*
 ** Convenience functions for opening and closing files using 
@@ -8209,7 +8447,7 @@
 
 /*
 ** These macros can be used to test, set, or clear bits in the 
-** Db.flags field.
+** Db.pSchema->flags field.
 */
 #define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))
 #define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->flags&(P))!=0)
@@ -8217,7 +8455,7 @@
 #define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->flags&=~(P)
 
 /*
-** Allowed values for the DB.flags field.
+** Allowed values for the DB.pSchema->flags field.
 **
 ** The DB_SchemaLoaded flag is set after the database schema has been
 ** read into internal hash tables.
@@ -8281,7 +8519,7 @@
 };
 
 /*
-** Each database is an instance of the following structure.
+** Each database connection is an instance of the following structure.
 **
 ** The sqlite.lastRowid records the last insert rowid generated by an
 ** insert statement.  Inserts on views do not affect its value.  Each
@@ -8351,6 +8589,10 @@
   void (*xRollbackCallback)(void*); /* Invoked at every commit. */
   void *pUpdateArg;
   void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);
+#ifndef SQLITE_OMIT_WAL
+  int (*xWalCallback)(void *, sqlite3 *, const char *, int);
+  void *pWalArg;
+#endif
   void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);
   void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);
   void *pCollNeededArg;
@@ -8440,6 +8682,8 @@
 #define SQLITE_ReverseOrder   0x01000000  /* Reverse unordered SELECTs */
 #define SQLITE_RecTriggers    0x02000000  /* Enable recursive triggers */
 #define SQLITE_ForeignKeys    0x04000000  /* Enforce foreign key constraints  */
+#define SQLITE_AutoIndex      0x08000000  /* Enable automatic indexes */
+#define SQLITE_PreferBuiltin  0x10000000  /* Preference to built-in funcs */
 
 /*
 ** Bits of the sqlite3.flags field that are used by the
@@ -8451,7 +8695,8 @@
 #define SQLITE_IndexSort      0x04        /* Disable indexes for sorting */
 #define SQLITE_IndexSearch    0x08        /* Disable indexes for searching */
 #define SQLITE_IndexCover     0x10        /* Disable index covering table */
-#define SQLITE_OptMask        0x1f        /* Mask of all disablable opts */
+#define SQLITE_GroupByOrder   0x20        /* Disable GROUPBY cover of ORDERBY */
+#define SQLITE_OptMask        0xff        /* Mask of all disablable opts */
 
 /*
 ** Possible values for the sqlite.magic field.
@@ -9302,6 +9547,9 @@
 ** and the next table on the list.  The parser builds the list this way.
 ** But sqlite3SrcListShiftJoinType() later shifts the jointypes so that each
 ** jointype expresses the join between the table and the previous table.
+**
+** In the colUsed field, the high-order bit (bit 63) is set if the table
+** contains more than 63 columns and the 64-th or later column is used.
 */
 struct SrcList {
   i16 nSrc;        /* Number of tables or subqueries in the FROM clause */
@@ -9413,7 +9661,7 @@
 #define WHERE_ORDERBY_MAX      0x0002 /* ORDER BY processing for max() func */
 #define WHERE_ONEPASS_DESIRED  0x0004 /* Want to do one-pass UPDATE/DELETE */
 #define WHERE_DUPLICATES_OK    0x0008 /* Ok to return a row more than once */
-#define WHERE_OMIT_OPEN        0x0010 /* Table cursor are already open */
+#define WHERE_OMIT_OPEN        0x0010 /* Table cursors are already open */
 #define WHERE_OMIT_CLOSE       0x0020 /* Omit close of table & index cursors */
 #define WHERE_FORCE_TABLE      0x0040 /* Do not use an index-only search */
 #define WHERE_ONETABLE_ONLY    0x0080 /* Only code the 1st table in pTabList */
@@ -9436,6 +9684,7 @@
   int iBreak;                    /* Jump here to break out of the loop */
   int nLevel;                    /* Number of nested loop */
   struct WhereClause *pWC;       /* Decomposition of the WHERE clause */
+  double savedNQueryLoop;        /* pParse->nQueryLoop outside the WHERE loop */
   WhereLevel a[1];               /* Information about each nest loop in WHERE */
 };
 
@@ -9677,6 +9926,7 @@
   u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
   u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
   u8 disableTriggers;  /* True to disable triggers */
+  double nQueryLoop;   /* Estimated number of iterations of a query */
 
   /* Above is constant between recursions.  Below is reset before and after
   ** each recursion */
@@ -9955,6 +10205,15 @@
 
 
 /*
+** FTS4 is really an extension for FTS3.  It is enabled using the
+** SQLITE_ENABLE_FTS3 macro.  But to avoid confusion we also all
+** the SQLITE_ENABLE_FTS4 macro to serve as an alisse for SQLITE_ENABLE_FTS3.
+*/
+#if defined(SQLITE_ENABLE_FTS4) && !defined(SQLITE_ENABLE_FTS3)
+# define SQLITE_ENABLE_FTS3
+#endif
+
+/*
 ** The ctype.h header is needed for non-ASCII systems.  It is also
 ** needed by FTS3 when FTS3 is included in the amalgamation.
 */
@@ -10043,7 +10302,8 @@
 
 
 #ifndef SQLITE_MUTEX_OMIT
-SQLITE_PRIVATE   sqlite3_mutex_methods *sqlite3DefaultMutex(void);
+SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3DefaultMutex(void);
+SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3NoopMutex(void);
 SQLITE_PRIVATE   sqlite3_mutex *sqlite3MutexAlloc(int);
 SQLITE_PRIVATE   int sqlite3MutexInit(void);
 SQLITE_PRIVATE   int sqlite3MutexEnd(void);
@@ -10053,7 +10313,11 @@
 SQLITE_PRIVATE void sqlite3StatusAdd(int, int);
 SQLITE_PRIVATE void sqlite3StatusSet(int, int);
 
-SQLITE_PRIVATE int sqlite3IsNaN(double);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+SQLITE_PRIVATE   int sqlite3IsNaN(double);
+#else
+# define sqlite3IsNaN(X)  0
+#endif
 
 SQLITE_PRIVATE void sqlite3VXPrintf(StrAccum*, int, const char*, va_list);
 #ifndef SQLITE_OMIT_TRACE
@@ -10171,6 +10435,7 @@
 SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**, u16);
 SQLITE_PRIVATE void sqlite3WhereEnd(WhereInfo*);
 SQLITE_PRIVATE int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int);
+SQLITE_PRIVATE void sqlite3ExprCodeGetColumnOfTable(Vdbe*, Table*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCodeMove(Parse*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCodeCopy(Parse*, int, int, int);
 SQLITE_PRIVATE void sqlite3ExprCacheStore(Parse*, int, int, int);
@@ -10197,6 +10462,7 @@
 SQLITE_PRIVATE int sqlite3RunVacuum(char**, sqlite3*);
 SQLITE_PRIVATE char *sqlite3NameFromToken(sqlite3*, Token*);
 SQLITE_PRIVATE int sqlite3ExprCompare(Expr*, Expr*);
+SQLITE_PRIVATE int sqlite3ExprListCompare(ExprList*, ExprList*);
 SQLITE_PRIVATE void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
 SQLITE_PRIVATE void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
 SQLITE_PRIVATE Vdbe *sqlite3GetVdbe(Parse*);
@@ -10374,7 +10640,7 @@
                         void(*)(void*));
 SQLITE_PRIVATE void sqlite3ValueFree(sqlite3_value*);
 SQLITE_PRIVATE sqlite3_value *sqlite3ValueNew(sqlite3 *);
-SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *, const void*, int);
+SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *, const void*, int, u8);
 #ifdef SQLITE_ENABLE_STAT2
 SQLITE_PRIVATE char *sqlite3Utf8to16(sqlite3 *, u8, char *, int, int *);
 #endif
@@ -10386,11 +10652,13 @@
 SQLITE_PRIVATE const unsigned char sqlite3CtypeMap[];
 SQLITE_PRIVATE SQLITE_WSD struct Sqlite3Config sqlite3Config;
 SQLITE_PRIVATE SQLITE_WSD FuncDefHash sqlite3GlobalFunctions;
+#ifndef SQLITE_OMIT_WSD
 SQLITE_PRIVATE int sqlite3PendingByte;
 #endif
+#endif
 SQLITE_PRIVATE void sqlite3RootPageMoved(Db*, int, int);
 SQLITE_PRIVATE void sqlite3Reindex(Parse*, Token*, Token*);
-SQLITE_PRIVATE void sqlite3AlterFunctions(sqlite3*);
+SQLITE_PRIVATE void sqlite3AlterFunctions(void);
 SQLITE_PRIVATE void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
 SQLITE_PRIVATE int sqlite3GetToken(const unsigned char *, int *);
 SQLITE_PRIVATE void sqlite3NestedParse(Parse*, const char*, ...);
@@ -10499,6 +10767,9 @@
 SQLITE_PRIVATE CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, Expr *);
 SQLITE_PRIVATE int sqlite3TempInMemory(const sqlite3*);
 SQLITE_PRIVATE VTable *sqlite3GetVTable(sqlite3*, Table*);
+SQLITE_PRIVATE const char *sqlite3JournalModename(int);
+SQLITE_PRIVATE int sqlite3Checkpoint(sqlite3*, int);
+SQLITE_PRIVATE int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);
 
 /* Declarations for functions in fkey.c. All of these are replaced by
 ** no-op macros if OMIT_FOREIGN_KEY is defined. In this case no foreign
@@ -10605,7 +10876,46 @@
 # define sqlite3VdbeIOTraceSql(X)
 #endif
 
+/*
+** These routines are available for the mem2.c debugging memory allocator
+** only.  They are used to verify that different "types" of memory
+** allocations are properly tracked by the system.
+**
+** sqlite3MemdebugSetType() sets the "type" of an allocation to one of
+** the MEMTYPE_* macros defined below.  The type must be a bitmask with
+** a single bit set.
+**
+** sqlite3MemdebugHasType() returns true if any of the bits in its second
+** argument match the type set by the previous sqlite3MemdebugSetType().
+** sqlite3MemdebugHasType() is intended for use inside assert() statements.
+** For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
+**
+** Perhaps the most important point is the difference between MEMTYPE_HEAP
+** and MEMTYPE_DB.  If an allocation is MEMTYPE_DB, that means it might have
+** been allocated by lookaside, except the allocation was too large or
+** lookaside was already full.  It is important to verify that allocations
+** that might have been satisfied by lookaside are not passed back to 
+** non-lookaside free() routines.  Asserts such as the example above are
+** placed on the non-lookaside free() routines to verify this constraint. 
+**
+** All of this is no-op for a production build.  It only comes into
+** play when the SQLITE_MEMDEBUG compile-time option is used.
+*/
+#ifdef SQLITE_MEMDEBUG
+SQLITE_PRIVATE   void sqlite3MemdebugSetType(void*,u8);
+SQLITE_PRIVATE   int sqlite3MemdebugHasType(void*,u8);
+#else
+# define sqlite3MemdebugSetType(X,Y)  /* no-op */
+# define sqlite3MemdebugHasType(X,Y)  1
 #endif
+#define MEMTYPE_HEAP     0x01    /* General heap allocations */
+#define MEMTYPE_DB       0x02    /* Associated with a database connection */
+#define MEMTYPE_SCRATCH  0x04    /* Scratch allocations */
+#define MEMTYPE_PCACHE   0x08    /* Page cache allocations */
+
+#endif /* _SQLITEINT_H_ */
 
 /************** End of sqliteInt.h *******************************************/
 /************** Begin file global.c ******************************************/
@@ -10804,7 +11114,9 @@
 ** Changing the pending byte during operating results in undefined
 ** and dileterious behavior.
 */
+#ifndef SQLITE_OMIT_WSD
 SQLITE_PRIVATE int sqlite3PendingByte = 0x40000000;
+#endif
 
 /*
 ** Properties of opcodes.  The OPFLG_INITIALIZER macro is
@@ -10815,6 +11127,396 @@
 SQLITE_PRIVATE const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
 
 /************** End of global.c **********************************************/
+/************** Begin file ctime.c *******************************************/
+/*
+** 2010 February 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file implements routines used to report what compile-time options
+** SQLite was built with.
+*/
+
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+
+
+/*
+** An array of names of all compile-time options.  This array should 
+** be sorted A-Z.
+**
+** This array looks large, but in a typical installation actually uses
+** only a handful of compile-time options, so most times this array is usually
+** rather short and uses little memory space.
+*/
+static const char * const azCompileOpt[] = {
+
+/* These macros are provided to "stringify" the value of the define
+** for those options in which the value is meaningful. */
+#define CTIMEOPT_VAL_(opt) #opt
+#define CTIMEOPT_VAL(opt) CTIMEOPT_VAL_(opt)
+
+#ifdef SQLITE_32BIT_ROWID
+  "32BIT_ROWID",
+#endif
+#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
+  "4_BYTE_ALIGNED_MALLOC",
+#endif
+#ifdef SQLITE_CASE_SENSITIVE_LIKE
+  "CASE_SENSITIVE_LIKE",
+#endif
+#ifdef SQLITE_CHECK_PAGES
+  "CHECK_PAGES",
+#endif
+#ifdef SQLITE_COVERAGE_TEST
+  "COVERAGE_TEST",
+#endif
+#ifdef SQLITE_DEBUG
+  "DEBUG",
+#endif
+#ifdef SQLITE_DEFAULT_LOCKING_MODE
+  "DEFAULT_LOCKING_MODE=" CTIMEOPT_VAL(SQLITE_DEFAULT_LOCKING_MODE),
+#endif
+#ifdef SQLITE_DISABLE_DIRSYNC
+  "DISABLE_DIRSYNC",
+#endif
+#ifdef SQLITE_DISABLE_LFS
+  "DISABLE_LFS",
+#endif
+#ifdef SQLITE_ENABLE_ATOMIC_WRITE
+  "ENABLE_ATOMIC_WRITE",
+#endif
+#ifdef SQLITE_ENABLE_CEROD
+  "ENABLE_CEROD",
+#endif
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  "ENABLE_COLUMN_METADATA",
+#endif
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  "ENABLE_EXPENSIVE_ASSERT",
+#endif
+#ifdef SQLITE_ENABLE_FTS1
+  "ENABLE_FTS1",
+#endif
+#ifdef SQLITE_ENABLE_FTS2
+  "ENABLE_FTS2",
+#endif
+#ifdef SQLITE_ENABLE_FTS3
+  "ENABLE_FTS3",
+#endif
+#ifdef SQLITE_ENABLE_FTS3_PARENTHESIS
+  "ENABLE_FTS3_PARENTHESIS",
+#endif
+#ifdef SQLITE_ENABLE_FTS4
+  "ENABLE_FTS4",
+#endif
+#ifdef SQLITE_ENABLE_ICU
+  "ENABLE_ICU",
+#endif
+#ifdef SQLITE_ENABLE_IOTRACE
+  "ENABLE_IOTRACE",
+#endif
+#ifdef SQLITE_ENABLE_LOAD_EXTENSION
+  "ENABLE_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_ENABLE_LOCKING_STYLE
+  "ENABLE_LOCKING_STYLE=" CTIMEOPT_VAL(SQLITE_ENABLE_LOCKING_STYLE),
+#endif
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+  "ENABLE_MEMORY_MANAGEMENT",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS3
+  "ENABLE_MEMSYS3",
+#endif
+#ifdef SQLITE_ENABLE_MEMSYS5
+  "ENABLE_MEMSYS5",
+#endif
+#ifdef SQLITE_ENABLE_OVERSIZE_CELL_CHECK
+  "ENABLE_OVERSIZE_CELL_CHECK",
+#endif
+#ifdef SQLITE_ENABLE_RTREE
+  "ENABLE_RTREE",
+#endif
+#ifdef SQLITE_ENABLE_STAT2
+  "ENABLE_STAT2",
+#endif
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+  "ENABLE_UNLOCK_NOTIFY",
+#endif
+#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
+  "ENABLE_UPDATE_DELETE_LIMIT",
+#endif
+#ifdef SQLITE_HAS_CODEC
+  "HAS_CODEC",
+#endif
+#ifdef SQLITE_HAVE_ISNAN
+  "HAVE_ISNAN",
+#endif
+#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
+  "HOMEGROWN_RECURSIVE_MUTEX",
+#endif
+#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
+  "IGNORE_AFP_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
+  "IGNORE_FLOCK_LOCK_ERRORS",
+#endif
+#ifdef SQLITE_INT64_TYPE
+  "INT64_TYPE",
+#endif
+#ifdef SQLITE_LOCK_TRACE
+  "LOCK_TRACE",
+#endif
+#ifdef SQLITE_MEMDEBUG
+  "MEMDEBUG",
+#endif
+#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
+  "MIXED_ENDIAN_64BIT_FLOAT",
+#endif
+#ifdef SQLITE_NO_SYNC
+  "NO_SYNC",
+#endif
+#ifdef SQLITE_OMIT_ALTERTABLE
+  "OMIT_ALTERTABLE",
+#endif
+#ifdef SQLITE_OMIT_ANALYZE
+  "OMIT_ANALYZE",
+#endif
+#ifdef SQLITE_OMIT_ATTACH
+  "OMIT_ATTACH",
+#endif
+#ifdef SQLITE_OMIT_AUTHORIZATION
+  "OMIT_AUTHORIZATION",
+#endif
+#ifdef SQLITE_OMIT_AUTOINCREMENT
+  "OMIT_AUTOINCREMENT",
+#endif
+#ifdef SQLITE_OMIT_AUTOINIT
+  "OMIT_AUTOINIT",
+#endif
+#ifdef SQLITE_OMIT_AUTOMATIC_INDEX
+  "OMIT_AUTOMATIC_INDEX",
+#endif
+#ifdef SQLITE_OMIT_AUTOVACUUM
+  "OMIT_AUTOVACUUM",
+#endif
+#ifdef SQLITE_OMIT_BETWEEN_OPTIMIZATION
+  "OMIT_BETWEEN_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_BLOB_LITERAL
+  "OMIT_BLOB_LITERAL",
+#endif
+#ifdef SQLITE_OMIT_BTREECOUNT
+  "OMIT_BTREECOUNT",
+#endif
+#ifdef SQLITE_OMIT_BUILTIN_TEST
+  "OMIT_BUILTIN_TEST",
+#endif
+#ifdef SQLITE_OMIT_CAST
+  "OMIT_CAST",
+#endif
+#ifdef SQLITE_OMIT_CHECK
+  "OMIT_CHECK",
+#endif
+#ifdef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  "OMIT_COMPILEOPTION_DIAGS",
+#endif
+#ifdef SQLITE_OMIT_COMPLETE
+  "OMIT_COMPLETE",
+#endif
+#ifdef SQLITE_OMIT_COMPOUND_SELECT
+  "OMIT_COMPOUND_SELECT",
+#endif
+#ifdef SQLITE_OMIT_DATETIME_FUNCS
+  "OMIT_DATETIME_FUNCS",
+#endif
+#ifdef SQLITE_OMIT_DECLTYPE
+  "OMIT_DECLTYPE",
+#endif
+#ifdef SQLITE_OMIT_DEPRECATED
+  "OMIT_DEPRECATED",
+#endif
+#ifdef SQLITE_OMIT_DISKIO
+  "OMIT_DISKIO",
+#endif
+#ifdef SQLITE_OMIT_EXPLAIN
+  "OMIT_EXPLAIN",
+#endif
+#ifdef SQLITE_OMIT_FLAG_PRAGMAS
+  "OMIT_FLAG_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  "OMIT_FLOATING_POINT",
+#endif
+#ifdef SQLITE_OMIT_FOREIGN_KEY
+  "OMIT_FOREIGN_KEY",
+#endif
+#ifdef SQLITE_OMIT_GET_TABLE
+  "OMIT_GET_TABLE",
+#endif
+#ifdef SQLITE_OMIT_GLOBALRECOVER
+  "OMIT_GLOBALRECOVER",
+#endif
+#ifdef SQLITE_OMIT_INCRBLOB
+  "OMIT_INCRBLOB",
+#endif
+#ifdef SQLITE_OMIT_INTEGRITY_CHECK
+  "OMIT_INTEGRITY_CHECK",
+#endif
+#ifdef SQLITE_OMIT_LIKE_OPTIMIZATION
+  "OMIT_LIKE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_LOAD_EXTENSION
+  "OMIT_LOAD_EXTENSION",
+#endif
+#ifdef SQLITE_OMIT_LOCALTIME
+  "OMIT_LOCALTIME",
+#endif
+#ifdef SQLITE_OMIT_LOOKASIDE
+  "OMIT_LOOKASIDE",
+#endif
+#ifdef SQLITE_OMIT_MEMORYDB
+  "OMIT_MEMORYDB",
+#endif
+#ifdef SQLITE_OMIT_OR_OPTIMIZATION
+  "OMIT_OR_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_PAGER_PRAGMAS
+  "OMIT_PAGER_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_PRAGMA
+  "OMIT_PRAGMA",
+#endif
+#ifdef SQLITE_OMIT_PROGRESS_CALLBACK
+  "OMIT_PROGRESS_CALLBACK",
+#endif
+#ifdef SQLITE_OMIT_QUICKBALANCE
+  "OMIT_QUICKBALANCE",
+#endif
+#ifdef SQLITE_OMIT_REINDEX
+  "OMIT_REINDEX",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_PRAGMAS
+  "OMIT_SCHEMA_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS
+  "OMIT_SCHEMA_VERSION_PRAGMAS",
+#endif
+#ifdef SQLITE_OMIT_SHARED_CACHE
+  "OMIT_SHARED_CACHE",
+#endif
+#ifdef SQLITE_OMIT_SUBQUERY
+  "OMIT_SUBQUERY",
+#endif
+#ifdef SQLITE_OMIT_TCL_VARIABLE
+  "OMIT_TCL_VARIABLE",
+#endif
+#ifdef SQLITE_OMIT_TEMPDB
+  "OMIT_TEMPDB",
+#endif
+#ifdef SQLITE_OMIT_TRACE
+  "OMIT_TRACE",
+#endif
+#ifdef SQLITE_OMIT_TRIGGER
+  "OMIT_TRIGGER",
+#endif
+#ifdef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
+  "OMIT_TRUNCATE_OPTIMIZATION",
+#endif
+#ifdef SQLITE_OMIT_UTF16
+  "OMIT_UTF16",
+#endif
+#ifdef SQLITE_OMIT_VACUUM
+  "OMIT_VACUUM",
+#endif
+#ifdef SQLITE_OMIT_VIEW
+  "OMIT_VIEW",
+#endif
+#ifdef SQLITE_OMIT_VIRTUALTABLE
+  "OMIT_VIRTUALTABLE",
+#endif
+#ifdef SQLITE_OMIT_WSD
+  "OMIT_WSD",
+#endif
+#ifdef SQLITE_OMIT_XFER_OPT
+  "OMIT_XFER_OPT",
+#endif
+#ifdef SQLITE_PERFORMANCE_TRACE
+  "PERFORMANCE_TRACE",
+#endif
+#ifdef SQLITE_PROXY_DEBUG
+  "PROXY_DEBUG",
+#endif
+#ifdef SQLITE_SECURE_DELETE
+  "SECURE_DELETE",
+#endif
+#ifdef SQLITE_SMALL_STACK
+  "SMALL_STACK",
+#endif
+#ifdef SQLITE_SOUNDEX
+  "SOUNDEX",
+#endif
+#ifdef SQLITE_TCL
+  "TCL",
+#endif
+#ifdef SQLITE_TEMP_STORE
+  "TEMP_STORE=" CTIMEOPT_VAL(SQLITE_TEMP_STORE),
+#endif
+#ifdef SQLITE_TEST
+  "TEST",
+#endif
+#ifdef SQLITE_THREADSAFE
+  "THREADSAFE=" CTIMEOPT_VAL(SQLITE_THREADSAFE),
+#endif
+#ifdef SQLITE_USE_ALLOCA
+  "USE_ALLOCA",
+#endif
+#ifdef SQLITE_ZERO_MALLOC
+  "ZERO_MALLOC"
+#endif
+};
+
+/*
+** Given the name of a compile-time option, return true if that option
+** was used and false if not.
+**
+** The name can optionally begin with "SQLITE_" but the "SQLITE_" prefix
+** is not required for a match.
+*/
+SQLITE_API int sqlite3_compileoption_used(const char *zOptName){
+  int i, n;
+  if( sqlite3StrNICmp(zOptName, "SQLITE_", 7)==0 ) zOptName += 7;
+  n = sqlite3Strlen30(zOptName);
+
+  /* Since ArraySize(azCompileOpt) is normally in single digits, a
+  ** linear search is adequate.  No need for a binary search. */
+  for(i=0; i<ArraySize(azCompileOpt); i++){
+    if(   (sqlite3StrNICmp(zOptName, azCompileOpt[i], n)==0)
+       && ( (azCompileOpt[i][n]==0) || (azCompileOpt[i][n]=='=') ) ) return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the N-th compile-time option string.  If N is out of range,
+** return a NULL pointer.
+*/
+SQLITE_API const char *sqlite3_compileoption_get(int N){
+  if( N>=0 && N<ArraySize(azCompileOpt) ){
+    return azCompileOpt[N];
+  }
+  return 0;
+}
+
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/************** End of ctime.c ***********************************************/
 /************** Begin file status.c ******************************************/
 /*
 ** 2008 June 18
@@ -10929,6 +11631,26 @@
       }
       break;
     }
+
+    /* 
+    ** Return an approximation for the amount of memory currently used
+    ** by all pagers associated with the given database connection.  The
+    ** highwater mark is meaningless and is returned as zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_USED: {
+      int totalUsed = 0;
+      int i;
+      for(i=0; i<db->nDb; i++){
+        Btree *pBt = db->aDb[i].pBt;
+        if( pBt ){
+          Pager *pPager = sqlite3BtreePager(pBt);
+          totalUsed += sqlite3PagerMemUsed(pPager);
+        }
+      }
+      *pCurrent = totalUsed;
+      *pHighwater = 0;
+      break;
+    }
     default: {
       return SQLITE_ERROR;
     }
@@ -11251,10 +11973,8 @@
 ** Set the time to the current time reported by the VFS
 */
 static void setDateTimeToCurrent(sqlite3_context *context, DateTime *p){
-  double r;
   sqlite3 *db = sqlite3_context_db_handle(context);
-  sqlite3OsCurrentTime(db->pVfs, &r);
-  p->iJD = (sqlite3_int64)(r*86400000.0 + 0.5);
+  sqlite3OsCurrentTimeInt64(db->pVfs, &p->iJD);
   p->validJD = 1;
 }
 
@@ -11975,22 +12695,15 @@
   time_t t;
   char *zFormat = (char *)sqlite3_user_data(context);
   sqlite3 *db;
-  double rT;
+  sqlite3_int64 iT;
   char zBuf[20];
 
   UNUSED_PARAMETER(argc);
   UNUSED_PARAMETER(argv);
 
   db = sqlite3_context_db_handle(context);
-  sqlite3OsCurrentTime(db->pVfs, &rT);
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  t = 86400.0*(rT - 2440587.5) + 0.5;
-#else
-  /* without floating point support, rT will have
-  ** already lost fractional day precision.
-  */
-  t = 86400 * (rT - 2440587) - 43200;
-#endif
+  sqlite3OsCurrentTimeInt64(db->pVfs, &iT);
+  t = iT/1000 - 10000*(sqlite3_int64)21086676;
 #ifdef HAVE_GMTIME_R
   {
     struct tm sNow;
@@ -12029,8 +12742,8 @@
     FUNCTION(current_date,      0, 0, 0, cdateFunc     ),
 #else
     STR_FUNCTION(current_time,      0, "%H:%M:%S",          0, currentTimeFunc),
-    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d",          0, currentTimeFunc),
-    STR_FUNCTION(current_date,      0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
+    STR_FUNCTION(current_date,      0, "%Y-%m-%d",          0, currentTimeFunc),
+    STR_FUNCTION(current_timestamp, 0, "%Y-%m-%d %H:%M:%S", 0, currentTimeFunc),
 #endif
   };
   int i;
@@ -12143,6 +12856,27 @@
 SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
   return id->pMethods->xDeviceCharacteristics(id);
 }
+SQLITE_PRIVATE int sqlite3OsShmOpen(sqlite3_file *id){
+  return id->pMethods->xShmOpen(id);
+}
+SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
+  return id->pMethods->xShmLock(id, offset, n, flags);
+}
+SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id){
+  id->pMethods->xShmBarrier(id);
+}
+SQLITE_PRIVATE int sqlite3OsShmClose(sqlite3_file *id, int deleteFlag){
+  return id->pMethods->xShmClose(id, deleteFlag);
+}
+SQLITE_PRIVATE int sqlite3OsShmMap(
+  sqlite3_file *id, 
+  int iPage, 
+  int pgsz, 
+  int isWrite, 
+  void volatile **pp
+){
+  return id->pMethods->xShmMap(id, iPage, pgsz, isWrite, pp);
+}
 
 /*
 ** The next group of routines are convenience wrappers around the
@@ -12157,11 +12891,11 @@
 ){
   int rc;
   DO_OS_MALLOC_TEST(0);
-  /* 0x7f1f is a mask of SQLITE_OPEN_ flags that are valid to be passed
+  /* 0x7f3f is a mask of SQLITE_OPEN_ flags that are valid to be passed
   ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
   ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
   ** reaching the VFS. */
-  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x7f1f, pFlagsOut);
+  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x7f3f, pFlagsOut);
   assert( rc==SQLITE_OK || pFile->pMethods==0 );
   return rc;
 }
@@ -12206,8 +12940,16 @@
 SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *pVfs, int nMicro){
   return pVfs->xSleep(pVfs, nMicro);
 }
-SQLITE_PRIVATE int sqlite3OsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
-  return pVfs->xCurrentTime(pVfs, pTimeOut);
+SQLITE_PRIVATE int sqlite3OsCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  int rc;
+  if( pVfs->iVersion>=2 && pVfs->xCurrentTimeInt64 ){
+    rc = pVfs->xCurrentTimeInt64(pVfs, pTimeOut);
+  }else{
+    double r;
+    rc = pVfs->xCurrentTime(pVfs, &r);
+    *pTimeOut = (sqlite3_int64)(r*86400000.0);
+  }
+  return rc;
 }
 
 SQLITE_PRIVATE int sqlite3OsOpenMalloc(
@@ -12584,7 +13326,6 @@
   sqlite3_int64 *p = (sqlite3_int64*)pPrior;
   assert( pPrior!=0 && nByte>0 );
   nByte = ROUND8(nByte);
-  p = (sqlite3_int64*)pPrior;
   p--;
   p = realloc(p, nByte+8 );
   if( p ){
@@ -12703,7 +13444,8 @@
   struct MemBlockHdr *pNext, *pPrev;  /* Linked list of all unfreed memory */
   char nBacktrace;                    /* Number of backtraces on this alloc */
   char nBacktraceSlots;               /* Available backtrace slots */
-  short nTitle;                       /* Bytes of title; includes '\0' */
+  u8 nTitle;                          /* Bytes of title; includes '\0' */
+  u8 eType;                           /* Allocation type code */
   int iForeGuard;                     /* Guard word for sanity */
 };
 
@@ -12911,6 +13653,7 @@
     }
     mem.pLast = pHdr;
     pHdr->iForeGuard = FOREGUARD;
+    pHdr->eType = MEMTYPE_HEAP;
     pHdr->nBacktraceSlots = mem.nBacktrace;
     pHdr->nTitle = mem.nTitle;
     if( mem.nBacktrace ){
@@ -12946,7 +13689,8 @@
   struct MemBlockHdr *pHdr;
   void **pBt;
   char *z;
-  assert( sqlite3GlobalConfig.bMemstat || mem.mutex!=0 );
+  assert( sqlite3GlobalConfig.bMemstat || sqlite3GlobalConfig.bCoreMutex==0 
+       || mem.mutex!=0 );
   pHdr = sqlite3MemsysGetHeader(pPrior);
   pBt = (void**)pHdr;
   pBt -= pHdr->nBacktraceSlots;
@@ -13018,6 +13762,47 @@
 }
 
 /*
+** Set the "type" of an allocation.
+*/
+SQLITE_PRIVATE void sqlite3MemdebugSetType(void *p, u8 eType){
+  if( p ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );
+    pHdr->eType = eType;
+  }
+}
+
+/*
+** Return TRUE if the mask of type in eType matches the type of the
+** allocation p.  Also return true if p==NULL.
+**
+** This routine is designed for use within an assert() statement, to
+** verify the type of an allocation.  For example:
+**
+**     assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );
+*/
+SQLITE_PRIVATE int sqlite3MemdebugHasType(void *p, u8 eType){
+  int rc = 1;
+  if( p ){
+    struct MemBlockHdr *pHdr;
+    pHdr = sqlite3MemsysGetHeader(p);
+    assert( pHdr->iForeGuard==FOREGUARD );         /* Allocation is valid */
+    assert( (pHdr->eType & (pHdr->eType-1))==0 );  /* Only one type bit set */
+    if( (pHdr->eType&eType)==0 ){
+      void **pBt;
+      pBt = (void**)pHdr;
+      pBt -= pHdr->nBacktraceSlots;
+      backtrace_symbols_fd(pBt, pHdr->nBacktrace, fileno(stderr));
+      fprintf(stderr, "\n");
+      rc = 0;
+    }
+  }
+  return rc;
+}
+ 
+
+/*
 ** Set the number of backtrace levels kept for each allocation.
 ** A value of zero turns off backtracing.  The number is always rounded
 ** up to a multiple of 2.
@@ -14418,23 +15203,26 @@
 */
 SQLITE_PRIVATE int sqlite3MutexInit(void){ 
   int rc = SQLITE_OK;
-  if( sqlite3GlobalConfig.bCoreMutex ){
-    if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
-      /* If the xMutexAlloc method has not been set, then the user did not
-      ** install a mutex implementation via sqlite3_config() prior to 
-      ** sqlite3_initialize() being called. This block copies pointers to
-      ** the default implementation into the sqlite3GlobalConfig structure.
-      */
-      sqlite3_mutex_methods *pFrom = sqlite3DefaultMutex();
-      sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
+  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
+    /* If the xMutexAlloc method has not been set, then the user did not
+    ** install a mutex implementation via sqlite3_config() prior to 
+    ** sqlite3_initialize() being called. This block copies pointers to
+    ** the default implementation into the sqlite3GlobalConfig structure.
+    */
+    sqlite3_mutex_methods const *pFrom;
+    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
 
-      memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
-      memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
-             sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
-      pTo->xMutexAlloc = pFrom->xMutexAlloc;
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pFrom = sqlite3DefaultMutex();
+    }else{
+      pFrom = sqlite3NoopMutex();
     }
-    rc = sqlite3GlobalConfig.mutex.xMutexInit();
+    memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
+    memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
+           sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
+    pTo->xMutexAlloc = pFrom->xMutexAlloc;
   }
+  rc = sqlite3GlobalConfig.mutex.xMutexInit();
 
 #ifdef SQLITE_DEBUG
   GLOBAL(int, mutexIsInit) = 1;
@@ -14566,15 +15354,14 @@
 ** called correctly.
 */
 
+#ifndef SQLITE_MUTEX_OMIT
 
-#if defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG)
+#ifndef SQLITE_DEBUG
 /*
 ** Stub routines for all mutex methods.
 **
 ** This routines provide no mutual exclusion or error checking.
 */
-static int noopMutexHeld(sqlite3_mutex *p){ return 1; }
-static int noopMutexNotheld(sqlite3_mutex *p){ return 1; }
 static int noopMutexInit(void){ return SQLITE_OK; }
 static int noopMutexEnd(void){ return SQLITE_OK; }
 static sqlite3_mutex *noopMutexAlloc(int id){ return (sqlite3_mutex*)8; }
@@ -14583,8 +15370,8 @@
 static int noopMutexTry(sqlite3_mutex *p){ return SQLITE_OK; }
 static void noopMutexLeave(sqlite3_mutex *p){ return; }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     noopMutexInit,
     noopMutexEnd,
     noopMutexAlloc,
@@ -14593,15 +15380,15 @@
     noopMutexTry,
     noopMutexLeave,
 
-    noopMutexHeld,
-    noopMutexNotheld
+    0,
+    0,
   };
 
   return &sMutex;
 }
-#endif /* defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG) */
+#endif /* !SQLITE_DEBUG */
 
-#if defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG)
+#ifdef SQLITE_DEBUG
 /*
 ** In this implementation, error checking is provided for testing
 ** and debugging purposes.  The mutexes still do not provide any
@@ -14611,19 +15398,21 @@
 /*
 ** The mutex object
 */
-struct sqlite3_mutex {
+typedef struct sqlite3_debug_mutex {
   int id;     /* The mutex type */
   int cnt;    /* Number of entries without a matching leave */
-};
+} sqlite3_debug_mutex;
 
 /*
 ** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
 ** intended for use inside assert() statements.
 */
-static int debugMutexHeld(sqlite3_mutex *p){
+static int debugMutexHeld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   return p==0 || p->cnt>0;
 }
-static int debugMutexNotheld(sqlite3_mutex *p){
+static int debugMutexNotheld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   return p==0 || p->cnt==0;
 }
 
@@ -14639,8 +15428,8 @@
 ** that means that a mutex could not be allocated. 
 */
 static sqlite3_mutex *debugMutexAlloc(int id){
-  static sqlite3_mutex aStatic[6];
-  sqlite3_mutex *pNew = 0;
+  static sqlite3_debug_mutex aStatic[6];
+  sqlite3_debug_mutex *pNew = 0;
   switch( id ){
     case SQLITE_MUTEX_FAST:
     case SQLITE_MUTEX_RECURSIVE: {
@@ -14659,13 +15448,14 @@
       break;
     }
   }
-  return pNew;
+  return (sqlite3_mutex*)pNew;
 }
 
 /*
 ** This routine deallocates a previously allocated mutex.
 */
-static void debugMutexFree(sqlite3_mutex *p){
+static void debugMutexFree(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
   assert( p->cnt==0 );
   assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
   sqlite3_free(p);
@@ -14682,12 +15472,14 @@
 ** can enter.  If the same thread tries to enter any other kind of mutex
 ** more than once, the behavior is undefined.
 */
-static void debugMutexEnter(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+static void debugMutexEnter(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
   p->cnt++;
 }
-static int debugMutexTry(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+static int debugMutexTry(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
   p->cnt++;
   return SQLITE_OK;
 }
@@ -14698,14 +15490,15 @@
 ** is undefined if the mutex is not currently entered or
 ** is not currently allocated.  SQLite will never do either.
 */
-static void debugMutexLeave(sqlite3_mutex *p){
-  assert( debugMutexHeld(p) );
+static void debugMutexLeave(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( debugMutexHeld(pX) );
   p->cnt--;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     debugMutexInit,
     debugMutexEnd,
     debugMutexAlloc,
@@ -14720,7 +15513,18 @@
 
   return &sMutex;
 }
-#endif /* defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG) */
+#endif /* SQLITE_DEBUG */
+
+/*
+** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
+** is used regardless of the run-time threadsafety setting.
+*/
+#ifdef SQLITE_MUTEX_NOOP
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  return sqliteNoopMutex();
+}
+#endif /* SQLITE_MUTEX_NOOP */
+#endif /* SQLITE_MUTEX_OMIT */
 
 /************** End of mutex_noop.c ******************************************/
 /************** Begin file mutex_os2.c ***************************************/
@@ -14976,8 +15780,8 @@
   DosReleaseMutexSem(p->mutex);
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     os2MutexInit,
     os2MutexEnd,
     os2MutexAlloc,
@@ -15022,23 +15826,33 @@
 
 #include <pthread.h>
 
+/*
+** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
+** are necessary under two condidtions:  (1) Debug builds and (2) using
+** home-grown mutexes.  Encapsulate these conditions into a single #define.
+*/
+#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
+# define SQLITE_MUTEX_NREF 1
+#else
+# define SQLITE_MUTEX_NREF 0
+#endif
 
 /*
 ** Each recursive mutex is an instance of the following structure.
 */
 struct sqlite3_mutex {
   pthread_mutex_t mutex;     /* Mutex controlling the lock */
+#if SQLITE_MUTEX_NREF
   int id;                    /* Mutex type */
-  int nRef;                  /* Number of entrances */
-  pthread_t owner;           /* Thread that is within this mutex */
-#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of entrances */
+  volatile pthread_t owner;  /* Thread that is within this mutex */
   int trace;                 /* True to trace changes */
 #endif
 };
-#ifdef SQLITE_DEBUG
+#if SQLITE_MUTEX_NREF
 #define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0, 0 }
 #else
-#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0 }
+#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
 #endif
 
 /*
@@ -15140,14 +15954,18 @@
         pthread_mutex_init(&p->mutex, &recursiveAttr);
         pthread_mutexattr_destroy(&recursiveAttr);
 #endif
+#if SQLITE_MUTEX_NREF
         p->id = iType;
+#endif
       }
       break;
     }
     case SQLITE_MUTEX_FAST: {
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){
+#if SQLITE_MUTEX_NREF
         p->id = iType;
+#endif
         pthread_mutex_init(&p->mutex, 0);
       }
       break;
@@ -15156,7 +15974,9 @@
       assert( iType-2 >= 0 );
       assert( iType-2 < ArraySize(staticMutexes) );
       p = &staticMutexes[iType-2];
+#if SQLITE_MUTEX_NREF
       p->id = iType;
+#endif
       break;
     }
   }
@@ -15216,9 +16036,11 @@
   /* Use the built-in recursive mutexes if they are available.
   */
   pthread_mutex_lock(&p->mutex);
+#if SQLITE_MUTEX_NREF
   p->owner = pthread_self();
   p->nRef++;
 #endif
+#endif
 
 #ifdef SQLITE_DEBUG
   if( p->trace ){
@@ -15259,8 +16081,10 @@
   /* Use the built-in recursive mutexes if they are available.
   */
   if( pthread_mutex_trylock(&p->mutex)==0 ){
+#if SQLITE_MUTEX_NREF
     p->owner = pthread_self();
     p->nRef++;
+#endif
     rc = SQLITE_OK;
   }else{
     rc = SQLITE_BUSY;
@@ -15283,7 +16107,9 @@
 */
 static void pthreadMutexLeave(sqlite3_mutex *p){
   assert( pthreadMutexHeld(p) );
+#if SQLITE_MUTEX_NREF
   p->nRef--;
+#endif
   assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
 
 #ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
@@ -15301,8 +16127,8 @@
 #endif
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     pthreadMutexInit,
     pthreadMutexEnd,
     pthreadMutexAlloc,
@@ -15352,9 +16178,18 @@
 struct sqlite3_mutex {
   CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
   int id;                    /* Mutex type */
-  int nRef;                  /* Number of enterances */
-  DWORD owner;               /* Thread holding this mutex */
+#ifdef SQLITE_DEBUG
+  volatile int nRef;         /* Number of enterances */
+  volatile DWORD owner;      /* Thread holding this mutex */
+  int trace;                 /* True to trace changes */
+#endif
 };
+#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
+#ifdef SQLITE_DEBUG
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, 0L, (DWORD)0, 0 }
+#else
+#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0 }
+#endif
 
 /*
 ** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
@@ -15398,8 +16233,12 @@
 static int winMutexHeld(sqlite3_mutex *p){
   return p->nRef!=0 && p->owner==GetCurrentThreadId();
 }
+static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
+  return p->nRef==0 || p->owner!=tid;
+}
 static int winMutexNotheld(sqlite3_mutex *p){
-  return p->nRef==0 || p->owner!=GetCurrentThreadId();
+  DWORD tid = GetCurrentThreadId(); 
+  return winMutexNotheld2(p, tid);
 }
 #endif
 
@@ -15407,7 +16246,14 @@
 /*
 ** Initialize and deinitialize the mutex subsystem.
 */
-static sqlite3_mutex winMutex_staticMutexes[6];
+static sqlite3_mutex winMutex_staticMutexes[6] = {
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER
+};
 static int winMutex_isInit = 0;
 /* As winMutexInit() and winMutexEnd() are called as part
 ** of the sqlite3_initialize and sqlite3_shutdown()
@@ -15498,7 +16344,9 @@
     case SQLITE_MUTEX_RECURSIVE: {
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){  
+#ifdef SQLITE_DEBUG
         p->id = iType;
+#endif
         InitializeCriticalSection(&p->mutex);
       }
       break;
@@ -15508,7 +16356,9 @@
       assert( iType-2 >= 0 );
       assert( iType-2 < ArraySize(winMutex_staticMutexes) );
       p = &winMutex_staticMutexes[iType-2];
+#ifdef SQLITE_DEBUG
       p->id = iType;
+#endif
       break;
     }
   }
@@ -15541,14 +16391,25 @@
 ** more than once, the behavior is undefined.
 */
 static void winMutexEnter(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld(p) );
+#ifdef SQLITE_DEBUG
+  DWORD tid = GetCurrentThreadId(); 
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+#endif
   EnterCriticalSection(&p->mutex);
-  p->owner = GetCurrentThreadId(); 
+#ifdef SQLITE_DEBUG
+  p->owner = tid; 
   p->nRef++;
+  if( p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
 }
 static int winMutexTry(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId(); 
+#endif
   int rc = SQLITE_BUSY;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld(p) );
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
   /*
   ** The sqlite3_mutex_try() routine is very rarely used, and when it
   ** is used it is merely an optimization.  So it is OK for it to always
@@ -15562,13 +16423,18 @@
   */
 #if 0
   if( mutexIsNT() && TryEnterCriticalSection(&p->mutex) ){
-    p->owner = GetCurrentThreadId();
+    p->owner = tid;
     p->nRef++;
     rc = SQLITE_OK;
   }
 #else
   UNUSED_PARAMETER(p);
 #endif
+#ifdef SQLITE_DEBUG
+  if( rc==SQLITE_OK && p->trace ){
+    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
   return rc;
 }
 
@@ -15579,15 +16445,23 @@
 ** is not currently allocated.  SQLite will never do either.
 */
 static void winMutexLeave(sqlite3_mutex *p){
+#ifndef NDEBUG
+  DWORD tid = GetCurrentThreadId();
   assert( p->nRef>0 );
-  assert( p->owner==GetCurrentThreadId() );
+  assert( p->owner==tid );
   p->nRef--;
   assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
+#endif
   LeaveCriticalSection(&p->mutex);
+#ifdef SQLITE_DEBUG
+  if( p->trace ){
+    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
+  }
+#endif
 }
 
-SQLITE_PRIVATE sqlite3_mutex_methods *sqlite3DefaultMutex(void){
-  static sqlite3_mutex_methods sMutex = {
+SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
     winMutexInit,
     winMutexEnd,
     winMutexAlloc,
@@ -15966,6 +16840,7 @@
   }else{
     p = sqlite3GlobalConfig.m.xMalloc(n);
   }
+  sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
 #if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
   scratchAllocOut = p!=0;
 #endif
@@ -15986,6 +16861,8 @@
     if( sqlite3GlobalConfig.pScratch==0
            || p<sqlite3GlobalConfig.pScratch
            || p>=(void*)mem0.aScratchFree ){
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
       if( sqlite3GlobalConfig.bMemstat ){
         int iSize = sqlite3MallocSize(p);
         sqlite3_mutex_enter(mem0.mutex);
@@ -16026,6 +16903,7 @@
 ** sqlite3Malloc() or sqlite3_malloc().
 */
 SQLITE_PRIVATE int sqlite3MallocSize(void *p){
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   return sqlite3GlobalConfig.m.xSize(p);
 }
 SQLITE_PRIVATE int sqlite3DbMallocSize(sqlite3 *db, void *p){
@@ -16033,6 +16911,8 @@
   if( isLookaside(db, p) ){
     return db->lookaside.sz;
   }else{
+    assert( sqlite3MemdebugHasType(p,
+             db ? (MEMTYPE_DB|MEMTYPE_HEAP) : MEMTYPE_HEAP) );
     return sqlite3GlobalConfig.m.xSize(p);
   }
 }
@@ -16042,6 +16922,7 @@
 */
 SQLITE_API void sqlite3_free(void *p){
   if( p==0 ) return;
+  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   if( sqlite3GlobalConfig.bMemstat ){
     sqlite3_mutex_enter(mem0.mutex);
     sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, -sqlite3MallocSize(p));
@@ -16064,6 +16945,8 @@
     db->lookaside.pFree = pBuf;
     db->lookaside.nOut--;
   }else{
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_DB|MEMTYPE_HEAP) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
     sqlite3_free(p);
   }
 }
@@ -16096,6 +16979,7 @@
           mem0.alarmThreshold ){
       sqlite3MallocAlarm(nNew-nOld);
     }
+    assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
     if( pNew==0 && mem0.alarmCallback ){
       sqlite3MallocAlarm(nBytes);
@@ -16193,6 +17077,8 @@
   if( !p && db ){
     db->mallocFailed = 1;
   }
+  sqlite3MemdebugSetType(p,
+            (db && db->lookaside.bEnabled) ? MEMTYPE_DB : MEMTYPE_HEAP);
   return p;
 }
 
@@ -16218,10 +17104,14 @@
         sqlite3DbFree(db, p);
       }
     }else{
+      assert( sqlite3MemdebugHasType(p, MEMTYPE_DB|MEMTYPE_HEAP) );
+      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
       pNew = sqlite3_realloc(p, n);
       if( !pNew ){
         db->mallocFailed = 1;
       }
+      sqlite3MemdebugSetType(pNew,
+            db->lookaside.bEnabled ? MEMTYPE_DB : MEMTYPE_HEAP);
     }
   }
   return pNew;
@@ -16782,7 +17672,9 @@
       case etEXP:
       case etGENERIC:
         realvalue = va_arg(ap,double);
-#ifndef SQLITE_OMIT_FLOATING_POINT
+#ifdef SQLITE_OMIT_FLOATING_POINT
+        length = 0;
+#else
         if( precision<0 ) precision = 6;         /* Set default precision */
         if( precision>etBUFSIZE/2-10 ) precision = etBUFSIZE/2-10;
         if( realvalue<0.0 ){
@@ -16928,7 +17820,7 @@
           while( nPad-- ) bufpt[i++] = '0';
           length = width;
         }
-#endif
+#endif /* !defined(SQLITE_OMIT_FLOATING_POINT) */
         break;
       case etSIZE:
         *(va_arg(ap,int*)) = pAccum->nChar;
@@ -16975,7 +17867,7 @@
         isnull = escarg==0;
         if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
         k = precision;
-        for(i=n=0; (ch=escarg[i])!=0 && k!=0; i++, k--){
+        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
           if( ch==q )  n++;
         }
         needQuote = !isnull && xtype==etSQLESCAPE2;
@@ -17269,12 +18161,8 @@
 ** mutex is held.
 */
 static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
-  StrAccum acc;                           /* String accumulator */
-#ifdef SQLITE_SMALL_STACK
-  char zMsg[150];                         /* Complete log message */
-#else
-  char zMsg[400];                         /* Complete log message */
-#endif
+  StrAccum acc;                          /* String accumulator */
+  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */
 
   sqlite3StrAccumInit(&acc, zMsg, sizeof(zMsg), 0);
   acc.useMalloc = 0;
@@ -17827,7 +18715,7 @@
   int btreeMask;          /* Bitmask of db->aDb[] entries referenced */
   i64 startTime;          /* Time when query started - used for profiling */
   BtreeMutexArray aMutex; /* An array of Btree used here and needing locks */
-  int aCounter[2];        /* Counters used by sqlite3_stmt_status() */
+  int aCounter[3];        /* Counters used by sqlite3_stmt_status() */
   char *zSql;             /* Text of the SQL statement that generated this */
   void *pFree;            /* Free this when deleting the vdbe */
   i64 nFkConstraint;      /* Number of imm. FK constraints this VM */
@@ -17879,7 +18767,11 @@
 SQLITE_PRIVATE int sqlite3VdbeMemNulTerminate(Mem*);
 SQLITE_PRIVATE int sqlite3VdbeMemSetStr(Mem*, const char*, int, u8, void(*)(void*));
 SQLITE_PRIVATE void sqlite3VdbeMemSetInt64(Mem*, i64);
-SQLITE_PRIVATE void sqlite3VdbeMemSetDouble(Mem*, double);
+#ifdef SQLITE_OMIT_FLOATING_POINT
+# define sqlite3VdbeMemSetDouble sqlite3VdbeMemSetInt64
+#else
+SQLITE_PRIVATE   void sqlite3VdbeMemSetDouble(Mem*, double);
+#endif
 SQLITE_PRIVATE void sqlite3VdbeMemSetNull(Mem*);
 SQLITE_PRIVATE void sqlite3VdbeMemSetZeroBlob(Mem*,int);
 SQLITE_PRIVATE void sqlite3VdbeMemSetRowSet(Mem*);
@@ -18332,11 +19224,11 @@
 **
 ** NULL is returned if there is an allocation error.
 */
-SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte){
+SQLITE_PRIVATE char *sqlite3Utf16to8(sqlite3 *db, const void *z, int nByte, u8 enc){
   Mem m;
   memset(&m, 0, sizeof(m));
   m.db = db;
-  sqlite3VdbeMemSetStr(&m, z, nByte, SQLITE_UTF16NATIVE, SQLITE_STATIC);
+  sqlite3VdbeMemSetStr(&m, z, nByte, enc, SQLITE_STATIC);
   sqlite3VdbeChangeEncoding(&m, SQLITE_UTF8);
   if( db->mallocFailed ){
     sqlite3VdbeMemRelease(&m);
@@ -18344,7 +19236,9 @@
   }
   assert( (m.flags & MEM_Term)!=0 || db->mallocFailed );
   assert( (m.flags & MEM_Str)!=0 || db->mallocFailed );
-  return (m.flags & MEM_Dyn)!=0 ? m.z : sqlite3DbStrDup(db, m.z);
+  assert( (m.flags & MEM_Dyn)!=0 || db->mallocFailed );
+  assert( m.z || db->mallocFailed );
+  return m.z;
 }
 
 /*
@@ -18485,6 +19379,7 @@
 }
 #endif
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Return true if the floating point value is Not a Number (NaN).
 **
@@ -18529,6 +19424,7 @@
   testcase( rc );
   return rc;
 }
+#endif /* SQLITE_OMIT_FLOATING_POINT */
 
 /*
 ** Compute a string length that is limited to what can be stored in
@@ -18706,6 +19602,7 @@
   z += incr;
   *realnum = 0;
   while( sqlite3Isdigit(*z) ){ z += incr; }
+#ifndef SQLITE_OMIT_FLOATING_POINT
   if( *z=='.' ){
     z += incr;
     if( !sqlite3Isdigit(*z) ) return 0;
@@ -18719,6 +19616,7 @@
     while( sqlite3Isdigit(*z) ){ z += incr; }
     *realnum = 1;
   }
+#endif
   return *z==0;
 }
 
@@ -18880,6 +19778,9 @@
   c = memcmp(zNum,"922337203685477580",18)*10;
   if( c==0 ){
     c = zNum[18] - '8';
+    testcase( c==(-1) );
+    testcase( c==0 );
+    testcase( c==(+1) );
   }
   return c;
 }
@@ -18916,6 +19817,9 @@
     v = v*10 + c - '0';
   }
   *pNum = neg ? -v : v;
+  testcase( i==18 );
+  testcase( i==19 );
+  testcase( i==20 );
   if( c!=0 || (i==0 && zStart==zNum) || i>19 ){
     /* zNum is empty or contains non-numeric text or is longer
     ** than 19 digits (thus guaranting that it is too large) */
@@ -18959,6 +19863,9 @@
     zNum++;   /* Skip leading zeros.  Ticket #2454 */
   }
   for(i=0; zNum[i]; i++){ assert( zNum[i]>='0' && zNum[i]<='9' ); }
+  testcase( i==18 );
+  testcase( i==19 );
+  testcase( i==20 );
   if( i<19 ){
     /* Guaranteed to fit if less than 19 digits */
     return 1;
@@ -18999,9 +19906,11 @@
   **             1234567890
   **     2^31 -> 2147483648
   */
+  testcase( i==10 );
   if( i>10 ){
     return 0;
   }
+  testcase( v-neg==2147483647 );
   if( v-neg>2147483647 ){
     return 0;
   }
@@ -19090,6 +19999,19 @@
 }
 
 /*
+** Bitmasks used by sqlite3GetVarint().  These precomputed constants
+** are defined here rather than simply putting the constant expressions
+** inline in order to work around bugs in the RVT compiler.
+**
+** SLOT_2_0     A mask for  (0x7f<<14) | 0x7f
+**
+** SLOT_4_2_0   A mask for  (0x7f<<28) | SLOT_2_0
+*/
+#define SLOT_2_0     0x001fc07f
+#define SLOT_4_2_0   0xf01fc07f
+
+
+/*
 ** Read a 64-bit variable-length integer from memory starting at p[0].
 ** Return the number of bytes read.  The value is stored in *v.
 */
@@ -19116,13 +20038,17 @@
     return 2;
   }
 
+  /* Verify that constants are precomputed correctly */
+  assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
+  assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
+
   p++;
   a = a<<14;
   a |= *p;
   /* a: p0<<14 | p2 (unmasked) */
   if (!(a&0x80))
   {
-    a &= (0x7f<<14)|(0x7f);
+    a &= SLOT_2_0;
     b &= 0x7f;
     b = b<<7;
     a |= b;
@@ -19131,14 +20057,14 @@
   }
 
   /* CSE1 from below */
-  a &= (0x7f<<14)|(0x7f);
+  a &= SLOT_2_0;
   p++;
   b = b<<14;
   b |= *p;
   /* b: p1<<14 | p3 (unmasked) */
   if (!(b&0x80))
   {
-    b &= (0x7f<<14)|(0x7f);
+    b &= SLOT_2_0;
     /* moved CSE1 up */
     /* a &= (0x7f<<14)|(0x7f); */
     a = a<<7;
@@ -19152,7 +20078,7 @@
   /* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
   /* moved CSE1 up */
   /* a &= (0x7f<<14)|(0x7f); */
-  b &= (0x7f<<14)|(0x7f);
+  b &= SLOT_2_0;
   s = a;
   /* s: p0<<14 | p2 (masked) */
 
@@ -19185,7 +20111,7 @@
   {
     /* we can skip this cause it was (effectively) done above in calc'ing s */
     /* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
-    a &= (0x7f<<14)|(0x7f);
+    a &= SLOT_2_0;
     a = a<<7;
     a |= b;
     s = s>>18;
@@ -19199,8 +20125,8 @@
   /* a: p2<<28 | p4<<14 | p6 (unmasked) */
   if (!(a&0x80))
   {
-    a &= (0x1f<<28)|(0x7f<<14)|(0x7f);
-    b &= (0x7f<<14)|(0x7f);
+    a &= SLOT_4_2_0;
+    b &= SLOT_2_0;
     b = b<<7;
     a |= b;
     s = s>>11;
@@ -19209,14 +20135,14 @@
   }
 
   /* CSE2 from below */
-  a &= (0x7f<<14)|(0x7f);
+  a &= SLOT_2_0;
   p++;
   b = b<<14;
   b |= *p;
   /* b: p3<<28 | p5<<14 | p7 (unmasked) */
   if (!(b&0x80))
   {
-    b &= (0x1f<<28)|(0x7f<<14)|(0x7f);
+    b &= SLOT_4_2_0;
     /* moved CSE2 up */
     /* a &= (0x7f<<14)|(0x7f); */
     a = a<<7;
@@ -19233,7 +20159,7 @@
 
   /* moved CSE2 up */
   /* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */
-  b &= (0x7f<<14)|(0x7f);
+  b &= SLOT_2_0;
   b = b<<8;
   a |= b;
 
@@ -19353,9 +20279,9 @@
   /* a: p0<<28 | p2<<14 | p4 (unmasked) */
   if (!(a&0x80))
   {
-    /* Walues  between 268435456 and 34359738367 */
-    a &= (0x1f<<28)|(0x7f<<14)|(0x7f);
-    b &= (0x1f<<28)|(0x7f<<14)|(0x7f);
+    /* Values  between 268435456 and 34359738367 */
+    a &= SLOT_4_2_0;
+    b &= SLOT_4_2_0;
     b = b<<7;
     *v = a | b;
     return 5;
@@ -19482,7 +20408,8 @@
   }
   magic = db->magic;
   if( magic!=SQLITE_MAGIC_OPEN ){
-    if( !sqlite3SafetyCheckSickOrOk(db) ){
+    if( sqlite3SafetyCheckSickOrOk(db) ){
+      testcase( sqlite3GlobalConfig.xLog!=0 );
       logBadConnection("unopened");
     }
     return 0;
@@ -19496,6 +20423,7 @@
   if( magic!=SQLITE_MAGIC_SICK &&
       magic!=SQLITE_MAGIC_OPEN &&
       magic!=SQLITE_MAGIC_BUSY ){
+    testcase( sqlite3GlobalConfig.xLog!=0 );
     logBadConnection("invalid");
     return 0;
   }else{
@@ -19827,39 +20755,39 @@
      /*  37 */ "VerifyCookie",
      /*  38 */ "OpenRead",
      /*  39 */ "OpenWrite",
-     /*  40 */ "OpenEphemeral",
-     /*  41 */ "OpenPseudo",
-     /*  42 */ "Close",
-     /*  43 */ "SeekLt",
-     /*  44 */ "SeekLe",
-     /*  45 */ "SeekGe",
-     /*  46 */ "SeekGt",
-     /*  47 */ "Seek",
-     /*  48 */ "NotFound",
-     /*  49 */ "Found",
-     /*  50 */ "IsUnique",
-     /*  51 */ "NotExists",
-     /*  52 */ "Sequence",
-     /*  53 */ "NewRowid",
-     /*  54 */ "Insert",
-     /*  55 */ "InsertInt",
-     /*  56 */ "Delete",
-     /*  57 */ "ResetCount",
-     /*  58 */ "RowKey",
-     /*  59 */ "RowData",
-     /*  60 */ "Rowid",
-     /*  61 */ "NullRow",
-     /*  62 */ "Last",
-     /*  63 */ "Sort",
-     /*  64 */ "Rewind",
-     /*  65 */ "Prev",
-     /*  66 */ "Next",
-     /*  67 */ "IdxInsert",
+     /*  40 */ "OpenAutoindex",
+     /*  41 */ "OpenEphemeral",
+     /*  42 */ "OpenPseudo",
+     /*  43 */ "Close",
+     /*  44 */ "SeekLt",
+     /*  45 */ "SeekLe",
+     /*  46 */ "SeekGe",
+     /*  47 */ "SeekGt",
+     /*  48 */ "Seek",
+     /*  49 */ "NotFound",
+     /*  50 */ "Found",
+     /*  51 */ "IsUnique",
+     /*  52 */ "NotExists",
+     /*  53 */ "Sequence",
+     /*  54 */ "NewRowid",
+     /*  55 */ "Insert",
+     /*  56 */ "InsertInt",
+     /*  57 */ "Delete",
+     /*  58 */ "ResetCount",
+     /*  59 */ "RowKey",
+     /*  60 */ "RowData",
+     /*  61 */ "Rowid",
+     /*  62 */ "NullRow",
+     /*  63 */ "Last",
+     /*  64 */ "Sort",
+     /*  65 */ "Rewind",
+     /*  66 */ "Prev",
+     /*  67 */ "Next",
      /*  68 */ "Or",
      /*  69 */ "And",
-     /*  70 */ "IdxDelete",
-     /*  71 */ "IdxRowid",
-     /*  72 */ "IdxLT",
+     /*  70 */ "IdxInsert",
+     /*  71 */ "IdxDelete",
+     /*  72 */ "IdxRowid",
      /*  73 */ "IsNull",
      /*  74 */ "NotNull",
      /*  75 */ "Ne",
@@ -19868,7 +20796,7 @@
      /*  78 */ "Le",
      /*  79 */ "Lt",
      /*  80 */ "Ge",
-     /*  81 */ "IdxGE",
+     /*  81 */ "IdxLT",
      /*  82 */ "BitAnd",
      /*  83 */ "BitOr",
      /*  84 */ "ShiftLeft",
@@ -19879,52 +20807,52 @@
      /*  89 */ "Divide",
      /*  90 */ "Remainder",
      /*  91 */ "Concat",
-     /*  92 */ "Destroy",
+     /*  92 */ "IdxGE",
      /*  93 */ "BitNot",
      /*  94 */ "String8",
-     /*  95 */ "Clear",
-     /*  96 */ "CreateIndex",
-     /*  97 */ "CreateTable",
-     /*  98 */ "ParseSchema",
-     /*  99 */ "LoadAnalysis",
-     /* 100 */ "DropTable",
-     /* 101 */ "DropIndex",
-     /* 102 */ "DropTrigger",
-     /* 103 */ "IntegrityCk",
-     /* 104 */ "RowSetAdd",
-     /* 105 */ "RowSetRead",
-     /* 106 */ "RowSetTest",
-     /* 107 */ "Program",
-     /* 108 */ "Param",
-     /* 109 */ "FkCounter",
-     /* 110 */ "FkIfZero",
-     /* 111 */ "MemMax",
-     /* 112 */ "IfPos",
-     /* 113 */ "IfNeg",
-     /* 114 */ "IfZero",
-     /* 115 */ "AggStep",
-     /* 116 */ "AggFinal",
-     /* 117 */ "Vacuum",
-     /* 118 */ "IncrVacuum",
-     /* 119 */ "Expire",
-     /* 120 */ "TableLock",
-     /* 121 */ "VBegin",
-     /* 122 */ "VCreate",
-     /* 123 */ "VDestroy",
-     /* 124 */ "VOpen",
-     /* 125 */ "VFilter",
-     /* 126 */ "VColumn",
-     /* 127 */ "VNext",
-     /* 128 */ "VRename",
-     /* 129 */ "VUpdate",
+     /*  95 */ "Destroy",
+     /*  96 */ "Clear",
+     /*  97 */ "CreateIndex",
+     /*  98 */ "CreateTable",
+     /*  99 */ "ParseSchema",
+     /* 100 */ "LoadAnalysis",
+     /* 101 */ "DropTable",
+     /* 102 */ "DropIndex",
+     /* 103 */ "DropTrigger",
+     /* 104 */ "IntegrityCk",
+     /* 105 */ "RowSetAdd",
+     /* 106 */ "RowSetRead",
+     /* 107 */ "RowSetTest",
+     /* 108 */ "Program",
+     /* 109 */ "Param",
+     /* 110 */ "FkCounter",
+     /* 111 */ "FkIfZero",
+     /* 112 */ "MemMax",
+     /* 113 */ "IfPos",
+     /* 114 */ "IfNeg",
+     /* 115 */ "IfZero",
+     /* 116 */ "AggStep",
+     /* 117 */ "AggFinal",
+     /* 118 */ "Checkpoint",
+     /* 119 */ "JournalMode",
+     /* 120 */ "Vacuum",
+     /* 121 */ "IncrVacuum",
+     /* 122 */ "Expire",
+     /* 123 */ "TableLock",
+     /* 124 */ "VBegin",
+     /* 125 */ "VCreate",
+     /* 126 */ "VDestroy",
+     /* 127 */ "VOpen",
+     /* 128 */ "VFilter",
+     /* 129 */ "VColumn",
      /* 130 */ "Real",
-     /* 131 */ "Pagecount",
-     /* 132 */ "Trace",
-     /* 133 */ "Noop",
-     /* 134 */ "Explain",
-     /* 135 */ "NotUsed_135",
-     /* 136 */ "NotUsed_136",
-     /* 137 */ "NotUsed_137",
+     /* 131 */ "VNext",
+     /* 132 */ "VRename",
+     /* 133 */ "VUpdate",
+     /* 134 */ "Pagecount",
+     /* 135 */ "Trace",
+     /* 136 */ "Noop",
+     /* 137 */ "Explain",
      /* 138 */ "NotUsed_138",
      /* 139 */ "NotUsed_139",
      /* 140 */ "NotUsed_140",
@@ -20029,23 +20957,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -20241,7 +21155,7 @@
   APIRET rc = NO_ERROR;
   os2File *pFile;
   if( id && (pFile = (os2File*)id) != 0 ){
-    OSTRACE2( "CLOSE %d\n", pFile->h );
+    OSTRACE(( "CLOSE %d\n", pFile->h ));
     rc = DosClose( pFile->h );
     pFile->locktype = NO_LOCK;
     if( pFile->pathToDel != NULL ){
@@ -20272,7 +21186,7 @@
   os2File *pFile = (os2File*)id;
   assert( id!=0 );
   SimulateIOError( return SQLITE_IOERR_READ );
-  OSTRACE3( "READ %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "READ %d lock=%d\n", pFile->h, pFile->locktype ));
   if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
     return SQLITE_IOERR;
   }
@@ -20305,7 +21219,7 @@
   assert( id!=0 );
   SimulateIOError( return SQLITE_IOERR_WRITE );
   SimulateDiskfullError( return SQLITE_FULL );
-  OSTRACE3( "WRITE %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "WRITE %d lock=%d\n", pFile->h, pFile->locktype ));
   if( DosSetFilePtr(pFile->h, offset, FILE_BEGIN, &fileLocation) != NO_ERROR ){
     return SQLITE_IOERR;
   }
@@ -20327,7 +21241,7 @@
 static int os2Truncate( sqlite3_file *id, i64 nByte ){
   APIRET rc = NO_ERROR;
   os2File *pFile = (os2File*)id;
-  OSTRACE3( "TRUNCATE %d %lld\n", pFile->h, nByte );
+  OSTRACE(( "TRUNCATE %d %lld\n", pFile->h, nByte ));
   SimulateIOError( return SQLITE_IOERR_TRUNCATE );
   rc = DosSetFileSize( pFile->h, nByte );
   return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR_TRUNCATE;
@@ -20347,7 +21261,7 @@
 */
 static int os2Sync( sqlite3_file *id, int flags ){
   os2File *pFile = (os2File*)id;
-  OSTRACE3( "SYNC %d lock=%d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "SYNC %d lock=%d\n", pFile->h, pFile->locktype ));
 #ifdef SQLITE_TEST
   if( flags & SQLITE_SYNC_FULL){
     sqlite3_fullsync_count++;
@@ -20397,7 +21311,7 @@
   UnlockArea.lOffset = 0L;
   UnlockArea.lRange = 0L;
   res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
-  OSTRACE3( "GETREADLOCK %d res=%d\n", pFile->h, res );
+  OSTRACE(( "GETREADLOCK %d res=%d\n", pFile->h, res ));
   return res;
 }
 
@@ -20415,7 +21329,7 @@
   UnlockArea.lOffset = SHARED_FIRST;
   UnlockArea.lRange = SHARED_SIZE;
   res = DosSetFileLocks( id->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 1L );
-  OSTRACE3( "UNLOCK-READLOCK file handle=%d res=%d?\n", id->h, res );
+  OSTRACE(( "UNLOCK-READLOCK file handle=%d res=%d?\n", id->h, res ));
   return res;
 }
 
@@ -20456,14 +21370,14 @@
   memset(&LockArea, 0, sizeof(LockArea));
   memset(&UnlockArea, 0, sizeof(UnlockArea));
   assert( pFile!=0 );
-  OSTRACE4( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype );
+  OSTRACE(( "LOCK %d %d was %d\n", pFile->h, locktype, pFile->locktype ));
 
   /* If there is already a lock of this type or more restrictive on the
   ** os2File, do nothing. Don't use the end_lock: exit path, as
   ** sqlite3_mutex_enter() hasn't been called yet.
   */
   if( pFile->locktype>=locktype ){
-    OSTRACE3( "LOCK %d %d ok (already held)\n", pFile->h, locktype );
+    OSTRACE(( "LOCK %d %d ok (already held)\n", pFile->h, locktype ));
     return SQLITE_OK;
   }
 
@@ -20490,7 +21404,7 @@
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, 100L, 0L );
     if( res == NO_ERROR ){
       gotPendingLock = 1;
-      OSTRACE3( "LOCK %d pending lock boolean set.  res=%d\n", pFile->h, res );
+      OSTRACE(( "LOCK %d pending lock boolean set.  res=%d\n", pFile->h, res ));
     }
   }
 
@@ -20502,7 +21416,7 @@
     if( res == NO_ERROR ){
       newLocktype = SHARED_LOCK;
     }
-    OSTRACE3( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire shared lock. res=%d\n", pFile->h, res ));
   }
 
   /* Acquire a RESERVED lock
@@ -20517,7 +21431,7 @@
     if( res == NO_ERROR ){
       newLocktype = RESERVED_LOCK;
     }
-    OSTRACE3( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire reserved lock. res=%d\n", pFile->h, res ));
   }
 
   /* Acquire a PENDING lock
@@ -20525,7 +21439,8 @@
   if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
     newLocktype = PENDING_LOCK;
     gotPendingLock = 0;
-    OSTRACE2( "LOCK %d acquire pending lock. pending lock boolean unset.\n", pFile->h );
+    OSTRACE(( "LOCK %d acquire pending lock. pending lock boolean unset.\n",
+               pFile->h ));
   }
 
   /* Acquire an EXCLUSIVE lock
@@ -20533,7 +21448,7 @@
   if( locktype==EXCLUSIVE_LOCK && res == NO_ERROR ){
     assert( pFile->locktype>=SHARED_LOCK );
     res = unlockReadLock(pFile);
-    OSTRACE2( "unreadlock = %d\n", res );
+    OSTRACE(( "unreadlock = %d\n", res ));
     LockArea.lOffset = SHARED_FIRST;
     LockArea.lRange = SHARED_SIZE;
     UnlockArea.lOffset = 0L;
@@ -20542,10 +21457,10 @@
     if( res == NO_ERROR ){
       newLocktype = EXCLUSIVE_LOCK;
     }else{
-      OSTRACE2( "OS/2 error-code = %d\n", res );
+      OSTRACE(( "OS/2 error-code = %d\n", res ));
       getReadLock(pFile);
     }
-    OSTRACE3( "LOCK %d acquire exclusive lock.  res=%d\n", pFile->h, res );
+    OSTRACE(( "LOCK %d acquire exclusive lock.  res=%d\n", pFile->h, res ));
   }
 
   /* If we are holding a PENDING lock that ought to be released, then
@@ -20558,7 +21473,7 @@
     UnlockArea.lOffset = PENDING_BYTE;
     UnlockArea.lRange = 1L;
     r = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r );
+    OSTRACE(( "LOCK %d unlocking pending/is shared. r=%d\n", pFile->h, r ));
   }
 
   /* Update the state of the lock has held in the file descriptor then
@@ -20567,12 +21482,12 @@
   if( res == NO_ERROR ){
     rc = SQLITE_OK;
   }else{
-    OSTRACE4( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
-              locktype, newLocktype );
+    OSTRACE(( "LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+              locktype, newLocktype ));
     rc = SQLITE_BUSY;
   }
   pFile->locktype = newLocktype;
-  OSTRACE3( "LOCK %d now %d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "LOCK %d now %d\n", pFile->h, pFile->locktype ));
   return rc;
 }
 
@@ -20587,7 +21502,7 @@
   assert( pFile!=0 );
   if( pFile->locktype>=RESERVED_LOCK ){
     r = 1;
-    OSTRACE3( "TEST WR-LOCK %d %d (local)\n", pFile->h, r );
+    OSTRACE(( "TEST WR-LOCK %d %d (local)\n", pFile->h, r ));
   }else{
     FILELOCK  LockArea,
               UnlockArea;
@@ -20599,7 +21514,7 @@
     UnlockArea.lOffset = 0L;
     UnlockArea.lRange = 0L;
     rc = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "TEST WR-LOCK %d lock reserved byte rc=%d\n", pFile->h, rc );
+    OSTRACE(( "TEST WR-LOCK %d lock reserved byte rc=%d\n", pFile->h, rc ));
     if( rc == NO_ERROR ){
       APIRET rcu = NO_ERROR; /* return code for unlocking */
       LockArea.lOffset = 0L;
@@ -20607,10 +21522,10 @@
       UnlockArea.lOffset = RESERVED_BYTE;
       UnlockArea.lRange = 1L;
       rcu = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-      OSTRACE3( "TEST WR-LOCK %d unlock reserved byte r=%d\n", pFile->h, rcu );
+      OSTRACE(( "TEST WR-LOCK %d unlock reserved byte r=%d\n", pFile->h, rcu ));
     }
     r = !(rc == NO_ERROR);
-    OSTRACE3( "TEST WR-LOCK %d %d (remote)\n", pFile->h, r );
+    OSTRACE(( "TEST WR-LOCK %d %d (remote)\n", pFile->h, r ));
   }
   *pOut = r;
   return SQLITE_OK;
@@ -20638,7 +21553,7 @@
   memset(&UnlockArea, 0, sizeof(UnlockArea));
   assert( pFile!=0 );
   assert( locktype<=SHARED_LOCK );
-  OSTRACE4( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype );
+  OSTRACE(( "UNLOCK %d to %d was %d\n", pFile->h, locktype, pFile->locktype ));
   type = pFile->locktype;
   if( type>=EXCLUSIVE_LOCK ){
     LockArea.lOffset = 0L;
@@ -20646,11 +21561,11 @@
     UnlockArea.lOffset = SHARED_FIRST;
     UnlockArea.lRange = SHARED_SIZE;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d exclusive lock res=%d\n", pFile->h, res ));
     if( locktype==SHARED_LOCK && getReadLock(pFile) != NO_ERROR ){
       /* This should never happen.  We should always be able to
       ** reacquire the read lock */
-      OSTRACE3( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype );
+      OSTRACE(( "UNLOCK %d to %d getReadLock() failed\n", pFile->h, locktype ));
       rc = SQLITE_IOERR_UNLOCK;
     }
   }
@@ -20660,11 +21575,12 @@
     UnlockArea.lOffset = RESERVED_BYTE;
     UnlockArea.lRange = 1L;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d reserved res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d reserved res=%d\n", pFile->h, res ));
   }
   if( locktype==NO_LOCK && type>=SHARED_LOCK ){
     res = unlockReadLock(pFile);
-    OSTRACE5( "UNLOCK %d is %d want %d res=%d\n", pFile->h, type, locktype, res );
+    OSTRACE(( "UNLOCK %d is %d want %d res=%d\n",
+              pFile->h, type, locktype, res ));
   }
   if( type>=PENDING_LOCK ){
     LockArea.lOffset = 0L;
@@ -20672,10 +21588,10 @@
     UnlockArea.lOffset = PENDING_BYTE;
     UnlockArea.lRange = 1L;
     res = DosSetFileLocks( pFile->h, &UnlockArea, &LockArea, LOCK_TIMEOUT, 0L );
-    OSTRACE3( "UNLOCK %d pending res=%d\n", pFile->h, res );
+    OSTRACE(( "UNLOCK %d pending res=%d\n", pFile->h, res ));
   }
   pFile->locktype = locktype;
-  OSTRACE3( "UNLOCK %d now %d\n", pFile->h, pFile->locktype );
+  OSTRACE(( "UNLOCK %d now %d\n", pFile->h, pFile->locktype ));
   return rc;
 }
 
@@ -20686,7 +21602,8 @@
   switch( op ){
     case SQLITE_FCNTL_LOCKSTATE: {
       *(int*)pArg = ((os2File*)id)->locktype;
-      OSTRACE3( "FCNTL_LOCKSTATE %d lock=%d\n", ((os2File*)id)->h, ((os2File*)id)->locktype );
+      OSTRACE(( "FCNTL_LOCKSTATE %d lock=%d\n",
+                ((os2File*)id)->h, ((os2File*)id)->locktype ));
       return SQLITE_OK;
     }
   }
@@ -20873,7 +21790,7 @@
     zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
   }
   zBuf[j] = 0;
-  OSTRACE2( "TEMP FILENAME: %s\n", zBuf );
+  OSTRACE(( "TEMP FILENAME: %s\n", zBuf ));
   return SQLITE_OK;
 }
 
@@ -20936,30 +21853,30 @@
 
   memset( pFile, 0, sizeof(*pFile) );
 
-  OSTRACE2( "OPEN want %d\n", flags );
+  OSTRACE( "OPEN want %d\n", flags ));
 
   if( flags & SQLITE_OPEN_READWRITE ){
     ulOpenMode |= OPEN_ACCESS_READWRITE;
-    OSTRACE1( "OPEN read/write\n" );
+    OSTRACE(( "OPEN read/write\n" ));
   }else{
     ulOpenMode |= OPEN_ACCESS_READONLY;
-    OSTRACE1( "OPEN read only\n" );
+    OSTRACE(( "OPEN read only\n" ));
   }
 
   if( flags & SQLITE_OPEN_CREATE ){
     ulOpenFlags |= OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_CREATE_IF_NEW;
-    OSTRACE1( "OPEN open new/create\n" );
+    OSTRACE(( "OPEN open new/create\n" ));
   }else{
     ulOpenFlags |= OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_FAIL_IF_NEW;
-    OSTRACE1( "OPEN open existing\n" );
+    OSTRACE(( "OPEN open existing\n" ));
   }
 
   if( flags & SQLITE_OPEN_MAIN_DB ){
     ulOpenMode |= OPEN_SHARE_DENYNONE;
-    OSTRACE1( "OPEN share read/write\n" );
+    OSTRACE(( "OPEN share read/write\n" ));
   }else{
     ulOpenMode |= OPEN_SHARE_DENYWRITE;
-    OSTRACE1( "OPEN share read only\n" );
+    OSTRACE(( "OPEN share read only\n" ));
   }
 
   if( flags & SQLITE_OPEN_DELETEONCLOSE ){
@@ -20969,10 +21886,10 @@
 #endif
     os2FullPathname( pVfs, zName, CCHMAXPATH, pathUtf8 );
     pFile->pathToDel = convertUtf8PathToCp( pathUtf8 );
-    OSTRACE1( "OPEN hidden/delete on close file attributes\n" );
+    OSTRACE(( "OPEN hidden/delete on close file attributes\n" ));
   }else{
     pFile->pathToDel = NULL;
-    OSTRACE1( "OPEN normal file attribute\n" );
+    OSTRACE(( "OPEN normal file attribute\n" ));
   }
 
   /* always open in random access mode for possibly better speed */
@@ -20991,13 +21908,14 @@
                 (PEAOP2)NULL );
   free( zNameCp );
   if( rc != NO_ERROR ){
-    OSTRACE7( "OPEN Invalid handle rc=%d: zName=%s, ulAction=%#lx, ulAttr=%#lx, ulFlags=%#lx, ulMode=%#lx\n",
-              rc, zName, ulAction, ulFileAttribute, ulOpenFlags, ulOpenMode );
+    OSTRACE(( "OPEN Invalid handle rc=%d: zName=%s, ulAction=%#lx, ulAttr=%#lx, ulFlags=%#lx, ulMode=%#lx\n",
+              rc, zName, ulAction, ulFileAttribute, ulOpenFlags, ulOpenMode ));
     if( pFile->pathToDel )
       free( pFile->pathToDel );
     pFile->pathToDel = NULL;
     if( flags & SQLITE_OPEN_READWRITE ){
-      OSTRACE2( "OPEN %d Invalid handle\n", ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE) );
+      OSTRACE(( "OPEN %d Invalid handle\n",
+                ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE) ));
       return os2Open( pVfs, zName, id,
                       ((flags | SQLITE_OPEN_READONLY) & ~SQLITE_OPEN_READWRITE),
                       pOutFlags );
@@ -21013,7 +21931,7 @@
   pFile->pMethod = &os2IoMethod;
   pFile->h = h;
   OpenCounter(+1);
-  OSTRACE3( "OPEN %d pOutFlags=%d\n", pFile->h, pOutFlags );
+  OSTRACE(( "OPEN %d pOutFlags=%d\n", pFile->h, pOutFlags ));
   return SQLITE_OK;
 }
 
@@ -21030,7 +21948,7 @@
   SimulateIOError( return SQLITE_IOERR_DELETE );
   rc = DosDelete( (PSZ)zFilenameCp );
   free( zFilenameCp );
-  OSTRACE2( "DELETE \"%s\"\n", zFilename );
+  OSTRACE(( "DELETE \"%s\"\n", zFilename ));
   return rc == NO_ERROR ? SQLITE_OK : SQLITE_IOERR_DELETE;
 }
 
@@ -21051,17 +21969,17 @@
   rc = DosQueryPathInfo( (PSZ)zFilenameCp, FIL_STANDARD,
                          &fsts3ConfigInfo, sizeof(FILESTATUS3) );
   free( zFilenameCp );
-  OSTRACE4( "ACCESS fsts3ConfigInfo.attrFile=%d flags=%d rc=%d\n",
-            fsts3ConfigInfo.attrFile, flags, rc );
+  OSTRACE(( "ACCESS fsts3ConfigInfo.attrFile=%d flags=%d rc=%d\n",
+            fsts3ConfigInfo.attrFile, flags, rc ));
   switch( flags ){
     case SQLITE_ACCESS_READ:
     case SQLITE_ACCESS_EXISTS:
       rc = (rc == NO_ERROR);
-      OSTRACE3( "ACCESS %s access of read and exists  rc=%d\n", zFilename, rc );
+      OSTRACE(( "ACCESS %s access of read and exists  rc=%d\n", zFilename, rc));
       break;
     case SQLITE_ACCESS_READWRITE:
       rc = (rc == NO_ERROR) && ( (fsts3ConfigInfo.attrFile & FILE_READONLY) == 0 );
-      OSTRACE3( "ACCESS %s access of read/write  rc=%d\n", zFilename, rc );
+      OSTRACE(( "ACCESS %s access of read/write  rc=%d\n", zFilename, rc ));
       break;
     default:
       assert( !"Invalid flags argument" );
@@ -21271,7 +22189,7 @@
     os2Randomness,     /* xRandomness */
     os2Sleep,          /* xSleep */
     os2CurrentTime,    /* xCurrentTime */
-    os2GetLastError    /* xGetLastError */
+    os2GetLastError,   /* xGetLastError */
   };
   sqlite3_vfs_register(&os2Vfs, 1);
   initUconvObjects();
@@ -21405,6 +22323,7 @@
 #include <unistd.h>
 #include <sys/time.h>
 #include <errno.h>
+#include <sys/mman.h>
 
 #if SQLITE_ENABLE_LOCKING_STYLE
 # include <sys/ioctl.h>
@@ -21414,10 +22333,18 @@
 # else
 #  include <sys/file.h>
 #  include <sys/param.h>
-#  include <sys/mount.h>
 # endif
 #endif /* SQLITE_ENABLE_LOCKING_STYLE */
 
+#if defined(__APPLE__) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
+# include <sys/mount.h>
+#endif
+
+/*
+** Allowed values of unixFile.fsFlags
+*/
+#define SQLITE_FSFLAGS_IS_MSDOS     0x1
+
 /*
 ** If we are to be thread-safe, include the pthreads header and define
 ** the SQLITE_UNIX_THREADS macro.
@@ -21451,6 +22378,11 @@
 */
 #define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
 
+/* Forward references */
+typedef struct unixShm unixShm;               /* Connection shared memory */
+typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
+typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
+typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
 
 /*
 ** Sometimes, after a file handle is closed by SQLite, the file descriptor
@@ -21458,7 +22390,6 @@
 ** structure are used to store the file descriptor while waiting for an
 ** opportunity to either close or reuse it.
 */
-typedef struct UnixUnusedFd UnixUnusedFd;
 struct UnixUnusedFd {
   int fd;                   /* File descriptor to close */
   int flags;                /* Flags this file descriptor was opened with */
@@ -21472,24 +22403,25 @@
 typedef struct unixFile unixFile;
 struct unixFile {
   sqlite3_io_methods const *pMethod;  /* Always the first entry */
-  struct unixOpenCnt *pOpen;       /* Info about all open fd's on this inode */
-  struct unixLockInfo *pLock;      /* Info about locks on this inode */
-  int h;                           /* The file descriptor */
-  int dirfd;                       /* File descriptor for the directory */
-  unsigned char locktype;          /* The type of lock held on this fd */
-  int lastErrno;                   /* The unix errno from the last I/O error */
-  void *lockingContext;            /* Locking style specific state */
-  UnixUnusedFd *pUnused;           /* Pre-allocated UnixUnusedFd */
-  int fileFlags;                   /* Miscellanous flags */
+  unixInodeInfo *pInode;              /* Info about locks on this inode */
+  int h;                              /* The file descriptor */
+  int dirfd;                          /* File descriptor for the directory */
+  unsigned char eFileLock;            /* The type of lock held on this fd */
+  int lastErrno;                      /* The unix errno from last I/O error */
+  void *lockingContext;               /* Locking style specific state */
+  UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
+  int fileFlags;                      /* Miscellanous flags */
+  const char *zPath;                  /* Name of the file */
+  unixShm *pShm;                      /* Shared memory segment information */
 #if SQLITE_ENABLE_LOCKING_STYLE
-  int openFlags;                   /* The flags specified at open() */
+  int openFlags;                      /* The flags specified at open() */
 #endif
-#if SQLITE_THREADSAFE && defined(__linux__)
-  pthread_t tid;                   /* The thread that "owns" this unixFile */
+#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
+  unsigned fsFlags;                   /* cached details from statfs() */
 #endif
 #if OS_VXWORKS
-  int isDelete;                    /* Delete on close if true */
-  struct vxworksFileId *pId;       /* Unique file ID */
+  int isDelete;                       /* Delete on close if true */
+  struct vxworksFileId *pId;          /* Unique file ID */
 #endif
 #ifndef NDEBUG
   /* The next group of variables are used to track whether or not the
@@ -21554,23 +22486,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -21780,7 +22698,7 @@
 
 /*
 ** Helper functions to obtain and relinquish the global mutex. The
-** global mutex is used to protect the unixOpenCnt, unixLockInfo and
+** global mutex is used to protect the unixInodeInfo and
 ** vxworksFileId objects used by this file, all of which may be 
 ** shared by multiple threads.
 **
@@ -21811,8 +22729,8 @@
 ** binaries. This returns the string represetation of the supplied
 ** integer lock-type.
 */
-static const char *locktypeName(int locktype){
-  switch( locktype ){
+static const char *azFileLock(int eFileLock){
+  switch( eFileLock ){
     case NO_LOCK: return "NONE";
     case SHARED_LOCK: return "SHARED";
     case RESERVED_LOCK: return "RESERVED";
@@ -22149,13 +23067,12 @@
 **
 ** If you close a file descriptor that points to a file that has locks,
 ** all locks on that file that are owned by the current process are
-** released.  To work around this problem, each unixFile structure contains
-** a pointer to an unixOpenCnt structure.  There is one unixOpenCnt structure
-** per open inode, which means that multiple unixFile can point to a single
-** unixOpenCnt.  When an attempt is made to close an unixFile, if there are
+** released.  To work around this problem, each unixInodeInfo object
+** maintains a count of the number of pending locks on tha inode.
+** When an attempt is made to close an unixFile, if there are
 ** other unixFile open on the same inode that are holding locks, the call
 ** to close() the file descriptor is deferred until all of the locks clear.
-** The unixOpenCnt structure keeps a list of file descriptors that need to
+** The unixInodeInfo structure keeps a list of file descriptors that need to
 ** be closed and that list is walked (and cleared) when the last lock
 ** clears.
 **
@@ -22170,46 +23087,19 @@
 ** in thread B.  But there is no way to know at compile-time which
 ** threading library is being used.  So there is no way to know at
 ** compile-time whether or not thread A can override locks on thread B.
-** We have to do a run-time check to discover the behavior of the
+** One has to do a run-time check to discover the behavior of the
 ** current process.
 **
-** On systems where thread A is unable to modify locks created by
-** thread B, we have to keep track of which thread created each
-** lock.  Hence there is an extra field in the key to the unixLockInfo
-** structure to record this information.  And on those systems it
-** is illegal to begin a transaction in one thread and finish it
-** in another.  For this latter restriction, there is no work-around.
-** It is a limitation of LinuxThreads.
+** SQLite used to support LinuxThreads.  But support for LinuxThreads
+** was dropped beginning with version 3.7.0.  SQLite will still work with
+** LinuxThreads provided that (1) there is no more than one connection 
+** per database file in the same process and (2) database connections
+** do not move across threads.
 */
 
 /*
-** Set or check the unixFile.tid field.  This field is set when an unixFile
-** is first opened.  All subsequent uses of the unixFile verify that the
-** same thread is operating on the unixFile.  Some operating systems do
-** not allow locks to be overridden by other threads and that restriction
-** means that sqlite3* database handles cannot be moved from one thread
-** to another while locks are held.
-**
-** Version 3.3.1 (2006-01-15):  unixFile can be moved from one thread to
-** another as long as we are running on a system that supports threads
-** overriding each others locks (which is now the most common behavior)
-** or if no locks are held.  But the unixFile.pLock field needs to be
-** recomputed because its key includes the thread-id.  See the 
-** transferOwnership() function below for additional information
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-# define SET_THREADID(X)   (X)->tid = pthread_self()
-# define CHECK_THREADID(X) (threadsOverrideEachOthersLocks==0 && \
-                            !pthread_equal((X)->tid, pthread_self()))
-#else
-# define SET_THREADID(X)
-# define CHECK_THREADID(X) 0
-#endif
-
-/*
 ** An instance of the following structure serves as the key used
-** to locate a particular unixOpenCnt structure given its inode.  This
-** is the same as the unixLockKey except that the thread ID is omitted.
+** to locate a particular unixInodeInfo object.
 */
 struct unixFileId {
   dev_t dev;                  /* Device number */
@@ -22221,23 +23111,6 @@
 };
 
 /*
-** An instance of the following structure serves as the key used
-** to locate a particular unixLockInfo structure given its inode.
-**
-** If threads cannot override each others locks (LinuxThreads), then we
-** set the unixLockKey.tid field to the thread ID.  If threads can override
-** each others locks (Posix and NPTL) then tid is always set to zero.
-** tid is omitted if we compile without threading support or on an OS
-** other than linux.
-*/
-struct unixLockKey {
-  struct unixFileId fid;  /* Unique identifier for the file */
-#if SQLITE_THREADSAFE && defined(__linux__)
-  pthread_t tid;  /* Thread ID of lock owner. Zero if not using LinuxThreads */
-#endif
-};
-
-/*
 ** An instance of the following structure is allocated for each open
 ** inode.  Or, on LinuxThreads, there is one of these structures for
 ** each inode opened by each thread.
@@ -22246,227 +23119,109 @@
 ** structure contains a pointer to an instance of this object and this
 ** object keeps a count of the number of unixFile pointing to it.
 */
-struct unixLockInfo {
-  struct unixLockKey lockKey;     /* The lookup key */
-  int cnt;                        /* Number of SHARED locks held */
-  int locktype;                   /* One of SHARED_LOCK, RESERVED_LOCK etc. */
+struct unixInodeInfo {
+  struct unixFileId fileId;       /* The lookup key */
+  int nShared;                    /* Number of SHARED locks held */
+  int eFileLock;                  /* One of SHARED_LOCK, RESERVED_LOCK etc. */
   int nRef;                       /* Number of pointers to this structure */
-  struct unixLockInfo *pNext;     /* List of all unixLockInfo objects */
-  struct unixLockInfo *pPrev;     /*    .... doubly linked */
-};
-
-/*
-** An instance of the following structure is allocated for each open
-** inode.  This structure keeps track of the number of locks on that
-** inode.  If a close is attempted against an inode that is holding
-** locks, the close is deferred until all locks clear by adding the
-** file descriptor to be closed to the pending list.
-**
-** TODO:  Consider changing this so that there is only a single file
-** descriptor for each open file, even when it is opened multiple times.
-** The close() system call would only occur when the last database
-** using the file closes.
-*/
-struct unixOpenCnt {
-  struct unixFileId fileId;   /* The lookup key */
-  int nRef;                   /* Number of pointers to this structure */
-  int nLock;                  /* Number of outstanding locks */
-  UnixUnusedFd *pUnused;      /* Unused file descriptors to close */
+  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
+  int nLock;                      /* Number of outstanding file locks */
+  UnixUnusedFd *pUnused;          /* Unused file descriptors to close */
+  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
+  unixInodeInfo *pPrev;           /*    .... doubly linked */
+#if defined(SQLITE_ENABLE_LOCKING_STYLE)
+  unsigned long long sharedByte;  /* for AFP simulated shared lock */
+#endif
 #if OS_VXWORKS
-  sem_t *pSem;                     /* Named POSIX semaphore */
-  char aSemName[MAX_PATHNAME+2];   /* Name of that semaphore */
+  sem_t *pSem;                    /* Named POSIX semaphore */
+  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
 #endif
-  struct unixOpenCnt *pNext, *pPrev;   /* List of all unixOpenCnt objects */
 };
 
 /*
-** Lists of all unixLockInfo and unixOpenCnt objects.  These used to be hash
-** tables.  But the number of objects is rarely more than a dozen and
-** never exceeds a few thousand.  And lookup is not on a critical
-** path so a simple linked list will suffice.
+** A lists of all unixInodeInfo objects.
 */
-static struct unixLockInfo *lockList = 0;
-static struct unixOpenCnt *openList = 0;
+static unixInodeInfo *inodeList = 0;
 
 /*
-** This variable remembers whether or not threads can override each others
-** locks.
+** Close all file descriptors accumuated in the unixInodeInfo->pUnused list.
+** If all such file descriptors are closed without error, the list is
+** cleared and SQLITE_OK returned.
 **
-**    0:  No.  Threads cannot override each others locks.  (LinuxThreads)
-**    1:  Yes.  Threads can override each others locks.  (Posix & NLPT)
-**   -1:  We don't know yet.
-**
-** On some systems, we know at compile-time if threads can override each
-** others locks.  On those systems, the SQLITE_THREAD_OVERRIDE_LOCK macro
-** will be set appropriately.  On other systems, we have to check at
-** runtime.  On these latter systems, SQLTIE_THREAD_OVERRIDE_LOCK is
-** undefined.
-**
-** This variable normally has file scope only.  But during testing, we make
-** it a global so that the test code can change its value in order to verify
-** that the right stuff happens in either case.
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-#  ifndef SQLITE_THREAD_OVERRIDE_LOCK
-#    define SQLITE_THREAD_OVERRIDE_LOCK -1
-#  endif
-#  ifdef SQLITE_TEST
-int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
-#  else
-static int threadsOverrideEachOthersLocks = SQLITE_THREAD_OVERRIDE_LOCK;
-#  endif
-#endif
-
-/*
-** This structure holds information passed into individual test
-** threads by the testThreadLockingBehavior() routine.
-*/
-struct threadTestData {
-  int fd;                /* File to be locked */
-  struct flock lock;     /* The locking operation */
-  int result;            /* Result of the locking operation */
-};
-
-#if SQLITE_THREADSAFE && defined(__linux__)
-/*
-** This function is used as the main routine for a thread launched by
-** testThreadLockingBehavior(). It tests whether the shared-lock obtained
-** by the main thread in testThreadLockingBehavior() conflicts with a
-** hypothetical write-lock obtained by this thread on the same file.
-**
-** The write-lock is not actually acquired, as this is not possible if 
-** the file is open in read-only mode (see ticket #3472).
+** Otherwise, if an error occurs, then successfully closed file descriptor
+** entries are removed from the list, and SQLITE_IOERR_CLOSE returned. 
+** not deleted and SQLITE_IOERR_CLOSE returned.
 */ 
-static void *threadLockingTest(void *pArg){
-  struct threadTestData *pData = (struct threadTestData*)pArg;
-  pData->result = fcntl(pData->fd, F_GETLK, &pData->lock);
-  return pArg;
-}
-#endif /* SQLITE_THREADSAFE && defined(__linux__) */
-
-
-#if SQLITE_THREADSAFE && defined(__linux__)
-/*
-** This procedure attempts to determine whether or not threads
-** can override each others locks then sets the 
-** threadsOverrideEachOthersLocks variable appropriately.
-*/
-static void testThreadLockingBehavior(int fd_orig){
-  int fd;
-  int rc;
-  struct threadTestData d;
-  struct flock l;
-  pthread_t t;
-
-  fd = dup(fd_orig);
-  if( fd<0 ) return;
-  memset(&l, 0, sizeof(l));
-  l.l_type = F_RDLCK;
-  l.l_len = 1;
-  l.l_start = 0;
-  l.l_whence = SEEK_SET;
-  rc = fcntl(fd_orig, F_SETLK, &l);
-  if( rc!=0 ) return;
-  memset(&d, 0, sizeof(d));
-  d.fd = fd;
-  d.lock = l;
-  d.lock.l_type = F_WRLCK;
-  if( pthread_create(&t, 0, threadLockingTest, &d)==0 ){
-    pthread_join(t, 0);
+static int closePendingFds(unixFile *pFile){
+  int rc = SQLITE_OK;
+  unixInodeInfo *pInode = pFile->pInode;
+  UnixUnusedFd *pError = 0;
+  UnixUnusedFd *p;
+  UnixUnusedFd *pNext;
+  for(p=pInode->pUnused; p; p=pNext){
+    pNext = p->pNext;
+    if( close(p->fd) ){
+      pFile->lastErrno = errno;
+      rc = SQLITE_IOERR_CLOSE;
+      p->pNext = pError;
+      pError = p;
+    }else{
+      sqlite3_free(p);
+    }
   }
-  close(fd);
-  if( d.result!=0 ) return;
-  threadsOverrideEachOthersLocks = (d.lock.l_type==F_UNLCK);
+  pInode->pUnused = pError;
+  return rc;
 }
-#endif /* SQLITE_THREADSAFE && defined(__linux__) */
 
 /*
-** Release a unixLockInfo structure previously allocated by findLockInfo().
+** Release a unixInodeInfo structure previously allocated by findInodeInfo().
 **
 ** The mutex entered using the unixEnterMutex() function must be held
 ** when this function is called.
 */
-static void releaseLockInfo(struct unixLockInfo *pLock){
+static void releaseInodeInfo(unixFile *pFile){
+  unixInodeInfo *pInode = pFile->pInode;
   assert( unixMutexHeld() );
-  if( pLock ){
-    pLock->nRef--;
-    if( pLock->nRef==0 ){
-      if( pLock->pPrev ){
-        assert( pLock->pPrev->pNext==pLock );
-        pLock->pPrev->pNext = pLock->pNext;
+  if( pInode ){
+    pInode->nRef--;
+    if( pInode->nRef==0 ){
+      assert( pInode->pShmNode==0 );
+      closePendingFds(pFile);
+      if( pInode->pPrev ){
+        assert( pInode->pPrev->pNext==pInode );
+        pInode->pPrev->pNext = pInode->pNext;
       }else{
-        assert( lockList==pLock );
-        lockList = pLock->pNext;
+        assert( inodeList==pInode );
+        inodeList = pInode->pNext;
       }
-      if( pLock->pNext ){
-        assert( pLock->pNext->pPrev==pLock );
-        pLock->pNext->pPrev = pLock->pPrev;
+      if( pInode->pNext ){
+        assert( pInode->pNext->pPrev==pInode );
+        pInode->pNext->pPrev = pInode->pPrev;
       }
-      sqlite3_free(pLock);
+      sqlite3_free(pInode);
     }
   }
 }
 
 /*
-** Release a unixOpenCnt structure previously allocated by findLockInfo().
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-*/
-static void releaseOpenCnt(struct unixOpenCnt *pOpen){
-  assert( unixMutexHeld() );
-  if( pOpen ){
-    pOpen->nRef--;
-    if( pOpen->nRef==0 ){
-      if( pOpen->pPrev ){
-        assert( pOpen->pPrev->pNext==pOpen );
-        pOpen->pPrev->pNext = pOpen->pNext;
-      }else{
-        assert( openList==pOpen );
-        openList = pOpen->pNext;
-      }
-      if( pOpen->pNext ){
-        assert( pOpen->pNext->pPrev==pOpen );
-        pOpen->pNext->pPrev = pOpen->pPrev;
-      }
-#if SQLITE_THREADSAFE && defined(__linux__)
-      assert( !pOpen->pUnused || threadsOverrideEachOthersLocks==0 );
-#endif
-
-      /* If pOpen->pUnused is not null, then memory and file-descriptors
-      ** are leaked.
-      **
-      ** This will only happen if, under Linuxthreads, the user has opened
-      ** a transaction in one thread, then attempts to close the database
-      ** handle from another thread (without first unlocking the db file).
-      ** This is a misuse.  */
-      sqlite3_free(pOpen);
-    }
-  }
-}
-
-/*
-** Given a file descriptor, locate unixLockInfo and unixOpenCnt structures that
-** describes that file descriptor.  Create new ones if necessary.  The
-** return values might be uninitialized if an error occurs.
+** Given a file descriptor, locate the unixInodeInfo object that
+** describes that file descriptor.  Create a new one if necessary.  The
+** return value might be uninitialized if an error occurs.
 **
 ** The mutex entered using the unixEnterMutex() function must be held
 ** when this function is called.
 **
 ** Return an appropriate error code.
 */
-static int findLockInfo(
+static int findInodeInfo(
   unixFile *pFile,               /* Unix file with file desc used in the key */
-  struct unixLockInfo **ppLock,  /* Return the unixLockInfo structure here */
-  struct unixOpenCnt **ppOpen    /* Return the unixOpenCnt structure here */
+  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
 ){
   int rc;                        /* System call return code */
   int fd;                        /* The file descriptor for pFile */
-  struct unixLockKey lockKey;    /* Lookup key for the unixLockInfo structure */
-  struct unixFileId fileId;      /* Lookup key for the unixOpenCnt struct */
+  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
   struct stat statbuf;           /* Low-level file information */
-  struct unixLockInfo *pLock = 0;/* Candidate unixLockInfo object */
-  struct unixOpenCnt *pOpen;     /* Candidate unixOpenCnt object */
+  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
 
   assert( unixMutexHeld() );
 
@@ -22494,9 +23249,10 @@
   ** is a race condition such that another thread has already populated
   ** the first page of the database, no damage is done.
   */
-  if( statbuf.st_size==0 ){
+  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
     rc = write(fd, "S", 1);
     if( rc!=1 ){
+      pFile->lastErrno = errno;
       return SQLITE_IOERR;
     }
     rc = fstat(fd, &statbuf);
@@ -22507,120 +23263,36 @@
   }
 #endif
 
-  memset(&lockKey, 0, sizeof(lockKey));
-  lockKey.fid.dev = statbuf.st_dev;
+  memset(&fileId, 0, sizeof(fileId));
+  fileId.dev = statbuf.st_dev;
 #if OS_VXWORKS
-  lockKey.fid.pId = pFile->pId;
+  fileId.pId = pFile->pId;
 #else
-  lockKey.fid.ino = statbuf.st_ino;
+  fileId.ino = statbuf.st_ino;
 #endif
-#if SQLITE_THREADSAFE && defined(__linux__)
-  if( threadsOverrideEachOthersLocks<0 ){
-    testThreadLockingBehavior(fd);
+  pInode = inodeList;
+  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
+    pInode = pInode->pNext;
   }
-  lockKey.tid = threadsOverrideEachOthersLocks ? 0 : pthread_self();
-#endif
-  fileId = lockKey.fid;
-  if( ppLock!=0 ){
-    pLock = lockList;
-    while( pLock && memcmp(&lockKey, &pLock->lockKey, sizeof(lockKey)) ){
-      pLock = pLock->pNext;
+  if( pInode==0 ){
+    pInode = sqlite3_malloc( sizeof(*pInode) );
+    if( pInode==0 ){
+      return SQLITE_NOMEM;
     }
-    if( pLock==0 ){
-      pLock = sqlite3_malloc( sizeof(*pLock) );
-      if( pLock==0 ){
-        rc = SQLITE_NOMEM;
-        goto exit_findlockinfo;
-      }
-      memcpy(&pLock->lockKey,&lockKey,sizeof(lockKey));
-      pLock->nRef = 1;
-      pLock->cnt = 0;
-      pLock->locktype = 0;
-      pLock->pNext = lockList;
-      pLock->pPrev = 0;
-      if( lockList ) lockList->pPrev = pLock;
-      lockList = pLock;
-    }else{
-      pLock->nRef++;
-    }
-    *ppLock = pLock;
+    memset(pInode, 0, sizeof(*pInode));
+    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
+    pInode->nRef = 1;
+    pInode->pNext = inodeList;
+    pInode->pPrev = 0;
+    if( inodeList ) inodeList->pPrev = pInode;
+    inodeList = pInode;
+  }else{
+    pInode->nRef++;
   }
-  if( ppOpen!=0 ){
-    pOpen = openList;
-    while( pOpen && memcmp(&fileId, &pOpen->fileId, sizeof(fileId)) ){
-      pOpen = pOpen->pNext;
-    }
-    if( pOpen==0 ){
-      pOpen = sqlite3_malloc( sizeof(*pOpen) );
-      if( pOpen==0 ){
-        releaseLockInfo(pLock);
-        rc = SQLITE_NOMEM;
-        goto exit_findlockinfo;
-      }
-      memset(pOpen, 0, sizeof(*pOpen));
-      pOpen->fileId = fileId;
-      pOpen->nRef = 1;
-      pOpen->pNext = openList;
-      if( openList ) openList->pPrev = pOpen;
-      openList = pOpen;
-    }else{
-      pOpen->nRef++;
-    }
-    *ppOpen = pOpen;
-  }
-
-exit_findlockinfo:
-  return rc;
+  *ppInode = pInode;
+  return SQLITE_OK;
 }
 
-/*
-** If we are currently in a different thread than the thread that the
-** unixFile argument belongs to, then transfer ownership of the unixFile
-** over to the current thread.
-**
-** A unixFile is only owned by a thread on systems that use LinuxThreads.
-**
-** Ownership transfer is only allowed if the unixFile is currently unlocked.
-** If the unixFile is locked and an ownership is wrong, then return
-** SQLITE_MISUSE.  SQLITE_OK is returned if everything works.
-*/
-#if SQLITE_THREADSAFE && defined(__linux__)
-static int transferOwnership(unixFile *pFile){
-  int rc;
-  pthread_t hSelf;
-  if( threadsOverrideEachOthersLocks ){
-    /* Ownership transfers not needed on this system */
-    return SQLITE_OK;
-  }
-  hSelf = pthread_self();
-  if( pthread_equal(pFile->tid, hSelf) ){
-    /* We are still in the same thread */
-    OSTRACE1("No-transfer, same thread\n");
-    return SQLITE_OK;
-  }
-  if( pFile->locktype!=NO_LOCK ){
-    /* We cannot change ownership while we are holding a lock! */
-    return SQLITE_MISUSE_BKPT;
-  }
-  OSTRACE4("Transfer ownership of %d from %d to %d\n",
-            pFile->h, pFile->tid, hSelf);
-  pFile->tid = hSelf;
-  if (pFile->pLock != NULL) {
-    releaseLockInfo(pFile->pLock);
-    rc = findLockInfo(pFile, &pFile->pLock, 0);
-    OSTRACE5("LOCK    %d is now %s(%s,%d)\n", pFile->h,
-           locktypeName(pFile->locktype),
-           locktypeName(pFile->pLock->locktype), pFile->pLock->cnt);
-    return rc;
-  } else {
-    return SQLITE_OK;
-  }
-}
-#else  /* if not SQLITE_THREADSAFE */
-  /* On single-threaded builds, ownership transfer is a no-op */
-# define transferOwnership(X) SQLITE_OK
-#endif /* SQLITE_THREADSAFE */
-
 
 /*
 ** This routine checks if there is a RESERVED lock held on the specified
@@ -22636,10 +23308,10 @@
   SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
 
   assert( pFile );
-  unixEnterMutex(); /* Because pFile->pLock is shared across threads */
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->pLock->locktype>SHARED_LOCK ){
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
 
@@ -22663,70 +23335,14 @@
 #endif
   
   unixLeaveMutex();
-  OSTRACE4("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
 
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Perform a file locking operation on a range of bytes in a file.
-** The "op" parameter should be one of F_RDLCK, F_WRLCK, or F_UNLCK.
-** Return 0 on success or -1 for failure.  On failure, write the error
-** code into *pErrcode.
-**
-** If the SQLITE_WHOLE_FILE_LOCKING bit is clear, then only lock
-** the range of bytes on the locking page between SHARED_FIRST and
-** SHARED_SIZE.  If SQLITE_WHOLE_FILE_LOCKING is set, then lock all
-** bytes from 0 up to but not including PENDING_BYTE, and all bytes
-** that follow SHARED_FIRST.
-**
-** In other words, of SQLITE_WHOLE_FILE_LOCKING if false (the historical
-** default case) then only lock a small range of bytes from SHARED_FIRST
-** through SHARED_FIRST+SHARED_SIZE-1.  But if SQLITE_WHOLE_FILE_LOCKING is
-** true then lock every byte in the file except for PENDING_BYTE and
-** RESERVED_BYTE.
-**
-** SQLITE_WHOLE_FILE_LOCKING=true overlaps SQLITE_WHOLE_FILE_LOCKING=false
-** and so the locking schemes are compatible.  One type of lock will
-** effectively exclude the other type.  The reason for using the
-** SQLITE_WHOLE_FILE_LOCKING=true is that by indicating the full range
-** of bytes to be read or written, we give hints to NFS to help it
-** maintain cache coherency.  On the other hand, whole file locking
-** is slower, so we don't want to use it except for NFS.
-*/
-static int rangeLock(unixFile *pFile, int op, int *pErrcode){
-  struct flock lock;
-  int rc;
-  lock.l_type = op;
-  lock.l_start = SHARED_FIRST;
-  lock.l_whence = SEEK_SET;
-  if( (pFile->fileFlags & SQLITE_WHOLE_FILE_LOCKING)==0 ){
-    lock.l_len = SHARED_SIZE;
-    rc = fcntl(pFile->h, F_SETLK, &lock);
-    *pErrcode = errno;
-  }else{
-    lock.l_len = 0;
-    rc = fcntl(pFile->h, F_SETLK, &lock);
-    *pErrcode = errno;
-    if( NEVER(op==F_UNLCK) || rc!=(-1) ){
-      lock.l_start = 0;
-      lock.l_len = PENDING_BYTE;
-      rc = fcntl(pFile->h, F_SETLK, &lock);
-      if( ALWAYS(op!=F_UNLCK) && rc==(-1) ){
-        *pErrcode = errno;
-        lock.l_type = F_UNLCK;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = 0;
-        fcntl(pFile->h, F_SETLK, &lock);
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -22749,7 +23365,7 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int unixLock(sqlite3_file *id, int locktype){
+static int unixLock(sqlite3_file *id, int eFileLock){
   /* The following describes the implementation of the various locks and
   ** lock transitions in terms of the POSIX advisory shared and exclusive
   ** lock primitives (called read-locks and write-locks below, to avoid
@@ -22790,23 +23406,23 @@
   */
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
-  struct unixLockInfo *pLock = pFile->pLock;
+  unixInodeInfo *pInode = pFile->pInode;
   struct flock lock;
   int s = 0;
-  int tErrno;
+  int tErrno = 0;
 
   assert( pFile );
-  OSTRACE7("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
-      locktypeName(locktype), locktypeName(pFile->locktype),
-      locktypeName(pLock->locktype), pLock->cnt , getpid());
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
+      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+      azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
 
   /* If there is already a lock of this type or more restrictive on the
   ** unixFile, do nothing. Don't use the end_lock: exit path, as
   ** unixEnterMutex() hasn't been called yet.
   */
-  if( pFile->locktype>=locktype ){
-    OSTRACE3("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
-            locktypeName(locktype));
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
+            azFileLock(eFileLock)));
     return SQLITE_OK;
   }
 
@@ -22815,28 +23431,20 @@
   **  (2) SQLite never explicitly requests a pendig lock.
   **  (3) A shared lock is always held when a reserve lock is requested.
   */
-  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
-  assert( locktype!=PENDING_LOCK );
-  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
 
-  /* This mutex is needed because pFile->pLock is shared across threads
+  /* This mutex is needed because pFile->pInode is shared across threads
   */
   unixEnterMutex();
-
-  /* Make sure the current thread owns the pFile.
-  */
-  rc = transferOwnership(pFile);
-  if( rc!=SQLITE_OK ){
-    unixLeaveMutex();
-    return rc;
-  }
-  pLock = pFile->pLock;
+  pInode = pFile->pInode;
 
   /* If some thread using this PID has a lock via a different unixFile*
   ** handle that precludes the requested lock, return BUSY.
   */
-  if( (pFile->locktype!=pLock->locktype && 
-          (pLock->locktype>=PENDING_LOCK || locktype>SHARED_LOCK))
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
   ){
     rc = SQLITE_BUSY;
     goto end_lock;
@@ -22846,14 +23454,14 @@
   ** has a SHARED or RESERVED lock, then increment reference counts and
   ** return SQLITE_OK.
   */
-  if( locktype==SHARED_LOCK && 
-      (pLock->locktype==SHARED_LOCK || pLock->locktype==RESERVED_LOCK) ){
-    assert( locktype==SHARED_LOCK );
-    assert( pFile->locktype==0 );
-    assert( pLock->cnt>0 );
-    pFile->locktype = SHARED_LOCK;
-    pLock->cnt++;
-    pFile->pOpen->nLock++;
+  if( eFileLock==SHARED_LOCK && 
+      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
     goto end_lock;
   }
 
@@ -22864,10 +23472,10 @@
   */
   lock.l_len = 1L;
   lock.l_whence = SEEK_SET;
-  if( locktype==SHARED_LOCK 
-      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
   ){
-    lock.l_type = (locktype==SHARED_LOCK?F_RDLCK:F_WRLCK);
+    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
     lock.l_start = PENDING_BYTE;
     s = fcntl(pFile->h, F_SETLK, &lock);
     if( s==(-1) ){
@@ -22884,13 +23492,16 @@
   /* If control gets to this point, then actually go ahead and make
   ** operating system calls for the specified lock.
   */
-  if( locktype==SHARED_LOCK ){
-    assert( pLock->cnt==0 );
-    assert( pLock->locktype==0 );
+  if( eFileLock==SHARED_LOCK ){
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
 
     /* Now get the read-lock */
-    s = rangeLock(pFile, F_RDLCK, &tErrno);
-
+    lock.l_start = SHARED_FIRST;
+    lock.l_len = SHARED_SIZE;
+    if( (s = fcntl(pFile->h, F_SETLK, &lock))==(-1) ){
+      tErrno = errno;
+    }
     /* Drop the temporary PENDING lock */
     lock.l_start = PENDING_BYTE;
     lock.l_len = 1L;
@@ -22912,11 +23523,11 @@
         pFile->lastErrno = tErrno;
       }
     }else{
-      pFile->locktype = SHARED_LOCK;
-      pFile->pOpen->nLock++;
-      pLock->cnt = 1;
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
     }
-  }else if( locktype==EXCLUSIVE_LOCK && pLock->cnt>1 ){
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
     /* We are trying for an exclusive lock but another thread in this
     ** same process is still holding a shared lock. */
     rc = SQLITE_BUSY;
@@ -22925,21 +23536,22 @@
     ** assumed that there is a SHARED or greater lock on the file
     ** already.
     */
-    assert( 0!=pFile->locktype );
+    assert( 0!=pFile->eFileLock );
     lock.l_type = F_WRLCK;
-    switch( locktype ){
+    switch( eFileLock ){
       case RESERVED_LOCK:
         lock.l_start = RESERVED_BYTE;
-        s = fcntl(pFile->h, F_SETLK, &lock);
-        tErrno = errno;
         break;
       case EXCLUSIVE_LOCK:
-        s = rangeLock(pFile, F_WRLCK, &tErrno);
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
         break;
       default:
         assert(0);
     }
+    s = fcntl(pFile->h, F_SETLK, &lock);
     if( s==(-1) ){
+      tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
       if( IS_LOCK_ERROR(rc) ){
         pFile->lastErrno = tErrno;
@@ -22955,8 +23567,8 @@
   ** write operation (not a hot journal rollback).
   */
   if( rc==SQLITE_OK
-   && pFile->locktype<=SHARED_LOCK
-   && locktype==RESERVED_LOCK
+   && pFile->eFileLock<=SHARED_LOCK
+   && eFileLock==RESERVED_LOCK
   ){
     pFile->transCntrChng = 0;
     pFile->dbUpdate = 0;
@@ -22966,47 +23578,17 @@
 
 
   if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-    pLock->locktype = locktype;
-  }else if( locktype==EXCLUSIVE_LOCK ){
-    pFile->locktype = PENDING_LOCK;
-    pLock->locktype = PENDING_LOCK;
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
   }
 
 end_lock:
   unixLeaveMutex();
-  OSTRACE4("LOCK    %d %s %s (unix)\n", pFile->h, locktypeName(locktype), 
-      rc==SQLITE_OK ? "ok" : "failed");
-  return rc;
-}
-
-/*
-** Close all file descriptors accumuated in the unixOpenCnt->pUnused list.
-** If all such file descriptors are closed without error, the list is
-** cleared and SQLITE_OK returned.
-**
-** Otherwise, if an error occurs, then successfully closed file descriptor
-** entries are removed from the list, and SQLITE_IOERR_CLOSE returned. 
-** not deleted and SQLITE_IOERR_CLOSE returned.
-*/ 
-static int closePendingFds(unixFile *pFile){
-  int rc = SQLITE_OK;
-  struct unixOpenCnt *pOpen = pFile->pOpen;
-  UnixUnusedFd *pError = 0;
-  UnixUnusedFd *p;
-  UnixUnusedFd *pNext;
-  for(p=pOpen->pUnused; p; p=pNext){
-    pNext = p->pNext;
-    if( close(p->fd) ){
-      pFile->lastErrno = errno;
-      rc = SQLITE_IOERR_CLOSE;
-      p->pNext = pError;
-      pError = p;
-    }else{
-      sqlite3_free(p);
-    }
-  }
-  pOpen->pUnused = pError;
+  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), 
+      rc==SQLITE_OK ? "ok" : "failed"));
   return rc;
 }
 
@@ -23015,46 +23597,50 @@
 ** pUnused list.
 */
 static void setPendingFd(unixFile *pFile){
-  struct unixOpenCnt *pOpen = pFile->pOpen;
+  unixInodeInfo *pInode = pFile->pInode;
   UnixUnusedFd *p = pFile->pUnused;
-  p->pNext = pOpen->pUnused;
-  pOpen->pUnused = p;
+  p->pNext = pInode->pUnused;
+  pInode->pUnused = p;
   pFile->h = -1;
   pFile->pUnused = 0;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
+** 
+** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
+** the byte range is divided into 2 parts and the first part is unlocked then
+** set to a read lock, then the other part is simply unlocked.  This works 
+** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to 
+** remove the write lock on a region when a read lock is set.
 */
-static int unixUnlock(sqlite3_file *id, int locktype){
-  unixFile *pFile = (unixFile*)id; /* The open file */
-  struct unixLockInfo *pLock;      /* Structure describing current lock state */
-  struct flock lock;               /* Information passed into fcntl() */
-  int rc = SQLITE_OK;              /* Return code from this interface */
-  int h;                           /* The underlying file descriptor */
+static int _posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
+  unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode;
+  struct flock lock;
+  int rc = SQLITE_OK;
+  int h;
   int tErrno;                      /* Error code from system call errors */
 
   assert( pFile );
-  OSTRACE7("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, locktype,
-      pFile->locktype, pFile->pLock->locktype, pFile->pLock->cnt, getpid());
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
+      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+      getpid()));
 
-  assert( locktype<=SHARED_LOCK );
-  if( pFile->locktype<=locktype ){
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
     return SQLITE_OK;
   }
-  if( CHECK_THREADID(pFile) ){
-    return SQLITE_MISUSE_BKPT;
-  }
   unixEnterMutex();
   h = pFile->h;
-  pLock = pFile->pLock;
-  assert( pLock->cnt!=0 );
-  if( pFile->locktype>SHARED_LOCK ){
-    assert( pLock->locktype==pFile->locktype );
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
     SimulateIOErrorBenign(1);
     SimulateIOError( h=(-1) )
     SimulateIOErrorBenign(0);
@@ -23068,20 +23654,76 @@
     ** the file has changed and hence might not know to flush their
     ** cache.  The use of a stale cache can lead to database corruption.
     */
+#if 0
     assert( pFile->inNormalWrite==0
          || pFile->dbUpdate==0
          || pFile->transCntrChng==1 );
+#endif
     pFile->inNormalWrite = 0;
 #endif
 
-
-    if( locktype==SHARED_LOCK ){
-      if( rangeLock(pFile, F_RDLCK, &tErrno)==(-1) ){
-        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
-        if( IS_LOCK_ERROR(rc) ){
-          pFile->lastErrno = tErrno;
+    /* downgrading to a shared lock on NFS involves clearing the write lock
+    ** before establishing the readlock - to avoid a race condition we downgrade
+    ** the lock in 2 blocks, so that part of the range will be covered by a 
+    ** write lock until the rest is covered by a read lock:
+    **  1:   [WWWWW]
+    **  2:   [....W]
+    **  3:   [RRRRW]
+    **  4:   [RRRR.]
+    */
+    if( eFileLock==SHARED_LOCK ){
+      if( handleNFSUnlock ){
+        off_t divSize = SHARED_SIZE - 1;
+        
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
         }
-        goto end_unlock;
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+        lock.l_type = F_UNLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST+divSize;
+        lock.l_len = SHARED_SIZE-divSize;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
+      }else{
+        lock.l_type = F_RDLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = SHARED_FIRST;
+        lock.l_len = SHARED_SIZE;
+        if( fcntl(h, F_SETLK, &lock)==(-1) ){
+          tErrno = errno;
+          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
+          if( IS_LOCK_ERROR(rc) ){
+            pFile->lastErrno = tErrno;
+          }
+          goto end_unlock;
+        }
       }
     }
     lock.l_type = F_UNLCK;
@@ -23089,7 +23731,7 @@
     lock.l_start = PENDING_BYTE;
     lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
     if( fcntl(h, F_SETLK, &lock)!=(-1) ){
-      pLock->locktype = SHARED_LOCK;
+      pInode->eFileLock = SHARED_LOCK;
     }else{
       tErrno = errno;
       rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
@@ -23099,15 +23741,13 @@
       goto end_unlock;
     }
   }
-  if( locktype==NO_LOCK ){
-    struct unixOpenCnt *pOpen;
-
+  if( eFileLock==NO_LOCK ){
     /* Decrement the shared lock counter.  Release the lock using an
     ** OS call only when all threads in this same process have released
     ** the lock.
     */
-    pLock->cnt--;
-    if( pLock->cnt==0 ){
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
       lock.l_type = F_UNLCK;
       lock.l_whence = SEEK_SET;
       lock.l_start = lock.l_len = 0L;
@@ -23115,15 +23755,15 @@
       SimulateIOError( h=(-1) )
       SimulateIOErrorBenign(0);
       if( fcntl(h, F_SETLK, &lock)!=(-1) ){
-        pLock->locktype = NO_LOCK;
+        pInode->eFileLock = NO_LOCK;
       }else{
         tErrno = errno;
         rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
         if( IS_LOCK_ERROR(rc) ){
           pFile->lastErrno = tErrno;
         }
-        pLock->locktype = NO_LOCK;
-        pFile->locktype = NO_LOCK;
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
       }
     }
 
@@ -23131,10 +23771,9 @@
     ** count reaches zero, close any other file descriptors whose close
     ** was deferred because of outstanding locks.
     */
-    pOpen = pFile->pOpen;
-    pOpen->nLock--;
-    assert( pOpen->nLock>=0 );
-    if( pOpen->nLock==0 ){
+    pInode->nLock--;
+    assert( pInode->nLock>=0 );
+    if( pInode->nLock==0 ){
       int rc2 = closePendingFds(pFile);
       if( rc==SQLITE_OK ){
         rc = rc2;
@@ -23144,11 +23783,22 @@
 	
 end_unlock:
   unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->locktype = locktype;
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
   return rc;
 }
 
 /*
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+** must be either NO_LOCK or SHARED_LOCK.
+**
+** If the locking level of the file descriptor is already at or below
+** the requested locking level, this routine is a no-op.
+*/
+static int unixUnlock(sqlite3_file *id, int eFileLock){
+  return _posixUnlock(id, eFileLock, 0);
+}
+
+/*
 ** This function performs the parts of the "close file" operation 
 ** common to all locking schemes. It closes the directory and file
 ** handles, if they are valid, and sets all fields of the unixFile
@@ -23186,7 +23836,7 @@
       pFile->pId = 0;
     }
 #endif
-    OSTRACE2("CLOSE   %-3d\n", pFile->h);
+    OSTRACE(("CLOSE   %-3d\n", pFile->h));
     OpenCounter(-1);
     sqlite3_free(pFile->pUnused);
     memset(pFile, 0, sizeof(unixFile));
@@ -23203,16 +23853,15 @@
     unixFile *pFile = (unixFile *)id;
     unixUnlock(id, NO_LOCK);
     unixEnterMutex();
-    if( pFile->pOpen && pFile->pOpen->nLock ){
+    if( pFile->pInode && pFile->pInode->nLock ){
       /* If there are outstanding locks, do not actually close the file just
       ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pOpen->pUnused list.  It will be automatically closed 
+      ** descriptor to pInode->pUnused list.  It will be automatically closed 
       ** when the last lock is cleared.
       */
       setPendingFd(pFile);
     }
-    releaseLockInfo(pFile->pLock);
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     rc = closeUnixFile(id);
     unixLeaveMutex();
   }
@@ -23311,7 +23960,7 @@
   assert( pFile );
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     /* Either this connection or some other connection in the same process
     ** holds a lock on the file.  No need to check further. */
     reserved = 1;
@@ -23320,13 +23969,13 @@
     const char *zLockFile = (const char*)pFile->lockingContext;
     reserved = access(zLockFile, 0)==0;
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23352,7 +24001,7 @@
 ** With dotfile locking, we really only support state (4): EXCLUSIVE.
 ** But we track the other locking levels internally.
 */
-static int dotlockLock(sqlite3_file *id, int locktype) {
+static int dotlockLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int fd;
   char *zLockFile = (char *)pFile->lockingContext;
@@ -23362,8 +24011,8 @@
   /* If we have any lock, then the lock file already exists.  All we have
   ** to do is adjust our internal record of the lock level.
   */
-  if( pFile->locktype > NO_LOCK ){
-    pFile->locktype = locktype;
+  if( pFile->eFileLock > NO_LOCK ){
+    pFile->eFileLock = eFileLock;
 #if !OS_VXWORKS
     /* Always update the timestamp on the old file */
     utimes(zLockFile, NULL);
@@ -23392,12 +24041,12 @@
   }
   
   /* got it, set the type and return ok */
-  pFile->locktype = locktype;
+  pFile->eFileLock = eFileLock;
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
@@ -23405,30 +24054,30 @@
 **
 ** When the locking level reaches NO_LOCK, delete the lock file.
 */
-static int dotlockUnlock(sqlite3_file *id, int locktype) {
+static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   char *zLockFile = (char *)pFile->lockingContext;
 
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, locktype,
-	   pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
 
   /* To downgrade to shared, simply update our internal notion of the
   ** lock state.  No need to mess with the file on disk.
   */
-  if( locktype==SHARED_LOCK ){
-    pFile->locktype = SHARED_LOCK;
+  if( eFileLock==SHARED_LOCK ){
+    pFile->eFileLock = SHARED_LOCK;
     return SQLITE_OK;
   }
   
   /* To fully unlock the database, delete the lock file */
-  assert( locktype==NO_LOCK );
+  assert( eFileLock==NO_LOCK );
   if( unlink(zLockFile) ){
     int rc = 0;
     int tErrno = errno;
@@ -23440,7 +24089,7 @@
     }
     return rc; 
   }
-  pFile->locktype = NO_LOCK;
+  pFile->eFileLock = NO_LOCK;
   return SQLITE_OK;
 }
 
@@ -23493,7 +24142,7 @@
   assert( pFile );
   
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
@@ -23524,7 +24173,7 @@
       }
     }
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
 
 #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
   if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
@@ -23537,7 +24186,7 @@
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23565,7 +24214,7 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int flockLock(sqlite3_file *id, int locktype) {
+static int flockLock(sqlite3_file *id, int eFileLock) {
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
 
@@ -23573,8 +24222,8 @@
 
   /* if we already have a lock, it is exclusive.  
   ** Just adjust level and punt on outta here. */
-  if (pFile->locktype > NO_LOCK) {
-    pFile->locktype = locktype;
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23589,10 +24238,10 @@
     }
   } else {
     /* got it, set the type and return ok */
-    pFile->locktype = locktype;
+    pFile->eFileLock = eFileLock;
   }
-  OSTRACE4("LOCK    %d %s %s (flock)\n", pFile->h, locktypeName(locktype), 
-           rc==SQLITE_OK ? "ok" : "failed");
+  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock), 
+           rc==SQLITE_OK ? "ok" : "failed"));
 #ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
   if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
     rc = SQLITE_BUSY;
@@ -23603,28 +24252,28 @@
 
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int flockUnlock(sqlite3_file *id, int locktype) {
+static int flockUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, locktype,
-           pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
+           pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
   
   /* shared can just be set because we always have an exclusive */
-  if (locktype==SHARED_LOCK) {
-    pFile->locktype = locktype;
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23644,7 +24293,7 @@
     
     return r;
   } else {
-    pFile->locktype = NO_LOCK;
+    pFile->eFileLock = NO_LOCK;
     return SQLITE_OK;
   }
 }
@@ -23692,13 +24341,13 @@
   assert( pFile );
 
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
   /* Otherwise see if some other process holds it. */
   if( !reserved ){
-    sem_t *pSem = pFile->pOpen->pSem;
+    sem_t *pSem = pFile->pInode->pSem;
     struct stat statBuf;
 
     if( sem_trywait(pSem)==-1 ){
@@ -23708,21 +24357,21 @@
         pFile->lastErrno = tErrno;
       } else {
         /* someone else has the lock when we are in NO_LOCK */
-        reserved = (pFile->locktype < SHARED_LOCK);
+        reserved = (pFile->eFileLock < SHARED_LOCK);
       }
     }else{
       /* we could have it if we want it */
       sem_post(pSem);
     }
   }
-  OSTRACE4("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved);
+  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
 
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23750,16 +24399,16 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int semLock(sqlite3_file *id, int locktype) {
+static int semLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int fd;
-  sem_t *pSem = pFile->pOpen->pSem;
+  sem_t *pSem = pFile->pInode->pSem;
   int rc = SQLITE_OK;
 
   /* if we already have a lock, it is exclusive.  
   ** Just adjust level and punt on outta here. */
-  if (pFile->locktype > NO_LOCK) {
-    pFile->locktype = locktype;
+  if (pFile->eFileLock > NO_LOCK) {
+    pFile->eFileLock = eFileLock;
     rc = SQLITE_OK;
     goto sem_end_lock;
   }
@@ -23771,37 +24420,37 @@
   }
 
   /* got it, set the type and return ok */
-  pFile->locktype = locktype;
+  pFile->eFileLock = eFileLock;
 
  sem_end_lock:
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int semUnlock(sqlite3_file *id, int locktype) {
+static int semUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pOpen->pSem;
+  sem_t *pSem = pFile->pInode->pSem;
 
   assert( pFile );
   assert( pSem );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, locktype,
-	   pFile->locktype, getpid());
-  assert( locktype<=SHARED_LOCK );
+  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
+	   pFile->eFileLock, getpid()));
+  assert( eFileLock<=SHARED_LOCK );
   
   /* no-op if possible */
-  if( pFile->locktype==locktype ){
+  if( pFile->eFileLock==eFileLock ){
     return SQLITE_OK;
   }
   
   /* shared can just be set because we always have an exclusive */
-  if (locktype==SHARED_LOCK) {
-    pFile->locktype = locktype;
+  if (eFileLock==SHARED_LOCK) {
+    pFile->eFileLock = eFileLock;
     return SQLITE_OK;
   }
   
@@ -23814,7 +24463,7 @@
     }
     return rc; 
   }
-  pFile->locktype = NO_LOCK;
+  pFile->eFileLock = NO_LOCK;
   return SQLITE_OK;
 }
 
@@ -23827,8 +24476,7 @@
     semUnlock(id, NO_LOCK);
     assert( pFile );
     unixEnterMutex();
-    releaseLockInfo(pFile->pLock);
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     unixLeaveMutex();
     closeUnixFile(id);
   }
@@ -23859,7 +24507,7 @@
 */
 typedef struct afpLockingContext afpLockingContext;
 struct afpLockingContext {
-  unsigned long long sharedByte;
+  int reserved;
   const char *dbPath;             /* Name of the open file */
 };
 
@@ -23897,15 +24545,15 @@
   pb.length = length; 
   pb.fd = pFile->h;
   
-  OSTRACE6("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
+  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
     (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
-    offset, length);
+    offset, length));
   err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
   if ( err==-1 ) {
     int rc;
     int tErrno = errno;
-    OSTRACE4("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
-             path, tErrno, strerror(tErrno));
+    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
+             path, tErrno, strerror(tErrno)));
 #ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
     rc = SQLITE_BUSY;
 #else
@@ -23936,9 +24584,14 @@
   
   assert( pFile );
   afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  if( context->reserved ){
+    *pResOut = 1;
+    return SQLITE_OK;
+  }
+  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
   
   /* Check if a thread in this process holds such a lock */
-  if( pFile->locktype>SHARED_LOCK ){
+  if( pFile->pInode->eFileLock>SHARED_LOCK ){
     reserved = 1;
   }
   
@@ -23960,14 +24613,15 @@
     }
   }
   
-  OSTRACE4("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved);
+  unixLeaveMutex();
+  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
   
   *pResOut = reserved;
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -23990,49 +24644,72 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int afpLock(sqlite3_file *id, int locktype){
+static int afpLock(sqlite3_file *id, int eFileLock){
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
+  unixInodeInfo *pInode = pFile->pInode;
   afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
   
   assert( pFile );
-  OSTRACE5("LOCK    %d %s was %s pid=%d (afp)\n", pFile->h,
-         locktypeName(locktype), locktypeName(pFile->locktype), getpid());
+  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
+           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
+           azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
 
   /* If there is already a lock of this type or more restrictive on the
   ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
   ** unixEnterMutex() hasn't been called yet.
   */
-  if( pFile->locktype>=locktype ){
-    OSTRACE3("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
-           locktypeName(locktype));
+  if( pFile->eFileLock>=eFileLock ){
+    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
+           azFileLock(eFileLock)));
     return SQLITE_OK;
   }
 
   /* Make sure the locking sequence is correct
+  **  (1) We never move from unlocked to anything higher than shared lock.
+  **  (2) SQLite never explicitly requests a pendig lock.
+  **  (3) A shared lock is always held when a reserve lock is requested.
   */
-  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
-  assert( locktype!=PENDING_LOCK );
-  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
+  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
+  assert( eFileLock!=PENDING_LOCK );
+  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
   
-  /* This mutex is needed because pFile->pLock is shared across threads
+  /* This mutex is needed because pFile->pInode is shared across threads
   */
   unixEnterMutex();
+  pInode = pFile->pInode;
 
-  /* Make sure the current thread owns the pFile.
+  /* If some thread using this PID has a lock via a different unixFile*
+  ** handle that precludes the requested lock, return BUSY.
   */
-  rc = transferOwnership(pFile);
-  if( rc!=SQLITE_OK ){
-    unixLeaveMutex();
-    return rc;
+  if( (pFile->eFileLock!=pInode->eFileLock && 
+       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
+     ){
+    rc = SQLITE_BUSY;
+    goto afp_end_lock;
+  }
+  
+  /* If a SHARED lock is requested, and some thread using this PID already
+  ** has a SHARED or RESERVED lock, then increment reference counts and
+  ** return SQLITE_OK.
+  */
+  if( eFileLock==SHARED_LOCK && 
+     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
+    assert( eFileLock==SHARED_LOCK );
+    assert( pFile->eFileLock==0 );
+    assert( pInode->nShared>0 );
+    pFile->eFileLock = SHARED_LOCK;
+    pInode->nShared++;
+    pInode->nLock++;
+    goto afp_end_lock;
   }
     
   /* A PENDING lock is needed before acquiring a SHARED lock and before
   ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
   ** be released.
   */
-  if( locktype==SHARED_LOCK 
-      || (locktype==EXCLUSIVE_LOCK && pFile->locktype<PENDING_LOCK)
+  if( eFileLock==SHARED_LOCK 
+      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
   ){
     int failed;
     failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
@@ -24045,16 +24722,20 @@
   /* If control gets to this point, then actually go ahead and make
   ** operating system calls for the specified lock.
   */
-  if( locktype==SHARED_LOCK ){
-    int lk, lrc1, lrc2;
-    int lrc1Errno = 0;
+  if( eFileLock==SHARED_LOCK ){
+    int lrc1, lrc2, lrc1Errno;
+    long lk, mask;
     
+    assert( pInode->nShared==0 );
+    assert( pInode->eFileLock==0 );
+        
+    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
     /* Now get the read-lock SHARED_LOCK */
     /* note that the quality of the randomness doesn't matter that much */
     lk = random(); 
-    context->sharedByte = (lk & 0x7fffffff)%(SHARED_SIZE - 1);
+    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
     lrc1 = afpSetLock(context->dbPath, pFile, 
-          SHARED_FIRST+context->sharedByte, 1, 1);
+          SHARED_FIRST+pInode->sharedByte, 1, 1);
     if( IS_LOCK_ERROR(lrc1) ){
       lrc1Errno = pFile->lastErrno;
     }
@@ -24071,34 +24752,42 @@
     } else if( lrc1 != SQLITE_OK ) {
       rc = lrc1;
     } else {
-      pFile->locktype = SHARED_LOCK;
-      pFile->pOpen->nLock++;
+      pFile->eFileLock = SHARED_LOCK;
+      pInode->nLock++;
+      pInode->nShared = 1;
     }
+  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
+    /* We are trying for an exclusive lock but another thread in this
+     ** same process is still holding a shared lock. */
+    rc = SQLITE_BUSY;
   }else{
     /* The request was for a RESERVED or EXCLUSIVE lock.  It is
     ** assumed that there is a SHARED or greater lock on the file
     ** already.
     */
     int failed = 0;
-    assert( 0!=pFile->locktype );
-    if (locktype >= RESERVED_LOCK && pFile->locktype < RESERVED_LOCK) {
+    assert( 0!=pFile->eFileLock );
+    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
         /* Acquire a RESERVED lock */
         failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
+      if( !failed ){
+        context->reserved = 1;
+      }
     }
-    if (!failed && locktype == EXCLUSIVE_LOCK) {
+    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
       /* Acquire an EXCLUSIVE lock */
         
       /* Remove the shared lock before trying the range.  we'll need to 
       ** reestablish the shared lock if we can't get the  afpUnlock
       */
       if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
-                         context->sharedByte, 1, 0)) ){
+                         pInode->sharedByte, 1, 0)) ){
         int failed2 = SQLITE_OK;
         /* now attemmpt to get the exclusive lock range */
         failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, 
                                SHARED_SIZE, 1);
         if( failed && (failed2 = afpSetLock(context->dbPath, pFile, 
-                       SHARED_FIRST + context->sharedByte, 1, 1)) ){
+                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
           /* Can't reestablish the shared lock.  Sqlite can't deal, this is
           ** a critical I/O error
           */
@@ -24116,78 +24805,124 @@
   }
   
   if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-  }else if( locktype==EXCLUSIVE_LOCK ){
-    pFile->locktype = PENDING_LOCK;
+    pFile->eFileLock = eFileLock;
+    pInode->eFileLock = eFileLock;
+  }else if( eFileLock==EXCLUSIVE_LOCK ){
+    pFile->eFileLock = PENDING_LOCK;
+    pInode->eFileLock = PENDING_LOCK;
   }
   
 afp_end_lock:
   unixLeaveMutex();
-  OSTRACE4("LOCK    %d %s %s (afp)\n", pFile->h, locktypeName(locktype), 
-         rc==SQLITE_OK ? "ok" : "failed");
+  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), 
+         rc==SQLITE_OK ? "ok" : "failed"));
   return rc;
 }
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int afpUnlock(sqlite3_file *id, int locktype) {
+static int afpUnlock(sqlite3_file *id, int eFileLock) {
   int rc = SQLITE_OK;
   unixFile *pFile = (unixFile*)id;
-  afpLockingContext *pCtx = (afpLockingContext *) pFile->lockingContext;
+  unixInodeInfo *pInode;
+  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
+  int skipShared = 0;
+#ifdef SQLITE_TEST
+  int h = pFile->h;
+#endif
 
   assert( pFile );
-  OSTRACE5("UNLOCK  %d %d was %d pid=%d (afp)\n", pFile->h, locktype,
-         pFile->locktype, getpid());
+  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
+           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
+           getpid()));
 
-  assert( locktype<=SHARED_LOCK );
-  if( pFile->locktype<=locktype ){
+  assert( eFileLock<=SHARED_LOCK );
+  if( pFile->eFileLock<=eFileLock ){
     return SQLITE_OK;
   }
-  if( CHECK_THREADID(pFile) ){
-    return SQLITE_MISUSE_BKPT;
-  }
   unixEnterMutex();
-  if( pFile->locktype>SHARED_LOCK ){
+  pInode = pFile->pInode;
+  assert( pInode->nShared!=0 );
+  if( pFile->eFileLock>SHARED_LOCK ){
+    assert( pInode->eFileLock==pFile->eFileLock );
+    SimulateIOErrorBenign(1);
+    SimulateIOError( h=(-1) )
+    SimulateIOErrorBenign(0);
     
-    if( pFile->locktype==EXCLUSIVE_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
-      if( rc==SQLITE_OK && locktype==SHARED_LOCK ){
+#ifndef NDEBUG
+    /* When reducing a lock such that other processes can start
+    ** reading the database file again, make sure that the
+    ** transaction counter was updated if any part of the database
+    ** file changed.  If the transaction counter is not updated,
+    ** other connections to the same file might not realize that
+    ** the file has changed and hence might not know to flush their
+    ** cache.  The use of a stale cache can lead to database corruption.
+    */
+    assert( pFile->inNormalWrite==0
+           || pFile->dbUpdate==0
+           || pFile->transCntrChng==1 );
+    pFile->inNormalWrite = 0;
+#endif
+    
+    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
+      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
         /* only re-establish the shared lock if necessary */
-        int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
-        rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 1);
+        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
+      } else {
+        skipShared = 1;
       }
     }
-    if( rc==SQLITE_OK && pFile->locktype>=PENDING_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, PENDING_BYTE, 1, 0);
+    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
+      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
     } 
-    if( rc==SQLITE_OK && pFile->locktype>=RESERVED_LOCK ){
-      rc = afpSetLock(pCtx->dbPath, pFile, RESERVED_BYTE, 1, 0);
+    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
+      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
+      if( !rc ){ 
+        context->reserved = 0; 
+      }
     }
-  }else if( locktype==NO_LOCK ){
-    /* clear the shared lock */
-    int sharedLockByte = SHARED_FIRST+pCtx->sharedByte;
-    rc = afpSetLock(pCtx->dbPath, pFile, sharedLockByte, 1, 0);
+    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
+      pInode->eFileLock = SHARED_LOCK;
+    }
   }
+  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
 
-  if( rc==SQLITE_OK ){
-    if( locktype==NO_LOCK ){
-      struct unixOpenCnt *pOpen = pFile->pOpen;
-      pOpen->nLock--;
-      assert( pOpen->nLock>=0 );
-      if( pOpen->nLock==0 ){
+    /* Decrement the shared lock counter.  Release the lock using an
+    ** OS call only when all threads in this same process have released
+    ** the lock.
+    */
+    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
+    pInode->nShared--;
+    if( pInode->nShared==0 ){
+      SimulateIOErrorBenign(1);
+      SimulateIOError( h=(-1) )
+      SimulateIOErrorBenign(0);
+      if( !skipShared ){
+        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
+      }
+      if( !rc ){
+        pInode->eFileLock = NO_LOCK;
+        pFile->eFileLock = NO_LOCK;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      pInode->nLock--;
+      assert( pInode->nLock>=0 );
+      if( pInode->nLock==0 ){
         rc = closePendingFds(pFile);
       }
     }
   }
+  
   unixLeaveMutex();
-  if( rc==SQLITE_OK ){
-    pFile->locktype = locktype;
-  }
+  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
   return rc;
 }
 
@@ -24195,24 +24930,25 @@
 ** Close a file & cleanup AFP specific locking context 
 */
 static int afpClose(sqlite3_file *id) {
+  int rc = SQLITE_OK;
   if( id ){
     unixFile *pFile = (unixFile*)id;
     afpUnlock(id, NO_LOCK);
     unixEnterMutex();
-    if( pFile->pOpen && pFile->pOpen->nLock ){
+    if( pFile->pInode && pFile->pInode->nLock ){
       /* If there are outstanding locks, do not actually close the file just
       ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pOpen->aPending.  It will be automatically closed when
+      ** descriptor to pInode->aPending.  It will be automatically closed when
       ** the last lock is cleared.
       */
       setPendingFd(pFile);
     }
-    releaseOpenCnt(pFile->pOpen);
+    releaseInodeInfo(pFile);
     sqlite3_free(pFile->lockingContext);
-    closeUnixFile(id);
+    rc = closeUnixFile(id);
     unixLeaveMutex();
   }
-  return SQLITE_OK;
+  return rc;
 }
 
 #endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
@@ -24225,6 +24961,29 @@
 ********************* End of the AFP lock implementation **********************
 ******************************************************************************/
 
+/******************************************************************************
+*************************** Begin NFS Locking ********************************/
+
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+/*
+ ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
+ ** must be either NO_LOCK or SHARED_LOCK.
+ **
+ ** If the locking level of the file descriptor is already at or below
+ ** the requested locking level, this routine is a no-op.
+ */
+static int nfsUnlock(sqlite3_file *id, int eFileLock){
+  return _posixUnlock(id, eFileLock, 1);
+}
+
+#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
+/*
+** The code above is the NFS lock implementation.  The code is specific
+** to MacOSX and does not work on other unix platforms.  No alternative
+** is available.  
+**
+********************* End of the NFS lock implementation **********************
+******************************************************************************/
 
 /******************************************************************************
 **************** Non-locking sqlite3_file methods *****************************
@@ -24251,7 +25010,9 @@
 */
 static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
   int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
   i64 newOffset;
+#endif
   TIMER_START;
 #if defined(USE_PREAD)
   got = pread(id->h, pBuf, cnt, offset);
@@ -24276,7 +25037,7 @@
   if( got<0 ){
     ((unixFile*)id)->lastErrno = errno;
   }
-  OSTRACE5("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
+  OSTRACE(("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
   return got;
 }
 
@@ -24297,10 +25058,12 @@
 
   /* If this is a database file (not a journal, master-journal or temp
   ** file), the bytes in the locking range should never be read or written. */
+#if 0
   assert( pFile->pUnused==0
        || offset>=PENDING_BYTE+512
        || offset+amt<=PENDING_BYTE 
   );
+#endif
 
   got = seekAndRead(pFile, offset, pBuf, amt);
   if( got==amt ){
@@ -24325,7 +25088,9 @@
 */
 static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
   int got;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
   i64 newOffset;
+#endif
   TIMER_START;
 #if defined(USE_PREAD)
   got = pwrite(id->h, pBuf, cnt, offset);
@@ -24348,7 +25113,7 @@
     ((unixFile*)id)->lastErrno = errno;
   }
 
-  OSTRACE5("WRITE   %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED);
+  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
   return got;
 }
 
@@ -24370,10 +25135,12 @@
 
   /* If this is a database file (not a journal, master-journal or temp
   ** file), the bytes in the locking range should never be read or written. */
+#if 0
   assert( pFile->pUnused==0
        || offset>=PENDING_BYTE+512
        || offset+amt<=PENDING_BYTE 
   );
+#endif
 
 #ifndef NDEBUG
   /* If we are doing a normal write to a database file (as opposed to
@@ -24519,6 +25286,11 @@
   */
   if( rc ) rc = fsync(fd);
 
+#elif defined(__APPLE__)
+  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
+  ** so currently we default to the macro that redefines fdatasync to fsync
+  */
+  rc = fsync(fd);
 #else 
   rc = fdatasync(fd);
 #if OS_VXWORKS
@@ -24567,7 +25339,7 @@
   SimulateDiskfullError( return SQLITE_FULL );
 
   assert( pFile );
-  OSTRACE2("SYNC    %-3d\n", pFile->h);
+  OSTRACE(("SYNC    %-3d\n", pFile->h));
   rc = full_fsync(pFile->h, isFullsync, isDataOnly);
   SimulateIOError( rc=1 );
   if( rc ){
@@ -24576,8 +25348,8 @@
   }
   if( pFile->dirfd>=0 ){
     int err;
-    OSTRACE4("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
-            HAVE_FULLFSYNC, isFullsync);
+    OSTRACE(("DIRSYNC %-3d (have_fullfsync=%d fullsync=%d)\n", pFile->dirfd,
+            HAVE_FULLFSYNC, isFullsync));
 #ifndef SQLITE_DISABLE_DIRSYNC
     /* The directory sync is only attempted if full_fsync is
     ** turned off or unavailable.  If a full_fsync occurred above,
@@ -24649,7 +25421,7 @@
   }
   *pSize = buf.st_size;
 
-  /* When opening a zero-size database, the findLockInfo() procedure
+  /* When opening a zero-size database, the findInodeInfo() procedure
   ** writes a single byte into that file in order to work around a bug
   ** in the OS-X msdos filesystem.  In order to avoid problems with upper
   ** layers, we need to report this file size as zero even though it is
@@ -24676,13 +25448,21 @@
 static int unixFileControl(sqlite3_file *id, int op, void *pArg){
   switch( op ){
     case SQLITE_FCNTL_LOCKSTATE: {
-      *(int*)pArg = ((unixFile*)id)->locktype;
+      *(int*)pArg = ((unixFile*)id)->eFileLock;
       return SQLITE_OK;
     }
     case SQLITE_LAST_ERRNO: {
       *(int*)pArg = ((unixFile*)id)->lastErrno;
       return SQLITE_OK;
     }
+    case SQLITE_FCNTL_SIZE_HINT: {
+#if 0 /* No performance advantage seen on Linux */
+      sqlite3_int64 szFile = *(sqlite3_int64*)pArg;
+      unixFile *pFile = (unixFile*)id;
+      ftruncate(pFile->h, szFile);
+#endif
+      return SQLITE_OK;
+    }
 #ifndef NDEBUG
     /* The pager calls this method to signal that it has done
     ** a rollback and that the database is therefore unchanged and
@@ -24727,6 +25507,561 @@
   return 0;
 }
 
+#ifndef SQLITE_OMIT_WAL
+
+
+/*
+** Object used to represent an shared memory buffer.  
+**
+** When multiple threads all reference the same wal-index, each thread
+** has its own unixShm object, but they all point to a single instance
+** of this unixShmNode object.  In other words, each wal-index is opened
+** only once per process.
+**
+** Each unixShmNode object is connected to a single unixInodeInfo object.
+** We could coalesce this object into unixInodeInfo, but that would mean
+** every open file that does not use shared memory (in other words, most
+** open files) would have to carry around this extra information.  So
+** the unixInodeInfo object contains a pointer to this unixShmNode object
+** and the unixShmNode object is created only when needed.
+**
+** unixMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either unixShmNode.mutex must be held or unixShmNode.nRef==0 and
+** unixMutexHeld() is true when reading or writing any other field
+** in this structure.
+*/
+struct unixShmNode {
+  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the mmapped file */
+  int h;                     /* Open file descriptor */
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  char **apRegion;           /* Array of mapped shared-memory regions */
+  int nRef;                  /* Number of unixShm objects pointing to this */
+  unixShm *pFirst;           /* All unixShm objects pointing to this */
+#ifdef SQLITE_DEBUG
+  u8 exclMask;               /* Mask of exclusive locks held */
+  u8 sharedMask;             /* Mask of shared locks held */
+  u8 nextShmId;              /* Next available unixShm.id value */
+#endif
+};
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** The following fields are initialized when this object is created and
+** are read-only thereafter:
+**
+**    unixShm.pFile
+**    unixShm.id
+**
+** All other fields are read/write.  The unixShm.pFile->mutex must be held
+** while accessing any read/write fields.
+*/
+struct unixShm {
+  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
+  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
+  u8 hasMutex;               /* True if holding the unixShmNode mutex */
+  u16 sharedMask;            /* Mask of shared locks held */
+  u16 exclMask;              /* Mask of exclusive locks held */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection within its unixShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define UNIX_SHM_BASE   ((18+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
+#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
+**
+** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
+** otherwise.
+*/
+static int unixShmSystemLock(
+  unixShmNode *pShmNode, /* Apply locks to this open shared-memory segment */
+  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
+  int ofst,              /* First byte of the locking range */
+  int n                  /* Number of bytes to lock */
+){
+  struct flock f;       /* The posix advisory locking structure */
+  int rc = SQLITE_OK;   /* Result code form fcntl() */
+
+  /* Access to the unixShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
+
+  /* Shared locks never span more than one byte */
+  assert( n==1 || lockType!=F_RDLCK );
+
+  /* Locks are within range */
+  assert( n>=1 && n<SQLITE_SHM_NLOCK );
+
+  /* Initialize the locking parameters */
+  memset(&f, 0, sizeof(f));
+  f.l_type = lockType;
+  f.l_whence = SEEK_SET;
+  f.l_start = ofst;
+  f.l_len = n;
+
+  rc = fcntl(pShmNode->h, F_SETLK, &f);
+  rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
+
+  /* Update the global lock state and do debug tracing */
+#ifdef SQLITE_DEBUG
+  { u16 mask;
+  OSTRACE(("SHM-LOCK "));
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  if( rc==SQLITE_OK ){
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask &= ~mask;
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock %d ok", ofst));
+      pShmNode->exclMask &= ~mask;
+      pShmNode->sharedMask |= mask;
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d ok", ofst));
+      pShmNode->exclMask |= mask;
+      pShmNode->sharedMask &= ~mask;
+    }
+  }else{
+    if( lockType==F_UNLCK ){
+      OSTRACE(("unlock %d failed", ofst));
+    }else if( lockType==F_RDLCK ){
+      OSTRACE(("read-lock failed"));
+    }else{
+      assert( lockType==F_WRLCK );
+      OSTRACE(("write-lock %d failed", ofst));
+    }
+  }
+  OSTRACE((" - afterwards %03x,%03x\n",
+           pShmNode->sharedMask, pShmNode->exclMask));
+  }
+#endif
+
+  return rc;        
+}
+
+
+/*
+** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void unixShmPurge(unixFile *pFd){
+  unixShmNode *p = pFd->pInode->pShmNode;
+  assert( unixMutexHeld() );
+  if( p && p->nRef==0 ){
+    int i;
+    assert( p->pInode==pFd->pInode );
+    if( p->mutex ) sqlite3_mutex_free(p->mutex);
+    for(i=0; i<p->nRegion; i++){
+      munmap(p->apRegion[i], p->szRegion);
+    }
+    sqlite3_free(p->apRegion);
+    if( p->h>=0 ) close(p->h);
+    p->pInode->pShmNode = 0;
+    sqlite3_free(p);
+  }
+}
+
+/*
+** Open a shared-memory area associated with open database file fd.  
+** This particular implementation uses mmapped files.
+**
+** The file used to implement shared-memory is in the same directory
+** as the open database file and has the same name as the open database
+** file with the "-shm" suffix added.  For example, if the database file
+** is "/home/user1/config.db" then the file that is created and mmapped
+** for shared memory will be called "/home/user1/config.db-shm".  We
+** experimented with using files in /dev/tmp or an some other tmpfs mount.
+** But if a file in a different directory from the database file is used,
+** then differing access permissions or a chroot() might cause two different 
+** processes on the same database to end up using different files for 
+** shared memory - meaning that their memory would not really be shared - 
+** resulting in database corruption.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int unixShmOpen(
+  sqlite3_file *fd      /* The file descriptor of the associated database */
+){
+  struct unixShm *p = 0;             /* The connection to be opened */
+  struct unixShmNode *pShmNode = 0;  /* The underlying mmapped file */
+  int rc;                            /* Result code */
+  struct unixFile *pDbFd;            /* Underlying database file */
+  unixInodeInfo *pInode;             /* The inode of fd */
+  char *zShmFilename;                /* Name of the file used for SHM */
+  int nShmFilename;                  /* Size of the SHM filename in bytes */
+
+  /* Allocate space for the new sqlite3_shm object.
+  */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  pDbFd = (struct unixFile*)fd;
+  assert( pDbFd->pShm==0 );
+
+  /* Check to see if a unixShmNode object already exists.  Reuse an existing
+  ** one if present.  Create a new one if necessary.
+  */
+  unixEnterMutex();
+  pInode = pDbFd->pInode;
+  pShmNode = pInode->pShmNode;
+  if( pShmNode==0 ){
+    nShmFilename = 5 + (int)strlen(pDbFd->zPath);
+    pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename );
+    if( pShmNode==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+    memset(pShmNode, 0, sizeof(*pShmNode));
+    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
+    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath);
+    pShmNode->h = -1;
+    pDbFd->pInode->pShmNode = pShmNode;
+    pShmNode->pInode = pDbFd->pInode;
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+
+    pShmNode->h = open(zShmFilename, O_RDWR|O_CREAT, 0664);
+    if( pShmNode->h<0 ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto shm_open_err;
+    }
+
+    /* Check to see if another process is holding the dead-man switch.
+    ** If not, truncate the file to zero length. 
+    */
+    rc = SQLITE_OK;
+    if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
+      if( ftruncate(pShmNode->h, 0) ){
+        rc = SQLITE_IOERR_SHMOPEN;
+      }
+    }
+    if( rc==SQLITE_OK ){
+      rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1);
+    }
+    if( rc ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the unixShmNode */
+  p->pShmNode = pShmNode;
+  p->pNext = pShmNode->pFirst;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->pFirst = p;
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  unixLeaveMutex();
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  unixLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+*/
+static int unixShmClose(
+  sqlite3_file *fd,          /* The underlying database file */
+  int deleteFlag             /* Delete shared-memory if true */
+){
+  unixShm *p;            /* The connection to be closed */
+  unixShmNode *pShmNode; /* The underlying shared-memory file */
+  unixShm **pp;          /* For looping over sibling connections */
+  unixFile *pDbFd;       /* The underlying database file */
+
+  pDbFd = (unixFile*)fd;
+  p = pDbFd->pShm;
+  if( p==0 ) return SQLITE_OK;
+  pShmNode = p->pShmNode;
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  unixEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    if( deleteFlag ) unlink(pShmNode->zFilename);
+    unixShmPurge(pDbFd);
+  }
+  unixLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+**
+** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
+** different here than in posix.  In xShmLock(), one can go from unlocked
+** to shared and back or from unlocked to exclusive and back.  But one may
+** not go from shared to exclusive or from exclusive to shared.
+*/
+static int unixShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
+  unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
+  unixShm *pX;                          /* For looping over all siblings */
+  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
+  int rc = SQLITE_OK;                   /* Result code */
+  u16 mask;                             /* Mask of locks to take or release */
+
+  assert( pShmNode==pDbFd->pInode->pShmNode );
+  assert( pShmNode->pInode==pDbFd->pInode );
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  mask = (1<<(ofst+n)) - (1<<ofst);
+  assert( n>1 || mask==(1<<ofst) );
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    u16 allMask = 0; /* Mask of locks held by siblings */
+
+    /* See if any siblings hold this same lock */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( pX==p ) continue;
+      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
+      allMask |= pX->sharedMask;
+    }
+
+    /* Unlock the system-level locks */
+    if( (mask & allMask)==0 ){
+      rc = unixShmSystemLock(pShmNode, F_UNLCK, ofst+UNIX_SHM_BASE, n);
+    }else{
+      rc = SQLITE_OK;
+    }
+
+    /* Undo the local locks */
+    if( rc==SQLITE_OK ){
+      p->exclMask &= ~mask;
+      p->sharedMask &= ~mask;
+    } 
+  }else if( flags & SQLITE_SHM_SHARED ){
+    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
+
+    /* Find out which shared locks are already held by sibling connections.
+    ** If any sibling already holds an exclusive lock, go ahead and return
+    ** SQLITE_BUSY.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+      allShared |= pX->sharedMask;
+    }
+
+    /* Get shared locks at the system level, if necessary */
+    if( rc==SQLITE_OK ){
+      if( (allShared & mask)==0 ){
+        rc = unixShmSystemLock(pShmNode, F_RDLCK, ofst+UNIX_SHM_BASE, n);
+      }else{
+        rc = SQLITE_OK;
+      }
+    }
+
+    /* Get the local shared locks */
+    if( rc==SQLITE_OK ){
+      p->sharedMask |= mask;
+    }
+  }else{
+    /* Make sure no sibling connections hold locks that will block this
+    ** lock.  If any do, return SQLITE_BUSY right away.
+    */
+    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+        rc = SQLITE_BUSY;
+        break;
+      }
+    }
+  
+    /* Get the exclusive locks at the system level.  Then if successful
+    ** also mark the local connection as being locked.
+    */
+    if( rc==SQLITE_OK ){
+      rc = unixShmSystemLock(pShmNode, F_WRLCK, ofst+UNIX_SHM_BASE, n);
+      if( rc==SQLITE_OK ){
+        assert( (p->sharedMask & mask)==0 );
+        p->exclMask |= mask;
+      }
+    }
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
+           p->id, getpid(), p->sharedMask, p->exclMask));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void unixShmBarrier(
+  sqlite3_file *fd                /* Database file holding the shared memory */
+){
+  unixEnterMutex();
+  unixLeaveMutex();
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** isWrite is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int unixShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  unixFile *pDbFd = (unixFile*)fd;
+  unixShm *p = pDbFd->pShm;
+  unixShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    char **apNew;                      /* New apRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    struct stat sStat;                 /* Used by fstat() */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    if( fstat(pShmNode->h, &sStat) ){
+      rc = SQLITE_IOERR_SHMSIZE;
+      goto shmpage_out;
+    }
+
+    if( sStat.st_size<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      if( ftruncate(pShmNode->h, nByte) ){
+        rc = SQLITE_IOERR_SHMSIZE;
+        goto shmpage_out;
+      }  
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (char **)sqlite3_realloc(
+        pShmNode->apRegion, (iRegion+1)*sizeof(char *)
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->apRegion = apNew;
+    while(pShmNode->nRegion<=iRegion){
+      void *pMem = mmap(0, szRegion, PROT_READ|PROT_WRITE, 
+          MAP_SHARED, pShmNode->h, iRegion*szRegion
+      );
+      if( pMem==MAP_FAILED ){
+        rc = SQLITE_IOERR;
+        goto shmpage_out;
+      }
+      pShmNode->apRegion[pShmNode->nRegion] = pMem;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    *pp = pShmNode->apRegion[iRegion];
+  }else{
+    *pp = 0;
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+#else
+# define unixShmOpen    0
+# define unixShmLock    0
+# define unixShmMap     0
+# define unixShmBarrier 0
+# define unixShmClose   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
 /*
 ** Here ends the implementation of all sqlite3_file methods.
 **
@@ -24767,9 +26102,9 @@
 **   *  An I/O method finder function called FINDER that returns a pointer
 **      to the METHOD object in the previous bullet.
 */
-#define IOMETHODS(FINDER, METHOD, CLOSE, LOCK, UNLOCK, CKLOCK)               \
+#define IOMETHODS(FINDER, METHOD, VERSION, CLOSE, LOCK, UNLOCK, CKLOCK)      \
 static const sqlite3_io_methods METHOD = {                                   \
-   1,                          /* iVersion */                                \
+   VERSION,                    /* iVersion */                                \
    CLOSE,                      /* xClose */                                  \
    unixRead,                   /* xRead */                                   \
    unixWrite,                  /* xWrite */                                  \
@@ -24781,7 +26116,12 @@
    CKLOCK,                     /* xCheckReservedLock */                      \
    unixFileControl,            /* xFileControl */                            \
    unixSectorSize,             /* xSectorSize */                             \
-   unixDeviceCharacteristics   /* xDeviceCapabilities */                     \
+   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
+   unixShmOpen,                /* xShmOpen */                                \
+   unixShmLock,                /* xShmLock */                                \
+   unixShmMap,                 /* xShmMap */                                 \
+   unixShmBarrier,             /* xShmBarrier */                             \
+   unixShmClose                /* xShmClose */                               \
 };                                                                           \
 static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
   UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
@@ -24798,6 +26138,7 @@
 IOMETHODS(
   posixIoFinder,            /* Finder function name */
   posixIoMethods,           /* sqlite3_io_methods object name */
+  2,                        /* ShmOpen is enabled */
   unixClose,                /* xClose method */
   unixLock,                 /* xLock method */
   unixUnlock,               /* xUnlock method */
@@ -24806,6 +26147,7 @@
 IOMETHODS(
   nolockIoFinder,           /* Finder function name */
   nolockIoMethods,          /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   nolockClose,              /* xClose method */
   nolockLock,               /* xLock method */
   nolockUnlock,             /* xUnlock method */
@@ -24814,6 +26156,7 @@
 IOMETHODS(
   dotlockIoFinder,          /* Finder function name */
   dotlockIoMethods,         /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   dotlockClose,             /* xClose method */
   dotlockLock,              /* xLock method */
   dotlockUnlock,            /* xUnlock method */
@@ -24824,6 +26167,7 @@
 IOMETHODS(
   flockIoFinder,            /* Finder function name */
   flockIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   flockClose,               /* xClose method */
   flockLock,                /* xLock method */
   flockUnlock,              /* xUnlock method */
@@ -24835,6 +26179,7 @@
 IOMETHODS(
   semIoFinder,              /* Finder function name */
   semIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   semClose,                 /* xClose method */
   semLock,                  /* xLock method */
   semUnlock,                /* xUnlock method */
@@ -24846,6 +26191,7 @@
 IOMETHODS(
   afpIoFinder,              /* Finder function name */
   afpIoMethods,             /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   afpClose,                 /* xClose method */
   afpLock,                  /* xLock method */
   afpUnlock,                /* xUnlock method */
@@ -24854,23 +26200,6 @@
 #endif
 
 /*
-** The "Whole File Locking" finder returns the same set of methods as
-** the posix locking finder.  But it also sets the SQLITE_WHOLE_FILE_LOCKING
-** flag to force the posix advisory locks to cover the whole file instead
-** of just a small span of bytes near the 1GiB boundary.  Whole File Locking
-** is useful on NFS-mounted files since it helps NFS to maintain cache
-** coherency.  But it is a detriment to other filesystems since it runs
-** slower.
-*/
-static const sqlite3_io_methods *posixWflIoFinderImpl(const char*z, unixFile*p){
-  UNUSED_PARAMETER(z);
-  p->fileFlags = SQLITE_WHOLE_FILE_LOCKING;
-  return &posixIoMethods;
-}
-static const sqlite3_io_methods 
-  *(*const posixWflIoFinder)(const char*,unixFile *p) = posixWflIoFinderImpl;
-
-/*
 ** The proxy locking method is a "super-method" in the sense that it
 ** opens secondary file descriptors for the conch and lock files and
 ** it uses proxy, dot-file, AFP, and flock() locking methods on those
@@ -24887,6 +26216,7 @@
 IOMETHODS(
   proxyIoFinder,            /* Finder function name */
   proxyIoMethods,           /* sqlite3_io_methods object name */
+  1,                        /* ShmOpen is disabled */
   proxyClose,               /* xClose method */
   proxyLock,                /* xLock method */
   proxyUnlock,              /* xUnlock method */
@@ -24894,6 +26224,18 @@
 )
 #endif
 
+/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+IOMETHODS(
+  nfsIoFinder,               /* Finder function name */
+  nfsIoMethods,              /* sqlite3_io_methods object name */
+  1,                         /* ShmOpen is disabled */
+  unixClose,                 /* xClose method */
+  unixLock,                  /* xLock method */
+  nfsUnlock,                 /* xUnlock method */
+  unixCheckReservedLock      /* xCheckReservedLock method */
+)
+#endif
 
 #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
 /* 
@@ -24914,11 +26256,7 @@
     { "hfs",    &posixIoMethods },
     { "ufs",    &posixIoMethods },
     { "afpfs",  &afpIoMethods },
-#ifdef SQLITE_ENABLE_AFP_LOCKING_SMB
     { "smbfs",  &afpIoMethods },
-#else
-    { "smbfs",  &flockIoMethods },
-#endif
     { "webdav", &nolockIoMethods },
     { 0, 0 }
   };
@@ -24951,8 +26289,11 @@
   lockInfo.l_whence = SEEK_SET;
   lockInfo.l_type = F_RDLCK;
   if( fcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    pNew->fileFlags = SQLITE_WHOLE_FILE_LOCKING;
-    return &posixIoMethods;
+    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
+      return &nfsIoMethods;
+    } else {
+      return &posixIoMethods;
+    }
   }else{
     return &dotlockIoMethods;
   }
@@ -25029,19 +26370,19 @@
   unixFile *pNew = (unixFile *)pId;
   int rc = SQLITE_OK;
 
-  assert( pNew->pLock==NULL );
-  assert( pNew->pOpen==NULL );
+  assert( pNew->pInode==NULL );
 
   /* Parameter isDelete is only used on vxworks. Express this explicitly 
   ** here to prevent compiler warnings about unused parameters.
   */
   UNUSED_PARAMETER(isDelete);
 
-  OSTRACE3("OPEN    %-3d %s\n", h, zFilename);    
+  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
   pNew->h = h;
   pNew->dirfd = dirfd;
-  SET_THREADID(pNew);
   pNew->fileFlags = 0;
+  assert( zFilename==0 || zFilename[0]=='/' );  /* Never a relative pathname */
+  pNew->zPath = zFilename;
 
 #if OS_VXWORKS
   pNew->pId = vxworksFindFileId(zFilename);
@@ -25063,12 +26404,16 @@
 #endif
   }
 
-  if( pLockingStyle == &posixIoMethods ){
+  if( pLockingStyle == &posixIoMethods
+#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
+    || pLockingStyle == &nfsIoMethods
+#endif
+  ){
     unixEnterMutex();
-    rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
+    rc = findInodeInfo(pNew, &pNew->pInode);
     if( rc!=SQLITE_OK ){
-      /* If an error occured in findLockInfo(), close the file descriptor
-      ** immediately, before releasing the mutex. findLockInfo() may fail
+      /* If an error occured in findInodeInfo(), close the file descriptor
+      ** immediately, before releasing the mutex. findInodeInfo() may fail
       ** in two scenarios:
       **
       **   (a) A call to fstat() failed.
@@ -25077,7 +26422,7 @@
       ** Scenario (b) may only occur if the process is holding no other
       ** file descriptors open on the same file. If there were other file
       ** descriptors on this file, then no malloc would be required by
-      ** findLockInfo(). If this is the case, it is quite safe to close
+      ** findInodeInfo(). If this is the case, it is quite safe to close
       ** handle h - as it is guaranteed that no posix locks will be released
       ** by doing so.
       **
@@ -25105,9 +26450,15 @@
       ** according to requirement F11141.  So we do not need to make a
       ** copy of the filename. */
       pCtx->dbPath = zFilename;
+      pCtx->reserved = 0;
       srandomdev();
       unixEnterMutex();
-      rc = findLockInfo(pNew, NULL, &pNew->pOpen);
+      rc = findInodeInfo(pNew, &pNew->pInode);
+      if( rc!=SQLITE_OK ){
+        sqlite3_free(pNew->lockingContext);
+        close(h);
+        h = -1;
+      }
       unixLeaveMutex();        
     }
   }
@@ -25135,18 +26486,18 @@
     ** included in the semLockingContext
     */
     unixEnterMutex();
-    rc = findLockInfo(pNew, &pNew->pLock, &pNew->pOpen);
-    if( (rc==SQLITE_OK) && (pNew->pOpen->pSem==NULL) ){
-      char *zSemName = pNew->pOpen->aSemName;
+    rc = findInodeInfo(pNew, &pNew->pInode);
+    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
+      char *zSemName = pNew->pInode->aSemName;
       int n;
       sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
                        pNew->pId->zCanonicalName);
       for( n=1; zSemName[n]; n++ )
         if( zSemName[n]=='/' ) zSemName[n] = '_';
-      pNew->pOpen->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
-      if( pNew->pOpen->pSem == SEM_FAILED ){
+      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
+      if( pNew->pInode->pSem == SEM_FAILED ){
         rc = SQLITE_NOMEM;
-        pNew->pOpen->aSemName[0] = '\0';
+        pNew->pInode->aSemName[0] = '\0';
       }
     }
     unixLeaveMutex();
@@ -25156,6 +26507,8 @@
   pNew->lastErrno = 0;
 #if OS_VXWORKS
   if( rc!=SQLITE_OK ){
+    if( h>=0 ) close(h);
+    h = -1;
     unlink(zFilename);
     isDelete = 0;
   }
@@ -25195,7 +26548,7 @@
 #ifdef FD_CLOEXEC
       fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
 #endif
-      OSTRACE3("OPENDIR %-3d %s\n", fd, zDirname);
+      OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
     }
   }
   *pFd = fd;
@@ -25203,26 +26556,46 @@
 }
 
 /*
-** Create a temporary file name in zBuf.  zBuf must be allocated
-** by the calling process and must be big enough to hold at least
-** pVfs->mxPathname bytes.
+** Return the name of a directory in which to put temporary files.
+** If no suitable temporary file directory can be found, return NULL.
 */
-static int getTempname(int nBuf, char *zBuf){
+static const char *unixTempFileDir(void){
   static const char *azDirs[] = {
      0,
      0,
      "/var/tmp",
      "/usr/tmp",
      "/tmp",
-     ".",
+     0        /* List terminator */
   };
+  unsigned int i;
+  struct stat buf;
+  const char *zDir = 0;
+
+  azDirs[0] = sqlite3_temp_directory;
+  if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
+  for(i==0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
+    if( zDir==0 ) continue;
+    if( stat(zDir, &buf) ) continue;
+    if( !S_ISDIR(buf.st_mode) ) continue;
+    if( access(zDir, 07) ) continue;
+    break;
+  }
+  return zDir;
+}
+
+/*
+** Create a temporary file name in zBuf.  zBuf must be allocated
+** by the calling process and must be big enough to hold at least
+** pVfs->mxPathname bytes.
+*/
+static int unixGetTempname(int nBuf, char *zBuf){
   static const unsigned char zChars[] =
     "abcdefghijklmnopqrstuvwxyz"
     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
     "0123456789";
   unsigned int i, j;
-  struct stat buf;
-  const char *zDir = ".";
+  const char *zDir;
 
   /* It's odd to simulate an io-error here, but really this is just
   ** using the io-error infrastructure to test that SQLite handles this
@@ -25230,19 +26603,8 @@
   */
   SimulateIOError( return SQLITE_IOERR );
 
-  azDirs[0] = sqlite3_temp_directory;
-  if (NULL == azDirs[1]) {
-    azDirs[1] = getenv("TMPDIR");
-  }
-  
-  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); i++){
-    if( azDirs[i]==0 ) continue;
-    if( stat(azDirs[i], &buf) ) continue;
-    if( !S_ISDIR(buf.st_mode) ) continue;
-    if( access(azDirs[i], 07) ) continue;
-    zDir = azDirs[i];
-    break;
-  }
+  zDir = unixTempFileDir();
+  if( zDir==0 ) zDir = ".";
 
   /* Check that the output buffer is large enough for the temporary file 
   ** name. If it is not, return SQLITE_ERROR.
@@ -25308,17 +26670,17 @@
   ** Even if a subsequent open() call does succeed, the consequences of
   ** not searching for a resusable file descriptor are not dire.  */
   if( 0==stat(zPath, &sStat) ){
-    struct unixOpenCnt *pOpen;
+    unixInodeInfo *pInode;
 
     unixEnterMutex();
-    pOpen = openList;
-    while( pOpen && (pOpen->fileId.dev!=sStat.st_dev
-                     || pOpen->fileId.ino!=sStat.st_ino) ){
-       pOpen = pOpen->pNext;
+    pInode = inodeList;
+    while( pInode && (pInode->fileId.dev!=sStat.st_dev
+                     || pInode->fileId.ino!=sStat.st_ino) ){
+       pInode = pInode->pNext;
     }
-    if( pOpen ){
+    if( pInode ){
       UnixUnusedFd **pp;
-      for(pp=&pOpen->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
+      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
       pUnused = *pp;
       if( pUnused ){
         *pp = pUnused->pNext;
@@ -25372,6 +26734,9 @@
   int isCreate     = (flags & SQLITE_OPEN_CREATE);
   int isReadonly   = (flags & SQLITE_OPEN_READONLY);
   int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
+#if SQLITE_ENABLE_LOCKING_STYLE
+  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
+#endif
 
   /* If creating a master or main-file journal, this function will open
   ** a file-descriptor on the directory too. The first time unixSync()
@@ -25429,7 +26794,7 @@
   }else if( !zName ){
     /* If zName is NULL, the upper layer is requesting a temp file. */
     assert(isDelete && !isOpenDirectory);
-    rc = getTempname(MAX_PATHNAME+1, zTmpname);
+    rc = unixGetTempname(MAX_PATHNAME+1, zTmpname);
     if( rc!=SQLITE_OK ){
       return rc;
     }
@@ -25449,7 +26814,7 @@
   if( fd<0 ){
     mode_t openMode = (isDelete?0600:SQLITE_DEFAULT_FILE_PERMISSIONS);
     fd = open(zName, openFlags, openMode);
-    OSTRACE4("OPENX   %-3d %s 0%o\n", fd, zName, openFlags);
+    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
     if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
       /* Failed to open the file for read/write access. Try read-only. */
       flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
@@ -25505,8 +26870,25 @@
 
   noLock = eType!=SQLITE_OPEN_MAIN_DB;
 
+  
+#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
+  struct statfs fsInfo;
+  if( fstatfs(fd, &fsInfo) == -1 ){
+    ((unixFile*)pFile)->lastErrno = errno;
+    if( dirfd>=0 ) close(dirfd); /* silently leak if fail, in error */
+    close(fd); /* silently leak if fail, in error */
+    return SQLITE_IOERR_ACCESS;
+  }
+  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
+    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
+  }
+#endif
+  
+#if SQLITE_ENABLE_LOCKING_STYLE
 #if SQLITE_PREFER_PROXY_LOCKING
-  if( zPath!=NULL && !noLock && pVfs->xOpen ){
+  isAutoProxy = 1;
+#endif
+  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
     char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
     int useProxy = 0;
 
@@ -25538,6 +26920,14 @@
       rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
       if( rc==SQLITE_OK ){
         rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
+        if( rc!=SQLITE_OK ){
+          /* Use unixClose to clean up the resources added in fillInUnixFile 
+          ** and clear all the structure's references.  Specifically, 
+          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op 
+          */
+          unixClose(pFile);
+          return rc;
+        }
       }
       goto open_finished;
     }
@@ -25810,35 +27200,48 @@
 #endif
 
 /*
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return 0.  Return 1 if the time and date cannot be found.
+*/
+static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#if defined(NO_GETTOD)
+  time_t t;
+  time(&t);
+  *piNow = ((sqlite3_int64)i)*1000 + unixEpoch;
+#elif OS_VXWORKS
+  struct timespec sNow;
+  clock_gettime(CLOCK_REALTIME, &sNow);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
+#else
+  struct timeval sNow;
+  gettimeofday(&sNow, 0);
+  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
+#endif
+
+#ifdef SQLITE_TEST
+  if( sqlite3_current_time ){
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
+  }
+#endif
+  UNUSED_PARAMETER(NotUsed);
+  return 0;
+}
+
+/*
 ** Find the current time (in Universal Coordinated Time).  Write the
 ** current time and date as a Julian Day number into *prNow and
 ** return 0.  Return 1 if the time and date cannot be found.
 */
 static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
-#if defined(SQLITE_OMIT_FLOATING_POINT)
-  time_t t;
-  time(&t);
-  *prNow = (((sqlite3_int64)t)/8640 + 24405875)/10;
-#elif defined(NO_GETTOD)
-  time_t t;
-  time(&t);
-  *prNow = t/86400.0 + 2440587.5;
-#elif OS_VXWORKS
-  struct timespec sNow;
-  clock_gettime(CLOCK_REALTIME, &sNow);
-  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_nsec/86400000000000.0;
-#else
-  struct timeval sNow;
-  gettimeofday(&sNow, 0);
-  *prNow = 2440587.5 + sNow.tv_sec/86400.0 + sNow.tv_usec/86400000000.0;
-#endif
-
-#ifdef SQLITE_TEST
-  if( sqlite3_current_time ){
-    *prNow = sqlite3_current_time/86400.0 + 2440587.5;
-  }
-#endif
-  UNUSED_PARAMETER(NotUsed);
+  sqlite3_int64 i;
+  unixCurrentTimeInt64(0, &i);
+  *prNow = i/86400000.0;
   return 0;
 }
 
@@ -25856,6 +27259,7 @@
   return 0;
 }
 
+
 /*
 ************************ End of sqlite3_vfs methods ***************************
 ******************************************************************************/
@@ -25965,11 +27369,6 @@
 ** of the database file for multiple readers and writers on the same
 ** host (the conch ensures that they all use the same local lock file).
 **
-** There is a third file - the host ID file - used as a persistent record
-** of a unique identifier for the host, a 128-byte unique host id file
-** in the path defined by the HOSTIDPATH macro (default value is
-** /Library/Caches/.com.apple.sqliteConchHostId).
-**
 ** Requesting the lock proxy does not immediately take the conch, it is
 ** only taken when the first request to lock database file is made.  
 ** This matches the semantics of the traditional locking behavior, where
@@ -25995,10 +27394,6 @@
 **       Enables the logging of error messages during host id file
 **       retrieval and creation
 **
-**  HOSTIDPATH
-**
-**       Overrides the default host ID file path location
-**
 **  LOCKPROXYDIR
 **
 **       Overrides the default directory used for lock proxy files that
@@ -26023,11 +27418,6 @@
 */
 #if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
 
-#ifdef SQLITE_TEST
-/* simulate multiple hosts by creating unique hostid file paths */
-SQLITE_API int sqlite3_hostid_num = 0;
-#endif
-
 /*
 ** The proxyLockingContext has the path and file structures for the remote 
 ** and local proxy files in it
@@ -26039,134 +27429,16 @@
   unixFile *lockProxy;         /* Open proxy lock file */
   char *lockProxyPath;         /* Name of the proxy lock file */
   char *dbPath;                /* Name of the open file */
-  int conchHeld;               /* True if the conch is currently held */
+  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
   void *oldLockingContext;     /* Original lockingcontext to restore on close */
   sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
 };
 
-/* HOSTIDLEN and CONCHLEN both include space for the string 
-** terminating nul 
+/* 
+** The proxy lock file path for the database at dbPath is written into lPath, 
+** which must point to valid, writable memory large enough for a maxLen length
+** file path. 
 */
-#define HOSTIDLEN         128
-#define CONCHLEN          (MAXPATHLEN+HOSTIDLEN+1)
-#ifndef HOSTIDPATH
-# define HOSTIDPATH       "/Library/Caches/.com.apple.sqliteConchHostId"
-#endif
-
-/* basically a copy of unixRandomness with different
-** test behavior built in */
-static int proxyGenerateHostID(char *pHostID){
-  int pid, fd, len;
-  unsigned char *key = (unsigned char *)pHostID;
-  
-  memset(key, 0, HOSTIDLEN);
-  len = 0;
-  fd = open("/dev/urandom", O_RDONLY);
-  if( fd>=0 ){
-    len = read(fd, key, HOSTIDLEN);
-    close(fd); /* silently leak the fd if it fails */
-  }
-  if( len < HOSTIDLEN ){
-    time_t t;
-    time(&t);
-    memcpy(key, &t, sizeof(t));
-    pid = getpid();
-    memcpy(&key[sizeof(t)], &pid, sizeof(pid));
-  }
-  
-#ifdef MAKE_PRETTY_HOSTID
-  {
-    int i;
-    /* filter the bytes into printable ascii characters and NUL terminate */
-    key[(HOSTIDLEN-1)] = 0x00;
-    for( i=0; i<(HOSTIDLEN-1); i++ ){
-      unsigned char pa = key[i]&0x7F;
-      if( pa<0x20 ){
-        key[i] = (key[i]&0x80 == 0x80) ? pa+0x40 : pa+0x20;
-      }else if( pa==0x7F ){
-        key[i] = (key[i]&0x80 == 0x80) ? pa=0x20 : pa+0x7E;
-      }
-    }
-  }
-#endif
-  return SQLITE_OK;
-}
-
-/* writes the host id path to path, path should be an pre-allocated buffer
-** with enough space for a path 
-*/
-static void proxyGetHostIDPath(char *path, size_t len){
-  strlcpy(path, HOSTIDPATH, len);
-#ifdef SQLITE_TEST
-  if( sqlite3_hostid_num>0 ){
-    char suffix[2] = "1";
-    suffix[0] = suffix[0] + sqlite3_hostid_num;
-    strlcat(path, suffix, len);
-  }
-#endif
-  OSTRACE3("GETHOSTIDPATH  %s pid=%d\n", path, getpid());
-}
-
-/* get the host ID from a sqlite hostid file stored in the 
-** user-specific tmp directory, create the ID if it's not there already 
-*/
-static int proxyGetHostID(char *pHostID, int *pError){
-  int fd;
-  char path[MAXPATHLEN]; 
-  size_t len;
-  int rc=SQLITE_OK;
-
-  proxyGetHostIDPath(path, MAXPATHLEN);
-  /* try to create the host ID file, if it already exists read the contents */
-  fd = open(path, O_CREAT|O_WRONLY|O_EXCL, 0644);
-  if( fd<0 ){
-    int err=errno;
-		
-    if( err!=EEXIST ){
-#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
-      fprintf(stderr, "sqlite error creating host ID file %s: %s\n",
-              path, strerror(err));
-#endif
-      return SQLITE_PERM;
-    }
-    /* couldn't create the file, read it instead */
-    fd = open(path, O_RDONLY|O_EXCL);
-    if( fd<0 ){
-#ifdef SQLITE_PROXY_DEBUG /* set the sqlite error message instead */
-      int err = errno;
-      fprintf(stderr, "sqlite error opening host ID file %s: %s\n",
-              path, strerror(err));
-#endif
-      return SQLITE_PERM;
-    }
-    len = pread(fd, pHostID, HOSTIDLEN, 0);
-    if( len<0 ){
-      *pError = errno;
-      rc = SQLITE_IOERR_READ;
-    }else if( len<HOSTIDLEN ){
-      *pError = 0;
-      rc = SQLITE_IOERR_SHORT_READ;
-    }
-    close(fd); /* silently leak the fd if it fails */
-    OSTRACE3("GETHOSTID  read %s pid=%d\n", pHostID, getpid());
-    return rc;
-  }else{
-    /* we're creating the host ID file (use a random string of bytes) */
-    proxyGenerateHostID(pHostID);
-    len = pwrite(fd, pHostID, HOSTIDLEN, 0);
-    if( len<0 ){
-      *pError = errno;
-      rc = SQLITE_IOERR_WRITE;
-    }else if( len<HOSTIDLEN ){
-      *pError = 0;
-      rc = SQLITE_IOERR_WRITE;
-    }
-    close(fd); /* silently leak the fd if it fails */
-    OSTRACE3("GETHOSTID  wrote %s pid=%d\n", pHostID, getpid());
-    return rc;
-  }
-}
-
 static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
   int len;
   int dbLen;
@@ -26177,21 +27449,12 @@
 #else
 # ifdef _CS_DARWIN_USER_TEMP_DIR
   {
-    confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen);
-    len = strlcat(lPath, "sqliteplocks", maxLen);    
-    if( mkdir(lPath, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
-      /* if mkdir fails, handle as lock file creation failure */
-#  ifdef SQLITE_DEBUG
-      int err = errno;
-      if( err!=EEXIST ){
-        fprintf(stderr, "proxyGetLockPath: mkdir(%s,0%o) error %d %s\n", lPath,
-                SQLITE_DEFAULT_PROXYDIR_PERMISSIONS, err, strerror(err));
-      }
-#  endif
-    }else{
-      OSTRACE3("GETLOCKPATH  mkdir %s pid=%d\n", lPath, getpid());
+    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
+      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
+               lPath, errno, getpid()));
+      return SQLITE_IOERR_LOCK;
     }
-    
+    len = strlcat(lPath, "sqliteplocks", maxLen);    
   }
 # else
   len = strlcpy(lPath, "/tmp/", maxLen);
@@ -26210,9 +27473,46 @@
   }
   lPath[i+len]='\0';
   strlcat(lPath, ":auto:", maxLen);
+  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, getpid()));
   return SQLITE_OK;
 }
 
+/* 
+ ** Creates the lock file and any missing directories in lockPath
+ */
+static int proxyCreateLockPath(const char *lockPath){
+  int i, len;
+  char buf[MAXPATHLEN];
+  int start = 0;
+  
+  assert(lockPath!=NULL);
+  /* try to create all the intermediate directories */
+  len = (int)strlen(lockPath);
+  buf[0] = lockPath[0];
+  for( i=1; i<len; i++ ){
+    if( lockPath[i] == '/' && (i - start > 0) ){
+      /* only mkdir if leaf dir != "." or "/" or ".." */
+      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') 
+         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
+        buf[i]='\0';
+        if( mkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
+          int err=errno;
+          if( err!=EEXIST ) {
+            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
+                     "'%s' proxy lock path=%s pid=%d\n",
+                     buf, strerror(err), lockPath, getpid()));
+            return err;
+          }
+        }
+      }
+      start=i+1;
+    }
+    buf[i] = lockPath[i];
+  }
+  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n", lockPath, getpid()));
+  return 0;
+}
+
 /*
 ** Create a new VFS file descriptor (stored in memory obtained from
 ** sqlite3_malloc) and open the file named "path" in the file descriptor.
@@ -26220,29 +27520,25 @@
 ** The caller is responsible not only for closing the file descriptor
 ** but also for freeing the memory associated with the file descriptor.
 */
-static int proxyCreateUnixFile(const char *path, unixFile **ppFile) {
+static int proxyCreateUnixFile(
+    const char *path,        /* path for the new unixFile */
+    unixFile **ppFile,       /* unixFile created and returned by ref */
+    int islockfile           /* if non zero missing dirs will be created */
+) {
+  int fd = -1;
+  int dirfd = -1;
   unixFile *pNew;
-  int flags = SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
   int rc = SQLITE_OK;
+  int openFlags = O_RDWR | O_CREAT;
   sqlite3_vfs dummyVfs;
+  int terrno = 0;
+  UnixUnusedFd *pUnused = NULL;
 
-  pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
-  if( !pNew ){
-    return SQLITE_NOMEM;
-  }
-  memset(pNew, 0, sizeof(unixFile));
-
-  /* Call unixOpen() to open the proxy file. The flags passed to unixOpen()
-  ** suggest that the file being opened is a "main database". This is
-  ** necessary as other file types do not necessarily support locking. It
-  ** is better to use unixOpen() instead of opening the file directly with
-  ** open(), as unixOpen() sets up the various mechanisms required to
-  ** make sure a call to close() does not cause the system to discard
-  ** POSIX locks prematurely.
-  **
-  ** It is important that the xOpen member of the VFS object passed to 
-  ** unixOpen() is NULL. This tells unixOpen() may try to open a proxy-file 
-  ** for the proxy-file (creating a potential infinite loop).
+  /* 1. first try to open/create the file
+  ** 2. if that fails, and this is a lock file (not-conch), try creating
+  ** the parent directories and then try again.
+  ** 3. if that fails, try to open the file read-only
+  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
   */
   pUnused = findReusableFd(path, openFlags);
   if( pUnused ){
@@ -26289,23 +27585,198 @@
   memset(pNew, 0, sizeof(unixFile));
   pNew->openFlags = openFlags;
   dummyVfs.pAppData = (void*)&autolockIoFinder;
-  dummyVfs.xOpen = 0;
-  rc = unixOpen(&dummyVfs, path, (sqlite3_file *)pNew, flags, &flags);
-  if( rc==SQLITE_OK && (flags&SQLITE_OPEN_READONLY) ){
-    pNew->pMethod->xClose((sqlite3_file *)pNew);
-    rc = SQLITE_CANTOPEN;
+  pUnused->fd = fd;
+  pUnused->flags = openFlags;
+  pNew->pUnused = pUnused;
+  
+  rc = fillInUnixFile(&dummyVfs, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0);
+  if( rc==SQLITE_OK ){
+    *ppFile = pNew;
+    return SQLITE_OK;
   }
-
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(pNew);
-    pNew = 0;
-  }
-
-  *ppFile = pNew;
+end_create_proxy:    
+  close(fd); /* silently leak fd if error, we're already in error */
+  sqlite3_free(pNew);
+  sqlite3_free(pUnused);
   return rc;
 }
 
-/* takes the conch by taking a shared lock and read the contents conch, if 
+#ifdef SQLITE_TEST
+/* simulate multiple hosts by creating unique hostid file paths */
+SQLITE_API int sqlite3_hostid_num = 0;
+#endif
+
+#define PROXY_HOSTIDLEN    16  /* conch file host id length */
+
+/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN 
+** bytes of writable memory.
+*/
+static int proxyGetHostID(unsigned char *pHostID, int *pError){
+  struct timespec timeout = {1, 0}; /* 1 sec timeout */
+  
+  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
+  memset(pHostID, 0, PROXY_HOSTIDLEN);
+  if( gethostuuid(pHostID, &timeout) ){
+    int err = errno;
+    if( pError ){
+      *pError = err;
+    }
+    return SQLITE_IOERR;
+  }
+#ifdef SQLITE_TEST
+  /* simulate multiple hosts by creating unique hostid file paths */
+  if( sqlite3_hostid_num != 0){
+    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
+  }
+#endif
+  
+  return SQLITE_OK;
+}
+
+/* The conch file contains the header, host id and lock file path
+ */
+#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
+#define PROXY_HEADERLEN    1   /* conch file header length */
+#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
+#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
+
+/* 
+** Takes an open conch file, copies the contents to a new path and then moves 
+** it back.  The newly created file's file descriptor is assigned to the
+** conch file structure and finally the original conch file descriptor is 
+** closed.  Returns zero if successful.
+*/
+static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  char tPath[MAXPATHLEN];
+  char buf[PROXY_MAXCONCHLEN];
+  char *cPath = pCtx->conchFilePath;
+  size_t readLen = 0;
+  size_t pathLen = 0;
+  char errmsg[64] = "";
+  int fd = -1;
+  int rc = -1;
+
+  /* create a new path by replace the trailing '-conch' with '-break' */
+  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
+  if( pathLen>MAXPATHLEN || pathLen<6 || 
+     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
+    sprintf(errmsg, "path error (len %d)", (int)pathLen);
+    goto end_breaklock;
+  }
+  /* read the conch content */
+  readLen = pread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
+  if( readLen<PROXY_PATHINDEX ){
+    sprintf(errmsg, "read error (len %d)", (int)readLen);
+    goto end_breaklock;
+  }
+  /* write it out to the temporary break file */
+  fd = open(tPath, (O_RDWR|O_CREAT|O_EXCL), SQLITE_DEFAULT_FILE_PERMISSIONS);
+  if( fd<0 ){
+    sprintf(errmsg, "create failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( pwrite(fd, buf, readLen, 0) != readLen ){
+    sprintf(errmsg, "write failed (%d)", errno);
+    goto end_breaklock;
+  }
+  if( rename(tPath, cPath) ){
+    sprintf(errmsg, "rename failed (%d)", errno);
+    goto end_breaklock;
+  }
+  rc = 0;
+  fprintf(stderr, "broke stale lock on %s\n", cPath);
+  close(conchFile->h);
+  conchFile->h = fd;
+  conchFile->openFlags = O_RDWR | O_CREAT;
+
+end_breaklock:
+  if( rc ){
+    if( fd>=0 ){
+      unlink(tPath);
+      close(fd);
+    }
+    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
+  }
+  return rc;
+}
+
+/* Take the requested lock on the conch file and break a stale lock if the 
+** host id matches.
+*/
+static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
+  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
+  unixFile *conchFile = pCtx->conchFile;
+  int rc = SQLITE_OK;
+  int nTries = 0;
+  struct timespec conchModTime;
+  
+  do {
+    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+    nTries ++;
+    if( rc==SQLITE_BUSY ){
+      /* If the lock failed (busy):
+       * 1st try: get the mod time of the conch, wait 0.5s and try again. 
+       * 2nd try: fail if the mod time changed or host id is different, wait 
+       *           10 sec and try again
+       * 3rd try: break the lock unless the mod time has changed.
+       */
+      struct stat buf;
+      if( fstat(conchFile->h, &buf) ){
+        pFile->lastErrno = errno;
+        return SQLITE_IOERR_LOCK;
+      }
+      
+      if( nTries==1 ){
+        conchModTime = buf.st_mtimespec;
+        usleep(500000); /* wait 0.5 sec and try the lock again*/
+        continue;  
+      }
+
+      assert( nTries>1 );
+      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || 
+         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
+        return SQLITE_BUSY;
+      }
+      
+      if( nTries==2 ){  
+        char tBuf[PROXY_MAXCONCHLEN];
+        int len = pread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
+        if( len<0 ){
+          pFile->lastErrno = errno;
+          return SQLITE_IOERR_LOCK;
+        }
+        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
+          /* don't break the lock if the host id doesn't match */
+          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
+            return SQLITE_BUSY;
+          }
+        }else{
+          /* don't break the lock on short read or a version mismatch */
+          return SQLITE_BUSY;
+        }
+        usleep(10000000); /* wait 10 sec and try the lock again */
+        continue; 
+      }
+      
+      assert( nTries==3 );
+      if( 0==proxyBreakConchLock(pFile, myHostID) ){
+        rc = SQLITE_OK;
+        if( lockType==EXCLUSIVE_LOCK ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);          
+        }
+        if( !rc ){
+          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
+        }
+      }
+    }
+  } while( rc==SQLITE_BUSY && nTries<3 );
+  
+  return rc;
+}
+
+/* Takes the conch by taking a shared lock and read the contents conch, if 
 ** lockPath is non-NULL, the host ID and lock file path must match.  A NULL 
 ** lockPath means that the lockPath in the conch file will be used if the 
 ** host IDs match, or a new lock path will be generated automatically 
@@ -26314,145 +27785,83 @@
 static int proxyTakeConch(unixFile *pFile){
   proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
   
-  if( pCtx->conchHeld>0 ){
+  if( pCtx->conchHeld!=0 ){
     return SQLITE_OK;
   }else{
     unixFile *conchFile = pCtx->conchFile;
-    char testValue[CONCHLEN];
-    char conchValue[CONCHLEN];
+    uuid_t myHostID;
+    int pError = 0;
+    char readBuf[PROXY_MAXCONCHLEN];
     char lockPath[MAXPATHLEN];
-    char *tLockPath = NULL;
+    char *tempLockPath = NULL;
     int rc = SQLITE_OK;
-    int readRc = SQLITE_OK;
-    int syncPerms = 0;
+    int createConch = 0;
+    int hostIdMatch = 0;
+    int readLen = 0;
+    int tryOldLockPath = 0;
+    int forceNewLockPath = 0;
+    
+    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
+             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()));
 
-    OSTRACE4("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
-             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid());
-
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);
-    if( rc==SQLITE_OK ){
-      int pError = 0;
-      memset(testValue, 0, CONCHLEN); /* conch is fixed size */
-      rc = proxyGetHostID(testValue, &pError);
-      if( (rc&0xff)==SQLITE_IOERR ){
-        pFile->lastErrno = pError;
-      }
-      if( pCtx->lockProxyPath ){
-        strlcpy(&testValue[HOSTIDLEN], pCtx->lockProxyPath, MAXPATHLEN);
-      }
+    rc = proxyGetHostID(myHostID, &pError);
+    if( (rc&0xff)==SQLITE_IOERR ){
+      pFile->lastErrno = pError;
+      goto end_takeconch;
     }
+    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
     if( rc!=SQLITE_OK ){
       goto end_takeconch;
     }
-    
-    readRc = unixRead((sqlite3_file *)conchFile, conchValue, CONCHLEN, 0);
-    if( readRc!=SQLITE_IOERR_SHORT_READ ){
-      if( readRc!=SQLITE_OK ){
-        if( (rc&0xff)==SQLITE_IOERR ){
-          pFile->lastErrno = conchFile->lastErrno;
-        }
-        rc = readRc;
-        goto end_takeconch;
-      }
-      /* if the conch has data compare the contents */
-      if( !pCtx->lockProxyPath ){
-        /* for auto-named local lock file, just check the host ID and we'll
-         ** use the local lock file path that's already in there */
-        if( !memcmp(testValue, conchValue, HOSTIDLEN) ){
-          tLockPath = (char *)&conchValue[HOSTIDLEN];
-          goto end_takeconch;
-        }
-      }else{
-        /* we've got the conch if conchValue matches our path and host ID */
-        if( !memcmp(testValue, conchValue, CONCHLEN) ){
-          goto end_takeconch;
-        }
-      }
-    }else{
-      /* a short read means we're "creating" the conch (even though it could 
-      ** have been user-intervention), if we acquire the exclusive lock,
-      ** we'll try to match the current on-disk permissions of the database
+    /* read the existing conch file */
+    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
+    if( readLen<0 ){
+      /* I/O error: lastErrno set by seekAndRead */
+      pFile->lastErrno = conchFile->lastErrno;
+      rc = SQLITE_IOERR_READ;
+      goto end_takeconch;
+    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || 
+             readBuf[0]!=(char)PROXY_CONCHVERSION ){
+      /* a short read or version format mismatch means we need to create a new 
+      ** conch file. 
       */
-      syncPerms = 1;
+      createConch = 1;
     }
-    
-    /* either conch was emtpy or didn't match */
-    if( !pCtx->lockProxyPath ){
-      proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
-      tLockPath = lockPath;
-      strlcpy(&testValue[HOSTIDLEN], lockPath, MAXPATHLEN);
-    }
-    
-    /* update conch with host and path (this will fail if other process
-     ** has a shared lock already) */
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK);
-    if( rc==SQLITE_OK ){
-      rc = unixWrite((sqlite3_file *)conchFile, testValue, CONCHLEN, 0);
-      if( rc==SQLITE_OK && syncPerms ){
-        struct stat buf;
-        int err = fstat(pFile->h, &buf);
-        if( err==0 ){
-          /* try to match the database file permissions, ignore failure */
-#ifndef SQLITE_PROXY_DEBUG
-          fchmod(conchFile->h, buf.st_mode);
-#else
-          if( fchmod(conchFile->h, buf.st_mode)!=0 ){
-            int code = errno;
-            fprintf(stderr, "fchmod %o FAILED with %d %s\n",
-                             buf.st_mode, code, strerror(code));
-          } else {
-            fprintf(stderr, "fchmod %o SUCCEDED\n",buf.st_mode);
-          }
-        }else{
-          int code = errno;
-          fprintf(stderr, "STAT FAILED[%d] with %d %s\n", 
-                          err, code, strerror(code));
-#endif
-        }
-      }
-    }
-    conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
-  
-end_takeconch:
-    OSTRACE2("TRANSPROXY: CLOSE  %d\n", pFile->h);
-    if( rc==SQLITE_OK && pFile->openFlags ){
-      if( pFile->h>=0 ){
-#ifdef STRICT_CLOSE_ERROR
-        if( close(pFile->h) ){
-          pFile->lastErrno = errno;
-          return SQLITE_IOERR_CLOSE;
-        }
-#else
-        close(pFile->h); /* silently leak fd if fail */
-#endif
-      }
-      pFile->h = -1;
-      int fd = open(pCtx->dbPath, pFile->openFlags,
-                    SQLITE_DEFAULT_FILE_PERMISSIONS);
-      OSTRACE2("TRANSPROXY: OPEN  %d\n", fd);
-      if( fd>=0 ){
-        pFile->h = fd;
-      }else{
-        rc=SQLITE_CANTOPEN; /* SQLITE_BUSY? proxyTakeConch called
-                               during locking */
-      }
-    }
-    if( rc==SQLITE_OK && !pCtx->lockProxy ){
-      char *path = tLockPath ? tLockPath : pCtx->lockProxyPath;
-      /* ACS: Need to make a copy of path sometimes */
-      rc = proxyCreateUnixFile(path, &pCtx->lockProxy);
-    }
-    if( rc==SQLITE_OK ){
-      pCtx->conchHeld = 1;
+    /* if the host id matches and the lock path already exists in the conch
+    ** we'll try to use the path there, if we can't open that path, we'll 
+    ** retry with a new auto-generated path 
+    */
+    do { /* in case we need to try again for an :auto: named lock file */
 
-      if( tLockPath ){
-        pCtx->lockProxyPath = sqlite3DbStrDup(0, tLockPath);
-        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
-          ((afpLockingContext *)pCtx->lockProxy->lockingContext)->dbPath =
-                     pCtx->lockProxyPath;
+      if( !createConch && !forceNewLockPath ){
+        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, 
+                                  PROXY_HOSTIDLEN);
+        /* if the conch has data compare the contents */
+        if( !pCtx->lockProxyPath ){
+          /* for auto-named local lock file, just check the host ID and we'll
+           ** use the local lock file path that's already in there
+           */
+          if( hostIdMatch ){
+            size_t pathLen = (readLen - PROXY_PATHINDEX);
+            
+            if( pathLen>=MAXPATHLEN ){
+              pathLen=MAXPATHLEN-1;
+            }
+            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
+            lockPath[pathLen] = 0;
+            tempLockPath = lockPath;
+            tryOldLockPath = 1;
+            /* create a copy of the lock path if the conch is taken */
+            goto end_takeconch;
+          }
+        }else if( hostIdMatch
+               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
+                           readLen-PROXY_PATHINDEX)
+        ){
+          /* conch host and lock path match */
+          goto end_takeconch; 
         }
       }
->>>>>>> BEGIN MERGE CONFLICT
       
       /* if the conch isn't writable and doesn't match, we can't take it */
       if( (conchFile->openFlags&O_RDWR) == 0 ){
@@ -26473,7 +27882,7 @@
       */
       futimes(conchFile->h, NULL);
       if( hostIdMatch && !createConch ){
-        if( conchFile->pLock && conchFile->pLock->cnt>1 ){
+        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
           /* We are trying for an exclusive lock but another thread in this
            ** same process is still holding a shared lock. */
           rc = SQLITE_BUSY;
@@ -26529,7 +27938,7 @@
       conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
       
     end_takeconch:
-      OSTRACE2("TRANSPROXY: CLOSE  %d\n", pFile->h);
+      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
       if( rc==SQLITE_OK && pFile->openFlags ){
         if( pFile->h>=0 ){
 #ifdef STRICT_CLOSE_ERROR
@@ -26544,7 +27953,7 @@
         pFile->h = -1;
         int fd = open(pCtx->dbPath, pFile->openFlags,
                       SQLITE_DEFAULT_FILE_PERMISSIONS);
-        OSTRACE2("TRANSPROXY: OPEN  %d\n", fd);
+        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
         if( fd>=0 ){
           pFile->h = fd;
         }else{
@@ -26586,16 +27995,11 @@
       } else {
         conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
       }
-      OSTRACE3("TAKECONCH  %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
+      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
+               rc==SQLITE_OK?"ok":"failed"));
       return rc;
-    } while (1); /* in case we need to retry the :auto: lock file - we should never get here except via the 'continue' call. */
-============================
-    } else {
-      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-    }
-    OSTRACE3("TAKECONCH  %d %s\n", conchFile->h, rc==SQLITE_OK?"ok":"failed");
-    return rc;
-<<<<<<< END MERGE CONFLICT
+    } while (1); /* in case we need to retry the :auto: lock file - 
+                 ** we should never get here except via the 'continue' call. */
   }
 }
 
@@ -26603,19 +28007,21 @@
 ** If pFile holds a lock on a conch file, then release that lock.
 */
 static int proxyReleaseConch(unixFile *pFile){
-  int rc;                     /* Subroutine return code */
+  int rc = SQLITE_OK;         /* Subroutine return code */
   proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
   unixFile *conchFile;        /* Name of the conch file */
 
   pCtx = (proxyLockingContext *)pFile->lockingContext;
   conchFile = pCtx->conchFile;
-  OSTRACE4("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
+  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
            (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), 
-           getpid());
+           getpid()));
+  if( pCtx->conchHeld>0 ){
+    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
+  }
   pCtx->conchHeld = 0;
-  rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-  OSTRACE3("RELEASECONCH  %d %s\n", conchFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed"));
+  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
   return rc;
 }
 
@@ -26672,7 +28078,7 @@
   char *oldPath = pCtx->lockProxyPath;
   int rc = SQLITE_OK;
 
-  if( pFile->locktype!=NO_LOCK ){
+  if( pFile->eFileLock!=NO_LOCK ){
     return SQLITE_BUSY;
   }  
 
@@ -26709,8 +28115,8 @@
     /* afp style keeps a reference to the db path in the filePath field 
     ** of the struct */
     assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath);
-  }else
+    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath, MAXPATHLEN);
+  } else
 #endif
   if( pFile->pMethod == &dotlockIoMethods ){
     /* dot lock style uses the locking context to store the dot lock
@@ -26720,7 +28126,7 @@
   }else{
     /* all other styles use the locking context to store the db file path */
     assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strcpy(dbPath, (char *)pFile->lockingContext);
+    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
   }
   return SQLITE_OK;
 }
@@ -26739,7 +28145,7 @@
   char *lockPath=NULL;
   int rc = SQLITE_OK;
   
-  if( pFile->locktype!=NO_LOCK ){
+  if( pFile->eFileLock!=NO_LOCK ){
     return SQLITE_BUSY;
   }
   proxyGetDbPathForUnixFile(pFile, dbPath);
@@ -26749,8 +28155,8 @@
     lockPath=(char *)path;
   }
   
-  OSTRACE4("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
-           (lockPath ? lockPath : ":auto:"), getpid());
+  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
+           (lockPath ? lockPath : ":auto:"), getpid()));
 
   pCtx = sqlite3_malloc( sizeof(*pCtx) );
   if( pCtx==0 ){
@@ -26760,32 +28166,58 @@
 
   rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
   if( rc==SQLITE_OK ){
-    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile);
+    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
+    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
+      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
+      ** (c) the file system is read-only, then enable no-locking access.
+      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
+      ** that openFlags will have only one of O_RDONLY or O_RDWR.
+      */
+      struct statfs fsInfo;
+      struct stat conchInfo;
+      int goLockless = 0;
+
+      if( stat(pCtx->conchFilePath, &conchInfo) == -1 ) {
+        int err = errno;
+        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
+          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
+        }
+      }
+      if( goLockless ){
+        pCtx->conchHeld = -1; /* read only FS/ lockless */
+        rc = SQLITE_OK;
+      }
+    }
   }  
   if( rc==SQLITE_OK && lockPath ){
     pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
   }
 
   if( rc==SQLITE_OK ){
+    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
+    if( pCtx->dbPath==NULL ){
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK ){
     /* all memory is allocated, proxys are created and assigned, 
     ** switch the locking context and pMethod then return.
     */
-    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
     pCtx->oldLockingContext = pFile->lockingContext;
     pFile->lockingContext = pCtx;
     pCtx->pOldMethod = pFile->pMethod;
     pFile->pMethod = &proxyIoMethods;
   }else{
     if( pCtx->conchFile ){ 
-      rc = pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
-      if( rc ) return rc;
+      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
       sqlite3_free(pCtx->conchFile);
     }
+    sqlite3_free(pCtx->lockProxyPath);
     sqlite3_free(pCtx->conchFilePath); 
     sqlite3_free(pCtx);
   }
-  OSTRACE3("TRANSPROXY  %d %s\n", pFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed"));
+  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
+           (rc==SQLITE_OK ? "ok" : "failed")));
   return rc;
 }
 
@@ -26869,14 +28301,18 @@
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
+    }else{ /* conchHeld < 0 is lockless */
+      pResOut=0;
+    }
   }
   return rc;
 }
 
 /*
-** Lock the file with the lock specified by parameter locktype - one
+** Lock the file with the lock specified by parameter eFileLock - one
 ** of the following:
 **
 **     (1) SHARED_LOCK
@@ -26899,34 +28335,42 @@
 ** This routine will only increase a lock.  Use the sqlite3OsUnlock()
 ** routine to lower a locking level.
 */
-static int proxyLock(sqlite3_file *id, int locktype) {
+static int proxyLock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    rc = proxy->pMethod->xLock((sqlite3_file*)proxy, locktype);
-    pFile->locktype = proxy->locktype;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
   }
   return rc;
 }
 
 
 /*
-** Lower the locking level on file descriptor pFile to locktype.  locktype
+** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
 ** must be either NO_LOCK or SHARED_LOCK.
 **
 ** If the locking level of the file descriptor is already at or below
 ** the requested locking level, this routine is a no-op.
 */
-static int proxyUnlock(sqlite3_file *id, int locktype) {
+static int proxyUnlock(sqlite3_file *id, int eFileLock) {
   unixFile *pFile = (unixFile*)id;
   int rc = proxyTakeConch(pFile);
   if( rc==SQLITE_OK ){
     proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *proxy = pCtx->lockProxy;
-    rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, locktype);
-    pFile->locktype = proxy->locktype;
+    if( pCtx->conchHeld>0 ){
+      unixFile *proxy = pCtx->lockProxy;
+      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
+      pFile->eFileLock = proxy->eFileLock;
+    }else{
+      /* conchHeld < 0 is lockless */
+    }
   }
   return rc;
 }
@@ -27018,7 +28462,7 @@
   ** that filesystem time.
   */
   #define UNIXVFS(VFSNAME, FINDER) {                        \
-    1,                    /* iVersion */                    \
+    2,                    /* iVersion */                    \
     sizeof(unixFile),     /* szOsFile */                    \
     MAX_PATHNAME,         /* mxPathname */                  \
     0,                    /* pNext */                       \
@@ -27035,7 +28479,9 @@
     unixRandomness,       /* xRandomness */                 \
     unixSleep,            /* xSleep */                      \
     unixCurrentTime,      /* xCurrentTime */                \
-    unixGetLastError      /* xGetLastError */               \
+    unixGetLastError,     /* xGetLastError */               \
+    0,                    /* xRename */                     \
+    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
   }
 
   /*
@@ -27053,7 +28499,6 @@
 #endif
     UNIXVFS("unix-none",     nolockIoFinder ),
     UNIXVFS("unix-dotfile",  dotlockIoFinder ),
-    UNIXVFS("unix-wfl",      posixWflIoFinder ),
 #if OS_VXWORKS
     UNIXVFS("unix-namedsem", semIoFinder ),
 #endif
@@ -27065,6 +28510,7 @@
 #endif
 #if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
     UNIXVFS("unix-afp",      afpIoFinder ),
+    UNIXVFS("unix-nfs",      nfsIoFinder ),
     UNIXVFS("unix-proxy",    proxyIoFinder ),
 #endif
   };
@@ -27186,23 +28632,9 @@
 
 #ifdef SQLITE_DEBUG
 SQLITE_PRIVATE int sqlite3OSTrace = 0;
-#define OSTRACE1(X)         if( sqlite3OSTrace ) sqlite3DebugPrintf(X)
-#define OSTRACE2(X,Y)       if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y)
-#define OSTRACE3(X,Y,Z)     if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)   if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B) if( sqlite3OSTrace ) sqlite3DebugPrintf(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D) \
-    if(sqlite3OSTrace) sqlite3DebugPrintf(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
 #else
-#define OSTRACE1(X)
-#define OSTRACE2(X,Y)
-#define OSTRACE3(X,Y,Z)
-#define OSTRACE4(X,Y,Z,A)
-#define OSTRACE5(X,Y,Z,A,B)
-#define OSTRACE6(X,Y,Z,A,B,C)
-#define OSTRACE7(X,Y,Z,A,B,C,D)
+#define OSTRACE(X)
 #endif
 
 /*
@@ -27388,6 +28820,10 @@
 # define FormatMessageW(a,b,c,d,e,f,g) 0
 #endif
 
+/* Forward references */
+typedef struct winShm winShm;           /* A connection to shared-memory */
+typedef struct winShmNode winShmNode;   /* A region of shared-memory */
+
 /*
 ** WinCE lacks native support for file locking so we have to fake it
 ** with some code of our own.
@@ -27407,12 +28843,15 @@
 */
 typedef struct winFile winFile;
 struct winFile {
-  const sqlite3_io_methods *pMethod;/* Must be first */
+  const sqlite3_io_methods *pMethod; /*** Must be first ***/
+  sqlite3_vfs *pVfs;      /* The VFS used to open this file */
   HANDLE h;               /* Handle for accessing the file */
   unsigned char locktype; /* Type of lock currently held on this file */
   short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
   DWORD lastErrno;        /* The Windows errno from the last I/O error */
   DWORD sectorSize;       /* Sector size of the device file is on */
+  winShm *pShm;           /* Instance of shared memory on this file */
+  const char *zPath;      /* Full pathname of this file */
 #if SQLITE_OS_WINCE
   WCHAR *zDeleteOnClose;  /* Name of file to delete when closing */
   HANDLE hMutex;          /* Mutex used to control access to shared lock */  
@@ -27940,7 +29379,8 @@
   winFile *pFile = (winFile*)id;
 
   assert( id!=0 );
-  OSTRACE2("CLOSE %d\n", pFile->h);
+  assert( pFile->pShm==0 );
+  OSTRACE(("CLOSE %d\n", pFile->h));
   do{
     rc = CloseHandle(pFile->h);
   }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (Sleep(100), 1) );
@@ -27959,6 +29399,7 @@
     free(pFile->zDeleteOnClose);
   }
 #endif
+  OSTRACE(("CLOSE %d %s\n", pFile->h, rc ? "ok" : "failed"));
   OpenCounter(-1);
   return rc ? SQLITE_OK : SQLITE_IOERR;
 }
@@ -27990,7 +29431,7 @@
 
   assert( id!=0 );
   SimulateIOError(return SQLITE_IOERR_READ);
-  OSTRACE3("READ %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("READ %d lock=%d\n", pFile->h, pFile->locktype));
   rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
   if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
@@ -28029,7 +29470,7 @@
   assert( id!=0 );
   SimulateIOError(return SQLITE_IOERR_WRITE);
   SimulateDiskfullError(return SQLITE_FULL);
-  OSTRACE3("WRITE %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("WRITE %d lock=%d\n", pFile->h, pFile->locktype));
   rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
   if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
@@ -28057,24 +29498,25 @@
 static int winTruncate(sqlite3_file *id, sqlite3_int64 nByte){
   LONG upperBits = (LONG)((nByte>>32) & 0x7fffffff);
   LONG lowerBits = (LONG)(nByte & 0xffffffff);
-  DWORD rc;
+  DWORD dwRet;
   winFile *pFile = (winFile*)id;
   DWORD error;
+  int rc = SQLITE_OK;
 
   assert( id!=0 );
-  OSTRACE3("TRUNCATE %d %lld\n", pFile->h, nByte);
+  OSTRACE(("TRUNCATE %d %lld\n", pFile->h, nByte));
   SimulateIOError(return SQLITE_IOERR_TRUNCATE);
-  rc = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
-  if( rc==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
+  dwRet = SetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
+  if( dwRet==INVALID_SET_FILE_POINTER && (error=GetLastError())!=NO_ERROR ){
     pFile->lastErrno = error;
-    return SQLITE_IOERR_TRUNCATE;
-  }
+    rc = SQLITE_IOERR_TRUNCATE;
   /* SetEndOfFile will fail if nByte is negative */
-  if( !SetEndOfFile(pFile->h) ){
+  }else if( !SetEndOfFile(pFile->h) ){
     pFile->lastErrno = GetLastError();
-    return SQLITE_IOERR_TRUNCATE;
+    rc = SQLITE_IOERR_TRUNCATE;
   }
-  return SQLITE_OK;
+  OSTRACE(("TRUNCATE %d %lld %s\n", pFile->h, nByte, rc==SQLITE_OK ? "ok" : "failed"));
+  return rc;
 }
 
 #ifdef SQLITE_TEST
@@ -28094,7 +29536,7 @@
   winFile *pFile = (winFile*)id;
 
   assert( id!=0 );
-  OSTRACE3("SYNC %d lock=%d\n", pFile->h, pFile->locktype);
+  OSTRACE(("SYNC %d lock=%d\n", pFile->h, pFile->locktype));
 #else
   UNUSED_PARAMETER(id);
 #endif
@@ -28235,8 +29677,8 @@
   DWORD error = NO_ERROR;
 
   assert( id!=0 );
-  OSTRACE5("LOCK %d %d was %d(%d)\n",
-          pFile->h, locktype, pFile->locktype, pFile->sharedLockByte);
+  OSTRACE(("LOCK %d %d was %d(%d)\n",
+           pFile->h, locktype, pFile->locktype, pFile->sharedLockByte));
 
   /* If there is already a lock of this type or more restrictive on the
   ** OsFile, do nothing. Don't use the end_lock: exit path, as
@@ -28266,7 +29708,7 @@
       /* Try 3 times to get the pending lock.  The pending lock might be
       ** held by another reader process who will release it momentarily.
       */
-      OSTRACE2("could not get a PENDING lock. cnt=%d\n", cnt);
+      OSTRACE(("could not get a PENDING lock. cnt=%d\n", cnt));
       Sleep(1);
     }
     gotPendingLock = res;
@@ -28311,13 +29753,13 @@
   if( locktype==EXCLUSIVE_LOCK && res ){
     assert( pFile->locktype>=SHARED_LOCK );
     res = unlockReadLock(pFile);
-    OSTRACE2("unreadlock = %d\n", res);
+    OSTRACE(("unreadlock = %d\n", res));
     res = LockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
     if( res ){
       newLocktype = EXCLUSIVE_LOCK;
     }else{
       error = GetLastError();
-      OSTRACE2("error-code = %d\n", error);
+      OSTRACE(("error-code = %d\n", error));
       getReadLock(pFile);
     }
   }
@@ -28335,8 +29777,8 @@
   if( res ){
     rc = SQLITE_OK;
   }else{
-    OSTRACE4("LOCK FAILED %d trying for %d but got %d\n", pFile->h,
-           locktype, newLocktype);
+    OSTRACE(("LOCK FAILED %d trying for %d but got %d\n", pFile->h,
+           locktype, newLocktype));
     pFile->lastErrno = error;
     rc = SQLITE_BUSY;
   }
@@ -28356,14 +29798,14 @@
   assert( id!=0 );
   if( pFile->locktype>=RESERVED_LOCK ){
     rc = 1;
-    OSTRACE3("TEST WR-LOCK %d %d (local)\n", pFile->h, rc);
+    OSTRACE(("TEST WR-LOCK %d %d (local)\n", pFile->h, rc));
   }else{
     rc = LockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
     if( rc ){
       UnlockFile(pFile->h, RESERVED_BYTE, 0, 1, 0);
     }
     rc = !rc;
-    OSTRACE3("TEST WR-LOCK %d %d (remote)\n", pFile->h, rc);
+    OSTRACE(("TEST WR-LOCK %d %d (remote)\n", pFile->h, rc));
   }
   *pResOut = rc;
   return SQLITE_OK;
@@ -28386,8 +29828,8 @@
   int rc = SQLITE_OK;
   assert( pFile!=0 );
   assert( locktype<=SHARED_LOCK );
-  OSTRACE5("UNLOCK %d to %d was %d(%d)\n", pFile->h, locktype,
-          pFile->locktype, pFile->sharedLockByte);
+  OSTRACE(("UNLOCK %d to %d was %d(%d)\n", pFile->h, locktype,
+          pFile->locktype, pFile->sharedLockByte));
   type = pFile->locktype;
   if( type>=EXCLUSIVE_LOCK ){
     UnlockFile(pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
@@ -28423,6 +29865,11 @@
       *(int*)pArg = (int)((winFile*)id)->lastErrno;
       return SQLITE_OK;
     }
+    case SQLITE_FCNTL_SIZE_HINT: {
+      sqlite3_int64 sz = *(sqlite3_int64*)pArg;
+      winTruncate(id, sz);
+      return SQLITE_OK;
+    }
   }
   return SQLITE_ERROR;
 }
@@ -28450,12 +29897,531 @@
   return 0;
 }
 
+/****************************************************************************
+********************************* Shared Memory *****************************
+**
+** The next subdivision of code manages the shared-memory primitives.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+/*
+** Helper functions to obtain and relinquish the global mutex. The
+** global mutex is used to protect the winLockInfo objects used by 
+** this file, all of which may be shared by multiple threads.
+**
+** Function winShmMutexHeld() is used to assert() that the global mutex 
+** is held when required. This function is only used as part of assert() 
+** statements. e.g.
+**
+**   winShmEnterMutex()
+**     assert( winShmMutexHeld() );
+**   winEnterLeave()
+*/
+static void winShmEnterMutex(void){
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+static void winShmLeaveMutex(void){
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#ifdef SQLITE_DEBUG
+static int winShmMutexHeld(void) {
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+}
+#endif
+
+/*
+** Object used to represent a single file opened and mmapped to provide
+** shared memory.  When multiple threads all reference the same
+** log-summary, each thread has its own winFile object, but they all
+** point to a single instance of this object.  In other words, each
+** log-summary is opened only once per process.
+**
+** winShmMutexHeld() must be true when creating or destroying
+** this object or while reading or writing the following fields:
+**
+**      nRef
+**      pNext 
+**
+** The following fields are read-only after the object is created:
+** 
+**      fid
+**      zFilename
+**
+** Either winShmNode.mutex must be held or winShmNode.nRef==0 and
+** winShmMutexHeld() is true when reading or writing any other field
+** in this structure.
+**
+** To avoid deadlocks, mutex and mutexBuf are always released in the
+** reverse order that they are acquired.  mutexBuf is always acquired
+** first and released last.  This invariant is check by asserting
+** sqlite3_mutex_notheld() on mutex whenever mutexBuf is acquired or
+** released.
+*/
+struct winShmNode {
+  sqlite3_mutex *mutex;      /* Mutex to access this object */
+  char *zFilename;           /* Name of the file */
+  winFile hFile;             /* File handle from winOpen */
+
+  int szRegion;              /* Size of shared-memory regions */
+  int nRegion;               /* Size of array apRegion */
+  struct ShmRegion {
+    HANDLE hMap;             /* File handle from CreateFileMapping */
+    void *pMap;
+  } *aRegion;
+  DWORD lastErrno;           /* The Windows errno from the last I/O error */
+
+  int nRef;                  /* Number of winShm objects pointing to this */
+  winShm *pFirst;            /* All winShm objects pointing to this */
+  winShmNode *pNext;         /* Next in list of all winShmNode objects */
+#ifdef SQLITE_DEBUG
+  u8 nextShmId;              /* Next available winShm.id value */
+#endif
+};
+
+/*
+** A global array of all winShmNode objects.
+**
+** The winShmMutexHeld() must be true while reading or writing this list.
+*/
+static winShmNode *winShmNodeList = 0;
+
+/*
+** Structure used internally by this VFS to record the state of an
+** open shared memory connection.
+**
+** winShm.pFile->mutex must be held while reading or writing the
+** winShm.pNext and winShm.locks[] elements.
+**
+** The winShm.pFile element is initialized when the object is created
+** and is read-only thereafter.
+*/
+struct winShm {
+  winShmNode *pShmNode;      /* The underlying winShmNode object */
+  winShm *pNext;             /* Next winShm with the same winShmNode */
+  u8 hasMutex;               /* True if holding the winShmNode mutex */
+  u8 hasMutexBuf;            /* True if holding pFile->mutexBuf */
+#ifdef SQLITE_DEBUG
+  u8 id;                     /* Id of this connection with its winShmNode */
+#endif
+};
+
+/*
+** Constants used for locking
+*/
+#define WIN_SHM_BASE   ((18+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
+#define WIN_SHM_DMS    (WIN_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
+
+/*
+** Apply advisory locks for all n bytes beginning at ofst.
+*/
+#define _SHM_UNLCK  1
+#define _SHM_RDLCK  2
+#define _SHM_WRLCK  3
+static int winShmSystemLock(
+  winShmNode *pFile,    /* Apply locks to this open shared-memory segment */
+  int lockType,         /* _SHM_UNLCK, _SHM_RDLCK, or _SHM_WRLCK */
+  int ofst,             /* Offset to first byte to be locked/unlocked */
+  int nByte             /* Number of bytes to lock or unlock */
+){
+  OVERLAPPED ovlp;
+  DWORD dwFlags;
+  int rc = 0;           /* Result code form Lock/UnlockFileEx() */
+
+  /* Access to the winShmNode object is serialized by the caller */
+  assert( sqlite3_mutex_held(pFile->mutex) || pFile->nRef==0 );
+
+  /* Initialize the locking parameters */
+  dwFlags = LOCKFILE_FAIL_IMMEDIATELY;
+  if( lockType == _SHM_WRLCK ) dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
+
+  /* Find the first bit in lockMask that is set */
+  memset(&ovlp, 0, sizeof(OVERLAPPED));
+  ovlp.Offset = ofst;
+
+  /* Release/Acquire the system-level lock */
+  if( lockType==_SHM_UNLCK ){
+    rc = UnlockFileEx(pFile->hFile.h, 0, nByte, 0, &ovlp);
+  }else{
+    rc = LockFileEx(pFile->hFile.h, dwFlags, 0, nByte, 0, &ovlp);
+  }
+  if( !rc ){
+    OSTRACE(("SHM-LOCK %d %s ERROR 0x%08lx\n", 
+             pFile->hFile.h,
+             lockType==_SHM_UNLCK ? "UnlockFileEx" : "LockFileEx",
+             GetLastError()));
+  }
+  rc = (rc!=0) ? SQLITE_OK : SQLITE_BUSY;
+
+  return rc;
+}
+
+/* Forward references to VFS methods */
+static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
+static int winDelete(sqlite3_vfs *,const char*,int);
+
+/*
+** Purge the winShmNodeList list of all entries with winShmNode.nRef==0.
+**
+** This is not a VFS shared-memory method; it is a utility function called
+** by VFS shared-memory methods.
+*/
+static void winShmPurge(sqlite3_vfs *pVfs, int deleteFlag){
+  winShmNode **pp;
+  winShmNode *p;
+  assert( winShmMutexHeld() );
+  pp = &winShmNodeList;
+  while( (p = *pp)!=0 ){
+    if( p->nRef==0 ){
+      int i;
+      if( p->mutex ) sqlite3_mutex_free(p->mutex);
+      for(i=0; i<p->nRegion; i++){
+        UnmapViewOfFile(p->aRegion[i].pMap);
+        CloseHandle(p->aRegion[i].hMap);
+      }
+      if( p->hFile.h != INVALID_HANDLE_VALUE ) {
+        winClose((sqlite3_file *)&p->hFile);
+      }
+      if( deleteFlag ) winDelete(pVfs, p->zFilename, 0);
+      *pp = p->pNext;
+      sqlite3_free(p->aRegion);
+      sqlite3_free(p);
+    }else{
+      pp = &p->pNext;
+    }
+  }
+}
+
+/*
+** Open a shared-memory area.  This particular implementation uses
+** mmapped files.
+**
+** zName is a filename used to identify the shared-memory area.  The
+** implementation does not (and perhaps should not) use this name
+** directly, but rather use it as a template for finding an appropriate
+** name for the shared-memory storage.  In this implementation, the
+** string "-index" is appended to zName and used as the name of the
+** mmapped file.
+**
+** When opening a new shared-memory file, if no other instances of that
+** file are currently open, in this process or in other processes, then
+** the file must be truncated to zero length or have its header cleared.
+*/
+static int winShmOpen(
+  sqlite3_file *fd      /* The file to which to attach shared memory */
+){
+  struct winFile *pDbFd;             /* Database to which to attach SHM */
+  struct winShm *p;                  /* The connection to be opened */
+  struct winShmNode *pShmNode = 0;   /* The underlying mmapped file */
+  int rc;                            /* Result code */
+  struct winShmNode *pNew;           /* Newly allocated winShmNode */
+  int nName;                         /* Size of zName in bytes */
+
+  pDbFd = (winFile*)fd;
+  assert( pDbFd->pShm==0 );    /* Not previously opened */
+
+  /* Allocate space for the new sqlite3_shm object.  Also speculatively
+  ** allocate space for a new winShmNode and filename.
+  */
+  p = sqlite3_malloc( sizeof(*p) );
+  if( p==0 ) return SQLITE_NOMEM;
+  memset(p, 0, sizeof(*p));
+  nName = sqlite3Strlen30(pDbFd->zPath);
+  pNew = sqlite3_malloc( sizeof(*pShmNode) + nName + 15 );
+  if( pNew==0 ){
+    sqlite3_free(p);
+    return SQLITE_NOMEM;
+  }
+  memset(pNew, 0, sizeof(*pNew));
+  pNew->zFilename = (char*)&pNew[1];
+  sqlite3_snprintf(nName+15, pNew->zFilename, "%s-wal-index", pDbFd->zPath);
+
+  /* Look to see if there is an existing winShmNode that can be used.
+  ** If no matching winShmNode currently exists, create a new one.
+  */
+  winShmEnterMutex();
+  for(pShmNode = winShmNodeList; pShmNode; pShmNode=pShmNode->pNext){
+    /* TBD need to come up with better match here.  Perhaps
+    ** use FILE_ID_BOTH_DIR_INFO Structure.
+    */
+    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
+  }
+  if( pShmNode ){
+    sqlite3_free(pNew);
+  }else{
+    pShmNode = pNew;
+    pNew = 0;
+    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
+    pShmNode->pNext = winShmNodeList;
+    winShmNodeList = pShmNode;
+
+    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
+    if( pShmNode->mutex==0 ){
+      rc = SQLITE_NOMEM;
+      goto shm_open_err;
+    }
+    rc = winOpen(pDbFd->pVfs,
+                 pShmNode->zFilename,             /* Name of the file (UTF-8) */
+                 (sqlite3_file*)&pShmNode->hFile,  /* File handle here */
+                 SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, /* Mode flags */
+                 0);
+    if( SQLITE_OK!=rc ){
+      rc = SQLITE_CANTOPEN_BKPT;
+      goto shm_open_err;
+    }
+
+    /* Check to see if another process is holding the dead-man switch.
+    ** If not, truncate the file to zero length. 
+    */
+    if( winShmSystemLock(pShmNode, _SHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
+    }
+    if( rc==SQLITE_OK ){
+      winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
+    }
+    if( rc ) goto shm_open_err;
+  }
+
+  /* Make the new connection a child of the winShmNode */
+  p->pShmNode = pShmNode;
+  p->pNext = pShmNode->pFirst;
+#ifdef SQLITE_DEBUG
+  p->id = pShmNode->nextShmId++;
+#endif
+  pShmNode->pFirst = p;
+  pShmNode->nRef++;
+  pDbFd->pShm = p;
+  winShmLeaveMutex();
+  return SQLITE_OK;
+
+  /* Jump here on any error */
+shm_open_err:
+  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
+  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
+  sqlite3_free(p);
+  sqlite3_free(pNew);
+  winShmLeaveMutex();
+  return rc;
+}
+
+/*
+** Close a connection to shared-memory.  Delete the underlying 
+** storage if deleteFlag is true.
+*/
+static int winShmClose(
+  sqlite3_file *fd,          /* Database holding shared memory */
+  int deleteFlag             /* Delete after closing if true */
+){
+  winFile *pDbFd;       /* Database holding shared-memory */
+  winShm *p;            /* The connection to be closed */
+  winShmNode *pShmNode; /* The underlying shared-memory file */
+  winShm **pp;          /* For looping over sibling connections */
+
+  pDbFd = (winFile*)fd;
+  p = pDbFd->pShm;
+  pShmNode = p->pShmNode;
+
+  /* Remove connection p from the set of connections associated
+  ** with pShmNode */
+  sqlite3_mutex_enter(pShmNode->mutex);
+  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
+  *pp = p->pNext;
+
+  /* Free the connection p */
+  sqlite3_free(p);
+  pDbFd->pShm = 0;
+  sqlite3_mutex_leave(pShmNode->mutex);
+
+  /* If pShmNode->nRef has reached 0, then close the underlying
+  ** shared-memory file, too */
+  winShmEnterMutex();
+  assert( pShmNode->nRef>0 );
+  pShmNode->nRef--;
+  if( pShmNode->nRef==0 ){
+    winShmPurge(pDbFd->pVfs, deleteFlag);
+  }
+  winShmLeaveMutex();
+
+  return SQLITE_OK;
+}
+
+/*
+** This function is called to obtain a pointer to region iRegion of the 
+** shared-memory associated with the database file fd. Shared-memory regions 
+** are numbered starting from zero. Each shared-memory region is szRegion 
+** bytes in size.
+**
+** If an error occurs, an error code is returned and *pp is set to NULL.
+**
+** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
+** region has not been allocated (by any client, including one running in a
+** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
+** isWrite is non-zero and the requested shared-memory region has not yet 
+** been allocated, it is allocated by this function.
+**
+** If the shared-memory region has already been allocated or is allocated by
+** this call as described above, then it is mapped into this processes 
+** address space (if it is not already), *pp is set to point to the mapped 
+** memory and SQLITE_OK returned.
+*/
+static int winShmMap(
+  sqlite3_file *fd,               /* Handle open on database file */
+  int iRegion,                    /* Region to retrieve */
+  int szRegion,                   /* Size of regions */
+  int isWrite,                    /* True to extend file if necessary */
+  void volatile **pp              /* OUT: Mapped memory */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *p = pDbFd->pShm;
+  winShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_OK;
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
+
+  if( pShmNode->nRegion<=iRegion ){
+    struct ShmRegion *apNew;           /* New aRegion[] array */
+    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
+    sqlite3_int64 sz;                  /* Current size of wal-index file */
+
+    pShmNode->szRegion = szRegion;
+
+    /* The requested region is not mapped into this processes address space.
+    ** Check to see if it has been allocated (i.e. if the wal-index file is
+    ** large enough to contain the requested region).
+    */
+    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
+    if( rc!=SQLITE_OK ){
+      goto shmpage_out;
+    }
+
+    if( sz<nByte ){
+      /* The requested memory region does not exist. If isWrite is set to
+      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
+      **
+      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
+      ** the requested memory region.
+      */
+      if( !isWrite ) goto shmpage_out;
+      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
+      if( rc!=SQLITE_OK ){
+        goto shmpage_out;
+      }
+    }
+
+    /* Map the requested memory region into this processes address space. */
+    apNew = (struct ShmRegion *)sqlite3_realloc(
+        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
+    );
+    if( !apNew ){
+      rc = SQLITE_IOERR_NOMEM;
+      goto shmpage_out;
+    }
+    pShmNode->aRegion = apNew;
+
+    while( pShmNode->nRegion<=iRegion ){
+      HANDLE hMap;                /* file-mapping handle */
+      void *pMap = 0;             /* Mapped memory region */
+     
+      hMap = CreateFileMapping(pShmNode->hFile.h, 
+          NULL, PAGE_READWRITE, 0, nByte, NULL
+      );
+      if( hMap ){
+        pMap = MapViewOfFile(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
+            0, 0, nByte
+        );
+      }
+      if( !pMap ){
+        pShmNode->lastErrno = GetLastError();
+        rc = SQLITE_IOERR;
+        if( hMap ) CloseHandle(hMap);
+        goto shmpage_out;
+      }
+
+      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
+      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
+      pShmNode->nRegion++;
+    }
+  }
+
+shmpage_out:
+  if( pShmNode->nRegion>iRegion ){
+    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
+    *pp = (void *)&p[iRegion*szRegion];
+  }else{
+    *pp = 0;
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  return rc;
+}
+
+/*
+** Change the lock state for a shared-memory segment.
+*/
+static int winShmLock(
+  sqlite3_file *fd,          /* Database file holding the shared memory */
+  int ofst,                  /* First lock to acquire or release */
+  int n,                     /* Number of locks to acquire or release */
+  int flags                  /* What to do with the lock */
+){
+  winFile *pDbFd = (winFile*)fd;
+  winShm *p = pDbFd->pShm;
+  winShmNode *pShmNode = p->pShmNode;
+  int rc = SQLITE_PROTOCOL;
+
+  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
+  assert( n>=1 );
+  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
+       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
+  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
+
+  sqlite3_mutex_enter(pShmNode->mutex);
+  if( flags & SQLITE_SHM_UNLOCK ){
+    rc = winShmSystemLock(pShmNode, _SHM_UNLCK, ofst+WIN_SHM_BASE, n);
+  }else if( flags & SQLITE_SHM_SHARED ){
+    rc = winShmSystemLock(pShmNode, _SHM_RDLCK, ofst+WIN_SHM_BASE, n);
+  }else{
+    rc = winShmSystemLock(pShmNode, _SHM_WRLCK, ofst+WIN_SHM_BASE, n);
+  }
+  sqlite3_mutex_leave(pShmNode->mutex);
+  OSTRACE(("SHM-LOCK shmid-%d, pid-%d %s\n",
+           p->id, (int)GetCurrentProcessId(), rc ? "failed" : "ok"));
+  return rc;
+}
+
+/*
+** Implement a memory barrier or memory fence on shared memory.  
+**
+** All loads and stores begun before the barrier must complete before
+** any load or store begun after the barrier.
+*/
+static void winShmBarrier(
+  sqlite3_file *fd          /* Database holding the shared memory */
+){
+  /* MemoryBarrier(); // does not work -- do not know why not */
+  winShmEnterMutex();
+  winShmLeaveMutex();
+}
+
+#else
+# define winShmOpen    0
+# define winShmMap     0
+# define winShmLock    0
+# define winShmBarrier 0
+# define winShmClose   0
+#endif /* #ifndef SQLITE_OMIT_WAL */
+/*
+***************************** End Shared Memory *****************************
+****************************************************************************/
+
 /*
 ** This vector defines all the methods that can operate on an
 ** sqlite3_file for win32.
 */
 static const sqlite3_io_methods winIoMethod = {
-  1,                        /* iVersion */
+  2,                        /* iVersion */
   winClose,
   winRead,
   winWrite,
@@ -28467,7 +30433,12 @@
   winCheckReservedLock,
   winFileControl,
   winSectorSize,
-  winDeviceCharacteristics
+  winDeviceCharacteristics,
+  winShmOpen,              /* xShmOpen */
+  winShmLock,              /* xShmLock */
+  winShmMap,               /* xShmMap */
+  winShmBarrier,           /* xShmBarrier */
+  winShmClose              /* xShmClose */
 };
 
 /***************************************************************************
@@ -28549,7 +30520,7 @@
     zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
   }
   zBuf[j] = 0;
-  OSTRACE2("TEMP FILENAME: %s\n", zBuf);
+  OSTRACE(("TEMP FILENAME: %s\n", zBuf));
   return SQLITE_OK; 
 }
 
@@ -28641,6 +30612,8 @@
   assert( id!=0 );
   UNUSED_PARAMETER(pVfs);
 
+  pFile->h = INVALID_HANDLE_VALUE;
+
   /* If the second argument to this function is NULL, generate a 
   ** temporary file name to use 
   */
@@ -28722,6 +30695,9 @@
     );
 #endif
   }
+  OSTRACE(("OPEN %d %s 0x%lx %s\n", 
+           h, zName, dwDesiredAccess, 
+           h==INVALID_HANDLE_VALUE ? "failed" : "ok"));
   if( h==INVALID_HANDLE_VALUE ){
     free(zConverted);
     if( flags & SQLITE_OPEN_READWRITE ){
@@ -28742,6 +30718,9 @@
   pFile->pMethod = &winIoMethod;
   pFile->h = h;
   pFile->lastErrno = NO_ERROR;
+  pFile->pVfs = pVfs;
+  pFile->pShm = 0;
+  pFile->zPath = zName;
   pFile->sectorSize = getSectorSize(pVfs, zUtf8Name);
 #if SQLITE_OS_WINCE
   if( (flags & (SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_DB)) ==
@@ -28813,7 +30792,10 @@
 #endif
   }
   free(zConverted);
-  OSTRACE2("DELETE \"%s\"\n", zFilename);
+  OSTRACE(("DELETE \"%s\" %s\n", zFilename,
+       ( (rc==INVALID_FILE_ATTRIBUTES) && (error==ERROR_FILE_NOT_FOUND)) ?
+         "ok" : "failed" ));
+ 
   return (   (rc == INVALID_FILE_ATTRIBUTES) 
           && (error == ERROR_FILE_NOT_FOUND)) ? SQLITE_OK : SQLITE_IOERR_DELETE;
 }
@@ -29106,34 +31088,32 @@
 }
 
 /*
-** The following variable, if set to a non-zero value, becomes the result
-** returned from sqlite3OsCurrentTime().  This is used for testing.
+** The following variable, if set to a non-zero value, is interpreted as
+** the number of seconds since 1970 and is used to set the result of
+** sqlite3OsCurrentTime() during testing.
 */
 #ifdef SQLITE_TEST
-SQLITE_API int sqlite3_current_time = 0;
+SQLITE_API int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
 #endif
 
 /*
-** Find the current time (in Universal Coordinated Time).  Write the
-** current time and date as a Julian Day number into *prNow and
-** return 0.  Return 1 if the time and date cannot be found.
+** Find the current time (in Universal Coordinated Time).  Write into *piNow
+** the current time and date as a Julian Day number times 86_400_000.  In
+** other words, write into *piNow the number of milliseconds since the Julian
+** epoch of noon in Greenwich on November 24, 4714 B.C according to the
+** proleptic Gregorian calendar.
+**
+** On success, return 0.  Return 1 if the time and date cannot be found.
 */
-int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
-  FILETIME ft;
+static int winCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
   /* FILETIME structure is a 64-bit value representing the number of 
      100-nanosecond intervals since January 1, 1601 (= JD 2305813.5). 
   */
-  sqlite3_int64 timeW;   /* Whole days */
-  sqlite3_int64 timeF;   /* Fractional Days */
-
-  /* Number of 100-nanosecond intervals in a single day */
-  static const sqlite3_int64 ntuPerDay = 
-      10000000*(sqlite3_int64)86400;
-
-  /* Number of 100-nanosecond intervals in half of a day */
-  static const sqlite3_int64 ntuPerHalfDay = 
-      10000000*(sqlite3_int64)43200;
-
+  FILETIME ft;
+  static const sqlite3_int64 winFiletimeEpoch = 23058135*(sqlite3_int64)8640000;
+#ifdef SQLITE_TEST
+  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
+#endif
   /* 2^32 - to avoid use of LL and warnings in gcc */
   static const sqlite3_int64 max32BitValue = 
       (sqlite3_int64)2000000000 + (sqlite3_int64)2000000000 + (sqlite3_int64)294967296;
@@ -29148,24 +31128,36 @@
 #else
   GetSystemTimeAsFileTime( &ft );
 #endif
-  UNUSED_PARAMETER(pVfs);
-  timeW = (((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) + (sqlite3_int64)ft.dwLowDateTime;
-  timeF = timeW % ntuPerDay;          /* fractional days (100-nanoseconds) */
-  timeW = timeW / ntuPerDay;          /* whole days */
-  timeW = timeW + 2305813;            /* add whole days (from 2305813.5) */
-  timeF = timeF + ntuPerHalfDay;      /* add half a day (from 2305813.5) */
-  timeW = timeW + (timeF/ntuPerDay);  /* add whole day if half day made one */
-  timeF = timeF % ntuPerDay;          /* compute new fractional days */
-  *prNow = (double)timeW + ((double)timeF / (double)ntuPerDay);
+
+  *piNow = winFiletimeEpoch +
+            ((((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) + 
+               (sqlite3_int64)ft.dwLowDateTime)/(sqlite3_int64)1000;
+
 #ifdef SQLITE_TEST
   if( sqlite3_current_time ){
-    *prNow = ((double)sqlite3_current_time + (double)43200) / (double)86400 + (double)2440587;
+    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
   }
 #endif
+  UNUSED_PARAMETER(pVfs);
   return 0;
 }
 
 /*
+** Find the current time (in Universal Coordinated Time).  Write the
+** current time and date as a Julian Day number into *prNow and
+** return 0.  Return 1 if the time and date cannot be found.
+*/
+int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
+  int rc;
+  sqlite3_int64 i;
+  rc = winCurrentTimeInt64(pVfs, &i);
+  if( !rc ){
+    *prNow = i/86400000.0;
+  }
+  return rc;
+}
+
+/*
 ** The idea is that this function works like a combination of
 ** GetLastError() and FormatMessage() on windows (or errno and
 ** strerror_r() on unix). After an error is returned by an OS
@@ -29200,30 +31192,33 @@
   return getLastErrorMsg(nBuf, zBuf);
 }
 
+
+
 /*
 ** Initialize and deinitialize the operating system interface.
 */
 SQLITE_API int sqlite3_os_init(void){
   static sqlite3_vfs winVfs = {
-    1,                 /* iVersion */
-    sizeof(winFile),   /* szOsFile */
-    MAX_PATH,          /* mxPathname */
-    0,                 /* pNext */
-    "win32",           /* zName */
-    0,                 /* pAppData */
- 
-    winOpen,           /* xOpen */
-    winDelete,         /* xDelete */
-    winAccess,         /* xAccess */
-    winFullPathname,   /* xFullPathname */
-    winDlOpen,         /* xDlOpen */
-    winDlError,        /* xDlError */
-    winDlSym,          /* xDlSym */
-    winDlClose,        /* xDlClose */
-    winRandomness,     /* xRandomness */
-    winSleep,          /* xSleep */
-    winCurrentTime,    /* xCurrentTime */
-    winGetLastError    /* xGetLastError */
+    2,                   /* iVersion */
+    sizeof(winFile),     /* szOsFile */
+    MAX_PATH,            /* mxPathname */
+    0,                   /* pNext */
+    "win32",             /* zName */
+    0,                   /* pAppData */
+    winOpen,             /* xOpen */
+    winDelete,           /* xDelete */
+    winAccess,           /* xAccess */
+    winFullPathname,     /* xFullPathname */
+    winDlOpen,           /* xDlOpen */
+    winDlError,          /* xDlError */
+    winDlSym,            /* xDlSym */
+    winDlClose,          /* xDlClose */
+    winRandomness,       /* xRandomness */
+    winSleep,            /* xSleep */
+    winCurrentTime,      /* xCurrentTime */
+    winGetLastError,     /* xGetLastError */
+    0,                   /* xRename */
+    winCurrentTimeInt64, /* xCurrentTimeInt64 */
   };
 
   sqlite3_vfs_register(&winVfs, 1);
@@ -29908,15 +31903,17 @@
 
   if( pPage ){
     if( !pPage->pData ){
-      memset(pPage, 0, sizeof(PgHdr) + pCache->szExtra);
-      pPage->pExtra = (void*)&pPage[1];
-      pPage->pData = (void *)&((char *)pPage)[sizeof(PgHdr) + pCache->szExtra];
+      memset(pPage, 0, sizeof(PgHdr));
+      pPage->pData = (void *)&pPage[1];
+      pPage->pExtra = (void*)&((char *)pPage->pData)[pCache->szPage];
+      memset(pPage->pExtra, 0, pCache->szExtra);
       pPage->pCache = pCache;
       pPage->pgno = pgno;
     }
     assert( pPage->pCache==pCache );
     assert( pPage->pgno==pgno );
-    assert( pPage->pExtra==(void *)&pPage[1] );
+    assert( pPage->pData==(void *)&pPage[1] );
+    assert( pPage->pExtra==(void *)&((char *)&pPage[1])[pCache->szPage] );
 
     if( 0==pPage->nRef ){
       pCache->nRef++;
@@ -30055,7 +32052,12 @@
     PgHdr *pNext;
     for(p=pCache->pDirty; p; p=pNext){
       pNext = p->pDirtyNext;
-      if( p->pgno>pgno ){
+      /* This routine never gets call with a positive pgno except right
+      ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
+      ** it must be that pgno==0.
+      */
+      assert( p->pgno>0 );
+      if( ALWAYS(p->pgno>pgno) ){
         assert( p->flags&PGHDR_DIRTY );
         sqlite3PcacheMakeClean(p);
       }
@@ -30399,6 +32401,7 @@
       int sz = sqlite3MallocSize(p);
       sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
     }
+    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
   }
   return p;
 }
@@ -30416,7 +32419,10 @@
     pSlot->pNext = pcache1.pFree;
     pcache1.pFree = pSlot;
   }else{
-    int iSize = sqlite3MallocSize(p);
+    int iSize;
+    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
+    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
+    iSize = sqlite3MallocSize(p);
     sqlite3StatusAdd(SQLITE_STATUS_PAGECACHE_OVERFLOW, -iSize);
     sqlite3_free(p);
   }
@@ -30938,7 +32944,7 @@
 ** already provided an alternative.
 */
 SQLITE_PRIVATE void sqlite3PCacheSetDefault(void){
-  static sqlite3_pcache_methods defaultMethods = {
+  static const sqlite3_pcache_methods defaultMethods = {
     0,                       /* pArg */
     pcache1Init,             /* xInit */
     pcache1Shutdown,         /* xShutdown */
@@ -31451,6 +33457,197 @@
 ** another is writing.
 */
 #ifndef SQLITE_OMIT_DISKIO
+/************** Include wal.h in the middle of pager.c ***********************/
+/************** Begin file wal.h *********************************************/
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This header file defines the interface to the write-ahead logging 
+** system. Refer to the comments below and the header comment attached to 
+** the implementation of each function in log.c for further details.
+*/
+
+#ifndef _WAL_H_
+#define _WAL_H_
+
+
+#ifdef SQLITE_OMIT_WAL
+# define sqlite3WalOpen(x,y,z)                 0
+# define sqlite3WalClose(w,x,y,z)              0
+# define sqlite3WalBeginReadTransaction(y,z)   0
+# define sqlite3WalEndReadTransaction(z)
+# define sqlite3WalRead(v,w,x,y,z)             0
+# define sqlite3WalDbsize(y,z)
+# define sqlite3WalBeginWriteTransaction(y)    0
+# define sqlite3WalEndWRiteTransaction(x)      0
+# define sqlite3WalUndo(x,y,z)                 0
+# define sqlite3WalSavepoint(y,z)
+# define sqlite3WalSavepointUndo(y,z)          0
+# define sqlite3WalFrames(u,v,w,x,y,z)         0
+# define sqlite3WalCheckpoint(u,v,w,x)         0
+# define sqlite3WalCallback(z)                 0
+#else
+
+#define WAL_SAVEPOINT_NDATA 4
+
+/* Connection to a write-ahead log (WAL) file. 
+** There is one object of this type for each pager. 
+*/
+typedef struct Wal Wal;
+
+/* Open and close a connection to a write-ahead log. */
+SQLITE_PRIVATE int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *zName, Wal**);
+SQLITE_PRIVATE int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
+
+/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
+** snapshot is like a read-transaction.  It is the state of the database
+** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
+** preserves the current state even if the other threads or processes
+** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
+** transaction and releases the lock.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
+SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal);
+
+/* Read a page from the write-ahead log, if it is present. */
+SQLITE_PRIVATE int sqlite3WalRead(Wal *pWal, Pgno pgno, int *pInWal, int nOut, u8 *pOut);
+
+/* Return the size of the database as it existed at the beginning
+** of the snapshot */
+SQLITE_PRIVATE void sqlite3WalDbsize(Wal *pWal, Pgno *pPgno);
+
+/* Obtain or release the WRITER lock. */
+SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal);
+SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal);
+
+/* Undo any frames written (but not committed) to the log */
+SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
+
+/* Return an integer that records the current (uncommitted) write
+** position in the WAL */
+SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
+
+/* Move the write position of the WAL back to iFrame.  Called in
+** response to a ROLLBACK TO command. */
+SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
+
+/* Write a frame or frames to the log. */
+SQLITE_PRIVATE int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
+
+/* Copy pages from the log to the database file */ 
+SQLITE_PRIVATE int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Write-ahead log connection */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of buffer nBuf */
+  u8 *zBuf                        /* Temporary buffer to use */
+);
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal);
+
+/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
+** by the pager layer on the database file.
+*/
+SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op);
+
+#endif /* ifndef SQLITE_OMIT_WAL */
+#endif /* _WAL_H_ */
+
+/************** End of wal.h *************************************************/
+/************** Continuing where we left off in pager.c **********************/
+
+/*
+******************** NOTES ON THE DESIGN OF THE PAGER ************************
+**
+** Within this comment block, a page is deemed to have been synced
+** automatically as soon as it is written when PRAGMA synchronous=OFF.
+** Otherwise, the page is not synced until the xSync method of the VFS
+** is called successfully on the file containing the page.
+**
+** Definition:  A page of the database file is said to be "overwriteable" if
+** one or more of the following are true about the page:
+** 
+**     (a)  The original content of the page as it was at the beginning of
+**          the transaction has been written into the rollback journal and
+**          synced.
+** 
+**     (b)  The page was a freelist leaf page at the start of the transaction.
+** 
+**     (c)  The page number is greater than the largest page that existed in
+**          the database file at the start of the transaction.
+** 
+** (1) A page of the database file is never overwritten unless one of the
+**     following are true:
+** 
+**     (a) The page and all other pages on the same sector are overwriteable.
+** 
+**     (b) The atomic page write optimization is enabled, and the entire
+**         transaction other than the update of the transaction sequence
+**         number consists of a single page change.
+** 
+** (2) The content of a page written into the rollback journal exactly matches
+**     both the content in the database when the rollback journal was written
+**     and the content in the database at the beginning of the current
+**     transaction.
+** 
+** (3) Writes to the database file are an integer multiple of the page size
+**     in length and are aligned to a page boundary.
+** 
+** (4) Reads from the database file are either aligned on a page boundary and
+**     an integer multiple of the page size in length or are taken from the
+**     first 100 bytes of the database file.
+** 
+** (5) All writes to the database file are synced prior to the rollback journal
+**     being deleted, truncated, or zeroed.
+** 
+** (6) If a master journal file is used, then all writes to the database file
+**     are synced prior to the master journal being deleted.
+** 
+** Definition: Two databases (or the same database at two points it time)
+** are said to be "logically equivalent" if they give the same answer to
+** all queries.  Note in particular the the content of freelist leaf
+** pages can be changed arbitarily without effecting the logical equivalence
+** of the database.
+** 
+** (7) At any time, if any subset, including the empty set and the total set,
+**     of the unsynced changes to a rollback journal are removed and the 
+**     journal is rolled back, the resulting database file will be logical
+**     equivalent to the database file at the beginning of the transaction.
+** 
+** (8) When a transaction is rolled back, the xTruncate method of the VFS
+**     is called to restore the database file to the same size it was at
+**     the beginning of the transaction.  (In some VFSes, the xTruncate
+**     method is a no-op, but that does not change the fact the SQLite will
+**     invoke it.)
+** 
+** (9) Whenever the database file is modified, at least one bit in the range
+**     of bytes from 24 through 39 inclusive will be changed prior to releasing
+**     the EXCLUSIVE lock.
+**
+** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
+**      than one billion transactions.
+**
+** (11) A database file is well-formed at the beginning and at the conclusion
+**      of every transaction.
+**
+** (12) An EXCLUSIVE lock is held on the database file when writing to
+**      the database file.
+**
+** (13) A SHARED lock is held on the database file while reading any
+**      content out of the database file.
+*/
 
 /*
 ** Macros for troubleshooting.  Normally turned off
@@ -31570,6 +33767,7 @@
   Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
   Pgno nOrig;                  /* Original number of pages in file */
   Pgno iSubRec;                /* Index of first record in sub-journal */
+  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
 };
 
 /*
@@ -31599,6 +33797,8 @@
 **   transaction was opened. The contents of all three of these variables is
 **   only guaranteed to be correct if the boolean Pager.dbSizeValid is true.
 **
+**   The dbFileSize value is not set or used in WAL mode.
+**
 **   TODO: Under what conditions is dbSizeValid set? Cleared?
 **
 ** changeCountDone
@@ -31628,7 +33828,8 @@
 **
 ** journalStarted
 **
-**   This flag is set whenever the the main journal is synced. 
+**   This flag is set whenever the the main journal is opened and
+**   initialized
 **
 **   The point of this flag is that it must be set after the 
 **   first journal header in a journal file has been synced to disk.
@@ -31654,7 +33855,10 @@
 **
 ** doNotSync
 **
-**   This variable is set and cleared by sqlite3PagerWrite().
+**   When enabled, cache spills are prohibited and the journal file cannot
+**   be synced.  This variable is set and cleared by sqlite3PagerWrite() 
+**   in order to prevent a journal sync from happening in between the
+**   journalling of two pages on the same sector.
 **
 ** needSync
 **
@@ -31714,6 +33918,7 @@
   sqlite3_file *sjfd;         /* File descriptor for sub-journal */
   i64 journalOff;             /* Current write offset in the journal file */
   i64 journalHdr;             /* Byte offset to previous journal header */
+  i64 journalSizeLimit;       /* Size limit for persistent journal files */
   PagerSavepoint *aSavepoint; /* Array of active savepoints */
   int nSavepoint;             /* Number of elements in aSavepoint[] */
   char dbFileVers[16];        /* Changes whenever database file changes */
@@ -31740,9 +33945,11 @@
   void *pCodec;               /* First argument to xCodec... methods */
 #endif
   char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
-  i64 journalSizeLimit;       /* Size limit for persistent journal files */
   PCache *pPCache;            /* Pointer to page cache object */
   sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
+#ifndef SQLITE_OMIT_WAL
+  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
+#endif
 };
 
 /*
@@ -32256,6 +34463,7 @@
   for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
     IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
     rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
+    assert( pPager->journalHdr <= pPager->journalOff );
     pPager->journalOff += nHeader;
   }
 
@@ -32414,6 +34622,7 @@
   }
   pPager->setMaster = 1;
   assert( isOpen(pPager->jfd) );
+  assert( pPager->journalHdr <= pPager->journalOff );
 
   /* Calculate the length in bytes and the checksum of zMaster */
   for(nMaster=0; zMaster[nMaster]; nMaster++){
@@ -32530,6 +34739,22 @@
 }
 
 /*
+** Return true if this pager uses a write-ahead log instead of the usual
+** rollback journal. Otherwise false.
+*/
+#ifndef SQLITE_OMIT_WAL
+static int pagerUseWal(Pager *pPager){
+  return (pPager->pWal!=0);
+}
+#else
+# define pagerUseWal(x) 0
+# define pagerRollbackWal(x) 0
+# define pagerWalFrames(v,w,x,y,z) 0
+# define pagerOpenWalIfPresent(z) SQLITE_OK
+# define pagerBeginReadTransaction(z) SQLITE_OK
+#endif
+
+/*
 ** Unlock the database file. This function is a no-op if the pager
 ** is in exclusive mode.
 **
@@ -32541,7 +34766,7 @@
 */
 static void pager_unlock(Pager *pPager){
   if( !pPager->exclusiveMode ){
-    int rc;                      /* Return code */
+    int rc = SQLITE_OK;          /* Return code */
 
     /* Always close the journal file when dropping the database lock.
     ** Otherwise, another connection with journal_mode=delete might
@@ -32554,12 +34779,17 @@
 
     /* If the file is unlocked, somebody else might change it. The
     ** values stored in Pager.dbSize etc. might become invalid if
-    ** this happens. TODO: Really, this doesn't need to be cleared
+    ** this happens.  One can argue that this doesn't need to be cleared
     ** until the change-counter check fails in PagerSharedLock().
+    ** Clearing the page size cache here is being conservative.
     */
     pPager->dbSizeValid = 0;
 
-    rc = osUnlock(pPager->fd, NO_LOCK);
+    if( pagerUseWal(pPager) ){
+      sqlite3WalEndReadTransaction(pPager->pWal);
+    }else{
+      rc = osUnlock(pPager->fd, NO_LOCK);
+    }
     if( rc ){
       pPager->errCode = rc;
     }
@@ -32708,6 +34938,7 @@
 
   assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
   if( isOpen(pPager->jfd) ){
+    assert( !pagerUseWal(pPager) );
 
     /* Finalize the journal file. */
     if( sqlite3IsMemJournal(pPager->jfd) ){
@@ -32721,8 +34952,8 @@
       }
       pPager->journalOff = 0;
       pPager->journalStarted = 0;
-    }else if( pPager->exclusiveMode 
-     || pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
+      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
     ){
       rc = zeroJournalHdr(pPager, hasMaster);
       pager_error(pPager, rc);
@@ -32732,9 +34963,11 @@
       /* This branch may be executed with Pager.journalMode==MEMORY if
       ** a hot-journal was just rolled back. In this case the journal
       ** file should be closed and deleted. If this connection writes to
-      ** the database file, it will do so using an in-memory journal.  */
+      ** the database file, it will do so using an in-memory journal. 
+      */
       assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
            || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
+           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
       );
       sqlite3OsClose(pPager->jfd);
       if( !pPager->tempFile ){
@@ -32745,14 +34978,30 @@
 #ifdef SQLITE_CHECK_PAGES
     sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
 #endif
-
-    sqlite3PcacheCleanAll(pPager->pPCache);
-    sqlite3BitvecDestroy(pPager->pInJournal);
-    pPager->pInJournal = 0;
-    pPager->nRec = 0;
   }
+  sqlite3BitvecDestroy(pPager->pInJournal);
+  pPager->pInJournal = 0;
+  pPager->nRec = 0;
+  sqlite3PcacheCleanAll(pPager->pPCache);
 
-  if( !pPager->exclusiveMode ){
+  if( pagerUseWal(pPager) ){
+    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
+    assert( rc2==SQLITE_OK );
+    pPager->state = PAGER_SHARED;
+
+    /* If the connection is not in locking_mode=exclusive mode then note
+    ** that the change counter is now invalid.  Also drop the EXCLUSIVE
+    ** lock if we currently hold it.  (We might be holding the EXCLUSIVE
+    ** lock if we were in locking_mode=exclusive but recently changed back
+    ** to locking_mode=normal.)
+    */
+    if( !pPager->exclusiveMode ){
+      pPager->changeCountDone = 0;
+      if( sqlite3WalExclusiveMode(pPager->pWal, 0) ){
+        rc2 = osUnlock(pPager->fd, SHARED_LOCK);
+      }
+    }
+  }else if( !pPager->exclusiveMode ){
     rc2 = osUnlock(pPager->fd, SHARED_LOCK);
     pPager->state = PAGER_SHARED;
     pPager->changeCountDone = 0;
@@ -32843,11 +35092,10 @@
 */
 static int pager_playback_one_page(
   Pager *pPager,                /* The pager being played back */
-  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
-  int isUnsync,                 /* True if reading from unsynced main journal */
   i64 *pOffset,                 /* Offset of record to playback */
-  int isSavepnt,                /* True for a savepoint rollback */
-  Bitvec *pDone                 /* Bitvec of pages already played back */
+  Bitvec *pDone,                /* Bitvec of pages already played back */
+  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
+  int isSavepnt                 /* True for a savepoint rollback */
 ){
   int rc;
   PgHdr *pPg;                   /* An existing page in the cache */
@@ -32855,6 +35103,7 @@
   u32 cksum;                    /* Checksum used for sanity checking */
   char *aData;                  /* Temporary storage for the page */
   sqlite3_file *jfd;            /* The file descriptor for the journal file */
+  int isSynced;                 /* True if journal page is synced */
 
   assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
   assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
@@ -32863,6 +35112,7 @@
 
   aData = pPager->pTmpSpace;
   assert( aData );         /* Temp storage must have already been allocated */
+  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
 
   /* Read the page number and page data from the journal or sub-journal
   ** file. Return an error code to the caller if an IO error occurs.
@@ -32932,18 +35182,28 @@
   ** is possible to fail a statement on a database that does not yet exist.
   ** Do not attempt to write if database file has never been opened.
   */
-  pPg = pager_lookup(pPager, pgno);
+  if( pagerUseWal(pPager) ){
+    pPg = 0;
+  }else{
+    pPg = pager_lookup(pPager, pgno);
+  }
   assert( pPg || !MEMDB );
   PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
            PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
            (isMainJrnl?"main-journal":"sub-journal")
   ));
+  if( isMainJrnl ){
+    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
+  }else{
+    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
+  }
   if( (pPager->state>=PAGER_EXCLUSIVE)
-   && (pPg==0 || 0==(pPg->flags&PGHDR_NEED_SYNC))
    && isOpen(pPager->fd)
-   && !isUnsync
+   && isSynced
   ){
     i64 ofst = (pgno-1)*(i64)pPager->pageSize;
+    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
+    assert( !pagerUseWal(pPager) );
     rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst);
     if( pgno>pPager->dbFileSize ){
       pPager->dbFileSize = pgno;
@@ -32992,7 +35252,8 @@
       /* If the contents of this page were just restored from the main 
       ** journal file, then its content must be as they were when the 
       ** transaction was first opened. In this case we can mark the page
-      ** as clean, since there will be no need to write it out to the.
+      ** as clean, since there will be no need to write it out to the
+      ** database.
       **
       ** There is one exception to this rule. If the page is being rolled
       ** back as part of a savepoint (or statement) rollback from an 
@@ -33007,6 +35268,7 @@
       ** segment is synced. If a crash occurs during or following this,
       ** database corruption may ensue.
       */
+      assert( !pagerUseWal(pPager) );
       sqlite3PcacheMakeClean(pPg);
     }
 #ifdef SQLITE_CHECK_PAGES
@@ -33339,8 +35601,6 @@
   ** occurs. 
   */
   while( 1 ){
-    int isUnsync = 0;
-
     /* Read the next journal header from the journal file.  If there are
     ** not enough bytes left in the journal file for a complete header, or
     ** it is corrupted, then a process must of failed while writing it.
@@ -33381,7 +35641,6 @@
     if( nRec==0 && !isHot &&
         pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
       nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
-      isUnsync = 1;
     }
 
     /* If this is the first header read from the journal, truncate the
@@ -33403,12 +35662,20 @@
         pager_reset(pPager);
         needPagerReset = 0;
       }
-      rc = pager_playback_one_page(pPager,1,isUnsync,&pPager->journalOff,0,0);
+      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
       if( rc!=SQLITE_OK ){
         if( rc==SQLITE_DONE ){
           rc = SQLITE_OK;
           pPager->journalOff = szJ;
           break;
+        }else if( rc==SQLITE_IOERR_SHORT_READ ){
+          /* If the journal has been truncated, simply stop reading and
+          ** processing the journal. This might happen if the journal was
+          ** not completely written and synced prior to a crash.  In that
+          ** case, the database should have never been written in the
+          ** first place so it is OK to simply abandon the rollback. */
+          rc = SQLITE_OK;
+          goto end_playback;
         }else{
           /* If we are unable to rollback, quit and return the error
           ** code.  This will cause the pager to enter the error state
@@ -33453,6 +35720,9 @@
   if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){
     rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
   }
+  if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){
+    rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+  }
   if( rc==SQLITE_OK ){
     rc = pager_end_transaction(pPager, zMaster[0]!='\0');
     testcase( rc!=SQLITE_OK );
@@ -33473,6 +35743,265 @@
   return rc;
 }
 
+
+/*
+** Read the content for page pPg out of the database file and into 
+** pPg->pData. A shared lock or greater must be held on the database
+** file before this function is called.
+**
+** If page 1 is read, then the value of Pager.dbFileVers[] is set to
+** the value read from the database file.
+**
+** If an IO error occurs, then the IO error is returned to the caller.
+** Otherwise, SQLITE_OK is returned.
+*/
+static int readDbPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
+  Pgno pgno = pPg->pgno;       /* Page number to read */
+  int rc = SQLITE_OK;          /* Return code */
+  int isInWal = 0;             /* True if page is in log file */
+  int pgsz = pPager->pageSize; /* Number of bytes to read */
+
+  assert( pPager->state>=PAGER_SHARED && !MEMDB );
+  assert( isOpen(pPager->fd) );
+
+  if( NEVER(!isOpen(pPager->fd)) ){
+    assert( pPager->tempFile );
+    memset(pPg->pData, 0, pPager->pageSize);
+    return SQLITE_OK;
+  }
+
+  if( pagerUseWal(pPager) ){
+    /* Try to pull the page from the write-ahead log. */
+    rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pgsz, pPg->pData);
+  }
+  if( rc==SQLITE_OK && !isInWal ){
+    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
+    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
+    if( rc==SQLITE_IOERR_SHORT_READ ){
+      rc = SQLITE_OK;
+    }
+  }
+
+  if( pgno==1 ){
+    if( rc ){
+      /* If the read is unsuccessful, set the dbFileVers[] to something
+      ** that will never be a valid file version.  dbFileVers[] is a copy
+      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
+      ** zero or the size of the database in page. Bytes 32..35 and 35..39
+      ** should be page numbers which are never 0xffffffff.  So filling
+      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
+      **
+      ** For an encrypted database, the situation is more complex:  bytes
+      ** 24..39 of the database are white noise.  But the probability of
+      ** white noising equaling 16 bytes of 0xff is vanishingly small so
+      ** we should still be ok.
+      */
+      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
+    }else{
+      u8 *dbFileVers = &((u8*)pPg->pData)[24];
+      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
+    }
+  }
+  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
+
+  PAGER_INCR(sqlite3_pager_readdb_count);
+  PAGER_INCR(pPager->nRead);
+  IOTRACE(("PGIN %p %d\n", pPager, pgno));
+  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
+               PAGERID(pPager), pgno, pager_pagehash(pPg)));
+
+  return rc;
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is invoked once for each page that has already been 
+** written into the log file when a WAL transaction is rolled back.
+** Parameter iPg is the page number of said page. The pCtx argument 
+** is actually a pointer to the Pager structure.
+**
+** If page iPg is present in the cache, and has no outstanding references,
+** it is discarded. Otherwise, if there are one or more outstanding
+** references, the page content is reloaded from the database. If the
+** attempt to reload content from the database is required and fails, 
+** return an SQLite error code. Otherwise, SQLITE_OK.
+*/
+static int pagerUndoCallback(void *pCtx, Pgno iPg){
+  int rc = SQLITE_OK;
+  Pager *pPager = (Pager *)pCtx;
+  PgHdr *pPg;
+
+  pPg = sqlite3PagerLookup(pPager, iPg);
+  if( pPg ){
+    if( sqlite3PcachePageRefcount(pPg)==1 ){
+      sqlite3PcacheDrop(pPg);
+    }else{
+      rc = readDbPage(pPg);
+      if( rc==SQLITE_OK ){
+        pPager->xReiniter(pPg);
+      }
+      sqlite3PagerUnref(pPg);
+    }
+  }
+
+  /* Normally, if a transaction is rolled back, any backup processes are
+  ** updated as data is copied out of the rollback journal and into the
+  ** database. This is not generally possible with a WAL database, as
+  ** rollback involves simply truncating the log file. Therefore, if one
+  ** or more frames have already been written to the log (and therefore 
+  ** also copied into the backup databases) as part of this transaction,
+  ** the backups must be restarted.
+  */
+  sqlite3BackupRestart(pPager->pBackup);
+
+  return rc;
+}
+
+/*
+** This function is called to rollback a transaction on a WAL database.
+*/
+static int pagerRollbackWal(Pager *pPager){
+  int rc;                         /* Return Code */
+  PgHdr *pList;                   /* List of dirty pages to revert */
+
+  /* For all pages in the cache that are currently dirty or have already
+  ** been written (but not committed) to the log file, do one of the 
+  ** following:
+  **
+  **   + Discard the cached page (if refcount==0), or
+  **   + Reload page content from the database (if refcount>0).
+  */
+  pPager->dbSize = pPager->dbOrigSize;
+  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
+  pList = sqlite3PcacheDirtyList(pPager->pPCache);
+  while( pList && rc==SQLITE_OK ){
+    PgHdr *pNext = pList->pDirty;
+    rc = pagerUndoCallback((void *)pPager, pList->pgno);
+    pList = pNext;
+  }
+
+  return rc;
+}
+
+/*
+** This function is a wrapper around sqlite3WalFrames(). As well as logging
+** the contents of the list of pages headed by pList (connected by pDirty),
+** this function notifies any active backup processes that the pages have
+** changed. 
+*/ 
+static int pagerWalFrames(
+  Pager *pPager,                  /* Pager object */
+  PgHdr *pList,                   /* List of frames to log */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Return code */
+
+  assert( pPager->pWal );
+  rc = sqlite3WalFrames(pPager->pWal, 
+      pPager->pageSize, pList, nTruncate, isCommit, sync_flags
+  );
+  if( rc==SQLITE_OK && pPager->pBackup ){
+    PgHdr *p;
+    for(p=pList; p; p=p->pDirty){
+      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
+    }
+  }
+  return rc;
+}
+
+/*
+** Begin a read transaction on the WAL.
+**
+** This routine used to be called "pagerOpenSnapshot()" because it essentially
+** makes a snapshot of the database at the current point in time and preserves
+** that snapshot for use by the reader in spite of concurrently changes by
+** other writers or checkpointers.
+*/
+static int pagerBeginReadTransaction(Pager *pPager){
+  int rc;                         /* Return code */
+  int changed = 0;                /* True if cache must be reset */
+
+  assert( pagerUseWal(pPager) );
+
+  /* sqlite3WalEndReadTransaction() was not called for the previous
+  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
+  ** are in locking_mode=NORMAL and EndRead() was previously called,
+  ** the duplicate call is harmless.
+  */
+  sqlite3WalEndReadTransaction(pPager->pWal);
+
+  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
+  if( rc==SQLITE_OK ){
+    int dummy;
+    if( changed ){
+      pager_reset(pPager);
+      assert( pPager->errCode || pPager->dbSizeValid==0 );
+    }
+    rc = sqlite3PagerPagecount(pPager, &dummy);
+  }
+  pPager->state = PAGER_SHARED;
+
+  return rc;
+}
+
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists. Assuming no error occurs, set *pExists to 1 if the file exists,
+** or 0 otherwise and return SQLITE_OK. If an IO or OOM error occurs, return
+** an SQLite error code.
+*/
+static int pagerHasWAL(Pager *pPager, int *pExists){
+  int rc;                         /* Return code */
+  char *zWal;                     /* Name of the WAL file */
+
+  assert( !pPager->tempFile );
+  zWal = sqlite3_mprintf("%s-wal", pPager->zFilename);
+  if( !zWal ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3OsAccess(pPager->pVfs, zWal, SQLITE_ACCESS_EXISTS, pExists);
+    sqlite3_free(zWal);
+  }
+  return rc;
+}
+
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists. If it does, open the pager in WAL mode. Otherwise, if no error
+** occurs, make sure Pager.journalMode is not set to PAGER_JOURNALMODE_WAL.
+** If an IO or OOM error occurs, return an SQLite error code.
+**
+** If the WAL file is opened, also open a snapshot (read transaction).
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function. Because an EXCLUSIVE lock on the db file is required to delete 
+** a WAL, this ensures there is no race condition between the xAccess() 
+** below and an xDelete() being executed by some other connection.
+*/
+static int pagerOpenWalIfPresent(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->tempFile ){
+    int isWal;                    /* True if WAL file exists */
+    rc = pagerHasWAL(pPager, &isWal);
+    if( rc==SQLITE_OK ){
+      if( isWal ){
+        pager_reset(pPager);
+        rc = sqlite3PagerOpenWal(pPager, 0);
+        if( rc==SQLITE_OK ){
+          rc = pagerBeginReadTransaction(pPager);
+        }
+      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
+      }
+    }
+  }
+  return rc;
+}
+#endif
+
 /*
 ** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
 ** the entire master journal file. The case pSavepoint==NULL occurs when 
@@ -33530,12 +36059,17 @@
   */
   pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
 
+  if( !pSavepoint && pagerUseWal(pPager) ){
+    return pagerRollbackWal(pPager);
+  }
+
   /* Use pPager->journalOff as the effective size of the main rollback
   ** journal.  The actual file might be larger than this in
   ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
   ** past pPager->journalOff is off-limits to us.
   */
   szJ = pPager->journalOff;
+  assert( pagerUseWal(pPager)==0 || szJ==0 );
 
   /* Begin by rolling back records from the main journal starting at
   ** PagerSavepoint.iOffset and continuing to the next journal header.
@@ -33544,11 +36078,11 @@
   ** will be skipped automatically.  Pages are added to pDone as they
   ** are played back.
   */
-  if( pSavepoint ){
+  if( pSavepoint && !pagerUseWal(pPager) ){
     iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
     pPager->journalOff = pSavepoint->iOffset;
     while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
-      rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
     }
     assert( rc!=SQLITE_DONE );
   }else{
@@ -33578,7 +36112,7 @@
       nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
     }
     for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
-      rc = pager_playback_one_page(pPager, 1, 0, &pPager->journalOff, 1, pDone);
+      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
     }
     assert( rc!=SQLITE_DONE );
   }
@@ -33591,9 +36125,13 @@
   if( pSavepoint ){
     u32 ii;            /* Loop counter */
     i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize);
+
+    if( pagerUseWal(pPager) ){
+      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
+    }
     for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
       assert( offset==ii*(4+pPager->pageSize) );
-      rc = pager_playback_one_page(pPager, 0, 0, &offset, 1, pDone);
+      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
     }
     assert( rc!=SQLITE_DONE );
   }
@@ -33602,6 +36140,7 @@
   if( rc==SQLITE_OK ){
     pPager->journalOff = szJ;
   }
+
   return rc;
 }
 
@@ -33814,10 +36353,14 @@
 ** Regardless of mxPage, return the current maximum page count.
 */
 SQLITE_PRIVATE int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
+  int nPage;
   if( mxPage>0 ){
     pPager->mxPgno = mxPage;
   }
-  sqlite3PagerPagecount(pPager, 0);
+  if( pPager->state!=PAGER_UNLOCK ){
+    sqlite3PagerPagecount(pPager, &nPage);
+    assert( pPager->mxPgno>=nPage );
+  }
   return pPager->mxPgno;
 }
 
@@ -33863,6 +36406,22 @@
   int rc = SQLITE_OK;
   memset(pDest, 0, N);
   assert( isOpen(pPager->fd) || pPager->tempFile );
+
+  /* This routine is only called by btree immediately after creating
+  ** the Pager object.  There has not been an opportunity to transition
+  ** to WAL mode yet.
+  */
+  assert( !pagerUseWal(pPager) );
+#if 0
+  if( pagerUseWal(pPager) ){
+    int isInWal = 0;
+    rc = sqlite3WalRead(pPager->pWal, 1, &isInWal, N, pDest);
+    if( rc!=SQLITE_OK || isInWal ){
+      return rc;
+    }
+  }
+#endif
+
   if( isOpen(pPager->fd) ){
     IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
     rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
@@ -33889,12 +36448,7 @@
 ** and *pnPage is set to the number of pages in the database.
 */
 SQLITE_PRIVATE int sqlite3PagerPagecount(Pager *pPager, int *pnPage){
-  Pgno nPage;               /* Value to return via *pnPage */
-
-  /* If the pager is already in the error state, return the error code. */
-  if( pPager->errCode ){
-    return pPager->errCode;
-  }
+  Pgno nPage = 0;           /* Value to return via *pnPage */
 
   /* Determine the number of pages in the file. Store this in nPage. */
   if( pPager->dbSizeValid ){
@@ -33903,15 +36457,23 @@
     int rc;                 /* Error returned by OsFileSize() */
     i64 n = 0;              /* File size in bytes returned by OsFileSize() */
 
-    assert( isOpen(pPager->fd) || pPager->tempFile );
-    if( isOpen(pPager->fd) && (0 != (rc = sqlite3OsFileSize(pPager->fd, &n))) ){
-      pager_error(pPager, rc);
-      return rc;
+    if( pagerUseWal(pPager) && pPager->state!=PAGER_UNLOCK ){
+      sqlite3WalDbsize(pPager->pWal, &nPage);
     }
-    if( n>0 && n<pPager->pageSize ){
-      nPage = 1;
-    }else{
-      nPage = (Pgno)(n / pPager->pageSize);
+
+    if( nPage==0 ){
+      assert( isOpen(pPager->fd) || pPager->tempFile );
+      if( isOpen(pPager->fd) ){
+        if( SQLITE_OK!=(rc = sqlite3OsFileSize(pPager->fd, &n)) ){
+          pager_error(pPager, rc);
+          return rc;
+        }
+      }
+      if( n>0 && n<pPager->pageSize ){
+        nPage = 1;
+      }else{
+        nPage = (Pgno)(n / pPager->pageSize);
+      }
     }
     if( pPager->state!=PAGER_UNLOCK ){
       pPager->dbSize = nPage;
@@ -33929,9 +36491,7 @@
   }
 
   /* Set the output variable and return SQLITE_OK */
-  if( pnPage ){
-    *pnPage = nPage;
-  }
+  *pnPage = nPage;
   return SQLITE_OK;
 }
 
@@ -34036,6 +36596,32 @@
   assertTruncateConstraint(pPager);
 }
 
+
+/*
+** This function is called before attempting a hot-journal rollback. It
+** syncs the journal file to disk, then sets pPager->journalHdr to the
+** size of the journal file so that the pager_playback() routine knows
+** that the entire journal file has been synced.
+**
+** Syncing a hot-journal to disk before attempting to roll it back ensures 
+** that if a power-failure occurs during the rollback, the process that
+** attempts rollback following system recovery sees the same journal
+** content as this process.
+**
+** If everything goes as planned, SQLITE_OK is returned. Otherwise, 
+** an SQLite error code.
+*/
+static int pagerSyncHotJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !pPager->noSync ){
+    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
+  }
+  return rc;
+}
+
 /*
 ** Shutdown the page cache.  Free all memory and close all files.
 **
@@ -34051,10 +36637,19 @@
 ** to the caller.
 */
 SQLITE_PRIVATE int sqlite3PagerClose(Pager *pPager){
+  u8 *pTmp = (u8 *)pPager->pTmpSpace;
+
   disable_simulated_io_errors();
   sqlite3BeginBenignMalloc();
   pPager->errCode = 0;
   pPager->exclusiveMode = 0;
+#ifndef SQLITE_OMIT_WAL
+  sqlite3WalClose(pPager->pWal,
+    (pPager->noSync ? 0 : pPager->sync_flags), 
+    pPager->pageSize, pTmp
+  );
+  pPager->pWal = 0;
+#endif
   pager_reset(pPager);
   if( MEMDB ){
     pager_unlock(pPager);
@@ -34065,7 +36660,9 @@
     ** be played back into the database. If a power failure occurs while
     ** this is happening, the database may become corrupt.
     */
-    pPager->journalHdr = -1;
+    if( isOpen(pPager->jfd) ){
+      pPager->errCode = pagerSyncHotJournal(pPager);
+    }
     pagerUnlockAndRollback(pPager);
   }
   sqlite3EndBenignMalloc();
@@ -34073,7 +36670,7 @@
   PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
   IOTRACE(("CLOSE %p\n", pPager))
   sqlite3OsClose(pPager->fd);
-  sqlite3PageFree(pPager->pTmpSpace);
+  sqlite3PageFree(pTmp);
   sqlite3PcacheClose(pPager->pPCache);
 
 #ifdef SQLITE_HAS_CODEC
@@ -34155,7 +36752,7 @@
         ** mode, then the journal file may at this point actually be larger
         ** than Pager.journalOff bytes. If the next thing in the journal
         ** file happens to be a journal-header (written as part of the
-        ** previous connections transaction), and a crash or power-failure 
+        ** previous connection's transaction), and a crash or power-failure 
         ** occurs after nRec is updated but before this connection writes 
         ** anything else to the journal file (or commits/rolls back its 
         ** transaction), then SQLite may become confused when doing the 
@@ -34174,10 +36771,10 @@
         */
         i64 iNextHdrOffset;
         u8 aMagic[8];
-	u8 zHeader[sizeof(aJournalMagic)+4];
+        u8 zHeader[sizeof(aJournalMagic)+4];
 
-	memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-	put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
+        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
+        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
 
         iNextHdrOffset = journalHdrOffset(pPager);
         rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
@@ -34209,7 +36806,7 @@
         IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
         rc = sqlite3OsWrite(
             pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
-	);
+        );
         if( rc!=SQLITE_OK ) return rc;
       }
       if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
@@ -34227,6 +36824,7 @@
     */
     pPager->needSync = 0;
     pPager->journalStarted = 1;
+    pPager->journalHdr = pPager->journalOff;
     sqlite3PcacheClearSyncFlags(pPager->pPCache);
   }
 
@@ -34288,6 +36886,7 @@
   ** EXCLUSIVE, it means the database file has been changed and any rollback
   ** will require a journal playback.
   */
+  assert( !pagerUseWal(pList->pPager) );
   assert( pPager->state>=PAGER_RESERVED );
   rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
 
@@ -34300,6 +36899,14 @@
     rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
   }
 
+  /* Before the first write, give the VFS a hint of what the final
+  ** file size will be.
+  */
+  if( pPager->dbSize > (pPager->dbOrigSize+1) && isOpen(pPager->fd) ){
+    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
+    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
+  }
+
   while( rc==SQLITE_OK && pList ){
     Pgno pgno = pList->pgno;
 
@@ -34309,9 +36916,7 @@
     ** any such pages to the file.
     **
     ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
-    ** set (set by sqlite3PagerDontWrite()).  Note that if compiled with
-    ** SQLITE_SECURE_DELETE the PGHDR_DONT_WRITE bit is never set and so
-    ** the second test is always true.
+    ** set (set by sqlite3PagerDontWrite()).
     */
     if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
       i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
@@ -34355,6 +36960,26 @@
 }
 
 /*
+** Ensure that the sub-journal file is open. If it is already open, this 
+** function is a no-op.
+**
+** SQLITE_OK is returned if everything goes according to plan. An 
+** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() 
+** fails.
+*/
+static int openSubJournal(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( !isOpen(pPager->sjfd) ){
+    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
+      sqlite3MemJournalOpen(pPager->sjfd);
+    }else{
+      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
+    }
+  }
+  return rc;
+}
+
+/*
 ** Append a record of the current state of page pPg to the sub-journal. 
 ** It is the callers responsibility to use subjRequiresPage() to check 
 ** that it is really required before calling this function.
@@ -34370,18 +36995,31 @@
 static int subjournalPage(PgHdr *pPg){
   int rc = SQLITE_OK;
   Pager *pPager = pPg->pPager;
-  if( isOpen(pPager->sjfd) ){
-    void *pData = pPg->pData;
-    i64 offset = pPager->nSubRec*(4+pPager->pageSize);
-    char *pData2;
+  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
 
-    CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-    PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
-  
-    assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize );
-    rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+    /* Open the sub-journal, if it has not already been opened */
+    assert( pPager->useJournal );
+    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
+    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
+    assert( pagerUseWal(pPager) 
+         || pageInJournal(pPg) 
+         || pPg->pgno>pPager->dbOrigSize 
+    );
+    rc = openSubJournal(pPager);
+
+    /* If the sub-journal was opened successfully (or was already open),
+    ** write the journal record into the file.  */
     if( rc==SQLITE_OK ){
-      rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      void *pData = pPg->pData;
+      i64 offset = pPager->nSubRec*(4+pPager->pageSize);
+      char *pData2;
+  
+      CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
+      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
+      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
+      }
     }
   }
   if( rc==SQLITE_OK ){
@@ -34392,7 +37030,6 @@
   return rc;
 }
 
-
 /*
 ** This function is called by the pcache layer when it has reached some
 ** soft memory limit. The first argument is a pointer to a Pager object
@@ -34419,74 +37056,84 @@
   assert( pPg->pPager==pPager );
   assert( pPg->flags&PGHDR_DIRTY );
 
-  /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
-  ** is journalling a set of two or more database pages that are stored
-  ** on the same disk sector. Syncing the journal is not allowed while
-  ** this is happening as it is important that all members of such a
-  ** set of pages are synced to disk together. So, if the page this function
-  ** is trying to make clean will require a journal sync and the doNotSync
-  ** flag is set, return without doing anything. The pcache layer will
-  ** just have to go ahead and allocate a new page buffer instead of
-  ** reusing pPg.
-  **
-  ** Similarly, if the pager has already entered the error state, do not
-  ** try to write the contents of pPg to disk.
-  */
-  if( NEVER(pPager->errCode)
-   || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC)
-  ){
-    return SQLITE_OK;
-  }
-
-  /* Sync the journal file if required. */
-  if( pPg->flags&PGHDR_NEED_SYNC ){
-    rc = syncJournal(pPager);
-    if( rc==SQLITE_OK && pPager->fullSync && 
-      !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
-      !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
-    ){
-      pPager->nRec = 0;
-      rc = writeJournalHdr(pPager);
+  pPg->pDirty = 0;
+  if( pagerUseWal(pPager) ){
+    /* Write a single frame for this page to the log. */
+    if( subjRequiresPage(pPg) ){ 
+      rc = subjournalPage(pPg); 
     }
-  }
-
-  /* If the page number of this page is larger than the current size of
-  ** the database image, it may need to be written to the sub-journal.
-  ** This is because the call to pager_write_pagelist() below will not
-  ** actually write data to the file in this case.
-  **
-  ** Consider the following sequence of events:
-  **
-  **   BEGIN;
-  **     <journal page X>
-  **     <modify page X>
-  **     SAVEPOINT sp;
-  **       <shrink database file to Y pages>
-  **       pagerStress(page X)
-  **     ROLLBACK TO sp;
-  **
-  ** If (X>Y), then when pagerStress is called page X will not be written
-  ** out to the database file, but will be dropped from the cache. Then,
-  ** following the "ROLLBACK TO sp" statement, reading page X will read
-  ** data from the database file. This will be the copy of page X as it
-  ** was when the transaction started, not as it was when "SAVEPOINT sp"
-  ** was executed.
-  **
-  ** The solution is to write the current data for page X into the 
-  ** sub-journal file now (if it is not already there), so that it will
-  ** be restored to its current value when the "ROLLBACK TO sp" is 
-  ** executed.
-  */
-  if( NEVER(
-      rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
-  ) ){
-    rc = subjournalPage(pPg);
-  }
-
-  /* Write the contents of the page out to the database file. */
-  if( rc==SQLITE_OK ){
-    pPg->pDirty = 0;
-    rc = pager_write_pagelist(pPg);
+    if( rc==SQLITE_OK ){
+      rc = pagerWalFrames(pPager, pPg, 0, 0, 0);
+    }
+  }else{
+    /* The doNotSync flag is set by the sqlite3PagerWrite() function while it
+    ** is journalling a set of two or more database pages that are stored
+    ** on the same disk sector. Syncing the journal is not allowed while
+    ** this is happening as it is important that all members of such a
+    ** set of pages are synced to disk together. So, if the page this function
+    ** is trying to make clean will require a journal sync and the doNotSync
+    ** flag is set, return without doing anything. The pcache layer will
+    ** just have to go ahead and allocate a new page buffer instead of
+    ** reusing pPg.
+    **
+    ** Similarly, if the pager has already entered the error state, do not
+    ** try to write the contents of pPg to disk.
+    */
+    if( NEVER(pPager->errCode)
+     || (pPager->doNotSync && pPg->flags&PGHDR_NEED_SYNC)
+    ){
+      return SQLITE_OK;
+    }
+  
+    /* Sync the journal file if required. */
+    if( pPg->flags&PGHDR_NEED_SYNC ){
+      rc = syncJournal(pPager);
+      if( rc==SQLITE_OK && pPager->fullSync && 
+        !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) &&
+        !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
+      ){
+        pPager->nRec = 0;
+        rc = writeJournalHdr(pPager);
+      }
+    }
+  
+    /* If the page number of this page is larger than the current size of
+    ** the database image, it may need to be written to the sub-journal.
+    ** This is because the call to pager_write_pagelist() below will not
+    ** actually write data to the file in this case.
+    **
+    ** Consider the following sequence of events:
+    **
+    **   BEGIN;
+    **     <journal page X>
+    **     <modify page X>
+    **     SAVEPOINT sp;
+    **       <shrink database file to Y pages>
+    **       pagerStress(page X)
+    **     ROLLBACK TO sp;
+    **
+    ** If (X>Y), then when pagerStress is called page X will not be written
+    ** out to the database file, but will be dropped from the cache. Then,
+    ** following the "ROLLBACK TO sp" statement, reading page X will read
+    ** data from the database file. This will be the copy of page X as it
+    ** was when the transaction started, not as it was when "SAVEPOINT sp"
+    ** was executed.
+    **
+    ** The solution is to write the current data for page X into the 
+    ** sub-journal file now (if it is not already there), so that it will
+    ** be restored to its current value when the "ROLLBACK TO sp" is 
+    ** executed.
+    */
+    if( NEVER(
+        rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
+    ) ){
+      rc = subjournalPage(pPg);
+    }
+  
+    /* Write the contents of the page out to the database file. */
+    if( rc==SQLITE_OK ){
+      rc = pager_write_pagelist(pPg);
+    }
   }
 
   /* Mark the page as clean. */
@@ -34775,6 +37422,7 @@
   /* pPager->pBusyHandlerArg = 0; */
   pPager->xReiniter = xReinit;
   /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
+
   *ppPager = pPager;
   return SQLITE_OK;
 }
@@ -34894,51 +37542,6 @@
 }
 
 /*
-** Read the content for page pPg out of the database file and into 
-** pPg->pData. A shared lock or greater must be held on the database
-** file before this function is called.
-**
-** If page 1 is read, then the value of Pager.dbFileVers[] is set to
-** the value read from the database file.
-**
-** If an IO error occurs, then the IO error is returned to the caller.
-** Otherwise, SQLITE_OK is returned.
-*/
-static int readDbPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
-  Pgno pgno = pPg->pgno;       /* Page number to read */
-  int rc;                      /* Return code */
-  i64 iOffset;                 /* Byte offset of file to read from */
-
-  assert( pPager->state>=PAGER_SHARED && !MEMDB );
-  assert( isOpen(pPager->fd) );
-
-  if( NEVER(!isOpen(pPager->fd)) ){
-    assert( pPager->tempFile );
-    memset(pPg->pData, 0, pPager->pageSize);
-    return SQLITE_OK;
-  }
-  iOffset = (pgno-1)*(i64)pPager->pageSize;
-  rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
-  if( rc==SQLITE_IOERR_SHORT_READ ){
-    rc = SQLITE_OK;
-  }
-  if( pgno==1 ){
-    u8 *dbFileVers = &((u8*)pPg->pData)[24];
-    memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
-  }
-  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
-
-  PAGER_INCR(sqlite3_pager_readdb_count);
-  PAGER_INCR(pPager->nRead);
-  IOTRACE(("PGIN %p %d\n", pPager, pgno));
-  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
-               PAGERID(pPager), pgno, pager_pagehash(pPg)));
-
-  return rc;
-}
-
-/*
 ** This function is called to obtain a shared lock on the database file.
 ** It is illegal to call sqlite3PagerAcquire() until after this function
 ** has been successfully called. If a shared-lock is already held when
@@ -34991,7 +37594,9 @@
     pager_reset(pPager);
   }
 
-  if( pPager->state==PAGER_UNLOCK || isErrorReset ){
+  if( pagerUseWal(pPager) ){
+    rc = pagerBeginReadTransaction(pPager);
+  }else if( pPager->state==PAGER_UNLOCK || isErrorReset ){
     sqlite3_vfs * const pVfs = pPager->pVfs;
     int isHotJournal = 0;
     assert( !MEMDB );
@@ -35074,19 +37679,28 @@
         goto failed;
       }
 
-      /* TODO: Why are these cleared here? Is it necessary? */
+      /* Reset the journal status fields to indicates that we have no
+      ** rollback journal at this time. */
       pPager->journalStarted = 0;
       pPager->journalOff = 0;
       pPager->setMaster = 0;
       pPager->journalHdr = 0;
  
+      /* Make sure the journal file has been synced to disk. */
+ 
       /* Playback and delete the journal.  Drop the database write
       ** lock and reacquire the read lock. Purge the cache before
       ** playing back the hot-journal so that we don't end up with
-      ** an inconsistent cache.
+      ** an inconsistent cache.  Sync the hot journal before playing
+      ** it back since the process that crashed and left the hot journal
+      ** probably did not sync it and we are required to always sync
+      ** the journal before playing it back.
       */
       if( isOpen(pPager->jfd) ){
-        rc = pager_playback(pPager, 1);
+        rc = pagerSyncHotJournal(pPager);
+        if( rc==SQLITE_OK ){
+          rc = pager_playback(pPager, 1);
+        }
         if( rc!=SQLITE_OK ){
           rc = pager_error(pPager, rc);
           goto failed;
@@ -35104,7 +37718,7 @@
       ** has been modified.  If the database has changed, flush the
       ** cache.
       **
-      ** Database changes is detected by looking at 15 bytes beginning
+      ** Database changes is detected by looking at 16 bytes beginning
       ** at offset 24 into the file.  The first 4 of these 16 bytes are
       ** a 32-bit counter that is incremented with each change.  The
       ** other bytes change randomly with each file change when
@@ -35114,16 +37728,16 @@
       ** detected.  The chance of an undetected change is so small that
       ** it can be neglected.
       */
+      int nPage;
       char dbFileVers[sizeof(pPager->dbFileVers)];
-      sqlite3PagerPagecount(pPager, 0);
+      sqlite3PagerPagecount(pPager, &nPage);
 
       if( pPager->errCode ){
         rc = pPager->errCode;
         goto failed;
       }
 
-      assert( pPager->dbSizeValid );
-      if( pPager->dbSize>0 ){
+      if( nPage>0 ){
         IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
         rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
         if( rc!=SQLITE_OK ){
@@ -35138,6 +37752,11 @@
       }
     }
     assert( pPager->exclusiveMode || pPager->state==PAGER_SHARED );
+
+    /* If there is a WAL file in the file-system, open this database in WAL
+    ** mode. Otherwise, the following function call is a no-op.
+    */
+    rc = pagerOpenWalIfPresent(pPager);
   }
 
  failed:
@@ -35192,7 +37811,7 @@
 **   a) When reading a free-list leaf page from the database, and
 **
 **   b) When a savepoint is being rolled back and we need to load
-**      a new page into the cache to populate with the data read
+**      a new page into the cache to be filled with the data read
 **      from the savepoint journal.
 **
 ** If noContent is true, then the data returned is zeroed instead of
@@ -35248,7 +37867,7 @@
   assert( (*ppPage)->pgno==pgno );
   assert( (*ppPage)->pPager==pPager || (*ppPage)->pPager==0 );
 
-  if( (*ppPage)->pPager ){
+  if( (*ppPage)->pPager && !noContent ){
     /* In this case the pcache already contains an initialized copy of
     ** the page. Return without further ado.  */
     assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
@@ -35278,8 +37897,8 @@
 
     if( MEMDB || nMax<(int)pgno || noContent || !isOpen(pPager->fd) ){
       if( pgno>pPager->mxPgno ){
-	rc = SQLITE_FULL;
-	goto pager_acquire_err;
+        rc = SQLITE_FULL;
+        goto pager_acquire_err;
       }
       if( noContent ){
         /* Failure to set the bits in the InJournal bit-vectors is benign.
@@ -35364,27 +37983,6 @@
 }
 
 /*
-** If the main journal file has already been opened, ensure that the
-** sub-journal file is open too. If the main journal is not open,
-** this function is a no-op.
-**
-** SQLITE_OK is returned if everything goes according to plan. 
-** An SQLITE_IOERR_XXX error code is returned if a call to 
-** sqlite3OsOpen() fails.
-*/
-static int openSubJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ){
-    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
-      sqlite3MemJournalOpen(pPager->sjfd);
-    }else{
-      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
-    }
-  }
-  return rc;
-}
-
-/*
 ** This function is called at the start of every write transaction.
 ** There must already be a RESERVED or EXCLUSIVE lock on the database 
 ** file when this routine is called.
@@ -35408,6 +38006,7 @@
 */
 static int pager_open_journal(Pager *pPager){
   int rc = SQLITE_OK;                        /* Return code */
+  int nPage;                                 /* Size of database file */
   sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
 
   assert( pPager->state>=PAGER_RESERVED );
@@ -35420,13 +38019,10 @@
   ** an error state. */
   if( NEVER(pPager->errCode) ) return pPager->errCode;
 
-  /* TODO: Is it really possible to get here with dbSizeValid==0? If not,
-  ** the call to PagerPagecount() can be removed.
-  */
   testcase( pPager->dbSizeValid==0 );
-  sqlite3PagerPagecount(pPager, 0);
-
-  pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
+  rc = sqlite3PagerPagecount(pPager, &nPage);
+  if( rc ) return rc;
+  pPager->pInJournal = sqlite3BitvecCreate(nPage);
   if( pPager->pInJournal==0 ){
     return SQLITE_NOMEM;
   }
@@ -35468,9 +38064,6 @@
     pPager->journalHdr = 0;
     rc = writeJournalHdr(pPager);
   }
-  if( rc==SQLITE_OK && pPager->nSavepoint ){
-    rc = openSubJournal(pPager);
-  }
 
   if( rc!=SQLITE_OK ){
     sqlite3BitvecDestroy(pPager->pInJournal);
@@ -35508,29 +38101,64 @@
   int rc = SQLITE_OK;
   assert( pPager->state!=PAGER_UNLOCK );
   pPager->subjInMemory = (u8)subjInMemory;
+
   if( pPager->state==PAGER_SHARED ){
     assert( pPager->pInJournal==0 );
     assert( !MEMDB && !pPager->tempFile );
 
-    /* Obtain a RESERVED lock on the database file. If the exFlag parameter
-    ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
-    ** busy-handler callback can be used when upgrading to the EXCLUSIVE
-    ** lock, but not when obtaining the RESERVED lock.
-    */
-    rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
-    if( rc==SQLITE_OK ){
-      pPager->state = PAGER_RESERVED;
-      if( exFlag ){
-        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+    if( pagerUseWal(pPager) ){
+      /* If the pager is configured to use locking_mode=exclusive, and an
+      ** exclusive lock on the database is not already held, obtain it now.
+      */
+      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
+        rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK);
+        pPager->state = PAGER_SHARED;
+        if( rc!=SQLITE_OK ){
+          return rc;
+        }
+        sqlite3WalExclusiveMode(pPager->pWal, 1);
+      }
+
+      /* Grab the write lock on the log file. If successful, upgrade to
+      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
+      ** The busy-handler is not invoked if another connection already
+      ** holds the write-lock. If possible, the upper layer will call it.
+      **
+      ** WAL mode sets Pager.state to PAGER_RESERVED when it has an open
+      ** transaction, but never to PAGER_EXCLUSIVE. This is because in 
+      ** PAGER_EXCLUSIVE state the code to roll back savepoint transactions
+      ** may copy data from the sub-journal into the database file as well
+      ** as into the page cache. Which would be incorrect in WAL mode.
+      */
+      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
+      if( rc==SQLITE_OK ){
+        pPager->dbOrigSize = pPager->dbSize;
+        pPager->state = PAGER_RESERVED;
+        pPager->journalOff = 0;
+      }
+
+      assert( rc!=SQLITE_OK || pPager->state==PAGER_RESERVED );
+      assert( rc==SQLITE_OK || pPager->state==PAGER_SHARED );
+    }else{
+      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
+      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
+      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
+      ** lock, but not when obtaining the RESERVED lock.
+      */
+      rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
+      if( rc==SQLITE_OK ){
+        pPager->state = PAGER_RESERVED;
+        if( exFlag ){
+          rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
+        }
       }
     }
 
-    /* If the required locks were successfully obtained, open the journal
-    ** file and write the first journal-header to it.
+    /* No need to open the journal file at this time.  It will be
+    ** opened before it is written to.  If we defer opening the journal,
+    ** we might save the work of creating a file if the transaction
+    ** ends up being a no-op.
     */
-    if( rc==SQLITE_OK && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-      rc = pager_open_journal(pPager);
-    }
   }else if( isOpen(pPager->jfd) && pPager->journalOff==0 ){
     /* This happens when the pager was in exclusive-access mode the last
     ** time a (read or write) transaction was successfully concluded
@@ -35538,6 +38166,7 @@
     ** kept open and either was truncated to 0 bytes or its header was
     ** overwritten with zeros.
     */
+    assert( pagerUseWal(pPager)==0 );
     assert( pPager->nRec==0 );
     assert( pPager->dbOrigSize==0 );
     assert( pPager->pInJournal==0 );
@@ -35545,7 +38174,6 @@
   }
 
   PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
-  assert( !isOpen(pPager->jfd) || pPager->journalOff>0 || rc!=SQLITE_OK );
   if( rc!=SQLITE_OK ){
     assert( !pPager->dbModified );
     /* Ignore any IO error that occurs within pager_end_transaction(). The
@@ -35575,8 +38203,8 @@
   */
   assert( pPager->state>=PAGER_RESERVED );
 
-  /* If an error has been previously detected, we should not be
-  ** calling this routine.  Repeat the error for robustness.
+  /* If an error has been previously detected, report the same error
+  ** again.
   */
   if( NEVER(pPager->errCode) )  return pPager->errCode;
 
@@ -35593,6 +38221,7 @@
   */
   sqlite3PcacheMakeDirty(pPg);
   if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){
+    assert( !pagerUseWal(pPager) );
     pPager->dbModified = 1;
   }else{
 
@@ -35601,14 +38230,17 @@
     ** or both.
     **
     ** Higher level routines should have already started a transaction,
-    ** which means they have acquired the necessary locks and opened
-    ** a rollback journal.  Double-check to makes sure this is the case.
+    ** which means they have acquired the necessary locks but the rollback
+    ** journal might not yet be open.
     */
     rc = sqlite3PagerBegin(pPager, 0, pPager->subjInMemory);
-    if( NEVER(rc!=SQLITE_OK) ){
+    if( rc!=SQLITE_OK ){
       return rc;
     }
-    if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
+    if( !isOpen(pPager->jfd) 
+     && pPager->journalMode!=PAGER_JOURNALMODE_OFF 
+     && !pagerUseWal(pPager)
+    ){
       assert( pPager->useJournal );
       rc = pager_open_journal(pPager);
       if( rc!=SQLITE_OK ) return rc;
@@ -35620,6 +38252,7 @@
     ** the transaction journal if it is not there already.
     */
     if( !pageInJournal(pPg) && isOpen(pPager->jfd) ){
+      assert( !pagerUseWal(pPager) );
       if( pPg->pgno<=pPager->dbOrigSize ){
         u32 cksum;
         char *pData2;
@@ -35628,6 +38261,8 @@
         ** contains the database locks.  The following assert verifies
         ** that we do not. */
         assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
+
+        assert( pPager->journalHdr <= pPager->journalOff );
         CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
         cksum = pager_cksum(pPager, (u8*)pData2);
         rc = write32bits(pPager->jfd, pPager->journalOff, pPg->pgno);
@@ -35747,7 +38382,8 @@
     */
     pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
 
-    sqlite3PagerPagecount(pPager, (int *)&nPageCount);
+    rc = sqlite3PagerPagecount(pPager, (int *)&nPageCount);
+    if( rc ) return rc;
     if( pPg->pgno>nPageCount ){
       nPage = (pPg->pgno - pg1)+1;
     }else if( (pg1+nPagePerSector-1)>nPageCount ){
@@ -35819,7 +38455,6 @@
 }
 #endif
 
-#ifndef SQLITE_SECURE_DELETE
 /*
 ** A call to this routine tells the pager that it is not necessary to
 ** write the information on page pPg back to the disk, even though
@@ -35845,7 +38480,6 @@
 #endif
   }
 }
-#endif /* !defined(SQLITE_SECURE_DELETE) */
 
 /*
 ** This routine is called to increment the value of the database file 
@@ -35910,6 +38544,12 @@
       change_counter++;
       put32bits(((char*)pPgHdr->pData)+24, change_counter);
 
+      /* Also store the SQLite version number in bytes 96..99 and in
+      ** bytes 92..95 store the change counter for which the version number
+      ** is valid. */
+      put32bits(((char*)pPgHdr->pData)+92, change_counter);
+      put32bits(((char*)pPgHdr->pData)+96, SQLITE_VERSION_NUMBER);
+
       /* If running in direct mode, write the contents of page 1 to the file. */
       if( DIRECT_MODE ){
         const void *zBuf = pPgHdr->pData;
@@ -35983,9 +38623,7 @@
   /* The dbOrigSize is never set if journal_mode=OFF */
   assert( pPager->journalMode!=PAGER_JOURNALMODE_OFF || pPager->dbOrigSize==0 );
 
-  /* If a prior error occurred, this routine should not be called.  ROLLBACK
-  ** is the appropriate response to an error, not COMMIT.  Guard against
-  ** coding errors by repeating the prior error. */
+  /* If a prior error occurred, report that error again. */
   if( NEVER(pPager->errCode) ) return pPager->errCode;
 
   PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
@@ -35998,129 +38636,156 @@
     */
     sqlite3BackupRestart(pPager->pBackup);
   }else if( pPager->state!=PAGER_SYNCED && pPager->dbModified ){
-
-    /* The following block updates the change-counter. Exactly how it
-    ** does this depends on whether or not the atomic-update optimization
-    ** was enabled at compile time, and if this transaction meets the 
-    ** runtime criteria to use the operation: 
-    **
-    **    * The file-system supports the atomic-write property for
-    **      blocks of size page-size, and 
-    **    * This commit is not part of a multi-file transaction, and
-    **    * Exactly one page has been modified and store in the journal file.
-    **
-    ** If the optimization was not enabled at compile time, then the
-    ** pager_incr_changecounter() function is called to update the change
-    ** counter in 'indirect-mode'. If the optimization is compiled in but
-    ** is not applicable to this transaction, call sqlite3JournalCreate()
-    ** to make sure the journal file has actually been created, then call
-    ** pager_incr_changecounter() to update the change-counter in indirect
-    ** mode. 
-    **
-    ** Otherwise, if the optimization is both enabled and applicable,
-    ** then call pager_incr_changecounter() to update the change-counter
-    ** in 'direct' mode. In this case the journal file will never be
-    ** created for this transaction.
-    */
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-    PgHdr *pPg;
-    assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF );
-    if( !zMaster && isOpen(pPager->jfd) 
-     && pPager->journalOff==jrnlBufferSize(pPager) 
-     && pPager->dbSize>=pPager->dbFileSize
-     && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
-    ){
-      /* Update the db file change counter via the direct-write method. The 
-      ** following call will modify the in-memory representation of page 1 
-      ** to include the updated change counter and then write page 1 
-      ** directly to the database file. Because of the atomic-write 
-      ** property of the host file-system, this is safe.
-      */
-      rc = pager_incr_changecounter(pPager, 1);
-    }else{
-      rc = sqlite3JournalCreate(pPager->jfd);
-      if( rc==SQLITE_OK ){
-        rc = pager_incr_changecounter(pPager, 0);
-      }
-    }
-#else
-    rc = pager_incr_changecounter(pPager, 0);
-#endif
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* If this transaction has made the database smaller, then all pages
-    ** being discarded by the truncation must be written to the journal
-    ** file. This can only happen in auto-vacuum mode.
-    **
-    ** Before reading the pages with page numbers larger than the 
-    ** current value of Pager.dbSize, set dbSize back to the value
-    ** that it took at the start of the transaction. Otherwise, the
-    ** calls to sqlite3PagerGet() return zeroed pages instead of 
-    ** reading data from the database file.
-    **
-    ** When journal_mode==OFF the dbOrigSize is always zero, so this
-    ** block never runs if journal_mode=OFF.
-    */
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pPager->dbSize<pPager->dbOrigSize 
-     && ALWAYS(pPager->journalMode!=PAGER_JOURNALMODE_OFF)
-    ){
-      Pgno i;                                   /* Iterator variable */
-      const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
-      const Pgno dbSize = pPager->dbSize;       /* Database image size */ 
-      pPager->dbSize = pPager->dbOrigSize;
-      for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
-        if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
-          PgHdr *pPage;             /* Page to journal */
-          rc = sqlite3PagerGet(pPager, i, &pPage);
-          if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-          rc = sqlite3PagerWrite(pPage);
-          sqlite3PagerUnref(pPage);
-          if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+    if( pagerUseWal(pPager) ){
+      PgHdr *pList;
+      pList = sqlite3PcacheDirtyList(pPager->pPCache);
+      if( pList ){
+        /* If page 1 has been modified (for example to change file-size or
+        ** the number of freelist blocks) then it will be first on the list.
+        ** Only increment the change-counter in WAL mode if page 1 is changing
+        ** anyhow, so as to avoid unnecessarily writing copies of page 1 into
+        ** the WAL.  We do not require the change-counter for change 
+        ** detection in WAL mode since the wal-index will show when the 
+        ** database has changed and a cache flush is needed.  But it does not
+        ** hurt to increment the change-counter either.
+        */
+        if( pList->pgno==1 ){
+          testcase( pPager->changeCountDone );
+          pager_incr_changecounter(pPager, 0);
         }
-      } 
-      pPager->dbSize = dbSize;
-    }
-#endif
 
-    /* Write the master journal name into the journal file. If a master 
-    ** journal file name has already been written to the journal file, 
-    ** or if zMaster is NULL (no master journal), then this call is a no-op.
-    */
-    rc = writeMasterJournal(pPager, zMaster);
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* Sync the journal file. If the atomic-update optimization is being
-    ** used, this call will not create the journal file or perform any
-    ** real IO.
-    */
-    rc = syncJournal(pPager);
-    if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-
-    /* Write all dirty pages to the database file. */
-    rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache));
-    if( rc!=SQLITE_OK ){
-      assert( rc!=SQLITE_IOERR_BLOCKED );
-      goto commit_phase_one_exit;
-    }
-    sqlite3PcacheCleanAll(pPager->pPCache);
-
-    /* If the file on disk is not the same size as the database image,
-    ** then use pager_truncate to grow or shrink the file here.
-    */
-    if( pPager->dbSize!=pPager->dbFileSize ){
-      Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
-      assert( pPager->state>=PAGER_EXCLUSIVE );
-      rc = pager_truncate(pPager, nNew);
+        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1, 
+            (pPager->fullSync ? pPager->sync_flags : 0)
+        );
+      }
+      if( rc==SQLITE_OK ){
+        sqlite3PcacheCleanAll(pPager->pPCache);
+      }
+    }else{
+      /* The following block updates the change-counter. Exactly how it
+      ** does this depends on whether or not the atomic-update optimization
+      ** was enabled at compile time, and if this transaction meets the 
+      ** runtime criteria to use the operation: 
+      **
+      **    * The file-system supports the atomic-write property for
+      **      blocks of size page-size, and 
+      **    * This commit is not part of a multi-file transaction, and
+      **    * Exactly one page has been modified and store in the journal file.
+      **
+      ** If the atomic-update optimization was not enabled at compile time,
+      ** then the pager_incr_changecounter() function is always called to
+      ** update the change counter in 'indirect-mode' since that is the only
+      ** safe way to update the change counter if we do not have atomic-write
+      ** capability.
+      **
+      ** If the atomic-write optimization is available and if the creation
+      ** of a rollback journal file can be avoided by writing page 1 separately
+      ** from the transaction (in other words, if the tranaction only involves
+      ** changing one other page in the database) then try to update the
+      ** change counter using an atomic write.  Otherwise, we have to fall
+      ** back to using a rollback journal.
+      */
+  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
+      PgHdr *pPg;
+      assert( isOpen(pPager->jfd)
+           || pPager->journalMode==PAGER_JOURNALMODE_OFF );
+      if( !zMaster && isOpen(pPager->jfd) 
+       && pPager->journalOff==jrnlBufferSize(pPager) 
+       && pPager->dbSize>=pPager->dbFileSize
+       && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
+      ){
+        /* Update the db file change counter via the direct-write method. The 
+        ** following call will modify the in-memory representation of page 1 
+        ** to include the updated change counter and then write page 1 
+        ** directly to the database file. Because of the atomic-write 
+        ** property of the host file-system, this is safe.
+        */
+        rc = pager_incr_changecounter(pPager, 1);
+      }else{
+        rc = sqlite3JournalCreate(pPager->jfd);
+        if( rc==SQLITE_OK ){
+          rc = pager_incr_changecounter(pPager, 0);
+        }
+      }
+  #else
+      rc = pager_incr_changecounter(pPager, 0);
+  #endif
       if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* If this transaction has made the database smaller, then all pages
+      ** being discarded by the truncation must be written to the journal
+      ** file. This can only happen in auto-vacuum mode.
+      **
+      ** Before reading the pages with page numbers larger than the 
+      ** current value of Pager.dbSize, set dbSize back to the value
+      ** that it took at the start of the transaction. Otherwise, the
+      ** calls to sqlite3PagerGet() return zeroed pages instead of 
+      ** reading data from the database file.
+      **
+      ** When journal_mode==OFF the dbOrigSize is always zero, so this
+      ** block never runs if journal_mode=OFF.
+      */
+  #ifndef SQLITE_OMIT_AUTOVACUUM
+      if( pPager->dbSize<pPager->dbOrigSize 
+       && ALWAYS(pPager->journalMode!=PAGER_JOURNALMODE_OFF)
+      ){
+        Pgno i;                                   /* Iterator variable */
+        const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */
+        const Pgno dbSize = pPager->dbSize;       /* Database image size */ 
+        pPager->dbSize = pPager->dbOrigSize;
+        for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){
+          if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){
+            PgHdr *pPage;             /* Page to journal */
+            rc = sqlite3PagerGet(pPager, i, &pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+            rc = sqlite3PagerWrite(pPage);
+            sqlite3PagerUnref(pPage);
+            if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+          }
+        }
+        pPager->dbSize = dbSize;
+      } 
+  #endif
+  
+      /* Write the master journal name into the journal file. If a master 
+      ** journal file name has already been written to the journal file, 
+      ** or if zMaster is NULL (no master journal), then this call is a no-op.
+      */
+      rc = writeMasterJournal(pPager, zMaster);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* Sync the journal file. If the atomic-update optimization is being
+      ** used, this call will not create the journal file or perform any
+      ** real IO.
+      */
+      rc = syncJournal(pPager);
+      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+  
+      /* Write all dirty pages to the database file. */
+      rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache));
+      if( rc!=SQLITE_OK ){
+        assert( rc!=SQLITE_IOERR_BLOCKED );
+        goto commit_phase_one_exit;
+      }
+      sqlite3PcacheCleanAll(pPager->pPCache);
+  
+      /* If the file on disk is not the same size as the database image,
+      ** then use pager_truncate to grow or shrink the file here.
+      */
+      if( pPager->dbSize!=pPager->dbFileSize ){
+        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
+        assert( pPager->state>=PAGER_EXCLUSIVE );
+        rc = pager_truncate(pPager, nNew);
+        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
+      }
+  
+      /* Finally, sync the database file. */
+      if( !pPager->noSync && !noSync ){
+        rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
+      }
+      IOTRACE(("DBSYNC %p\n", pPager))
     }
 
-    /* Finally, sync the database file. */
-    if( !pPager->noSync && !noSync ){
-      rc = sqlite3OsSync(pPager->fd, pPager->sync_flags);
-    }
-    IOTRACE(("DBSYNC %p\n", pPager))
-
     pPager->state = PAGER_SYNCED;
   }
 
@@ -36228,7 +38893,14 @@
 SQLITE_PRIVATE int sqlite3PagerRollback(Pager *pPager){
   int rc = SQLITE_OK;                  /* Return code */
   PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
-  if( !pPager->dbModified || !isOpen(pPager->jfd) ){
+  if( pagerUseWal(pPager) ){
+    int rc2;
+
+    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
+    rc2 = pager_end_transaction(pPager, pPager->setMaster);
+    if( rc==SQLITE_OK ) rc = rc2;
+    rc = pager_error(pPager, rc);
+  }else if( !pPager->dbModified || !isOpen(pPager->jfd) ){
     rc = pager_end_transaction(pPager, pPager->setMaster);
   }else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){
     if( pPager->state>=PAGER_EXCLUSIVE ){
@@ -36276,6 +38948,16 @@
 }
 
 /*
+** Return the approximate number of bytes of memory currently
+** used by the pager and its associated cache.
+*/
+SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager *pPager){
+  int perPageSize = pPager->pageSize + pPager->nExtra + 20;
+  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+           + sqlite3MallocSize(pPager);
+}
+
+/*
 ** Return the number of references to the specified page.
 */
 SQLITE_PRIVATE int sqlite3PagerPageRefcount(DbPage *pPage){
@@ -36327,11 +39009,10 @@
   if( nSavepoint>nCurrent && pPager->useJournal ){
     int ii;                                 /* Iterator variable */
     PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */
+    int nPage;                              /* Size of database file */
 
-    /* Either there is no active journal or the sub-journal is open or 
-    ** the journal is always stored in memory */
-    assert( pPager->nSavepoint==0 || isOpen(pPager->sjfd) ||
-            pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
+    rc = sqlite3PagerPagecount(pPager, &nPage);
+    if( rc ) return rc;
 
     /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
     ** if the allocation fails. Otherwise, zero the new portion in case a 
@@ -36345,26 +39026,26 @@
     }
     memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
     pPager->aSavepoint = aNew;
-    pPager->nSavepoint = nSavepoint;
 
     /* Populate the PagerSavepoint structures just allocated. */
     for(ii=nCurrent; ii<nSavepoint; ii++){
-      assert( pPager->dbSizeValid );
-      aNew[ii].nOrig = pPager->dbSize;
-      if( isOpen(pPager->jfd) && ALWAYS(pPager->journalOff>0) ){
+      aNew[ii].nOrig = nPage;
+      if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
         aNew[ii].iOffset = pPager->journalOff;
       }else{
         aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
       }
       aNew[ii].iSubRec = pPager->nSubRec;
-      aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+      aNew[ii].pInSavepoint = sqlite3BitvecCreate(nPage);
       if( !aNew[ii].pInSavepoint ){
         return SQLITE_NOMEM;
       }
+      if( pagerUseWal(pPager) ){
+        sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
+      }
+      pPager->nSavepoint = ii+1;
     }
-
-    /* Open the sub-journal, if it is not already opened. */
-    rc = openSubJournal(pPager);
+    assert( pPager->nSavepoint==nSavepoint );
     assertTruncateConstraint(pPager);
   }
 
@@ -36428,6 +39109,7 @@
         /* Only truncate if it is an in-memory sub-journal. */
         if( sqlite3IsMemJournal(pPager->sjfd) ){
           rc = sqlite3OsTruncate(pPager->sjfd, 0);
+          assert( rc==SQLITE_OK );
         }
         pPager->nSubRec = 0;
       }
@@ -36437,7 +39119,7 @@
     ** not yet been opened. In this case there have been no changes to
     ** the database file, so the playback operation can be skipped.
     */
-    else if( isOpen(pPager->jfd) ){
+    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
       PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
       rc = pagerPlaybackSavepoint(pPager, pSavepoint);
       assert(rc!=SQLITE_DONE);
@@ -36706,49 +39388,132 @@
 }
 
 /*
-** Get/set the journal-mode for this pager. Parameter eMode must be one of:
+** Set the journal-mode for this pager. Parameter eMode must be one of:
 **
-**    PAGER_JOURNALMODE_QUERY
 **    PAGER_JOURNALMODE_DELETE
 **    PAGER_JOURNALMODE_TRUNCATE
 **    PAGER_JOURNALMODE_PERSIST
 **    PAGER_JOURNALMODE_OFF
 **    PAGER_JOURNALMODE_MEMORY
+**    PAGER_JOURNALMODE_WAL
 **
-** If the parameter is not _QUERY, then the journal_mode is set to the
-** value specified if the change is allowed.  The change is disallowed
-** for the following reasons:
+** The journalmode is set to the value specified if the change is allowed.
+** The change may be disallowed for the following reasons:
 **
 **   *  An in-memory database can only have its journal_mode set to _OFF
 **      or _MEMORY.
 **
-**   *  The journal mode may not be changed while a transaction is active.
+**   *  Temporary databases cannot have _WAL journalmode.
 **
 ** The returned indicate the current (possibly updated) journal-mode.
 */
-SQLITE_PRIVATE int sqlite3PagerJournalMode(Pager *pPager, int eMode){
-  assert( eMode==PAGER_JOURNALMODE_QUERY
-            || eMode==PAGER_JOURNALMODE_DELETE
+SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
+  u8 eOld = pPager->journalMode;    /* Prior journalmode */
+
+  /* The eMode parameter is always valid */
+  assert(      eMode==PAGER_JOURNALMODE_DELETE
             || eMode==PAGER_JOURNALMODE_TRUNCATE
             || eMode==PAGER_JOURNALMODE_PERSIST
             || eMode==PAGER_JOURNALMODE_OFF 
+            || eMode==PAGER_JOURNALMODE_WAL 
             || eMode==PAGER_JOURNALMODE_MEMORY );
-  assert( PAGER_JOURNALMODE_QUERY<0 );
-  if( eMode>=0
-   && (!MEMDB || eMode==PAGER_JOURNALMODE_MEMORY 
-              || eMode==PAGER_JOURNALMODE_OFF)
-   && !pPager->dbModified
-   && (!isOpen(pPager->jfd) || 0==pPager->journalOff)
-  ){
-    if( isOpen(pPager->jfd) ){
+
+  /* Do not allow the journalmode of a TEMP database to be changed to WAL
+  */
+  if( pPager->tempFile && eMode==PAGER_JOURNALMODE_WAL ){
+    assert( eOld!=PAGER_JOURNALMODE_WAL );
+    eMode = eOld;
+  }
+
+  /* Do allow the journalmode of an in-memory database to be set to
+  ** anything other than MEMORY or OFF
+  */
+  if( MEMDB ){
+    assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
+    if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
+      eMode = eOld;
+    }
+  }
+
+  if( eMode!=eOld ){
+    /* When changing between rollback modes, close the journal file prior
+    ** to the change.  But when changing from a rollback mode to WAL, keep
+    ** the journal open since there is a rollback-style transaction in play
+    ** used to convert the version numbers in the btree header.
+    */
+    if( isOpen(pPager->jfd) && eMode!=PAGER_JOURNALMODE_WAL ){
       sqlite3OsClose(pPager->jfd);
     }
+
+    /* Change the journal mode. */
     pPager->journalMode = (u8)eMode;
+
+    /* When transistioning from TRUNCATE or PERSIST to any other journal
+    ** mode except WAL (and we are not in locking_mode=EXCLUSIVE) then 
+    ** delete the journal file.
+    */
+    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
+    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
+    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
+    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
+    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
+    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
+
+    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
+    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
+
+      /* In this case we would like to delete the journal file. If it is
+      ** not possible, then that is not a problem. Deleting the journal file
+      ** here is an optimization only.
+      **
+      ** Before deleting the journal file, obtain a RESERVED lock on the
+      ** database file. This ensures that the journal file is not deleted
+      ** while it is in use by some other client.
+      */
+      int rc = SQLITE_OK;
+      int state = pPager->state;
+      if( state<PAGER_SHARED ){
+        rc = sqlite3PagerSharedLock(pPager);
+      }
+      if( pPager->state==PAGER_SHARED ){
+        assert( rc==SQLITE_OK );
+        rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK);
+      }
+      if( rc==SQLITE_OK ){
+        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
+      }
+      if( rc==SQLITE_OK && state==PAGER_SHARED ){
+        sqlite3OsUnlock(pPager->fd, SHARED_LOCK);
+      }else if( state==PAGER_UNLOCK ){
+        pager_unlock(pPager);
+      }
+      assert( state==pPager->state );
+    }
   }
+
+  /* Return the new journal mode */
   return (int)pPager->journalMode;
 }
 
 /*
+** Return the current journal mode.
+*/
+SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager *pPager){
+  return (int)pPager->journalMode;
+}
+
+/*
+** Return TRUE if the pager is in a state where it is OK to change the
+** journalmode.  Journalmode changes can only happen when the database
+** is unmodified.
+*/
+SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
+  if( pPager->dbModified ) return 0;
+  if( isOpen(pPager->jfd) && pPager->journalOff>0 ) return 0;
+  return 1;
+}
+
+/*
 ** Get/set the size-limit used for persistent journal files.
 **
 ** Setting the size limit to -1 means no limit is enforced.
@@ -36771,9 +39536,2616 @@
   return &pPager->pBackup;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/*
+** This function is called when the user invokes "PRAGMA checkpoint".
+*/
+SQLITE_PRIVATE int sqlite3PagerCheckpoint(Pager *pPager){
+  int rc = SQLITE_OK;
+  if( pPager->pWal ){
+    u8 *zBuf = (u8 *)pPager->pTmpSpace;
+    rc = sqlite3WalCheckpoint(pPager->pWal,
+        (pPager->noSync ? 0 : pPager->sync_flags),
+        pPager->pageSize, zBuf
+    );
+  }
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3PagerWalCallback(Pager *pPager){
+  return sqlite3WalCallback(pPager->pWal);
+}
+
+/*
+** Return true if the underlying VFS for the given pager supports the
+** primitives necessary for write-ahead logging.
+*/
+SQLITE_PRIVATE int sqlite3PagerWalSupported(Pager *pPager){
+  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
+  return pMethods->iVersion>=2 && pMethods->xShmOpen!=0;
+}
+
+/*
+** Open a connection to the write-ahead log file for pager pPager. If
+** the log connection is already open, this function is a no-op.
+**
+** The caller must be holding a SHARED lock on the database file to call
+** this function.
+*/
+SQLITE_PRIVATE int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen){
+  int rc = SQLITE_OK;             /* Return code */
+
+  assert( pPager->state>=PAGER_SHARED );
+  if( !pPager->pWal ){
+    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
+
+    /* Open the connection to the log file. If this operation fails, 
+    ** (e.g. due to malloc() failure), unlock the database file and 
+    ** return an error code.
+    */
+    rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,
+                        pPager->zFilename, &pPager->pWal);
+    if( rc==SQLITE_OK ){
+      pPager->journalMode = PAGER_JOURNALMODE_WAL;
+    }
+  }else{
+    *pisOpen = 1;
+  }
+
+  return rc;
+}
+
+/*
+** This function is called to close the connection to the log file prior
+** to switching from WAL to rollback mode.
+**
+** Before closing the log file, this function attempts to take an 
+** EXCLUSIVE lock on the database file. If this cannot be obtained, an
+** error (SQLITE_BUSY) is returned and the log connection is not closed.
+** If successful, the EXCLUSIVE lock is not released before returning.
+*/
+SQLITE_PRIVATE int sqlite3PagerCloseWal(Pager *pPager){
+  int rc = SQLITE_OK;
+
+  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
+
+  /* If the log file is not already open, but does exist in the file-system,
+  ** it may need to be checkpointed before the connection can switch to
+  ** rollback mode. Open it now so this can happen.
+  */
+  if( !pPager->pWal ){
+    int logexists = 0;
+    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_SHARED);
+    if( rc==SQLITE_OK ){
+      rc = pagerHasWAL(pPager, &logexists);
+    }
+    if( rc==SQLITE_OK && logexists ){
+      rc = sqlite3WalOpen(pPager->pVfs, pPager->fd,
+                          pPager->zFilename, &pPager->pWal);
+    }
+  }
+    
+  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
+  ** the database file, the log and log-summary files will be deleted.
+  */
+  if( rc==SQLITE_OK && pPager->pWal ){
+    rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_EXCLUSIVE);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3WalClose(pPager->pWal,
+                           (pPager->noSync ? 0 : pPager->sync_flags), 
+        pPager->pageSize, (u8*)pPager->pTmpSpace
+      );
+      pPager->pWal = 0;
+    }else{
+      /* If we cannot get an EXCLUSIVE lock, downgrade the PENDING lock
+      ** that we did get back to SHARED. */
+      sqlite3OsUnlock(pPager->fd, SQLITE_LOCK_SHARED);
+    }
+  }
+  return rc;
+}
+#endif
+
 #endif /* SQLITE_OMIT_DISKIO */
 
 /************** End of pager.c ***********************************************/
+/************** Begin file wal.c *********************************************/
+/*
+** 2010 February 1
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the implementation of a write-ahead log (WAL) used in 
+** "journal_mode=WAL" mode.
+**
+** WRITE-AHEAD LOG (WAL) FILE FORMAT
+**
+** A WAL file consists of a header followed by zero or more "frames".
+** Each frame records the revised content of a single page from the
+** database file.  All changes to the database are recorded by writing
+** frames into the WAL.  Transactions commit when a frame is written that
+** contains a commit marker.  A single WAL can and usually does record 
+** multiple transactions.  Periodically, the content of the WAL is
+** transferred back into the database file in an operation called a
+** "checkpoint".
+**
+** A single WAL file can be used multiple times.  In other words, the
+** WAL can fill up with frames and then be checkpointed and then new
+** frames can overwrite the old ones.  A WAL always grows from beginning
+** toward the end.  Checksums and counters attached to each frame are
+** used to determine which frames within the WAL are valid and which
+** are leftovers from prior checkpoints.
+**
+** The WAL header is 24 bytes in size and consists of the following six
+** big-endian 32-bit unsigned integer values:
+**
+**     0: Magic number.  0x377f0682 or 0x377f0683
+**     4: File format version.  Currently 3007000
+**     8: Database page size.  Example: 1024
+**    12: Checkpoint sequence number
+**    16: Salt-1, random integer incremented with each checkpoint
+**    20: Salt-2, a different random integer changing with each ckpt
+**
+** Immediately following the wal-header are zero or more frames. Each
+** frame consists of a 24-byte frame-header followed by a <page-size> bytes
+** of page data. The frame-header is broken into 6 big-endian 32-bit unsigned 
+** integer values, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the header)
+**    12: Salt-2 (copied from the header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+**
+** A frame is considered valid if and only if the following conditions are
+** true:
+**
+**    (1) The salt-1 and salt-2 values in the frame-header match
+**        salt values in the wal-header
+**
+**    (2) The checksum values in the final 8 bytes of the frame-header
+**        exactly match the checksum computed consecutively on the
+**        WAL header and the first 8 bytes and the content of all frames
+**        up to and including the current frame.
+**
+** The checksum is computed using 32-bit big-endian integers if the
+** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
+** is computed using little-endian if the magic number is 0x377f0682.
+** The checksum values are always stored in the frame header in a
+** big-endian format regardless of which byte order is used to compute
+** the checksum.  The checksum is computed by interpreting the input as
+** an even number of unsigned 32-bit integers: x[0] through x[N].  The
+** algorithm used for the checksum is as follows:
+** 
+**   for i from 0 to n-1 step 2:
+**     s0 += x[i] + s1;
+**     s1 += x[i+1] + s0;
+**   endfor
+**
+** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
+** WAL is transferred into the database, then the database is VFS.xSync-ed.
+** The VFS.xSync operations serve as write barriers - all writes launched
+** before the xSync must complete before any write that launches after the
+** xSync begins.
+**
+** After each checkpoint, the salt-1 value is incremented and the salt-2
+** value is randomized.  This prevents old and new frames in the WAL from
+** being considered valid at the same time and being checkpointing together
+** following a crash.
+**
+** READER ALGORITHM
+**
+** To read a page from the database (call it page number P), a reader
+** first checks the WAL to see if it contains page P.  If so, then the
+** last valid instance of page P that is a followed by a commit frame
+** or is a commit frame itself becomes the value read.  If the WAL
+** contains no copies of page P that are valid and which are a commit
+** frame or are followed by a commit frame, then page P is read from
+** the database file.
+**
+** To start a read transaction, the reader records the index of the last
+** valid frame in the WAL.  The reader uses this recorded "mxFrame" value
+** for all subsequent read operations.  New transactions can be appended
+** to the WAL, but as long as the reader uses its original mxFrame value
+** and ignores the newly appended content, it will see a consistent snapshot
+** of the database from a single point in time.  This technique allows
+** multiple concurrent readers to view different versions of the database
+** content simultaneously.
+**
+** The reader algorithm in the previous paragraphs works correctly, but 
+** because frames for page P can appear anywhere within the WAL, the
+** reader has to scan the entire WAL looking for page P frames.  If the
+** WAL is large (multiple megabytes is typical) that scan can be slow,
+** and read performance suffers.  To overcome this problem, a separate
+** data structure called the wal-index is maintained to expedite the
+** search for frames of a particular page.
+** 
+** WAL-INDEX FORMAT
+**
+** Conceptually, the wal-index is shared memory, though VFS implementations
+** might choose to implement the wal-index using a mmapped file.  Because
+** the wal-index is shared memory, SQLite does not support journal_mode=WAL 
+** on a network filesystem.  All users of the database must be able to
+** share memory.
+**
+** The wal-index is transient.  After a crash, the wal-index can (and should
+** be) reconstructed from the original WAL file.  In fact, the VFS is required
+** to either truncate or zero the header of the wal-index when the last
+** connection to it closes.  Because the wal-index is transient, it can
+** use an architecture-specific format; it does not have to be cross-platform.
+** Hence, unlike the database and WAL file formats which store all values
+** as big endian, the wal-index can store multi-byte values in the native
+** byte order of the host computer.
+**
+** The purpose of the wal-index is to answer this question quickly:  Given
+** a page number P, return the index of the last frame for page P in the WAL,
+** or return NULL if there are no frames for page P in the WAL.
+**
+** The wal-index consists of a header region, followed by an one or
+** more index blocks.  
+**
+** The wal-index header contains the total number of frames within the WAL
+** in the the mxFrame field.  
+**
+** Each index block except for the first contains information on 
+** HASHTABLE_NPAGE frames. The first index block contains information on
+** HASHTABLE_NPAGE_ONE frames. The values of HASHTABLE_NPAGE_ONE and 
+** HASHTABLE_NPAGE are selected so that together the wal-index header and
+** first index block are the same size as all other index blocks in the
+** wal-index.
+**
+** Each index block contains two sections, a page-mapping that contains the
+** database page number associated with each wal frame, and a hash-table 
+** that allows readers to query an index block for a specific page number.
+** The page-mapping is an array of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE
+** for the first index block) 32-bit page numbers. The first entry in the 
+** first index-block contains the database page number corresponding to the
+** first frame in the WAL file. The first entry in the second index block
+** in the WAL file corresponds to the (HASHTABLE_NPAGE_ONE+1)th frame in
+** the log, and so on.
+**
+** The last index block in a wal-index usually contains less than the full
+** complement of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE) page-numbers,
+** depending on the contents of the WAL file. This does not change the
+** allocated size of the page-mapping array - the page-mapping array merely
+** contains unused entries.
+**
+** Even without using the hash table, the last frame for page P
+** can be found by scanning the page-mapping sections of each index block
+** starting with the last index block and moving toward the first, and
+** within each index block, starting at the end and moving toward the
+** beginning.  The first entry that equals P corresponds to the frame
+** holding the content for that page.
+**
+** The hash table consists of HASHTABLE_NSLOT 16-bit unsigned integers.
+** HASHTABLE_NSLOT = 2*HASHTABLE_NPAGE, and there is one entry in the
+** hash table for each page number in the mapping section, so the hash 
+** table is never more than half full.  The expected number of collisions 
+** prior to finding a match is 1.  Each entry of the hash table is an
+** 1-based index of an entry in the mapping section of the same
+** index block.   Let K be the 1-based index of the largest entry in
+** the mapping section.  (For index blocks other than the last, K will
+** always be exactly HASHTABLE_NPAGE (4096) and for the last index block
+** K will be (mxFrame%HASHTABLE_NPAGE).)  Unused slots of the hash table
+** contain a value of 0.
+**
+** To look for page P in the hash table, first compute a hash iKey on
+** P as follows:
+**
+**      iKey = (P * 383) % HASHTABLE_NSLOT
+**
+** Then start scanning entries of the hash table, starting with iKey
+** (wrapping around to the beginning when the end of the hash table is
+** reached) until an unused hash slot is found. Let the first unused slot
+** be at index iUnused.  (iUnused might be less than iKey if there was
+** wrap-around.) Because the hash table is never more than half full,
+** the search is guaranteed to eventually hit an unused entry.  Let 
+** iMax be the value between iKey and iUnused, closest to iUnused,
+** where aHash[iMax]==P.  If there is no iMax entry (if there exists
+** no hash slot such that aHash[i]==p) then page P is not in the
+** current index block.  Otherwise the iMax-th mapping entry of the
+** current index block corresponds to the last entry that references 
+** page P.
+**
+** A hash search begins with the last index block and moves toward the
+** first index block, looking for entries corresponding to page P.  On
+** average, only two or three slots in each index block need to be
+** examined in order to either find the last entry for page P, or to
+** establish that no such entry exists in the block.  Each index block
+** holds over 4000 entries.  So two or three index blocks are sufficient
+** to cover a typical 10 megabyte WAL file, assuming 1K pages.  8 or 10
+** comparisons (on average) suffice to either locate a frame in the
+** WAL or to establish that the frame does not exist in the WAL.  This
+** is much faster than scanning the entire 10MB WAL.
+**
+** Note that entries are added in order of increasing K.  Hence, one
+** reader might be using some value K0 and a second reader that started
+** at a later time (after additional transactions were added to the WAL
+** and to the wal-index) might be using a different value K1, where K1>K0.
+** Both readers can use the same hash table and mapping section to get
+** the correct result.  There may be entries in the hash table with
+** K>K0 but to the first reader, those entries will appear to be unused
+** slots in the hash table and so the first reader will get an answer as
+** if no values greater than K0 had ever been inserted into the hash table
+** in the first place - which is what reader one wants.  Meanwhile, the
+** second reader using K1 will see additional values that were inserted
+** later, which is exactly what reader two wants.  
+**
+** When a rollback occurs, the value of K is decreased. Hash table entries
+** that correspond to frames greater than the new K value are removed
+** from the hash table at this point.
+*/
+#ifndef SQLITE_OMIT_WAL
+
+
+/*
+** Trace output macros
+*/
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+SQLITE_PRIVATE int sqlite3WalTrace = 0;
+# define WALTRACE(X)  if(sqlite3WalTrace) sqlite3DebugPrintf X
+#else
+# define WALTRACE(X)
+#endif
+
+
+/*
+** Indices of various locking bytes.   WAL_NREADER is the number
+** of available reader locks and should be at least 3.
+*/
+#define WAL_WRITE_LOCK         0
+#define WAL_ALL_BUT_WRITE      1
+#define WAL_CKPT_LOCK          1
+#define WAL_RECOVER_LOCK       2
+#define WAL_READ_LOCK(I)       (3+(I))
+#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)
+
+
+/* Object declarations */
+typedef struct WalIndexHdr WalIndexHdr;
+typedef struct WalIterator WalIterator;
+typedef struct WalCkptInfo WalCkptInfo;
+
+
+/*
+** The following object holds a copy of the wal-index header content.
+**
+** The actual header in the wal-index consists of two copies of this
+** object.
+*/
+struct WalIndexHdr {
+  u32 iChange;                    /* Counter incremented each transaction */
+  u8 isInit;                      /* 1 when initialized */
+  u8 bigEndCksum;                 /* True if checksums in WAL are big-endian */
+  u16 szPage;                     /* Database page size in bytes */
+  u32 mxFrame;                    /* Index of last valid frame in the WAL */
+  u32 nPage;                      /* Size of database in pages */
+  u32 aFrameCksum[2];             /* Checksum of last frame in log */
+  u32 aSalt[2];                   /* Two salt values copied from WAL header */
+  u32 aCksum[2];                  /* Checksum over all prior fields */
+};
+
+/*
+** A copy of the following object occurs in the wal-index immediately
+** following the second copy of the WalIndexHdr.  This object stores
+** information used by checkpoint.
+**
+** nBackfill is the number of frames in the WAL that have been written
+** back into the database. (We call the act of moving content from WAL to
+** database "backfilling".)  The nBackfill number is never greater than
+** WalIndexHdr.mxFrame.  nBackfill can only be increased by threads
+** holding the WAL_CKPT_LOCK lock (which includes a recovery thread).
+** However, a WAL_WRITE_LOCK thread can move the value of nBackfill from
+** mxFrame back to zero when the WAL is reset.
+**
+** There is one entry in aReadMark[] for each reader lock.  If a reader
+** holds read-lock K, then the value in aReadMark[K] is no greater than
+** the mxFrame for that reader.  The value READMARK_NOT_USED (0xffffffff)
+** for any aReadMark[] means that entry is unused.  aReadMark[0] is 
+** a special case; its value is never used and it exists as a place-holder
+** to avoid having to offset aReadMark[] indexs by one.  Readers holding
+** WAL_READ_LOCK(0) always ignore the entire WAL and read all content
+** directly from the database.
+**
+** The value of aReadMark[K] may only be changed by a thread that
+** is holding an exclusive lock on WAL_READ_LOCK(K).  Thus, the value of
+** aReadMark[K] cannot changed while there is a reader is using that mark
+** since the reader will be holding a shared lock on WAL_READ_LOCK(K).
+**
+** The checkpointer may only transfer frames from WAL to database where
+** the frame numbers are less than or equal to every aReadMark[] that is
+** in use (that is, every aReadMark[j] for which there is a corresponding
+** WAL_READ_LOCK(j)).  New readers (usually) pick the aReadMark[] with the
+** largest value and will increase an unused aReadMark[] to mxFrame if there
+** is not already an aReadMark[] equal to mxFrame.  The exception to the
+** previous sentence is when nBackfill equals mxFrame (meaning that everything
+** in the WAL has been backfilled into the database) then new readers
+** will choose aReadMark[0] which has value 0 and hence such reader will
+** get all their all content directly from the database file and ignore 
+** the WAL.
+**
+** Writers normally append new frames to the end of the WAL.  However,
+** if nBackfill equals mxFrame (meaning that all WAL content has been
+** written back into the database) and if no readers are using the WAL
+** (in other words, if there are no WAL_READ_LOCK(i) where i>0) then
+** the writer will first "reset" the WAL back to the beginning and start
+** writing new content beginning at frame 1.
+**
+** We assume that 32-bit loads are atomic and so no locks are needed in
+** order to read from any aReadMark[] entries.
+*/
+struct WalCkptInfo {
+  u32 nBackfill;                  /* Number of WAL frames backfilled into DB */
+  u32 aReadMark[WAL_NREADER];     /* Reader marks */
+};
+#define READMARK_NOT_USED  0xffffffff
+
+
+/* A block of WALINDEX_LOCK_RESERVED bytes beginning at
+** WALINDEX_LOCK_OFFSET is reserved for locks. Since some systems
+** only support mandatory file-locks, we do not read or write data
+** from the region of the file on which locks are applied.
+*/
+#define WALINDEX_LOCK_OFFSET   (sizeof(WalIndexHdr)*2 + sizeof(WalCkptInfo))
+#define WALINDEX_LOCK_RESERVED 16
+#define WALINDEX_HDR_SIZE      (WALINDEX_LOCK_OFFSET+WALINDEX_LOCK_RESERVED)
+
+/* Size of header before each frame in wal */
+#define WAL_FRAME_HDRSIZE 24
+
+/* Size of write ahead log header */
+#define WAL_HDRSIZE 24
+
+/* WAL magic value. Either this value, or the same value with the least
+** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
+** big-endian format in the first 4 bytes of a WAL file.
+**
+** If the LSB is set, then the checksums for each frame within the WAL
+** file are calculated by treating all data as an array of 32-bit 
+** big-endian words. Otherwise, they are calculated by interpreting 
+** all data as 32-bit little-endian words.
+*/
+#define WAL_MAGIC 0x377f0682
+
+/*
+** Return the offset of frame iFrame in the write-ahead log file, 
+** assuming a database page size of szPage bytes. The offset returned
+** is to the start of the write-ahead log frame-header.
+*/
+#define walFrameOffset(iFrame, szPage) (                               \
+  WAL_HDRSIZE + ((iFrame)-1)*((szPage)+WAL_FRAME_HDRSIZE)        \
+)
+
+/*
+** An open write-ahead log file is represented by an instance of the
+** following object.
+*/
+struct Wal {
+  sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
+  sqlite3_file *pDbFd;       /* File handle for the database file */
+  sqlite3_file *pWalFd;      /* File handle for WAL file */
+  u32 iCallback;             /* Value to pass to log callback (or 0) */
+  int nWiData;               /* Size of array apWiData */
+  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
+  u16 szPage;                /* Database page size */
+  i16 readLock;              /* Which read lock is being held.  -1 for none */
+  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
+  u8 isWIndexOpen;           /* True if ShmOpen() called on pDbFd */
+  u8 writeLock;              /* True if in a write transaction */
+  u8 ckptLock;               /* True if holding a checkpoint lock */
+  WalIndexHdr hdr;           /* Wal-index header for current transaction */
+  char *zWalName;            /* Name of WAL file */
+  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
+#ifdef SQLITE_DEBUG
+  u8 lockError;              /* True if a locking error has occurred */
+#endif
+};
+
+/*
+** Each page of the wal-index mapping contains a hash-table made up of
+** an array of HASHTABLE_NSLOT elements of the following type.
+*/
+typedef u16 ht_slot;
+
+/*
+** This structure is used to implement an iterator that loops through
+** all frames in the WAL in database page order. Where two or more frames
+** correspond to the same database page, the iterator visits only the 
+** frame most recently written to the WAL (in other words, the frame with
+** the largest index).
+**
+** The internals of this structure are only accessed by:
+**
+**   walIteratorInit() - Create a new iterator,
+**   walIteratorNext() - Step an iterator,
+**   walIteratorFree() - Free an iterator.
+**
+** This functionality is used by the checkpoint code (see walCheckpoint()).
+*/
+struct WalIterator {
+  int iPrior;                     /* Last result returned from the iterator */
+  int nSegment;                   /* Size of the aSegment[] array */
+  struct WalSegment {
+    int iNext;                    /* Next slot in aIndex[] not yet returned */
+    ht_slot *aIndex;              /* i0, i1, i2... such that aPgno[iN] ascend */
+    u32 *aPgno;                   /* Array of page numbers. */
+    int nEntry;                   /* Max size of aPgno[] and aIndex[] arrays */
+    int iZero;                    /* Frame number associated with aPgno[0] */
+  } aSegment[1];                  /* One for every 32KB page in the WAL */
+};
+
+/*
+** Define the parameters of the hash tables in the wal-index file. There
+** is a hash-table following every HASHTABLE_NPAGE page numbers in the
+** wal-index.
+**
+** Changing any of these constants will alter the wal-index format and
+** create incompatibilities.
+*/
+#define HASHTABLE_NPAGE      4096                 /* Must be power of 2 */
+#define HASHTABLE_HASH_1     383                  /* Should be prime */
+#define HASHTABLE_NSLOT      (HASHTABLE_NPAGE*2)  /* Must be a power of 2 */
+
+/* 
+** The block of page numbers associated with the first hash-table in a
+** wal-index is smaller than usual. This is so that there is a complete
+** hash-table on each aligned 32KB page of the wal-index.
+*/
+#define HASHTABLE_NPAGE_ONE  (HASHTABLE_NPAGE - (WALINDEX_HDR_SIZE/sizeof(u32)))
+
+/* The wal-index is divided into pages of WALINDEX_PGSZ bytes each. */
+#define WALINDEX_PGSZ   (                                         \
+    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
+)
+
+/*
+** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
+** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
+** numbered from zero.
+**
+** If this call is successful, *ppPage is set to point to the wal-index
+** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
+** then an SQLite error code is returned and *ppPage is set to 0.
+*/
+static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
+  int rc = SQLITE_OK;
+
+  /* Enlarge the pWal->apWiData[] array if required */
+  if( pWal->nWiData<=iPage ){
+    int nByte = sizeof(u32 *)*(iPage+1);
+    volatile u32 **apNew;
+    apNew = (volatile u32 **)sqlite3_realloc(pWal->apWiData, nByte);
+    if( !apNew ){
+      *ppPage = 0;
+      return SQLITE_NOMEM;
+    }
+    memset(&apNew[pWal->nWiData], 0, sizeof(u32 *)*(iPage+1-pWal->nWiData));
+    pWal->apWiData = apNew;
+    pWal->nWiData = iPage+1;
+  }
+
+  /* Request a pointer to the required page from the VFS */
+  if( pWal->apWiData[iPage]==0 ){
+    rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
+        pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
+    );
+  }
+
+  *ppPage = pWal->apWiData[iPage];
+  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
+  return rc;
+}
+
+/*
+** Return a pointer to the WalCkptInfo structure in the wal-index.
+*/
+static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]);
+}
+
+/*
+** Return a pointer to the WalIndexHdr structure in the wal-index.
+*/
+static volatile WalIndexHdr *walIndexHdr(Wal *pWal){
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+  return (volatile WalIndexHdr*)pWal->apWiData[0];
+}
+
+/*
+** The argument to this macro must be of type u32. On a little-endian
+** architecture, it returns the u32 value that results from interpreting
+** the 4 bytes as a big-endian value. On a big-endian architecture, it
+** returns the value that would be produced by intepreting the 4 bytes
+** of the input value as a little-endian integer.
+*/
+#define BYTESWAP32(x) ( \
+    (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)  \
+  + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24) \
+)
+
+/*
+** Generate or extend an 8 byte checksum based on the data in 
+** array aByte[] and the initial values of aIn[0] and aIn[1] (or
+** initial values of 0 and 0 if aIn==NULL).
+**
+** The checksum is written back into aOut[] before returning.
+**
+** nByte must be a positive multiple of 8.
+*/
+static void walChecksumBytes(
+  int nativeCksum, /* True for native byte-order, false for non-native */
+  u8 *a,           /* Content to be checksummed */
+  int nByte,       /* Bytes of content in a[].  Must be a multiple of 8. */
+  const u32 *aIn,  /* Initial checksum value input */
+  u32 *aOut        /* OUT: Final checksum value output */
+){
+  u32 s1, s2;
+  u32 *aData = (u32 *)a;
+  u32 *aEnd = (u32 *)&a[nByte];
+
+  if( aIn ){
+    s1 = aIn[0];
+    s2 = aIn[1];
+  }else{
+    s1 = s2 = 0;
+  }
+
+  assert( nByte>=8 );
+  assert( (nByte&0x00000007)==0 );
+
+  if( nativeCksum ){
+    do {
+      s1 += *aData++ + s2;
+      s2 += *aData++ + s1;
+    }while( aData<aEnd );
+  }else{
+    do {
+      s1 += BYTESWAP32(aData[0]) + s2;
+      s2 += BYTESWAP32(aData[1]) + s1;
+      aData += 2;
+    }while( aData<aEnd );
+  }
+
+  aOut[0] = s1;
+  aOut[1] = s2;
+}
+
+/*
+** Write the header information in pWal->hdr into the wal-index.
+**
+** The checksum on pWal->hdr is updated before it is written.
+*/
+static void walIndexWriteHdr(Wal *pWal){
+  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
+  const int nCksum = offsetof(WalIndexHdr, aCksum);
+
+  assert( pWal->writeLock );
+  pWal->hdr.isInit = 1;
+  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
+  memcpy((void *)&aHdr[1], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+  sqlite3OsShmBarrier(pWal->pDbFd);
+  memcpy((void *)&aHdr[0], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+}
+
+/*
+** This function encodes a single frame header and writes it to a buffer
+** supplied by the caller. A frame-header is made up of a series of 
+** 4-byte big-endian integers, as follows:
+**
+**     0: Page number.
+**     4: For commit records, the size of the database image in pages 
+**        after the commit. For all other records, zero.
+**     8: Salt-1 (copied from the wal-header)
+**    12: Salt-2 (copied from the wal-header)
+**    16: Checksum-1.
+**    20: Checksum-2.
+*/
+static void walEncodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 iPage,                      /* Database page number for frame */
+  u32 nTruncate,                  /* New db size (or 0 for non-commit frames) */
+  u8 *aData,                      /* Pointer to page data */
+  u8 *aFrame                      /* OUT: Write encoded frame here */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  assert( WAL_FRAME_HDRSIZE==24 );
+  sqlite3Put4byte(&aFrame[0], iPage);
+  sqlite3Put4byte(&aFrame[4], nTruncate);
+  memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
+
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+
+  sqlite3Put4byte(&aFrame[16], aCksum[0]);
+  sqlite3Put4byte(&aFrame[20], aCksum[1]);
+}
+
+/*
+** Check to see if the frame with header in aFrame[] and content
+** in aData[] is valid.  If it is a valid frame, fill *piPage and
+** *pnTruncate and return true.  Return if the frame is not valid.
+*/
+static int walDecodeFrame(
+  Wal *pWal,                      /* The write-ahead log */
+  u32 *piPage,                    /* OUT: Database page number for frame */
+  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
+  u8 *aData,                      /* Pointer to page data (for checksum) */
+  u8 *aFrame                      /* Frame data */
+){
+  int nativeCksum;                /* True for native byte-order checksums */
+  u32 *aCksum = pWal->hdr.aFrameCksum;
+  u32 pgno;                       /* Page number of the frame */
+  assert( WAL_FRAME_HDRSIZE==24 );
+
+  /* A frame is only valid if the salt values in the frame-header
+  ** match the salt values in the wal-header. 
+  */
+  if( memcmp(&pWal->hdr.aSalt, &aFrame[8], 8)!=0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if the page number is creater than zero.
+  */
+  pgno = sqlite3Get4byte(&aFrame[0]);
+  if( pgno==0 ){
+    return 0;
+  }
+
+  /* A frame is only valid if a checksum of the first 16 bytes
+  ** of the frame-header, and the frame-data matches
+  ** the checksum in the last 8 bytes of the frame-header.
+  */
+  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
+  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
+  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
+  if( aCksum[0]!=sqlite3Get4byte(&aFrame[16]) 
+   || aCksum[1]!=sqlite3Get4byte(&aFrame[20]) 
+  ){
+    /* Checksum failed. */
+    return 0;
+  }
+
+  /* If we reach this point, the frame is valid.  Return the page number
+  ** and the new database size.
+  */
+  *piPage = pgno;
+  *pnTruncate = sqlite3Get4byte(&aFrame[4]);
+  return 1;
+}
+
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+/*
+** Names of locks.  This routine is used to provide debugging output and is not
+** a part of an ordinary build.
+*/
+static const char *walLockName(int lockIdx){
+  if( lockIdx==WAL_WRITE_LOCK ){
+    return "WRITE-LOCK";
+  }else if( lockIdx==WAL_CKPT_LOCK ){
+    return "CKPT-LOCK";
+  }else if( lockIdx==WAL_RECOVER_LOCK ){
+    return "RECOVER-LOCK";
+  }else{
+    static char zName[15];
+    sqlite3_snprintf(sizeof(zName), zName, "READ-LOCK[%d]",
+                     lockIdx-WAL_READ_LOCK(0));
+    return zName;
+  }
+}
+#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
+    
+
+/*
+** Set or release locks on the WAL.  Locks are either shared or exclusive.
+** A lock cannot be moved directly between shared and exclusive - it must go
+** through the unlocked state first.
+**
+** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
+*/
+static int walLockShared(Wal *pWal, int lockIdx){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
+            walLockName(lockIdx), rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockShared(Wal *pWal, int lockIdx){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
+  WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
+}
+static int walLockExclusive(Wal *pWal, int lockIdx, int n){
+  int rc;
+  if( pWal->exclusiveMode ) return SQLITE_OK;
+  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                        SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
+            walLockName(lockIdx), n, rc ? "failed" : "ok"));
+  VVA_ONLY( pWal->lockError = (rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
+  return rc;
+}
+static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){
+  if( pWal->exclusiveMode ) return;
+  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
+                         SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE);
+  WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal,
+             walLockName(lockIdx), n));
+}
+
+/*
+** Compute a hash on a page number.  The resulting hash value must land
+** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
+** the hash to the next value in the event of a collision.
+*/
+static int walHash(u32 iPage){
+  assert( iPage>0 );
+  assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 );
+  return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1);
+}
+static int walNextHash(int iPriorHash){
+  return (iPriorHash+1)&(HASHTABLE_NSLOT-1);
+}
+
+/* 
+** Return pointers to the hash table and page number array stored on
+** page iHash of the wal-index. The wal-index is broken into 32KB pages
+** numbered starting from 0.
+**
+** Set output variable *paHash to point to the start of the hash table
+** in the wal-index file. Set *piZero to one less than the frame 
+** number of the first frame indexed by this hash table. If a
+** slot in the hash table is set to N, it refers to frame number 
+** (*piZero+N) in the log.
+**
+** Finally, set *paPgno so that *paPgno[1] is the page number of the
+** first frame indexed by the hash table, frame (*piZero+1).
+*/
+static int walHashGet(
+  Wal *pWal,                      /* WAL handle */
+  int iHash,                      /* Find the iHash'th table */
+  volatile ht_slot **paHash,      /* OUT: Pointer to hash index */
+  volatile u32 **paPgno,          /* OUT: Pointer to page number array */
+  u32 *piZero                     /* OUT: Frame associated with *paPgno[0] */
+){
+  int rc;                         /* Return code */
+  volatile u32 *aPgno;
+
+  rc = walIndexPage(pWal, iHash, &aPgno);
+  assert( rc==SQLITE_OK || iHash>0 );
+
+  if( rc==SQLITE_OK ){
+    u32 iZero;
+    volatile ht_slot *aHash;
+
+    aHash = (volatile ht_slot *)&aPgno[HASHTABLE_NPAGE];
+    if( iHash==0 ){
+      aPgno = &aPgno[WALINDEX_HDR_SIZE/sizeof(u32)];
+      iZero = 0;
+    }else{
+      iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
+    }
+  
+    *paPgno = &aPgno[-1];
+    *paHash = aHash;
+    *piZero = iZero;
+  }
+  return rc;
+}
+
+/*
+** Return the number of the wal-index page that contains the hash-table
+** and page-number array that contain entries corresponding to WAL frame
+** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages 
+** are numbered starting from 0.
+*/
+static int walFramePage(u32 iFrame){
+  int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE;
+  assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE)
+       && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE)
+       && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE))
+       && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)
+       && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE))
+  );
+  return iHash;
+}
+
+/*
+** Return the page number associated with frame iFrame in this WAL.
+*/
+static u32 walFramePgno(Wal *pWal, u32 iFrame){
+  int iHash = walFramePage(iFrame);
+  if( iHash==0 ){
+    return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1];
+  }
+  return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE];
+}
+
+/*
+** Remove entries from the hash table that point to WAL slots greater
+** than pWal->hdr.mxFrame.
+**
+** This function is called whenever pWal->hdr.mxFrame is decreased due
+** to a rollback or savepoint.
+**
+** At most only the hash table containing pWal->hdr.mxFrame needs to be
+** updated.  Any later hash tables will be automatically cleared when
+** pWal->hdr.mxFrame advances to the point where those hash tables are
+** actually needed.
+*/
+static void walCleanupHash(Wal *pWal){
+  volatile ht_slot *aHash;        /* Pointer to hash table to clear */
+  volatile u32 *aPgno;            /* Page number array for hash table */
+  u32 iZero;                      /* frame == (aHash[x]+iZero) */
+  int iLimit = 0;                 /* Zero values greater than this */
+  int nByte;                      /* Number of bytes to zero in aPgno[] */
+  int i;                          /* Used to iterate through aHash[] */
+
+  assert( pWal->writeLock );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE-1 );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE );
+  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE+1 );
+
+  if( pWal->hdr.mxFrame==0 ) return;
+
+  /* Obtain pointers to the hash-table and page-number array containing 
+  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
+  ** that the page said hash-table and array reside on is already mapped.
+  */
+  assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) );
+  assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] );
+  walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &aHash, &aPgno, &iZero);
+
+  /* Zero all hash-table entries that correspond to frame numbers greater
+  ** than pWal->hdr.mxFrame.
+  */
+  iLimit = pWal->hdr.mxFrame - iZero;
+  assert( iLimit>0 );
+  for(i=0; i<HASHTABLE_NSLOT; i++){
+    if( aHash[i]>iLimit ){
+      aHash[i] = 0;
+    }
+  }
+  
+  /* Zero the entries in the aPgno array that correspond to frames with
+  ** frame numbers greater than pWal->hdr.mxFrame. 
+  */
+  nByte = ((char *)aHash - (char *)&aPgno[iLimit+1]);
+  memset((void *)&aPgno[iLimit+1], 0, nByte);
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* Verify that the every entry in the mapping region is still reachable
+  ** via the hash table even after the cleanup.
+  */
+  if( iLimit ){
+    int i;           /* Loop counter */
+    int iKey;        /* Hash key */
+    for(i=1; i<=iLimit; i++){
+      for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+        if( aHash[iKey]==i ) break;
+      }
+      assert( aHash[iKey]==i );
+    }
+  }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+}
+
+
+/*
+** Set an entry in the wal-index that will map database page number
+** pPage into WAL frame iFrame.
+*/
+static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
+  int rc;                         /* Return code */
+  u32 iZero;                      /* One less than frame number of aPgno[1] */
+  volatile u32 *aPgno;            /* Page number array */
+  volatile ht_slot *aHash;        /* Hash table */
+
+  rc = walHashGet(pWal, walFramePage(iFrame), &aHash, &aPgno, &iZero);
+
+  /* Assuming the wal-index file was successfully mapped, populate the
+  ** page number array and hash table entry.
+  */
+  if( rc==SQLITE_OK ){
+    int iKey;                     /* Hash table key */
+    int idx;                      /* Value to write to hash-table slot */
+    TESTONLY( int nCollide = 0;   /* Number of hash collisions */ )
+
+    idx = iFrame - iZero;
+    assert( idx <= HASHTABLE_NSLOT/2 + 1 );
+    
+    /* If this is the first entry to be added to this hash-table, zero the
+    ** entire hash table and aPgno[] array before proceding. 
+    */
+    if( idx==1 ){
+      int nByte = (u8 *)&aHash[HASHTABLE_NSLOT] - (u8 *)&aPgno[1];
+      memset((void*)&aPgno[1], 0, nByte);
+    }
+
+    /* If the entry in aPgno[] is already set, then the previous writer
+    ** must have exited unexpectedly in the middle of a transaction (after
+    ** writing one or more dirty pages to the WAL to free up memory). 
+    ** Remove the remnants of that writers uncommitted transaction from 
+    ** the hash-table before writing any new entries.
+    */
+    if( aPgno[idx] ){
+      walCleanupHash(pWal);
+      assert( !aPgno[idx] );
+    }
+
+    /* Write the aPgno[] array entry and the hash-table slot. */
+    for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
+      assert( nCollide++ < idx );
+    }
+    aPgno[idx] = iPage;
+    aHash[iKey] = idx;
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+    /* Verify that the number of entries in the hash table exactly equals
+    ** the number of entries in the mapping region.
+    */
+    {
+      int i;           /* Loop counter */
+      int nEntry = 0;  /* Number of entries in the hash table */
+      for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i] ) nEntry++; }
+      assert( nEntry==idx );
+    }
+
+    /* Verify that the every entry in the mapping region is reachable
+    ** via the hash table.  This turns out to be a really, really expensive
+    ** thing to check, so only do this occasionally - not on every
+    ** iteration.
+    */
+    if( (idx&0x3ff)==0 ){
+      int i;           /* Loop counter */
+      for(i=1; i<=idx; i++){
+        for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
+          if( aHash[iKey]==i ) break;
+        }
+        assert( aHash[iKey]==i );
+      }
+    }
+#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
+  }
+
+
+  return rc;
+}
+
+
+/*
+** Recover the wal-index by reading the write-ahead log file. 
+**
+** This routine first tries to establish an exclusive lock on the
+** wal-index to prevent other threads/processes from doing anything
+** with the WAL or wal-index while recovery is running.  The
+** WAL_RECOVER_LOCK is also held so that other threads will know
+** that this thread is running recovery.  If unable to establish
+** the necessary locks, this routine returns SQLITE_BUSY.
+*/
+static int walIndexRecover(Wal *pWal){
+  int rc;                         /* Return Code */
+  i64 nSize;                      /* Size of log file */
+  u32 aFrameCksum[2] = {0, 0};
+  int iLock;                      /* Lock offset to lock for checkpoint */
+  int nLock;                      /* Number of locks to hold */
+
+  /* Obtain an exclusive lock on all byte in the locking range not already
+  ** locked by the caller. The caller is guaranteed to have locked the
+  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
+  ** If successful, the same bytes that are locked here are unlocked before
+  ** this function returns.
+  */
+  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
+  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
+  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
+  assert( pWal->writeLock );
+  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
+  nLock = SQLITE_SHM_NLOCK - iLock;
+  rc = walLockExclusive(pWal, iLock, nLock);
+  if( rc ){
+    return rc;
+  }
+  WALTRACE(("WAL%p: recovery begin...\n", pWal));
+
+  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+
+  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
+  if( rc!=SQLITE_OK ){
+    goto recovery_error;
+  }
+
+  if( nSize>WAL_HDRSIZE ){
+    u8 aBuf[WAL_HDRSIZE];         /* Buffer to load WAL header into */
+    u8 *aFrame = 0;               /* Malloc'd buffer to load entire frame */
+    int szFrame;                  /* Number of bytes in buffer aFrame[] */
+    u8 *aData;                    /* Pointer to data part of aFrame buffer */
+    int iFrame;                   /* Index of last frame read */
+    i64 iOffset;                  /* Next offset to read from log file */
+    int szPage;                   /* Page size according to the log */
+    u32 magic;                    /* Magic value read from WAL header */
+
+    /* Read in the WAL header. */
+    rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
+    if( rc!=SQLITE_OK ){
+      goto recovery_error;
+    }
+
+    /* If the database page size is not a power of two, or is greater than
+    ** SQLITE_MAX_PAGE_SIZE, conclude that the WAL file contains no valid 
+    ** data. Similarly, if the 'magic' value is invalid, ignore the whole
+    ** WAL file.
+    */
+    magic = sqlite3Get4byte(&aBuf[0]);
+    szPage = sqlite3Get4byte(&aBuf[8]);
+    if( (magic&0xFFFFFFFE)!=WAL_MAGIC 
+     || szPage&(szPage-1) 
+     || szPage>SQLITE_MAX_PAGE_SIZE 
+     || szPage<512 
+    ){
+      goto finished;
+    }
+    pWal->hdr.bigEndCksum = (magic&0x00000001);
+    pWal->szPage = szPage;
+    pWal->nCkpt = sqlite3Get4byte(&aBuf[12]);
+    memcpy(&pWal->hdr.aSalt, &aBuf[16], 8);
+    walChecksumBytes(pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN, 
+        aBuf, WAL_HDRSIZE, 0, pWal->hdr.aFrameCksum
+    );
+
+    /* Malloc a buffer to read frames into. */
+    szFrame = szPage + WAL_FRAME_HDRSIZE;
+    aFrame = (u8 *)sqlite3_malloc(szFrame);
+    if( !aFrame ){
+      rc = SQLITE_NOMEM;
+      goto recovery_error;
+    }
+    aData = &aFrame[WAL_FRAME_HDRSIZE];
+
+    /* Read all frames from the log file. */
+    iFrame = 0;
+    for(iOffset=WAL_HDRSIZE; (iOffset+szFrame)<=nSize; iOffset+=szFrame){
+      u32 pgno;                   /* Database page number for frame */
+      u32 nTruncate;              /* dbsize field from frame header */
+      int isValid;                /* True if this frame is valid */
+
+      /* Read and decode the next log frame. */
+      rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
+      if( rc!=SQLITE_OK ) break;
+      isValid = walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame);
+      if( !isValid ) break;
+      rc = walIndexAppend(pWal, ++iFrame, pgno);
+      if( rc!=SQLITE_OK ) break;
+
+      /* If nTruncate is non-zero, this is a commit record. */
+      if( nTruncate ){
+        pWal->hdr.mxFrame = iFrame;
+        pWal->hdr.nPage = nTruncate;
+        pWal->hdr.szPage = szPage;
+        aFrameCksum[0] = pWal->hdr.aFrameCksum[0];
+        aFrameCksum[1] = pWal->hdr.aFrameCksum[1];
+      }
+    }
+
+    sqlite3_free(aFrame);
+  }
+
+finished:
+  if( rc==SQLITE_OK ){
+    volatile WalCkptInfo *pInfo;
+    int i;
+    pWal->hdr.aFrameCksum[0] = aFrameCksum[0];
+    pWal->hdr.aFrameCksum[1] = aFrameCksum[1];
+    walIndexWriteHdr(pWal);
+
+    /* Reset the checkpoint-header. This is safe because this thread is 
+    ** currently holding locks that exclude all other readers, writers and
+    ** checkpointers.
+    */
+    pInfo = walCkptInfo(pWal);
+    pInfo->nBackfill = 0;
+    pInfo->aReadMark[0] = 0;
+    for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+  }
+
+recovery_error:
+  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
+  walUnlockExclusive(pWal, iLock, nLock);
+  return rc;
+}
+
+/*
+** Close an open wal-index.
+*/
+static void walIndexClose(Wal *pWal, int isDelete){
+  if( pWal->isWIndexOpen ){
+    sqlite3OsShmClose(pWal->pDbFd, isDelete);
+    pWal->isWIndexOpen = 0;
+  }
+}
+
+/* 
+** Open a connection to the WAL file associated with database zDbName.
+** The database file must already be opened on connection pDbFd.
+**
+** A SHARED lock should be held on the database file when this function
+** is called. The purpose of this SHARED lock is to prevent any other
+** client from unlinking the WAL or wal-index file. If another process
+** were to do this just after this client opened one of these files, the
+** system would be badly broken.
+**
+** If the log file is successfully opened, SQLITE_OK is returned and 
+** *ppWal is set to point to a new WAL handle. If an error occurs,
+** an SQLite error code is returned and *ppWal is left unmodified.
+*/
+SQLITE_PRIVATE int sqlite3WalOpen(
+  sqlite3_vfs *pVfs,              /* vfs module to open wal and wal-index */
+  sqlite3_file *pDbFd,            /* The open database file */
+  const char *zDbName,            /* Name of the database file */
+  Wal **ppWal                     /* OUT: Allocated Wal handle */
+){
+  int rc;                         /* Return Code */
+  Wal *pRet;                      /* Object to allocate and return */
+  int flags;                      /* Flags passed to OsOpen() */
+  char *zWal;                     /* Name of write-ahead log file */
+  int nWal;                       /* Length of zWal in bytes */
+
+  assert( zDbName && zDbName[0] );
+  assert( pDbFd );
+
+  /* In the amalgamation, the os_unix.c and os_win.c source files come before
+  ** this source file.  Verify that the #defines of the locking byte offsets
+  ** in os_unix.c and os_win.c agree with the WALINDEX_LOCK_OFFSET value.
+  */
+#ifdef WIN_SHM_BASE
+  assert( WIN_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+#ifdef UNIX_SHM_BASE
+  assert( UNIX_SHM_BASE==WALINDEX_LOCK_OFFSET );
+#endif
+
+
+  /* Allocate an instance of struct Wal to return. */
+  *ppWal = 0;
+  nWal = sqlite3Strlen30(zDbName) + 5;
+  pRet = (Wal*)sqlite3MallocZero(sizeof(Wal) + pVfs->szOsFile + nWal);
+  if( !pRet ){
+    return SQLITE_NOMEM;
+  }
+
+  pRet->pVfs = pVfs;
+  pRet->pWalFd = (sqlite3_file *)&pRet[1];
+  pRet->pDbFd = pDbFd;
+  pRet->readLock = -1;
+  sqlite3_randomness(8, &pRet->hdr.aSalt);
+  pRet->zWalName = zWal = pVfs->szOsFile + (char*)pRet->pWalFd;
+  sqlite3_snprintf(nWal, zWal, "%s-wal", zDbName);
+  rc = sqlite3OsShmOpen(pDbFd);
+
+  /* Open file handle on the write-ahead log file. */
+  if( rc==SQLITE_OK ){
+    pRet->isWIndexOpen = 1;
+    flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_MAIN_JOURNAL);
+    rc = sqlite3OsOpen(pVfs, zWal, pRet->pWalFd, flags, &flags);
+  }
+
+  if( rc!=SQLITE_OK ){
+    walIndexClose(pRet, 0);
+    sqlite3OsClose(pRet->pWalFd);
+    sqlite3_free(pRet);
+  }else{
+    *ppWal = pRet;
+    WALTRACE(("WAL%d: opened\n", pRet));
+  }
+  return rc;
+}
+
+/*
+** Find the smallest page number out of all pages held in the WAL that
+** has not been returned by any prior invocation of this method on the
+** same WalIterator object.   Write into *piFrame the frame index where
+** that page was last written into the WAL.  Write into *piPage the page
+** number.
+**
+** Return 0 on success.  If there are no pages in the WAL with a page
+** number larger than *piPage, then return 1.
+*/
+static int walIteratorNext(
+  WalIterator *p,               /* Iterator */
+  u32 *piPage,                  /* OUT: The page number of the next page */
+  u32 *piFrame                  /* OUT: Wal frame index of next page */
+){
+  u32 iMin;                     /* Result pgno must be greater than iMin */
+  u32 iRet = 0xFFFFFFFF;        /* 0xffffffff is never a valid page number */
+  int i;                        /* For looping through segments */
+
+  iMin = p->iPrior;
+  assert( iMin<0xffffffff );
+  for(i=p->nSegment-1; i>=0; i--){
+    struct WalSegment *pSegment = &p->aSegment[i];
+    while( pSegment->iNext<pSegment->nEntry ){
+      u32 iPg = pSegment->aPgno[pSegment->aIndex[pSegment->iNext]];
+      if( iPg>iMin ){
+        if( iPg<iRet ){
+          iRet = iPg;
+          *piFrame = pSegment->iZero + pSegment->aIndex[pSegment->iNext];
+        }
+        break;
+      }
+      pSegment->iNext++;
+    }
+  }
+
+  *piPage = p->iPrior = iRet;
+  return (iRet==0xFFFFFFFF);
+}
+
+
+static void walMergesort(
+  u32 *aContent,                  /* Pages in wal */
+  ht_slot *aBuffer,               /* Buffer of at least *pnList items to use */
+  ht_slot *aList,                 /* IN/OUT: List to sort */
+  int *pnList                     /* IN/OUT: Number of elements in aList[] */
+){
+  int nList = *pnList;
+  if( nList>1 ){
+    int nLeft = nList / 2;        /* Elements in left list */
+    int nRight = nList - nLeft;   /* Elements in right list */
+    int iLeft = 0;                /* Current index in aLeft */
+    int iRight = 0;               /* Current index in aright */
+    int iOut = 0;                 /* Current index in output buffer */
+    ht_slot *aLeft = aList;       /* Left list */
+    ht_slot *aRight = aList+nLeft;/* Right list */
+
+    /* TODO: Change to non-recursive version. */
+    walMergesort(aContent, aBuffer, aLeft, &nLeft);
+    walMergesort(aContent, aBuffer, aRight, &nRight);
+
+    while( iRight<nRight || iLeft<nLeft ){
+      ht_slot logpage;
+      Pgno dbpage;
+
+      if( (iLeft<nLeft) 
+       && (iRight>=nRight || aContent[aLeft[iLeft]]<aContent[aRight[iRight]])
+      ){
+        logpage = aLeft[iLeft++];
+      }else{
+        logpage = aRight[iRight++];
+      }
+      dbpage = aContent[logpage];
+
+      aBuffer[iOut++] = logpage;
+      if( iLeft<nLeft && aContent[aLeft[iLeft]]==dbpage ) iLeft++;
+
+      assert( iLeft>=nLeft || aContent[aLeft[iLeft]]>dbpage );
+      assert( iRight>=nRight || aContent[aRight[iRight]]>dbpage );
+    }
+    memcpy(aList, aBuffer, sizeof(aList[0])*iOut);
+    *pnList = iOut;
+  }
+
+#ifdef SQLITE_DEBUG
+  {
+    int i;
+    for(i=1; i<*pnList; i++){
+      assert( aContent[aList[i]] > aContent[aList[i-1]] );
+    }
+  }
+#endif
+}
+
+/* 
+** Free an iterator allocated by walIteratorInit().
+*/
+static void walIteratorFree(WalIterator *p){
+  sqlite3_free(p);
+}
+
+/*
+** Map the wal-index into memory owned by this thread, if it is not
+** mapped already.  Then construct a WalInterator object that can be
+** used to loop over all pages in the WAL in ascending order.  
+**
+** On success, make *pp point to the newly allocated WalInterator object
+** return SQLITE_OK.  Otherwise, leave *pp unchanged and return an error
+** code.
+**
+** The calling routine should invoke walIteratorFree() to destroy the
+** WalIterator object when it has finished with it.  The caller must
+** also unmap the wal-index.  But the wal-index must not be unmapped
+** prior to the WalIterator object being destroyed.
+*/
+static int walIteratorInit(Wal *pWal, WalIterator **pp){
+  WalIterator *p;                 /* Return value */
+  int nSegment;                   /* Number of segments to merge */
+  u32 iLast;                      /* Last frame in log */
+  int nByte;                      /* Number of bytes to allocate */
+  int i;                          /* Iterator variable */
+  ht_slot *aTmp;                  /* Temp space used by merge-sort */
+  ht_slot *aSpace;                /* Space at the end of the allocation */
+
+  /* This routine only runs while holding SQLITE_SHM_CHECKPOINT.  No other
+  ** thread is able to write to shared memory while this routine is
+  ** running (or, indeed, while the WalIterator object exists).  Hence,
+  ** we can cast off the volatile qualification from shared memory
+  */
+  assert( pWal->ckptLock );
+  iLast = pWal->hdr.mxFrame;
+
+  /* Allocate space for the WalIterator object */
+  nSegment = walFramePage(iLast) + 1;
+  nByte = sizeof(WalIterator) 
+        + nSegment*(sizeof(struct WalSegment))
+        + (nSegment+1)*(HASHTABLE_NPAGE * sizeof(ht_slot));
+  p = (WalIterator *)sqlite3_malloc(nByte);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, nByte);
+
+  /* Allocate space for the WalIterator object */
+  p->nSegment = nSegment;
+  aSpace = (ht_slot *)&p->aSegment[nSegment];
+  aTmp = &aSpace[HASHTABLE_NPAGE*nSegment];
+  for(i=0; i<nSegment; i++){
+    volatile ht_slot *aHash;
+    int j;
+    u32 iZero;
+    int nEntry;
+    volatile u32 *aPgno;
+    int rc;
+
+    rc = walHashGet(pWal, i, &aHash, &aPgno, &iZero);
+    if( rc!=SQLITE_OK ){
+      walIteratorFree(p);
+      return rc;
+    }
+    aPgno++;
+    nEntry = ((i+1)==nSegment)?iLast-iZero:(u32 *)aHash-(u32 *)aPgno;
+    iZero++;
+
+    for(j=0; j<nEntry; j++){
+      aSpace[j] = j;
+    }
+    walMergesort((u32 *)aPgno, aTmp, aSpace, &nEntry);
+    p->aSegment[i].iZero = iZero;
+    p->aSegment[i].nEntry = nEntry;
+    p->aSegment[i].aIndex = aSpace;
+    p->aSegment[i].aPgno = (u32 *)aPgno;
+    aSpace += HASHTABLE_NPAGE;
+  }
+  assert( aSpace==aTmp );
+
+  /* Return the fully initialized WalIterator object */
+  *pp = p;
+  return SQLITE_OK ;
+}
+
+/*
+** Copy as much content as we can from the WAL back into the database file
+** in response to an sqlite3_wal_checkpoint() request or the equivalent.
+**
+** The amount of information copies from WAL to database might be limited
+** by active readers.  This routine will never overwrite a database page
+** that a concurrent reader might be using.
+**
+** All I/O barrier operations (a.k.a fsyncs) occur in this routine when
+** SQLite is in WAL-mode in synchronous=NORMAL.  That means that if 
+** checkpoints are always run by a background thread or background 
+** process, foreground threads will never block on a lengthy fsync call.
+**
+** Fsync is called on the WAL before writing content out of the WAL and
+** into the database.  This ensures that if the new content is persistent
+** in the WAL and can be recovered following a power-loss or hard reset.
+**
+** Fsync is also called on the database file if (and only if) the entire
+** WAL content is copied into the database file.  This second fsync makes
+** it safe to delete the WAL since the new content will persist in the
+** database file.
+**
+** This routine uses and updates the nBackfill field of the wal-index header.
+** This is the only routine tha will increase the value of nBackfill.  
+** (A WAL reset or recovery will revert nBackfill to zero, but not increase
+** its value.)
+**
+** The caller must be holding sufficient locks to ensure that no other
+** checkpoint is running (in any other thread or process) at the same
+** time.
+*/
+static int walCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int sync_flags,                 /* Flags for OsSync() (or 0) */
+  int nBuf,                       /* Size of zBuf in bytes */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc;                         /* Return code */
+  int szPage = pWal->hdr.szPage;  /* Database page-size */
+  WalIterator *pIter = 0;         /* Wal iterator context */
+  u32 iDbpage = 0;                /* Next database page to write */
+  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
+  u32 mxSafeFrame;                /* Max frame that can be backfilled */
+  int i;                          /* Loop counter */
+  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
+
+  /* Allocate the iterator */
+  rc = walIteratorInit(pWal, &pIter);
+  if( rc!=SQLITE_OK || pWal->hdr.mxFrame==0 ){
+    goto walcheckpoint_out;
+  }
+
+  /*** TODO:  Move this test out to the caller.  Make it an assert() here ***/
+  if( pWal->hdr.szPage!=nBuf ){
+    rc = SQLITE_CORRUPT_BKPT;
+    goto walcheckpoint_out;
+  }
+
+  /* Compute in mxSafeFrame the index of the last frame of the WAL that is
+  ** safe to write into the database.  Frames beyond mxSafeFrame might
+  ** overwrite database pages that are in use by active readers and thus
+  ** cannot be backfilled from the WAL.
+  */
+  mxSafeFrame = pWal->hdr.mxFrame;
+  pInfo = walCkptInfo(pWal);
+  for(i=1; i<WAL_NREADER; i++){
+    u32 y = pInfo->aReadMark[i];
+    if( mxSafeFrame>=y ){
+      assert( y<=pWal->hdr.mxFrame );
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      if( rc==SQLITE_OK ){
+        pInfo->aReadMark[i] = READMARK_NOT_USED;
+        walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+      }else if( rc==SQLITE_BUSY ){
+        mxSafeFrame = y;
+      }else{
+        goto walcheckpoint_out;
+      }
+    }
+  }
+
+  if( pInfo->nBackfill<mxSafeFrame
+   && (rc = walLockExclusive(pWal, WAL_READ_LOCK(0), 1))==SQLITE_OK
+  ){
+    u32 nBackfill = pInfo->nBackfill;
+
+    /* Sync the WAL to disk */
+    if( sync_flags ){
+      rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+    }
+
+    /* Iterate through the contents of the WAL, copying data to the db file. */
+    while( rc==SQLITE_OK && 0==walIteratorNext(pIter, &iDbpage, &iFrame) ){
+      assert( walFramePgno(pWal, iFrame)==iDbpage );
+      if( iFrame<=nBackfill || iFrame>mxSafeFrame ) continue;
+      rc = sqlite3OsRead(pWal->pWalFd, zBuf, szPage, 
+          walFrameOffset(iFrame, szPage) + WAL_FRAME_HDRSIZE
+      );
+      if( rc!=SQLITE_OK ) break;
+      rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, (iDbpage-1)*szPage);
+      if( rc!=SQLITE_OK ) break;
+    }
+
+    /* If work was actually accomplished... */
+    if( rc==SQLITE_OK ){
+      if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){
+        rc = sqlite3OsTruncate(pWal->pDbFd, ((i64)pWal->hdr.nPage*(i64)szPage));
+        if( rc==SQLITE_OK && sync_flags ){
+          rc = sqlite3OsSync(pWal->pDbFd, sync_flags);
+        }
+      }
+      if( rc==SQLITE_OK ){
+        pInfo->nBackfill = mxSafeFrame;
+      }
+    }
+
+    /* Release the reader lock held while backfilling */
+    walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
+  }else if( rc==SQLITE_BUSY ){
+    /* Reset the return code so as not to report a checkpoint failure
+    ** just because active readers prevent any backfill.
+    */
+    rc = SQLITE_OK;
+  }
+
+ walcheckpoint_out:
+  walIteratorFree(pIter);
+  return rc;
+}
+
+/*
+** Close a connection to a log file.
+*/
+SQLITE_PRIVATE int sqlite3WalClose(
+  Wal *pWal,                      /* Wal to close */
+  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
+  int nBuf,
+  u8 *zBuf                        /* Buffer of at least nBuf bytes */
+){
+  int rc = SQLITE_OK;
+  if( pWal ){
+    int isDelete = 0;             /* True to unlink wal and wal-index files */
+
+    /* If an EXCLUSIVE lock can be obtained on the database file (using the
+    ** ordinary, rollback-mode locking methods, this guarantees that the
+    ** connection associated with this log file is the only connection to
+    ** the database. In this case checkpoint the database and unlink both
+    ** the wal and wal-index files.
+    **
+    ** The EXCLUSIVE lock is not released before returning.
+    */
+    rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE);
+    if( rc==SQLITE_OK ){
+      pWal->exclusiveMode = 1;
+      rc = sqlite3WalCheckpoint(pWal, sync_flags, nBuf, zBuf);
+      if( rc==SQLITE_OK ){
+        isDelete = 1;
+      }
+    }
+
+    walIndexClose(pWal, isDelete);
+    sqlite3OsClose(pWal->pWalFd);
+    if( isDelete ){
+      sqlite3OsDelete(pWal->pVfs, pWal->zWalName, 0);
+    }
+    WALTRACE(("WAL%p: closed\n", pWal));
+    sqlite3_free(pWal->apWiData);
+    sqlite3_free(pWal);
+  }
+  return rc;
+}
+
+/*
+** Try to read the wal-index header.  Return 0 on success and 1 if
+** there is a problem.
+**
+** The wal-index is in shared memory.  Another thread or process might
+** be writing the header at the same time this procedure is trying to
+** read it, which might result in inconsistency.  A dirty read is detected
+** by verifying that both copies of the header are the same and also by
+** a checksum on the header.
+**
+** If and only if the read is consistent and the header is different from
+** pWal->hdr, then pWal->hdr is updated to the content of the new header
+** and *pChanged is set to 1.
+**
+** If the checksum cannot be verified return non-zero. If the header
+** is read successfully and the checksum verified, return zero.
+*/
+int walIndexTryHdr(Wal *pWal, int *pChanged){
+  u32 aCksum[2];                  /* Checksum on the header content */
+  WalIndexHdr h1, h2;             /* Two copies of the header content */
+  WalIndexHdr volatile *aHdr;     /* Header in shared memory */
+
+  /* The first page of the wal-index must be mapped at this point. */
+  assert( pWal->nWiData>0 && pWal->apWiData[0] );
+
+  /* Read the header. This might happen currently with a write to the
+  ** same area of shared memory on a different CPU in a SMP,
+  ** meaning it is possible that an inconsistent snapshot is read
+  ** from the file. If this happens, return non-zero.
+  **
+  ** There are two copies of the header at the beginning of the wal-index.
+  ** When reading, read [0] first then [1].  Writes are in the reverse order.
+  ** Memory barriers are used to prevent the compiler or the hardware from
+  ** reordering the reads and writes.
+  */
+  aHdr = walIndexHdr(pWal);
+  memcpy(&h1, (void *)&aHdr[0], sizeof(h1));
+  sqlite3OsShmBarrier(pWal->pDbFd);
+  memcpy(&h2, (void *)&aHdr[1], sizeof(h2));
+
+  if( memcmp(&h1, &h2, sizeof(h1))!=0 ){
+    return 1;   /* Dirty read */
+  }  
+  if( h1.isInit==0 ){
+    return 1;   /* Malformed header - probably all zeros */
+  }
+  walChecksumBytes(1, (u8*)&h1, sizeof(h1)-sizeof(h1.aCksum), 0, aCksum);
+  if( aCksum[0]!=h1.aCksum[0] || aCksum[1]!=h1.aCksum[1] ){
+    return 1;   /* Checksum does not match */
+  }
+
+  if( memcmp(&pWal->hdr, &h1, sizeof(WalIndexHdr)) ){
+    *pChanged = 1;
+    memcpy(&pWal->hdr, &h1, sizeof(WalIndexHdr));
+    pWal->szPage = pWal->hdr.szPage;
+  }
+
+  /* The header was successfully read. Return zero. */
+  return 0;
+}
+
+/*
+** Read the wal-index header from the wal-index and into pWal->hdr.
+** If the wal-header appears to be corrupt, try to recover the log
+** before returning.
+**
+** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
+** changed by this opertion.  If pWal->hdr is unchanged, set *pChanged
+** to 0.
+**
+** This routine also maps the wal-index content into memory and assigns
+** ownership of that mapping to the current thread.  In some implementations,
+** only one thread at a time can hold a mapping of the wal-index.  Hence,
+** the caller should strive to invoke walIndexUnmap() as soon as possible
+** after this routine returns.
+**
+** If the wal-index header is successfully read, return SQLITE_OK. 
+** Otherwise an SQLite error code.
+*/
+static int walIndexReadHdr(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int badHdr;                     /* True if a header read failed */
+  volatile u32 *page0;
+
+  /* Ensure that page 0 of the wal-index (the page that contains the 
+  ** wal-index header) is mapped. Return early if an error occurs here.
+  */
+  assert( pChanged );
+  rc = walIndexPage(pWal, 0, &page0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  };
+  assert( page0 || pWal->writeLock==0 );
+
+  /* If the first page of the wal-index has been mapped, try to read the
+  ** wal-index header immediately, without holding any lock. This usually
+  ** works, but may fail if the wal-index header is corrupt or currently 
+  ** being modified by another user.
+  */
+  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
+
+  /* If the first attempt failed, it might have been due to a race
+  ** with a writer.  So get a WRITE lock and try again.
+  */
+  assert( badHdr==0 || pWal->writeLock==0 );
+  if( badHdr && SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
+    pWal->writeLock = 1;
+    if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
+      badHdr = walIndexTryHdr(pWal, pChanged);
+      if( badHdr ){
+        /* If the wal-index header is still malformed even while holding
+        ** a WRITE lock, it can only mean that the header is corrupted and
+        ** needs to be reconstructed.  So run recovery to do exactly that.
+        */
+        rc = walIndexRecover(pWal);
+        *pChanged = 1;
+      }
+    }
+    pWal->writeLock = 0;
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  }
+
+  return rc;
+}
+
+/*
+** This is the value that walTryBeginRead returns when it needs to
+** be retried.
+*/
+#define WAL_RETRY  (-1)
+
+/*
+** Attempt to start a read transaction.  This might fail due to a race or
+** other transient condition.  When that happens, it returns WAL_RETRY to
+** indicate to the caller that it is safe to retry immediately.
+**
+** On success return SQLITE_OK.  On a permantent failure (such an
+** I/O error or an SQLITE_BUSY because another process is running
+** recovery) return a positive error code.
+**
+** On success, this routine obtains a read lock on 
+** WAL_READ_LOCK(pWal->readLock).  The pWal->readLock integer is
+** in the range 0 <= pWal->readLock < WAL_NREADER.  If pWal->readLock==(-1)
+** that means the Wal does not hold any read lock.  The reader must not
+** access any database page that is modified by a WAL frame up to and
+** including frame number aReadMark[pWal->readLock].  The reader will
+** use WAL frames up to and including pWal->hdr.mxFrame if pWal->readLock>0
+** Or if pWal->readLock==0, then the reader will ignore the WAL
+** completely and get all content directly from the database file.
+** When the read transaction is completed, the caller must release the
+** lock on WAL_READ_LOCK(pWal->readLock) and set pWal->readLock to -1.
+**
+** This routine uses the nBackfill and aReadMark[] fields of the header
+** to select a particular WAL_READ_LOCK() that strives to let the
+** checkpoint process do as much work as possible.  This routine might
+** update values of the aReadMark[] array in the header, but if it does
+** so it takes care to hold an exclusive lock on the corresponding
+** WAL_READ_LOCK() while changing values.
+*/
+static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
+  volatile WalCkptInfo *pInfo;    /* Checkpoint information in wal-index */
+  u32 mxReadMark;                 /* Largest aReadMark[] value */
+  int mxI;                        /* Index of largest aReadMark[] value */
+  int i;                          /* Loop counter */
+  int rc = SQLITE_OK;             /* Return code  */
+
+  assert( pWal->readLock<0 );     /* Not currently locked */
+
+  /* Take steps to avoid spinning forever if there is a protocol error. */
+  if( cnt>5 ){
+    if( cnt>100 ) return SQLITE_PROTOCOL;
+    sqlite3OsSleep(pWal->pVfs, 1);
+  }
+
+  if( !useWal ){
+    rc = walIndexReadHdr(pWal, pChanged);
+    if( rc==SQLITE_BUSY ){
+      /* If there is not a recovery running in another thread or process
+      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
+      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
+      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
+      ** would be technically correct.  But the race is benign since with
+      ** WAL_RETRY this routine will be called again and will probably be
+      ** right on the second iteration.
+      */
+      rc = walLockShared(pWal, WAL_RECOVER_LOCK);
+      if( rc==SQLITE_OK ){
+        walUnlockShared(pWal, WAL_RECOVER_LOCK);
+        rc = WAL_RETRY;
+      }else if( rc==SQLITE_BUSY ){
+        rc = SQLITE_BUSY_RECOVERY;
+      }
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  pInfo = walCkptInfo(pWal);
+  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){
+    /* The WAL has been completely backfilled (or it is empty).
+    ** and can be safely ignored.
+    */
+    rc = walLockShared(pWal, WAL_READ_LOCK(0));
+    sqlite3OsShmBarrier(pWal->pDbFd);
+    if( rc==SQLITE_OK ){
+      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
+        /* It is not safe to allow the reader to continue here if frames
+        ** may have been appended to the log before READ_LOCK(0) was obtained.
+        ** When holding READ_LOCK(0), the reader ignores the entire log file,
+        ** which implies that the database file contains a trustworthy
+        ** snapshoT. Since holding READ_LOCK(0) prevents a checkpoint from
+        ** happening, this is usually correct.
+        **
+        ** However, if frames have been appended to the log (or if the log 
+        ** is wrapped and written for that matter) before the READ_LOCK(0)
+        ** is obtained, that is not necessarily true. A checkpointer may
+        ** have started to backfill the appended frames but crashed before
+        ** it finished. Leaving a corrupt image in the database file.
+        */
+        walUnlockShared(pWal, WAL_READ_LOCK(0));
+        return WAL_RETRY;
+      }
+      pWal->readLock = 0;
+      return SQLITE_OK;
+    }else if( rc!=SQLITE_BUSY ){
+      return rc;
+    }
+  }
+
+  /* If we get this far, it means that the reader will want to use
+  ** the WAL to get at content from recent commits.  The job now is
+  ** to select one of the aReadMark[] entries that is closest to
+  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
+  */
+  mxReadMark = 0;
+  mxI = 0;
+  for(i=1; i<WAL_NREADER; i++){
+    u32 thisMark = pInfo->aReadMark[i];
+    if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){
+      assert( thisMark!=READMARK_NOT_USED );
+      mxReadMark = thisMark;
+      mxI = i;
+    }
+  }
+  if( mxI==0 ){
+    /* If we get here, it means that all of the aReadMark[] entries between
+    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
+    ** be mxFrame, then retry.
+    */
+    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
+    if( rc==SQLITE_OK ){
+      pInfo->aReadMark[1] = pWal->hdr.mxFrame;
+      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);
+      rc = WAL_RETRY;
+    }else if( rc==SQLITE_BUSY ){
+      rc = WAL_RETRY;
+    }
+    return rc;
+  }else{
+    if( mxReadMark < pWal->hdr.mxFrame ){
+      for(i=1; i<WAL_NREADER; i++){
+        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
+        if( rc==SQLITE_OK ){
+          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
+          mxI = i;
+          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
+          break;
+        }else if( rc!=SQLITE_BUSY ){
+          return rc;
+        }
+      }
+    }
+
+    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
+    if( rc ){
+      return rc==SQLITE_BUSY ? WAL_RETRY : rc;
+    }
+    /* Now that the read-lock has been obtained, check that neither the
+    ** value in the aReadMark[] array or the contents of the wal-index
+    ** header have changed.
+    **
+    ** It is necessary to check that the wal-index header did not change
+    ** between the time it was read and when the shared-lock was obtained
+    ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
+    ** that the log file may have been wrapped by a writer, or that frames
+    ** that occur later in the log than pWal->hdr.mxFrame may have been
+    ** copied into the database by a checkpointer. If either of these things
+    ** happened, then reading the database with the current value of
+    ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
+    ** instead.
+    **
+    ** This does not guarantee that the copy of the wal-index header is up to
+    ** date before proceeding. That would not be possible without somehow
+    ** blocking writers. It only guarantees that a dangerous checkpoint or 
+    ** log-wrap (either of which would require an exclusive lock on
+    ** WAL_READ_LOCK(mxI)) has not occurred since the snapshot was valid.
+    */
+    sqlite3OsShmBarrier(pWal->pDbFd);
+    if( pInfo->aReadMark[mxI]!=mxReadMark
+     || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
+    ){
+      walUnlockShared(pWal, WAL_READ_LOCK(mxI));
+      return WAL_RETRY;
+    }else{
+      assert( mxReadMark<=pWal->hdr.mxFrame );
+      pWal->readLock = mxI;
+    }
+  }
+  return rc;
+}
+
+/*
+** Begin a read transaction on the database.
+**
+** This routine used to be called sqlite3OpenSnapshot() and with good reason:
+** it takes a snapshot of the state of the WAL and wal-index for the current
+** instant in time.  The current thread will continue to use this snapshot.
+** Other threads might append new content to the WAL and wal-index but
+** that extra content is ignored by the current thread.
+**
+** If the database contents have changes since the previous read
+** transaction, then *pChanged is set to 1 before returning.  The
+** Pager layer will use this to know that is cache is stale and
+** needs to be flushed.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
+  int rc;                         /* Return code */
+  int cnt = 0;                    /* Number of TryBeginRead attempts */
+
+  do{
+    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
+  }while( rc==WAL_RETRY );
+  return rc;
+}
+
+/*
+** Finish with a read transaction.  All this does is release the
+** read-lock.
+*/
+SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal){
+  if( pWal->readLock>=0 ){
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->readLock = -1;
+  }
+}
+
+/*
+** Read a page from the WAL, if it is present in the WAL and if the 
+** current read transaction is configured to use the WAL.  
+**
+** The *pInWal is set to 1 if the requested page is in the WAL and
+** has been loaded.  Or *pInWal is set to 0 if the page was not in 
+** the WAL and needs to be read out of the database.
+*/
+SQLITE_PRIVATE int sqlite3WalRead(
+  Wal *pWal,                      /* WAL handle */
+  Pgno pgno,                      /* Database page number to read data for */
+  int *pInWal,                    /* OUT: True if data is read from WAL */
+  int nOut,                       /* Size of buffer pOut in bytes */
+  u8 *pOut                        /* Buffer to write page data to */
+){
+  u32 iRead = 0;                  /* If !=0, WAL frame to return data from */
+  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
+  int iHash;                      /* Used to loop through N hash tables */
+
+  /* This routine is only be called from within a read transaction. */
+  assert( pWal->readLock>=0 || pWal->lockError );
+
+  /* If the "last page" field of the wal-index header snapshot is 0, then
+  ** no data will be read from the wal under any circumstances. Return early
+  ** in this case to avoid the walIndexMap/Unmap overhead.  Likewise, if
+  ** pWal->readLock==0, then the WAL is ignored by the reader so
+  ** return early, as if the WAL were empty.
+  */
+  if( iLast==0 || pWal->readLock==0 ){
+    *pInWal = 0;
+    return SQLITE_OK;
+  }
+
+  /* Search the hash table or tables for an entry matching page number
+  ** pgno. Each iteration of the following for() loop searches one
+  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).
+  **
+  ** This code may run concurrently to the code in walIndexAppend()
+  ** that adds entries to the wal-index (and possibly to this hash 
+  ** table). This means the value just read from the hash 
+  ** slot (aHash[iKey]) may have been added before or after the 
+  ** current read transaction was opened. Values added after the
+  ** read transaction was opened may have been written incorrectly -
+  ** i.e. these slots may contain garbage data. However, we assume
+  ** that any slots written before the current read transaction was
+  ** opened remain unmodified.
+  **
+  ** For the reasons above, the if(...) condition featured in the inner
+  ** loop of the following block is more stringent that would be required 
+  ** if we had exclusive access to the hash-table:
+  **
+  **   (aPgno[iFrame]==pgno): 
+  **     This condition filters out normal hash-table collisions.
+  **
+  **   (iFrame<=iLast): 
+  **     This condition filters out entries that were added to the hash
+  **     table after the current read-transaction had started.
+  */
+  for(iHash=walFramePage(iLast); iHash>=0 && iRead==0; iHash--){
+    volatile ht_slot *aHash;      /* Pointer to hash table */
+    volatile u32 *aPgno;          /* Pointer to array of page numbers */
+    u32 iZero;                    /* Frame number corresponding to aPgno[0] */
+    int iKey;                     /* Hash slot index */
+    int rc;
+
+    rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
+      u32 iFrame = aHash[iKey] + iZero;
+      if( iFrame<=iLast && aPgno[aHash[iKey]]==pgno ){
+        assert( iFrame>iRead );
+        iRead = iFrame;
+      }
+    }
+  }
+
+#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
+  /* If expensive assert() statements are available, do a linear search
+  ** of the wal-index file content. Make sure the results agree with the
+  ** result obtained using the hash indexes above.  */
+  {
+    u32 iRead2 = 0;
+    u32 iTest;
+    for(iTest=iLast; iTest>0; iTest--){
+      if( walFramePgno(pWal, iTest)==pgno ){
+        iRead2 = iTest;
+        break;
+      }
+    }
+    assert( iRead==iRead2 );
+  }
+#endif
+
+  /* If iRead is non-zero, then it is the log frame number that contains the
+  ** required page. Read and return data from the log file.
+  */
+  if( iRead ){
+    i64 iOffset = walFrameOffset(iRead, pWal->hdr.szPage) + WAL_FRAME_HDRSIZE;
+    *pInWal = 1;
+    return sqlite3OsRead(pWal->pWalFd, pOut, nOut, iOffset);
+  }
+
+  *pInWal = 0;
+  return SQLITE_OK;
+}
+
+
+/* 
+** Set *pPgno to the size of the database file (or zero, if unknown).
+*/
+SQLITE_PRIVATE void sqlite3WalDbsize(Wal *pWal, Pgno *pPgno){
+  assert( pWal->readLock>=0 || pWal->lockError );
+  *pPgno = pWal->hdr.nPage;
+}
+
+
+/* 
+** This function starts a write transaction on the WAL.
+**
+** A read transaction must have already been started by a prior call
+** to sqlite3WalBeginReadTransaction().
+**
+** If another thread or process has written into the database since
+** the read transaction was started, then it is not possible for this
+** thread to write as doing so would cause a fork.  So this routine
+** returns SQLITE_BUSY in that case and no write transaction is started.
+**
+** There can only be a single writer active at a time.
+*/
+SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal){
+  int rc;
+
+  /* Cannot start a write transaction without first holding a read
+  ** transaction. */
+  assert( pWal->readLock>=0 );
+
+  /* Only one writer allowed at a time.  Get the write lock.  Return
+  ** SQLITE_BUSY if unable.
+  */
+  rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  if( rc ){
+    return rc;
+  }
+  pWal->writeLock = 1;
+
+  /* If another connection has written to the database file since the
+  ** time the read transaction on this connection was started, then
+  ** the write is disallowed.
+  */
+  if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){
+    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+    pWal->writeLock = 0;
+    rc = SQLITE_BUSY;
+  }
+
+  return rc;
+}
+
+/*
+** End a write transaction.  The commit has already been done.  This
+** routine merely releases the lock.
+*/
+SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal){
+  walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
+  pWal->writeLock = 0;
+  return SQLITE_OK;
+}
+
+/*
+** If any data has been written (but not committed) to the log file, this
+** function moves the write-pointer back to the start of the transaction.
+**
+** Additionally, the callback function is invoked for each frame written
+** to the WAL since the start of the transaction. If the callback returns
+** other than SQLITE_OK, it is not invoked again and the error code is
+** returned to the caller.
+**
+** Otherwise, if the callback function does not return an error, this
+** function returns SQLITE_OK.
+*/
+SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
+  int rc = SQLITE_OK;
+  if( pWal->writeLock ){
+    Pgno iMax = pWal->hdr.mxFrame;
+    Pgno iFrame;
+  
+    /* Restore the clients cache of the wal-index header to the state it
+    ** was in before the client began writing to the database. 
+    */
+    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
+
+    for(iFrame=pWal->hdr.mxFrame+1; 
+        ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; 
+        iFrame++
+    ){
+      /* This call cannot fail. Unless the page for which the page number
+      ** is passed as the second argument is (a) in the cache and 
+      ** (b) has an outstanding reference, then xUndo is either a no-op
+      ** (if (a) is false) or simply expels the page from the cache (if (b)
+      ** is false).
+      **
+      ** If the upper layer is doing a rollback, it is guaranteed that there
+      ** are no outstanding references to any page other than page 1. And
+      ** page 1 is never written to the log until the transaction is
+      ** committed. As a result, the call to xUndo may not fail.
+      */
+      assert( walFramePgno(pWal, iFrame)!=1 );
+      rc = xUndo(pUndoCtx, walFramePgno(pWal, iFrame));
+    }
+    walCleanupHash(pWal);
+  }
+  assert( rc==SQLITE_OK );
+  return rc;
+}
+
+/* 
+** Argument aWalData must point to an array of WAL_SAVEPOINT_NDATA u32 
+** values. This function populates the array with values required to 
+** "rollback" the write position of the WAL handle back to the current 
+** point in the event of a savepoint rollback (via WalSavepointUndo()).
+*/
+SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
+  assert( pWal->writeLock );
+  aWalData[0] = pWal->hdr.mxFrame;
+  aWalData[1] = pWal->hdr.aFrameCksum[0];
+  aWalData[2] = pWal->hdr.aFrameCksum[1];
+  aWalData[3] = pWal->nCkpt;
+}
+
+/* 
+** Move the write position of the WAL back to the point identified by
+** the values in the aWalData[] array. aWalData must point to an array
+** of WAL_SAVEPOINT_NDATA u32 values that has been previously populated
+** by a call to WalSavepoint().
+*/
+SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
+  int rc = SQLITE_OK;
+
+  assert( pWal->writeLock );
+  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
+
+  if( aWalData[3]!=pWal->nCkpt ){
+    /* This savepoint was opened immediately after the write-transaction
+    ** was started. Right after that, the writer decided to wrap around
+    ** to the start of the log. Update the savepoint values to match.
+    */
+    aWalData[0] = 0;
+    aWalData[3] = pWal->nCkpt;
+  }
+
+  if( aWalData[0]<pWal->hdr.mxFrame ){
+    pWal->hdr.mxFrame = aWalData[0];
+    pWal->hdr.aFrameCksum[0] = aWalData[1];
+    pWal->hdr.aFrameCksum[1] = aWalData[2];
+    walCleanupHash(pWal);
+  }
+
+  return rc;
+}
+
+/*
+** This function is called just before writing a set of frames to the log
+** file (see sqlite3WalFrames()). It checks to see if, instead of appending
+** to the current log file, it is possible to overwrite the start of the
+** existing log file with the new frames (i.e. "reset" the log). If so,
+** it sets pWal->hdr.mxFrame to 0. Otherwise, pWal->hdr.mxFrame is left
+** unchanged.
+**
+** SQLITE_OK is returned if no error is encountered (regardless of whether
+** or not pWal->hdr.mxFrame is modified). An SQLite error code is returned
+** if some error 
+*/
+static int walRestartLog(Wal *pWal){
+  int rc = SQLITE_OK;
+  int cnt;
+
+  if( pWal->readLock==0 ){
+    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+    assert( pInfo->nBackfill==pWal->hdr.mxFrame );
+    if( pInfo->nBackfill>0 ){
+      rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      if( rc==SQLITE_OK ){
+        /* If all readers are using WAL_READ_LOCK(0) (in other words if no
+        ** readers are currently using the WAL), then the transactions
+        ** frames will overwrite the start of the existing log. Update the
+        ** wal-index header to reflect this.
+        **
+        ** In theory it would be Ok to update the cache of the header only
+        ** at this point. But updating the actual wal-index header is also
+        ** safe and means there is no special case for sqlite3WalUndo()
+        ** to handle if this transaction is rolled back.
+        */
+        int i;                    /* Loop counter */
+        u32 *aSalt = pWal->hdr.aSalt;       /* Big-endian salt values */
+        pWal->nCkpt++;
+        pWal->hdr.mxFrame = 0;
+        sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
+        sqlite3_randomness(4, &aSalt[1]);
+        walIndexWriteHdr(pWal);
+        pInfo->nBackfill = 0;
+        for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
+        assert( pInfo->aReadMark[0]==0 );
+        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+      }
+    }
+    walUnlockShared(pWal, WAL_READ_LOCK(0));
+    pWal->readLock = -1;
+    cnt = 0;
+    do{
+      int notUsed;
+      rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
+    }while( rc==WAL_RETRY );
+  }
+  return rc;
+}
+
+/* 
+** Write a set of frames to the log. The caller must hold the write-lock
+** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
+*/
+SQLITE_PRIVATE int sqlite3WalFrames(
+  Wal *pWal,                      /* Wal handle to write to */
+  int szPage,                     /* Database page-size in bytes */
+  PgHdr *pList,                   /* List of dirty pages to write */
+  Pgno nTruncate,                 /* Database size after this commit */
+  int isCommit,                   /* True if this is a commit */
+  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
+){
+  int rc;                         /* Used to catch return codes */
+  u32 iFrame;                     /* Next frame address */
+  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-header in */
+  PgHdr *p;                       /* Iterator to run through pList with. */
+  PgHdr *pLast = 0;               /* Last frame in list */
+  int nLast = 0;                  /* Number of extra copies of last page */
+
+  assert( pList );
+  assert( pWal->writeLock );
+
+#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
+  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
+    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
+              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
+  }
+#endif
+
+  /* See if it is possible to write these frames into the start of the
+  ** log file, instead of appending to it at pWal->hdr.mxFrame.
+  */
+  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
+    return rc;
+  }
+
+  /* If this is the first frame written into the log, write the WAL
+  ** header to the start of the WAL file. See comments at the top of
+  ** this source file for a description of the WAL header format.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  if( iFrame==0 ){
+    u8 aWalHdr[WAL_HDRSIZE];        /* Buffer to assembly wal-header in */
+    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
+    sqlite3Put4byte(&aWalHdr[4], 3007000);
+    sqlite3Put4byte(&aWalHdr[8], szPage);
+    pWal->szPage = szPage;
+    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;
+    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
+    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
+    rc = sqlite3OsWrite(pWal->pWalFd, aWalHdr, sizeof(aWalHdr), 0);
+    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    walChecksumBytes(1, aWalHdr, sizeof(aWalHdr), 0, pWal->hdr.aFrameCksum);
+  }
+  assert( pWal->szPage==szPage );
+
+  /* Write the log file. */
+  for(p=pList; p; p=p->pDirty){
+    u32 nDbsize;                  /* Db-size field for frame header */
+    i64 iOffset;                  /* Write offset in log file */
+
+    iOffset = walFrameOffset(++iFrame, szPage);
+    
+    /* Populate and write the frame header */
+    nDbsize = (isCommit && p->pDirty==0) ? nTruncate : 0;
+    walEncodeFrame(pWal, p->pgno, nDbsize, p->pData, aFrame);
+    rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+
+    /* Write the page data */
+    rc = sqlite3OsWrite(pWal->pWalFd, p->pData, szPage, iOffset+sizeof(aFrame));
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    pLast = p;
+  }
+
+  /* Sync the log file if the 'isSync' flag was specified. */
+  if( sync_flags ){
+    i64 iSegment = sqlite3OsSectorSize(pWal->pWalFd);
+    i64 iOffset = walFrameOffset(iFrame+1, szPage);
+
+    assert( isCommit );
+    assert( iSegment>0 );
+
+    iSegment = (((iOffset+iSegment-1)/iSegment) * iSegment);
+    while( iOffset<iSegment ){
+      walEncodeFrame(pWal, pLast->pgno, nTruncate, pLast->pData, aFrame);
+      rc = sqlite3OsWrite(pWal->pWalFd, aFrame, sizeof(aFrame), iOffset);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+
+      iOffset += WAL_FRAME_HDRSIZE;
+      rc = sqlite3OsWrite(pWal->pWalFd, pLast->pData, szPage, iOffset); 
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      nLast++;
+      iOffset += szPage;
+    }
+
+    rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
+  }
+
+  /* Append data to the wal-index. It is not necessary to lock the 
+  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
+  ** guarantees that there are no other writers, and no data that may
+  ** be in use by existing readers is being overwritten.
+  */
+  iFrame = pWal->hdr.mxFrame;
+  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
+    iFrame++;
+    rc = walIndexAppend(pWal, iFrame, p->pgno);
+  }
+  while( nLast>0 && rc==SQLITE_OK ){
+    iFrame++;
+    nLast--;
+    rc = walIndexAppend(pWal, iFrame, pLast->pgno);
+  }
+
+  if( rc==SQLITE_OK ){
+    /* Update the private copy of the header. */
+    pWal->hdr.szPage = szPage;
+    pWal->hdr.mxFrame = iFrame;
+    if( isCommit ){
+      pWal->hdr.iChange++;
+      pWal->hdr.nPage = nTruncate;
+    }
+    /* If this is a commit, update the wal-index header too. */
+    if( isCommit ){
+      walIndexWriteHdr(pWal);
+      pWal->iCallback = iFrame;
+    }
+  }
+
+  WALTRACE(("WAL%p: frame write %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* 
+** This routine is called to implement sqlite3_wal_checkpoint() and
+** related interfaces.
+**
+** Obtain a CHECKPOINT lock and then backfill as much information as
+** we can from WAL into the database.
+*/
+SQLITE_PRIVATE int sqlite3WalCheckpoint(
+  Wal *pWal,                      /* Wal connection */
+  int sync_flags,                 /* Flags to sync db file with (or 0) */
+  int nBuf,                       /* Size of temporary buffer */
+  u8 *zBuf                        /* Temporary buffer to use */
+){
+  int rc;                         /* Return code */
+  int isChanged = 0;              /* True if a new wal-index header is loaded */
+
+  assert( pWal->ckptLock==0 );
+
+  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
+  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  if( rc ){
+    /* Usually this is SQLITE_BUSY meaning that another thread or process
+    ** is already running a checkpoint, or maybe a recovery.  But it might
+    ** also be SQLITE_IOERR. */
+    return rc;
+  }
+  pWal->ckptLock = 1;
+
+  /* Copy data from the log to the database file. */
+  rc = walIndexReadHdr(pWal, &isChanged);
+  if( rc==SQLITE_OK ){
+    rc = walCheckpoint(pWal, sync_flags, nBuf, zBuf);
+  }
+  if( isChanged ){
+    /* If a new wal-index header was loaded before the checkpoint was 
+    ** performed, then the pager-cache associated with pWal is now
+    ** out of date. So zero the cached wal-index header to ensure that
+    ** next time the pager opens a snapshot on this database it knows that
+    ** the cache needs to be reset.
+    */
+    memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
+  }
+
+  /* Release the locks. */
+  walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
+  pWal->ckptLock = 0;
+  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
+  return rc;
+}
+
+/* Return the value to pass to a sqlite3_wal_hook callback, the
+** number of frames in the WAL at the point of the last commit since
+** sqlite3WalCallback() was called.  If no commits have occurred since
+** the last call, then return 0.
+*/
+SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal){
+  u32 ret = 0;
+  if( pWal ){
+    ret = pWal->iCallback;
+    pWal->iCallback = 0;
+  }
+  return (int)ret;
+}
+
+/*
+** This function is called to change the WAL subsystem into or out
+** of locking_mode=EXCLUSIVE.
+**
+** If op is zero, then attempt to change from locking_mode=EXCLUSIVE
+** into locking_mode=NORMAL.  This means that we must acquire a lock
+** on the pWal->readLock byte.  If the WAL is already in locking_mode=NORMAL
+** or if the acquisition of the lock fails, then return 0.  If the
+** transition out of exclusive-mode is successful, return 1.  This
+** operation must occur while the pager is still holding the exclusive
+** lock on the main database file.
+**
+** If op is one, then change from locking_mode=NORMAL into 
+** locking_mode=EXCLUSIVE.  This means that the pWal->readLock must
+** be released.  Return 1 if the transition is made and 0 if the
+** WAL is already in exclusive-locking mode - meaning that this
+** routine is a no-op.  The pager must already hold the exclusive lock
+** on the main database file before invoking this operation.
+**
+** If op is negative, then do a dry-run of the op==1 case but do
+** not actually change anything.  The pager uses this to see if it
+** should acquire the database exclusive lock prior to invoking
+** the op==1 case.
+*/
+SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op){
+  int rc;
+  assert( pWal->writeLock==0 );
+
+  /* pWal->readLock is usually set, but might be -1 if there was a 
+  ** prior error while attempting to acquire are read-lock. This cannot 
+  ** happen if the connection is actually in exclusive mode (as no xShmLock
+  ** locks are taken in this case). Nor should the pager attempt to
+  ** upgrade to exclusive-mode following such an error.
+  */
+  assert( pWal->readLock>=0 || pWal->lockError );
+  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );
+
+  if( op==0 ){
+    if( pWal->exclusiveMode ){
+      pWal->exclusiveMode = 0;
+      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
+        pWal->exclusiveMode = 1;
+      }
+      rc = pWal->exclusiveMode==0;
+    }else{
+      /* Already in locking_mode=NORMAL */
+      rc = 0;
+    }
+  }else if( op>0 ){
+    assert( pWal->exclusiveMode==0 );
+    assert( pWal->readLock>=0 );
+    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+    pWal->exclusiveMode = 1;
+    rc = 1;
+  }else{
+    rc = pWal->exclusiveMode==0;
+  }
+  return rc;
+}
+
+#endif /* #ifndef SQLITE_OMIT_WAL */
+
+/************** End of wal.c *************************************************/
 /************** Begin file btmutex.c *****************************************/
 /*
 ** 2007 August 27
@@ -37202,6 +42574,8 @@
   MemPage *pPage1;      /* First page of the database */
   u8 readOnly;          /* True if the underlying file is readonly */
   u8 pageSizeFixed;     /* True if the page size can no longer be changed */
+  u8 secureDelete;      /* True if secure_delete is enabled */
+  u8 initiallyEmpty;    /* Database is empty at start of transaction */
 #ifndef SQLITE_OMIT_AUTOVACUUM
   u8 autoVacuum;        /* True if auto-vacuum is enabled */
   u8 incrVacuum;        /* True if incr-vacuum is enabled */
@@ -37213,7 +42587,9 @@
   u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
   u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
   u8 inTransaction;     /* Transaction state */
+  u8 doNotUseWAL;       /* If true, do not open write-ahead-log file */
   int nTransaction;     /* Number of open transactions (read + write) */
+  u32 nPage;            /* Number of pages in the database */
   void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
   void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
   sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */
@@ -38294,11 +43670,8 @@
 static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
   int rc = SQLITE_OK;
   if( !pBt->pHasContent ){
-    int nPage = 100;
-    sqlite3PagerPagecount(pBt->pPager, &nPage);
-    /* If sqlite3PagerPagecount() fails there is no harm because the
-    ** nPage variable is unchanged from its default value of 100 */
-    pBt->pHasContent = sqlite3BitvecCreate((u32)nPage);
+    assert( pgno<=pBt->nPage );
+    pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
     if( !pBt->pHasContent ){
       rc = SQLITE_NOMEM;
     }
@@ -39025,11 +44398,11 @@
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( size>=0 );   /* Minimum cell size is 4 */
 
-#ifdef SQLITE_SECURE_DELETE
-  /* Overwrite deleted information with zeros when the SECURE_DELETE 
-  ** option is enabled at compile-time */
-  memset(&data[start], 0, size);
-#endif
+  if( pPage->pBt->secureDelete ){
+    /* Overwrite deleted information with zeros when the secure_delete
+    ** option is enabled */
+    memset(&data[start], 0, size);
+  }
 
   /* Add the space back into the linked list of freeblocks.  Note that
   ** even though the freeblock list was checked by btreeInitPage(),
@@ -39261,9 +44634,9 @@
   assert( sqlite3PagerGetData(pPage->pDbPage) == data );
   assert( sqlite3PagerIswriteable(pPage->pDbPage) );
   assert( sqlite3_mutex_held(pBt->mutex) );
-#ifdef SQLITE_SECURE_DELETE
-  memset(&data[hdr], 0, pBt->usableSize - hdr);
-#endif
+  if( pBt->secureDelete ){
+    memset(&data[hdr], 0, pBt->usableSize - hdr);
+  }
   data[hdr] = (char)flags;
   first = hdr + 8 + 4*((flags&PTF_LEAF)==0 ?1:0);
   memset(&data[hdr+1], 0, 4);
@@ -39341,13 +44714,13 @@
 ** Return the size of the database file in pages. If there is any kind of
 ** error, return ((unsigned int)-1).
 */
-static Pgno pagerPagecount(BtShared *pBt){
-  int nPage = -1;
-  int rc;
-  assert( pBt->pPage1 );
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  assert( rc==SQLITE_OK || nPage==-1 );
-  return (Pgno)nPage;
+static Pgno btreePagecount(BtShared *pBt){
+  return pBt->nPage;
+}
+SQLITE_PRIVATE u32 sqlite3BtreeLastPage(Btree *p){
+  assert( sqlite3BtreeHoldsMutex(p) );
+  assert( ((p->pBt->nPage)&0x8000000)==0 );
+  return (int)btreePagecount(p->pBt);
 }
 
 /*
@@ -39364,9 +44737,11 @@
   MemPage **ppPage     /* Write the page pointer here */
 ){
   int rc;
-  TESTONLY( Pgno iLastPg = pagerPagecount(pBt); )
   assert( sqlite3_mutex_held(pBt->mutex) );
 
+  if( pgno<=0 || pgno>btreePagecount(pBt) ){
+    return SQLITE_CORRUPT_BKPT;
+  }
   rc = btreeGetPage(pBt, pgno, ppPage, 0);
   if( rc==SQLITE_OK ){
     rc = btreeInitPage(*ppPage);
@@ -39374,15 +44749,6 @@
       releasePage(*ppPage);
     }
   }
-
-  /* If the requested page number was either 0 or greater than the page
-  ** number of the last page in the database, this function should return
-  ** SQLITE_CORRUPT or some other error (i.e. SQLITE_FULL). Check that this
-  ** is the case.  */
-  assert( (pgno>0 && pgno<=iLastPg) || rc!=SQLITE_OK );
-  testcase( pgno==0 );
-  testcase( pgno==iLastPg );
-
   return rc;
 }
 
@@ -39583,6 +44949,9 @@
     pBt->pCursor = 0;
     pBt->pPage1 = 0;
     pBt->readOnly = sqlite3PagerIsreadonly(pBt->pPager);
+#ifdef SQLITE_SECURE_DELETE
+    pBt->secureDelete = 1;
+#endif
     pBt->pageSize = get2byte(&zDbHeader[16]);
     if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
          || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
@@ -39939,6 +45308,23 @@
   sqlite3BtreeLeave(p);
   return n;
 }
+
+/*
+** Set the secureDelete flag if newFlag is 0 or 1.  If newFlag is -1,
+** then make no changes.  Always return the value of the secureDelete
+** setting after the change.
+*/
+SQLITE_PRIVATE int sqlite3BtreeSecureDelete(Btree *p, int newFlag){
+  int b;
+  if( p==0 ) return 0;
+  sqlite3BtreeEnter(p);
+  if( newFlag>=0 ){
+    p->pBt->secureDelete = (newFlag!=0) ? 1 : 0;
+  } 
+  b = p->pBt->secureDelete;
+  sqlite3BtreeLeave(p);
+  return b;
+}
 #endif /* !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM) */
 
 /*
@@ -39998,9 +45384,11 @@
 ** is returned if we run out of memory. 
 */
 static int lockBtree(BtShared *pBt){
-  int rc;
-  MemPage *pPage1;
-  int nPage;
+  int rc;              /* Result code from subfunctions */
+  MemPage *pPage1;     /* Page 1 of the database file */
+  int nPage;           /* Number of pages in the database */
+  int nPageFile = 0;   /* Number of pages in the database file */
+  int nPageHeader;     /* Number of pages in the database according to hdr */
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   assert( pBt->pPage1==0 );
@@ -40012,10 +45400,14 @@
   /* Do some checking to help insure the file we opened really is
   ** a valid database file. 
   */
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  if( rc!=SQLITE_OK ){
+  nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
+  if( (rc = sqlite3PagerPagecount(pBt->pPager, &nPageFile))!=SQLITE_OK ){;
     goto page1_init_failed;
-  }else if( nPage>0 ){
+  }
+  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
+    nPage = nPageFile;
+  }
+  if( nPage>0 ){
     int pageSize;
     int usableSize;
     u8 *page1 = pPage1->aData;
@@ -40023,12 +45415,42 @@
     if( memcmp(page1, zMagicHeader, 16)!=0 ){
       goto page1_init_failed;
     }
+
+#ifdef SQLITE_OMIT_WAL
     if( page1[18]>1 ){
       pBt->readOnly = 1;
     }
     if( page1[19]>1 ){
       goto page1_init_failed;
     }
+#else
+    if( page1[18]>2 ){
+      pBt->readOnly = 1;
+    }
+    if( page1[19]>2 ){
+      goto page1_init_failed;
+    }
+
+    /* If the write version is set to 2, this database should be accessed
+    ** in WAL mode. If the log is not already open, open it now. Then 
+    ** return SQLITE_OK and return without populating BtShared.pPage1.
+    ** The caller detects this and calls this function again. This is
+    ** required as the version of page 1 currently in the page1 buffer
+    ** may not be the latest version - there may be a newer one in the log
+    ** file.
+    */
+    if( page1[19]==2 && pBt->doNotUseWAL==0 ){
+      int isOpen = 0;
+      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
+      if( rc!=SQLITE_OK ){
+        goto page1_init_failed;
+      }else if( isOpen==0 ){
+        releasePage(pPage1);
+        return SQLITE_OK;
+      }
+      rc = SQLITE_NOTADB;
+    }
+#endif
 
     /* The maximum embedded fraction must be exactly 25%.  And the minimum
     ** embedded fraction must be 12.5% for both leaf-data and non-leaf-data.
@@ -40061,6 +45483,10 @@
                                    pageSize-usableSize);
       return rc;
     }
+    if( nPageHeader>nPageFile ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto page1_init_failed;
+    }
     if( usableSize<480 ){
       goto page1_init_failed;
     }
@@ -40091,6 +45517,7 @@
   pBt->minLeaf = (pBt->usableSize-12)*32/255 - 23;
   assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
   pBt->pPage1 = pPage1;
+  pBt->nPage = nPage;
   return SQLITE_OK;
 
 page1_init_failed:
@@ -40128,12 +45555,10 @@
   MemPage *pP1;
   unsigned char *data;
   int rc;
-  int nPage;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
-  rc = sqlite3PagerPagecount(pBt->pPager, &nPage);
-  if( rc!=SQLITE_OK || nPage>0 ){
-    return rc;
+  if( pBt->nPage>0 ){
+    return SQLITE_OK;
   }
   pP1 = pBt->pPage1;
   assert( pP1!=0 );
@@ -40159,6 +45584,8 @@
   put4byte(&data[36 + 4*4], pBt->autoVacuum);
   put4byte(&data[36 + 7*4], pBt->incrVacuum);
 #endif
+  pBt->nPage = 1;
+  data[31] = 1;
   return SQLITE_OK;
 }
 
@@ -40248,6 +45675,7 @@
   rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
   if( SQLITE_OK!=rc ) goto trans_begun;
 
+  pBt->initiallyEmpty = pBt->nPage==0;
   do {
     /* Call lockBtree() until either pBt->pPage1 is populated or
     ** lockBtree() returns something other than SQLITE_OK. lockBtree()
@@ -40272,7 +45700,7 @@
     if( rc!=SQLITE_OK ){
       unlockBtreeIfUnused(pBt);
     }
-  }while( rc==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
+  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
           btreeInvokeBusyHandler(pBt) );
 
   if( rc==SQLITE_OK ){
@@ -40527,12 +45955,12 @@
 */
 static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
   Pgno nFreeList;           /* Number of pages still on the free-list */
+  int rc;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   assert( iLastPg>nFin );
 
   if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
-    int rc;
     u8 eType;
     Pgno iPtrPage;
 
@@ -40608,7 +46036,7 @@
     while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
       if( PTRMAP_ISPAGE(pBt, iLastPg) ){
         MemPage *pPg;
-        int rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
+        rc = btreeGetPage(pBt, iLastPg, &pPg, 0);
         if( rc!=SQLITE_OK ){
           return rc;
         }
@@ -40621,6 +46049,7 @@
       iLastPg--;
     }
     sqlite3PagerTruncateImage(pBt->pPager, iLastPg);
+    pBt->nPage = iLastPg;
   }
   return SQLITE_OK;
 }
@@ -40643,7 +46072,11 @@
     rc = SQLITE_DONE;
   }else{
     invalidateAllOverflowCache(pBt);
-    rc = incrVacuumStep(pBt, 0, pagerPagecount(pBt));
+    rc = incrVacuumStep(pBt, 0, btreePagecount(pBt));
+    if( rc==SQLITE_OK ){
+      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+      put4byte(&pBt->pPage1->aData[28], pBt->nPage);
+    }
   }
   sqlite3BtreeLeave(p);
   return rc;
@@ -40674,7 +46107,7 @@
     int nEntry;        /* Number of entries on one ptrmap page */
     Pgno nOrig;        /* Database size before freeing */
 
-    nOrig = pagerPagecount(pBt);
+    nOrig = btreePagecount(pBt);
     if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
       /* It is not possible to create a database for which the final page
       ** is either a pointer-map page or the pending-byte page. If one
@@ -40699,11 +46132,12 @@
       rc = incrVacuumStep(pBt, nFin, iFree);
     }
     if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
-      rc = SQLITE_OK;
       rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
       put4byte(&pBt->pPage1->aData[32], 0);
       put4byte(&pBt->pPage1->aData[36], 0);
+      put4byte(&pBt->pPage1->aData[28], nFin);
       sqlite3PagerTruncateImage(pBt->pPager, nFin);
+      pBt->nPage = nFin;
     }
     if( rc!=SQLITE_OK ){
       sqlite3PagerRollback(pPager);
@@ -40953,6 +46387,11 @@
     ** call btreeGetPage() on page 1 again to make
     ** sure pPage1->aData is set correctly. */
     if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
+      int nPage = get4byte(28+(u8*)pPage1->aData);
+      testcase( nPage==0 );
+      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
+      testcase( pBt->nPage!=nPage );
+      pBt->nPage = nPage;
       releasePage(pPage1);
     }
     assert( countWriteCursors(pBt)==0 );
@@ -40990,17 +46429,13 @@
   assert( pBt->readOnly==0 );
   assert( iStatement>0 );
   assert( iStatement>p->db->nSavepoint );
-  if( NEVER(p->inTrans!=TRANS_WRITE || pBt->readOnly) ){
-    rc = SQLITE_INTERNAL;
-  }else{
-    assert( pBt->inTransaction==TRANS_WRITE );
-    /* At the pager level, a statement transaction is a savepoint with
-    ** an index greater than all savepoints created explicitly using
-    ** SQL statements. It is illegal to open, release or rollback any
-    ** such savepoints while the statement transaction savepoint is active.
-    */
-    rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
-  }
+  assert( pBt->inTransaction==TRANS_WRITE );
+  /* At the pager level, a statement transaction is a savepoint with
+  ** an index greater than all savepoints created explicitly using
+  ** SQL statements. It is illegal to open, release or rollback any
+  ** such savepoints while the statement transaction savepoint is active.
+  */
+  rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
   sqlite3BtreeLeave(p);
   return rc;
 }
@@ -41026,7 +46461,12 @@
     sqlite3BtreeEnter(p);
     rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
     if( rc==SQLITE_OK ){
+      if( iSavepoint<0 && pBt->initiallyEmpty ) pBt->nPage = 0;
       rc = newDatabase(pBt);
+      pBt->nPage = get4byte(28 + pBt->pPage1->aData);
+      if( pBt->nPage==0 ){
+        sqlite3PagerPagecount(pBt->pPager, (int*)&pBt->nPage);
+      }
     }
     sqlite3BtreeLeave(p);
   }
@@ -41092,7 +46532,7 @@
   if( NEVER(wrFlag && pBt->readOnly) ){
     return SQLITE_READONLY;
   }
-  if( iTable==1 && pagerPagecount(pBt)==0 ){
+  if( iTable==1 && btreePagecount(pBt)==0 ){
     return SQLITE_EMPTY;
   }
 
@@ -41363,7 +46803,7 @@
       iGuess++;
     }
 
-    if( iGuess<=pagerPagecount(pBt) ){
+    if( iGuess<=btreePagecount(pBt) ){
       rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
       if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
         next = iGuess;
@@ -42395,7 +47835,7 @@
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   pPage1 = pBt->pPage1;
-  mxPage = pagerPagecount(pBt);
+  mxPage = btreePagecount(pBt);
   n = get4byte(&pPage1->aData[36]);
   testcase( n==mxPage-1 );
   if( n>=mxPage ){
@@ -42591,35 +48031,35 @@
   }else{
     /* There are no pages on the freelist, so create a new page at the
     ** end of the file */
-    int nPage = pagerPagecount(pBt);
-    *pPgno = nPage + 1;
-
-    if( *pPgno==PENDING_BYTE_PAGE(pBt) ){
-      (*pPgno)++;
-    }
+    rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+    if( rc ) return rc;
+    pBt->nPage++;
+    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
 
 #ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, *pPgno) ){
+    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
       /* If *pPgno refers to a pointer-map page, allocate two new pages
       ** at the end of the file instead of one. The first allocated page
       ** becomes a new pointer-map page, the second is used by the caller.
       */
       MemPage *pPg = 0;
-      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", *pPgno));
-      assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-      rc = btreeGetPage(pBt, *pPgno, &pPg, 0);
+      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
+      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
+      rc = btreeGetPage(pBt, pBt->nPage, &pPg, 1);
       if( rc==SQLITE_OK ){
         rc = sqlite3PagerWrite(pPg->pDbPage);
         releasePage(pPg);
       }
       if( rc ) return rc;
-      (*pPgno)++;
-      if( *pPgno==PENDING_BYTE_PAGE(pBt) ){ (*pPgno)++; }
+      pBt->nPage++;
+      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
     }
 #endif
+    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
+    *pPgno = pBt->nPage;
 
     assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-    rc = btreeGetPage(pBt, *pPgno, ppPage, 0);
+    rc = btreeGetPage(pBt, *pPgno, ppPage, 1);
     if( rc ) return rc;
     rc = sqlite3PagerWrite((*ppPage)->pDbPage);
     if( rc!=SQLITE_OK ){
@@ -42682,17 +48122,17 @@
   nFree = get4byte(&pPage1->aData[36]);
   put4byte(&pPage1->aData[36], nFree+1);
 
-#ifdef SQLITE_SECURE_DELETE
-  /* If the SQLITE_SECURE_DELETE compile-time option is enabled, then
-  ** always fully overwrite deleted information with zeros.
-  */
-  if( (!pPage && (rc = btreeGetPage(pBt, iPage, &pPage, 0)))
-   ||            (rc = sqlite3PagerWrite(pPage->pDbPage))
-  ){
-    goto freepage_out;
+  if( pBt->secureDelete ){
+    /* If the secure_delete option is enabled, then
+    ** always fully overwrite deleted information with zeros.
+    */
+    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
+     ||            ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
+    ){
+      goto freepage_out;
+    }
+    memset(pPage->aData, 0, pPage->pBt->pageSize);
   }
-  memset(pPage->aData, 0, pPage->pBt->pageSize);
-#endif
 
   /* If the database supports auto-vacuum, write an entry in the pointer-map
   ** to indicate that the page is free.
@@ -42743,11 +48183,9 @@
       if( rc==SQLITE_OK ){
         put4byte(&pTrunk->aData[4], nLeaf+1);
         put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
-#ifndef SQLITE_SECURE_DELETE
-        if( pPage ){
+        if( pPage && !pBt->secureDelete ){
           sqlite3PagerDontWrite(pPage->pDbPage);
         }
-#endif
         rc = btreeSetHasContent(pBt, iPage);
       }
       TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
@@ -42811,7 +48249,7 @@
   while( nOvfl-- ){
     Pgno iNext = 0;
     MemPage *pOvfl = 0;
-    if( ovflPgno<2 || ovflPgno>pagerPagecount(pBt) ){
+    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
       /* 0 is not a legal page number and page 1 cannot be an 
       ** overflow page. Therefore if ovflPgno<2 or past the end of the 
       ** file the database must be corrupt. */
@@ -42821,7 +48259,25 @@
       rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
       if( rc ) return rc;
     }
-    rc = freePage2(pBt, pOvfl, ovflPgno);
+
+    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
+     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
+    ){
+      /* There is no reason any cursor should have an outstanding reference 
+      ** to an overflow page belonging to a cell that is being deleted/updated.
+      ** So if there exists more than one reference to this page, then it 
+      ** must not really be an overflow page and the database must be corrupt. 
+      ** It is helpful to detect this before calling freePage2(), as 
+      ** freePage2() may zero the page contents if secure-delete mode is
+      ** enabled. If this 'overflow' page happens to be a page that the
+      ** caller is iterating through or using in some other way, this
+      ** can be problematic.
+      */
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = freePage2(pBt, pOvfl, ovflPgno);
+    }
+
     if( pOvfl ){
       sqlite3PagerUnref(pOvfl->pDbPage);
     }
@@ -43065,7 +48521,7 @@
   Pgno iChild,      /* If non-zero, replace first 4 bytes with this value */
   int *pRC          /* Read and write return code from here */
 ){
-  int idx;          /* Where to write new cell content in data[] */
+  int idx = 0;      /* Where to write new cell content in data[] */
   int j;            /* Loop counter */
   int end;          /* First byte past the last cell pointer in data[] */
   int ins;          /* Index in data[] where new cell pointer is inserted */
@@ -43556,10 +49012,17 @@
       ** In this case, temporarily copy the cell into the aOvflSpace[]
       ** buffer. It will be copied out again as soon as the aSpace[] buffer
       ** is allocated.  */
-#ifdef SQLITE_SECURE_DELETE
-      memcpy(&aOvflSpace[apDiv[i]-pParent->aData], apDiv[i], szNew[i]);
-      apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
-#endif
+      if( pBt->secureDelete ){
+        int iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
+        if( (iOff+szNew[i])>pBt->usableSize ){
+          rc = SQLITE_CORRUPT_BKPT;
+          memset(apOld, 0, (i+1)*sizeof(MemPage*));
+          goto balance_cleanup;
+        }else{
+          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
+          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
+        }
+      }
       dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
     }
   }
@@ -44618,8 +50081,14 @@
       releasePage(pRoot);
       return rc;
     }
+
+    /* When the new root page was allocated, page 1 was made writable in
+    ** order either to increase the database filesize, or to decrement the
+    ** freelist count.  Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
+    */
+    assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
     rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
-    if( rc ){
+    if( NEVER(rc) ){
       releasePage(pRoot);
       return rc;
     }
@@ -44659,7 +50128,7 @@
   int i;
 
   assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pgno>pagerPagecount(pBt) ){
+  if( pgno>btreePagecount(pBt) ){
     return SQLITE_CORRUPT_BKPT;
   }
 
@@ -45410,7 +50879,7 @@
   nRef = sqlite3PagerRefcount(pBt->pPager);
   sCheck.pBt = pBt;
   sCheck.pPager = pBt->pPager;
-  sCheck.nPage = pagerPagecount(sCheck.pBt);
+  sCheck.nPage = btreePagecount(sCheck.pBt);
   sCheck.mxErr = mxErr;
   sCheck.nErr = 0;
   sCheck.mallocFailed = 0;
@@ -45679,6 +51148,42 @@
 }
 #endif
 
+/*
+** Set both the "read version" (single byte at byte offset 18) and 
+** "write version" (single byte at byte offset 19) fields in the database
+** header to iVersion.
+*/
+SQLITE_PRIVATE int sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
+  BtShared *pBt = pBtree->pBt;
+  int rc;                         /* Return code */
+ 
+  assert( pBtree->inTrans==TRANS_NONE );
+  assert( iVersion==1 || iVersion==2 );
+
+  /* If setting the version fields to 1, do not automatically open the
+  ** WAL connection, even if the version fields are currently set to 2.
+  */
+  pBt->doNotUseWAL = (iVersion==1);
+
+  rc = sqlite3BtreeBeginTrans(pBtree, 0);
+  if( rc==SQLITE_OK ){
+    u8 *aData = pBt->pPage1->aData;
+    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
+      rc = sqlite3BtreeBeginTrans(pBtree, 2);
+      if( rc==SQLITE_OK ){
+        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
+        if( rc==SQLITE_OK ){
+          aData[18] = (u8)iVersion;
+          aData[19] = (u8)iVersion;
+        }
+      }
+    }
+  }
+
+  pBt->doNotUseWAL = 0;
+  return rc;
+}
+
 /************** End of btree.c ***********************************************/
 /************** Begin file backup.c ******************************************/
 /*
@@ -45898,7 +51403,7 @@
   /* Catch the case where the destination is an in-memory database and the
   ** page sizes of the source and destination differ. 
   */
-  if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(sqlite3BtreePager(p->pDest)) ){
+  if( nSrcPgsz!=nDestPgsz && sqlite3PagerIsMemdb(pDestPager) ){
     rc = SQLITE_READONLY;
   }
 
@@ -45968,6 +51473,9 @@
 */
 SQLITE_API int sqlite3_backup_step(sqlite3_backup *p, int nPage){
   int rc;
+  int destMode;       /* Destination journal mode */
+  int pgszSrc = 0;    /* Source page size */
+  int pgszDest = 0;   /* Destination page size */
 
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
@@ -46008,13 +51516,21 @@
       rc = sqlite3BtreeBeginTrans(p->pSrc, 0);
       bCloseTrans = 1;
     }
+
+    /* Do not allow backup if the destination database is in WAL mode
+    ** and the page sizes are different between source and destination */
+    pgszSrc = sqlite3BtreeGetPageSize(p->pSrc);
+    pgszDest = sqlite3BtreeGetPageSize(p->pDest);
+    destMode = sqlite3PagerGetJournalMode(sqlite3BtreePager(p->pDest));
+    if( SQLITE_OK==rc && destMode==PAGER_JOURNALMODE_WAL && pgszSrc!=pgszDest ){
+      rc = SQLITE_READONLY;
+    }
   
     /* Now that there is a read-lock on the source database, query the
     ** source pager for the number of pages in the database.
     */
-    if( rc==SQLITE_OK ){
-      rc = sqlite3PagerPagecount(pSrcPager, &nSrcPage);
-    }
+    nSrcPage = (int)sqlite3BtreeLastPage(p->pSrc);
+    assert( nSrcPage>=0 );
     for(ii=0; (nPage<0 || ii<nPage) && p->iNext<=(Pgno)nSrcPage && !rc; ii++){
       const Pgno iSrcPg = p->iNext;                 /* Source page number */
       if( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) ){
@@ -46045,8 +51561,6 @@
     if( rc==SQLITE_DONE 
      && (rc = sqlite3BtreeUpdateMeta(p->pDest,1,p->iDestSchema+1))==SQLITE_OK
     ){
-      const int nSrcPagesize = sqlite3BtreeGetPageSize(p->pSrc);
-      const int nDestPagesize = sqlite3BtreeGetPageSize(p->pDest);
       int nDestTruncate;
   
       if( p->pDestDb ){
@@ -46065,18 +51579,20 @@
       ** journalled by PagerCommitPhaseOne() before they are destroyed
       ** by the file truncation.
       */
-      if( nSrcPagesize<nDestPagesize ){
-        int ratio = nDestPagesize/nSrcPagesize;
+      assert( pgszSrc==sqlite3BtreeGetPageSize(p->pSrc) );
+      assert( pgszDest==sqlite3BtreeGetPageSize(p->pDest) );
+      if( pgszSrc<pgszDest ){
+        int ratio = pgszDest/pgszSrc;
         nDestTruncate = (nSrcPage+ratio-1)/ratio;
         if( nDestTruncate==(int)PENDING_BYTE_PAGE(p->pDest->pBt) ){
           nDestTruncate--;
         }
       }else{
-        nDestTruncate = nSrcPage * (nSrcPagesize/nDestPagesize);
+        nDestTruncate = nSrcPage * (pgszSrc/pgszDest);
       }
       sqlite3PagerTruncateImage(pDestPager, nDestTruncate);
 
-      if( nSrcPagesize<nDestPagesize ){
+      if( pgszSrc<pgszDest ){
         /* If the source page-size is smaller than the destination page-size,
         ** two extra things may need to happen:
         **
@@ -46086,31 +51602,31 @@
         **     pending-byte page in the source database may need to be
         **     copied into the destination database.
         */
-        const i64 iSize = (i64)nSrcPagesize * (i64)nSrcPage;
+        const i64 iSize = (i64)pgszSrc * (i64)nSrcPage;
         sqlite3_file * const pFile = sqlite3PagerFile(pDestPager);
 
         assert( pFile );
-        assert( (i64)nDestTruncate*(i64)nDestPagesize >= iSize || (
+        assert( (i64)nDestTruncate*(i64)pgszDest >= iSize || (
               nDestTruncate==(int)(PENDING_BYTE_PAGE(p->pDest->pBt)-1)
-           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+nDestPagesize
+           && iSize>=PENDING_BYTE && iSize<=PENDING_BYTE+pgszDest
         ));
         if( SQLITE_OK==(rc = sqlite3PagerCommitPhaseOne(pDestPager, 0, 1))
          && SQLITE_OK==(rc = backupTruncateFile(pFile, iSize))
          && SQLITE_OK==(rc = sqlite3PagerSync(pDestPager))
         ){
           i64 iOff;
-          i64 iEnd = MIN(PENDING_BYTE + nDestPagesize, iSize);
+          i64 iEnd = MIN(PENDING_BYTE + pgszDest, iSize);
           for(
-            iOff=PENDING_BYTE+nSrcPagesize; 
+            iOff=PENDING_BYTE+pgszSrc; 
             rc==SQLITE_OK && iOff<iEnd; 
-            iOff+=nSrcPagesize
+            iOff+=pgszSrc
           ){
             PgHdr *pSrcPg = 0;
-            const Pgno iSrcPg = (Pgno)((iOff/nSrcPagesize)+1);
+            const Pgno iSrcPg = (Pgno)((iOff/pgszSrc)+1);
             rc = sqlite3PagerGet(pSrcPager, iSrcPg, &pSrcPg);
             if( rc==SQLITE_OK ){
               u8 *zData = sqlite3PagerGetData(pSrcPg);
-              rc = sqlite3OsWrite(pFile, zData, nSrcPagesize, iOff);
+              rc = sqlite3OsWrite(pFile, zData, pgszSrc, iOff);
             }
             sqlite3PagerUnref(pSrcPg);
           }
@@ -46625,6 +52141,10 @@
 ** before attempting the conversion.
 */
 static i64 doubleToInt64(double r){
+#ifdef SQLITE_OMIT_FLOATING_POINT
+  /* When floating-point is omitted, double and int64 are the same thing */
+  return r;
+#else
   /*
   ** Many compilers we encounter do not define constants for the
   ** minimum and maximum 64-bit integers, or they define them
@@ -46646,6 +52166,7 @@
   }else{
     return (i64)r;
   }
+#endif
 }
 
 /*
@@ -46773,21 +52294,26 @@
 /*
 ** Convert pMem so that it has types MEM_Real or MEM_Int or both.
 ** Invalidate any prior representations.
+**
+** Every effort is made to force the conversion, even if the input
+** is a string that does not look completely like a number.  Convert
+** as much of the string as we can and ignore the rest.
 */
 SQLITE_PRIVATE int sqlite3VdbeMemNumerify(Mem *pMem){
-  double r1, r2;
-  i64 i;
+  int rc;
   assert( (pMem->flags & (MEM_Int|MEM_Real|MEM_Null))==0 );
   assert( (pMem->flags & (MEM_Blob|MEM_Str))!=0 );
   assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
-  r1 = sqlite3VdbeRealValue(pMem);
-  i = doubleToInt64(r1);
-  r2 = (double)i;
-  if( r1==r2 ){
-    sqlite3VdbeMemIntegerify(pMem);
+  rc = sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8);
+  if( rc ) return rc;
+  rc = sqlite3VdbeMemNulTerminate(pMem);
+  if( rc ) return rc;
+  if( sqlite3Atoi64(pMem->z, &pMem->u.i) ){
+    MemSetTypeFlag(pMem, MEM_Int);
   }else{
-    pMem->r = r1;
+    pMem->r = sqlite3VdbeRealValue(pMem);
     MemSetTypeFlag(pMem, MEM_Real);
+    sqlite3VdbeIntegerAffinity(pMem);
   }
   return SQLITE_OK;
 }
@@ -46839,6 +52365,7 @@
   pMem->type = SQLITE_INTEGER;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Delete any previous value and set the value stored in *pMem to val,
 ** manifest type REAL.
@@ -46853,6 +52380,7 @@
     pMem->type = SQLITE_FLOAT;
   }
 }
+#endif
 
 /*
 ** Delete any previous value and set the value of pMem to be an
@@ -46907,7 +52435,7 @@
   sqlite3VdbeMemReleaseExternal(pTo);
   memcpy(pTo, pFrom, MEMCELLSIZE);
   pTo->xDel = 0;
-  if( (pFrom->flags&MEM_Dyn)!=0 || pFrom->z==pFrom->zMalloc ){
+  if( (pFrom->flags&MEM_Static)==0 ){
     pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
     assert( srcType==MEM_Ephem || srcType==MEM_Static );
     pTo->flags |= srcType;
@@ -47478,7 +53006,7 @@
 */
 SQLITE_API const char *sqlite3_sql(sqlite3_stmt *pStmt){
   Vdbe *p = (Vdbe *)pStmt;
-  return (p->isPrepareV2 ? p->zSql : 0);
+  return (p && p->isPrepareV2) ? p->zSql : 0;
 }
 
 /*
@@ -48155,7 +53683,7 @@
     pOp->p4.pKeyInfo = pKeyInfo;
     if( pKeyInfo ){
       u8 *aSortOrder;
-      memcpy(pKeyInfo, zP4, nByte);
+      memcpy((char*)pKeyInfo, zP4, nByte - nField);
       aSortOrder = pKeyInfo->aSortOrder;
       if( aSortOrder ){
         pKeyInfo->aSortOrder = (unsigned char*)&pKeyInfo->aColl[nField];
@@ -48226,9 +53754,12 @@
 **
 ** If a memory allocation error has occurred prior to the calling of this
 ** routine, then a pointer to a dummy VdbeOp will be returned.  That opcode
-** is readable and writable, but it has no effect.  The return of a dummy
-** opcode allows the call to continue functioning after a OOM fault without
-** having to check to see if the return from this routine is a valid pointer.
+** is readable but not writable, though it is cast to a writable value.
+** The return of a dummy opcode allows the call to continue functioning
+** after a OOM fault without having to check to see if the return from 
+** this routine is a valid pointer.  But because the dummy.opcode is 0,
+** dummy will never be written to.  This is verified by code inspection and
+** by running with Valgrind.
 **
 ** About the #ifdef SQLITE_OMIT_TRACE:  Normally, this routine is never called
 ** unless p->nOp>0.  This is because in the absense of SQLITE_OMIT_TRACE,
@@ -48239,17 +53770,17 @@
 ** check the value of p->nOp-1 before continuing.
 */
 SQLITE_PRIVATE VdbeOp *sqlite3VdbeGetOp(Vdbe *p, int addr){
-  static VdbeOp dummy;
+  static const VdbeOp dummy;
   assert( p->magic==VDBE_MAGIC_INIT );
   if( addr<0 ){
 #ifdef SQLITE_OMIT_TRACE
-    if( p->nOp==0 ) return &dummy;
+    if( p->nOp==0 ) return (VdbeOp*)&dummy;
 #endif
     addr = p->nOp - 1;
   }
   assert( (addr>=0 && addr<p->nOp) || p->db->mallocFailed );
   if( p->db->mallocFailed ){
-    return &dummy;
+    return (VdbeOp*)&dummy;
   }else{
     return &p->aOp[addr];
   }
@@ -48362,6 +53893,11 @@
 
 /*
 ** Declare to the Vdbe that the BTree object at db->aDb[i] is used.
+**
+** The prepared statement has to know in advance which Btree objects
+** will be used so that it can acquire mutexes on them all in sorted
+** order (via sqlite3VdbeMutexArrayEnter().  Mutexes are acquired
+** in order (and released in reverse order) to avoid deadlocks.
 */
 SQLITE_PRIVATE void sqlite3VdbeUsesBtree(Vdbe *p, int i){
   int mask;
@@ -48861,6 +54397,7 @@
   p->cacheCtr = 1;
   p->minWriteFileFormat = 255;
   p->iStatement = 0;
+  p->nFkConstraint = 0;
 #ifdef VDBE_PROFILE
   {
     int i;
@@ -49539,15 +55076,27 @@
     /* If eStatementOp is non-zero, then a statement transaction needs to
     ** be committed or rolled back. Call sqlite3VdbeCloseStatement() to
     ** do so. If this operation returns an error, and the current statement
-    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then set the error
-    ** code to the new value.
+    ** error code is SQLITE_OK or SQLITE_CONSTRAINT, then promote the
+    ** current statement error code.
+    **
+    ** Note that sqlite3VdbeCloseStatement() can only fail if eStatementOp
+    ** is SAVEPOINT_ROLLBACK.  But if p->rc==SQLITE_OK then eStatementOp
+    ** must be SAVEPOINT_RELEASE.  Hence the NEVER(p->rc==SQLITE_OK) in 
+    ** the following code.
     */
     if( eStatementOp ){
       rc = sqlite3VdbeCloseStatement(p, eStatementOp);
-      if( rc && (p->rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT) ){
-        p->rc = rc;
-        sqlite3DbFree(db, p->zErrMsg);
-        p->zErrMsg = 0;
+      if( rc ){
+        assert( eStatementOp==SAVEPOINT_ROLLBACK );
+        if( NEVER(p->rc==SQLITE_OK) || p->rc==SQLITE_CONSTRAINT ){
+          p->rc = rc;
+          sqlite3DbFree(db, p->zErrMsg);
+          p->zErrMsg = 0;
+        }
+        invalidateCursorsOnModifiedBtrees(db);
+        sqlite3RollbackAll(db);
+        sqlite3CloseSavepoints(db);
+        db->autoCommit = 1;
       }
     }
   
@@ -49749,6 +55298,7 @@
   sqlite3DbFree(db, p->zSql);
   p->magic = VDBE_MAGIC_DEAD;
   sqlite3DbFree(db, p->pFree);
+  p->db = 0;
   sqlite3DbFree(db, p);
 }
 
@@ -50832,6 +56382,27 @@
 }
 
 /*
+** This function is called after a transaction has been committed. It 
+** invokes callbacks registered with sqlite3_wal_hook() as required.
+*/
+static int doWalCallbacks(sqlite3 *db){
+  int rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_WAL
+  int i;
+  for(i=0; i<db->nDb; i++){
+    Btree *pBt = db->aDb[i].pBt;
+    if( pBt ){
+      int nEntry = sqlite3PagerWalCallback(sqlite3BtreePager(pBt));
+      if( db->xWalCallback && nEntry>0 && rc==SQLITE_OK ){
+        rc = db->xWalCallback(db->pWalArg, db, db->aDb[i].zName, nEntry);
+      }
+    }
+  }
+#endif
+  return rc;
+}
+
+/*
 ** Execute the statement pStmt, either until a row of data is ready, the
 ** statement is completely executed or an error occurs.
 **
@@ -50846,21 +56417,23 @@
 
   assert(p);
   if( p->magic!=VDBE_MAGIC_RUN ){
-    sqlite3_log(SQLITE_MISUSE, 
-          "attempt to step a halted statement: [%s]", p->zSql);
-    return SQLITE_MISUSE_BKPT;
+    /* We used to require that sqlite3_reset() be called before retrying
+    ** sqlite3_step() after any error.  But after 3.6.23, we changed this
+    ** so that sqlite3_reset() would be called automatically instead of
+    ** throwing the error.
+    */
+    sqlite3_reset((sqlite3_stmt*)p);
   }
 
-  /* Assert that malloc() has not failed */
+  /* Check that malloc() has not failed. If it has, return early. */
   db = p->db;
   if( db->mallocFailed ){
+    p->rc = SQLITE_NOMEM;
     return SQLITE_NOMEM;
   }
 
   if( p->pc<=0 && p->expired ){
-    if( p->rc==SQLITE_OK ){
-      p->rc = SQLITE_SCHEMA;
-    }
+    p->rc = SQLITE_SCHEMA;
     rc = SQLITE_ERROR;
     goto end_of_step;
   }
@@ -50877,9 +56450,7 @@
 
 #ifndef SQLITE_OMIT_TRACE
     if( db->xProfile && !db->init.busy ){
-      double rNow;
-      sqlite3OsCurrentTime(db->pVfs, &rNow);
-      p->startTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
+      sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
     }
 #endif
 
@@ -50900,16 +56471,20 @@
   /* Invoke the profile callback if there is one
   */
   if( rc!=SQLITE_ROW && db->xProfile && !db->init.busy && p->zSql ){
-    double rNow;
-    u64 elapseTime;
-
-    sqlite3OsCurrentTime(db->pVfs, &rNow);
-    elapseTime = (u64)((rNow - (int)rNow)*3600.0*24.0*1000000000.0);
-    elapseTime -= p->startTime;
-    db->xProfile(db->pProfileArg, p->zSql, elapseTime);
+    sqlite3_int64 iNow;
+    sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
+    db->xProfile(db->pProfileArg, p->zSql, iNow - p->startTime);
   }
 #endif
 
+  if( rc==SQLITE_DONE ){
+    assert( p->rc==SQLITE_OK );
+    p->rc = doWalCallbacks(db);
+    if( p->rc!=SQLITE_OK ){
+      rc = SQLITE_ERROR;
+    }
+  }
+
   db->errCode = rc;
   if( SQLITE_NOMEM==sqlite3ApiExit(p->db, p->rc) ){
     p->rc = SQLITE_NOMEM;
@@ -50959,7 +56534,7 @@
     sqlite3_reset(pStmt);
     v->expired = 0;
   }
-  if( rc2!=SQLITE_OK && v->isPrepareV2 && db->pErr ){
+  if( rc2!=SQLITE_OK && ALWAYS(v->isPrepareV2) && ALWAYS(db->pErr) ){
     /* This case occurs after failing to recompile an sql statement. 
     ** The error message from the SQL compiler has already been loaded 
     ** into the database handle. This block copies the error message 
@@ -52163,17 +57738,30 @@
 static void applyNumericAffinity(Mem *pRec){
   if( (pRec->flags & (MEM_Real|MEM_Int))==0 ){
     int realnum;
+    u8 enc = pRec->enc;
     sqlite3VdbeMemNulTerminate(pRec);
-    if( (pRec->flags&MEM_Str)
-         && sqlite3IsNumber(pRec->z, &realnum, pRec->enc) ){
+    if( (pRec->flags&MEM_Str) && sqlite3IsNumber(pRec->z, &realnum, enc) ){
       i64 value;
-      sqlite3VdbeChangeEncoding(pRec, SQLITE_UTF8);
-      if( !realnum && sqlite3Atoi64(pRec->z, &value) ){
+      char *zUtf8 = pRec->z;
+#ifndef SQLITE_OMIT_UTF16
+      if( enc!=SQLITE_UTF8 ){
+        assert( pRec->db );
+        zUtf8 = sqlite3Utf16to8(pRec->db, pRec->z, pRec->n, enc);
+        if( !zUtf8 ) return;
+      }
+#endif
+      if( !realnum && sqlite3Atoi64(zUtf8, &value) ){
         pRec->u.i = value;
         MemSetTypeFlag(pRec, MEM_Int);
       }else{
-        sqlite3VdbeMemRealify(pRec);
+        sqlite3AtoF(zUtf8, &pRec->r);
+        MemSetTypeFlag(pRec, MEM_Real);
       }
+#ifndef SQLITE_OMIT_UTF16
+      if( enc!=SQLITE_UTF8 ){
+        sqlite3DbFree(pRec->db, zUtf8);
+      }
+#endif
     }
   }
 }
@@ -52480,22 +58068,6 @@
 #define CHECK_FOR_INTERRUPT \
    if( db->u1.isInterrupted ) goto abort_due_to_interrupt;
 
-#ifdef SQLITE_DEBUG
-static int fileExists(sqlite3 *db, const char *zFile){
-  int res = 0;
-  int rc = SQLITE_OK;
-#ifdef SQLITE_TEST
-  /* If we are currently testing IO errors, then do not call OsAccess() to
-  ** test for the presence of zFile. This is because any IO error that
-  ** occurs here will not be reported, causing the test to fail.
-  */
-  extern int sqlite3_io_error_pending;
-  if( sqlite3_io_error_pending<=0 )
-#endif
-    rc = sqlite3OsAccess(db->pVfs, zFile, SQLITE_ACCESS_EXISTS, &res);
-  return (res && rc==SQLITE_OK);
-}
-#endif
 
 #ifndef NDEBUG
 /*
@@ -52551,7 +58123,7 @@
 SQLITE_PRIVATE int sqlite3VdbeExec(
   Vdbe *p                    /* The VDBE */
 ){
-  int pc;                    /* The program counter */
+  int pc=0;                  /* The program counter */
   Op *aOp = p->aOp;          /* Copy of p->aOp */
   Op *pOp;                   /* Current operation */
   int rc = SQLITE_OK;        /* Value to return */
@@ -52586,9 +58158,6 @@
       int pcDest;
     } aa;
     struct OP_Variable_stack_vars {
-      int p1;          /* Variable to copy from */
-      int p2;          /* Register to copy to */
-      int n;           /* Number of values left to copy */
       Mem *pVar;       /* Value being transferred */
     } ab;
     struct OP_Move_stack_vars {
@@ -52625,6 +58194,8 @@
     struct OP_Ge_stack_vars {
       int res;            /* Result of the comparison of pIn1 against pIn3 */
       char affinity;      /* Affinity to use for comparison */
+      u16 flags1;         /* Copy of initial value of pIn1->flags */
+      u16 flags3;         /* Copy of initial value of pIn3->flags */
     } ai;
     struct OP_Compare_stack_vars {
       int n;
@@ -52911,18 +58482,25 @@
     struct OP_AggFinal_stack_vars {
       Mem *pMem;
     } cc;
+    struct OP_JournalMode_stack_vars {
+      Btree *pBt;                     /* Btree to change journal mode of */
+      Pager *pPager;                  /* Pager associated with pBt */
+      int eNew;                       /* New journal mode */
+      int eOld;                       /* The old journal mode */
+      const char *zFilename;          /* Name of database file for pPager */
+    } cd;
     struct OP_IncrVacuum_stack_vars {
       Btree *pBt;
-    } cd;
+    } ce;
     struct OP_VBegin_stack_vars {
       VTable *pVTab;
-    } ce;
+    } cf;
     struct OP_VOpen_stack_vars {
       VdbeCursor *pCur;
       sqlite3_vtab_cursor *pVtabCursor;
       sqlite3_vtab *pVtab;
       sqlite3_module *pModule;
-    } cf;
+    } cg;
     struct OP_VFilter_stack_vars {
       int nArg;
       int iQuery;
@@ -52935,23 +58513,23 @@
       int res;
       int i;
       Mem **apArg;
-    } cg;
+    } ch;
     struct OP_VColumn_stack_vars {
       sqlite3_vtab *pVtab;
       const sqlite3_module *pModule;
       Mem *pDest;
       sqlite3_context sContext;
-    } ch;
+    } ci;
     struct OP_VNext_stack_vars {
       sqlite3_vtab *pVtab;
       const sqlite3_module *pModule;
       int res;
       VdbeCursor *pCur;
-    } ci;
+    } cj;
     struct OP_VRename_stack_vars {
       sqlite3_vtab *pVtab;
       Mem *pName;
-    } cj;
+    } ck;
     struct OP_VUpdate_stack_vars {
       sqlite3_vtab *pVtab;
       sqlite3_module *pModule;
@@ -52960,11 +58538,6 @@
       sqlite_int64 rowid;
       Mem **apArg;
       Mem *pX;
-    } ck;
-    struct OP_Pagecount_stack_vars {
-      int p1;
-      int nPage;
-      Pager *pPager;
     } cl;
     struct OP_Trace_stack_vars {
       char *zTrace;
@@ -52992,9 +58565,7 @@
 #endif
 #ifdef SQLITE_DEBUG
   sqlite3BeginBenignMalloc();
-  if( p->pc==0 
-   && ((p->db->flags & SQLITE_VdbeListing) || fileExists(db, "vdbe_explain"))
-  ){
+  if( p->pc==0  && (p->db->flags & SQLITE_VdbeListing)!=0 ){
     int i;
     printf("VDBE Program Listing:\n");
     sqlite3VdbePrintSql(p);
@@ -53002,9 +58573,6 @@
       sqlite3VdbePrintOp(stdout, i, &aOp[i]);
     }
   }
-  if( fileExists(db, "vdbe_trace") ){
-    p->trace = stdout;
-  }
   sqlite3EndBenignMalloc();
 #endif
   for(pc=p->pc; rc==SQLITE_OK; pc++){
@@ -53026,13 +58594,6 @@
       }
       sqlite3VdbePrintOp(p->trace, pc, pOp);
     }
-    if( p->trace==0 && pc==0 ){
-      sqlite3BeginBenignMalloc();
-      if( fileExists(db, "vdbe_sqltrace") ){
-        sqlite3VdbePrintSql(p);
-      }
-      sqlite3EndBenignMalloc();
-    }
 #endif
       
 
@@ -53300,6 +58861,7 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /* Opcode: Real * P2 * P4 *
 **
 ** P4 is a pointer to a 64-bit floating point value.
@@ -53311,6 +58873,7 @@
   pOut->r = *pOp->p4.pReal;
   break;
 }
+#endif
 
 /* Opcode: String8 * P2 * P4 *
 **
@@ -53387,40 +58950,25 @@
   break;
 }
 
-/* Opcode: Variable P1 P2 P3 P4 *
+/* Opcode: Variable P1 P2 * P4 *
 **
-** Transfer the values of bound parameters P1..P1+P3-1 into registers
-** P2..P2+P3-1.
+** Transfer the values of bound parameter P1 into register P2
 **
 ** If the parameter is named, then its name appears in P4 and P3==1.
 ** The P4 value is used by sqlite3_bind_parameter_name().
 */
-case OP_Variable: {
+case OP_Variable: {            /* out2-prerelease */
 #if 0  /* local variables moved into u.ab */
-  int p1;          /* Variable to copy from */
-  int p2;          /* Register to copy to */
-  int n;           /* Number of values left to copy */
   Mem *pVar;       /* Value being transferred */
 #endif /* local variables moved into u.ab */
 
-  u.ab.p1 = pOp->p1 - 1;
-  u.ab.p2 = pOp->p2;
-  u.ab.n = pOp->p3;
-  assert( u.ab.p1>=0 && u.ab.p1+u.ab.n<=p->nVar );
-  assert( u.ab.p2>=1 && u.ab.p2+u.ab.n-1<=p->nMem );
-  assert( pOp->p4.z==0 || pOp->p3==1 || pOp->p3==0 );
-
-  while( u.ab.n-- > 0 ){
-    u.ab.pVar = &p->aVar[u.ab.p1++];
-    if( sqlite3VdbeMemTooBig(u.ab.pVar) ){
-      goto too_big;
-    }
-    pOut = &aMem[u.ab.p2++];
-    sqlite3VdbeMemReleaseExternal(pOut);
-    pOut->flags = MEM_Null;
-    sqlite3VdbeMemShallowCopy(pOut, u.ab.pVar, MEM_Static);
-    UPDATE_MAX_BLOBSIZE(pOut);
+  assert( pOp->p1>0 && pOp->p1<=p->nVar );
+  u.ab.pVar = &p->aVar[pOp->p1 - 1];
+  if( sqlite3VdbeMemTooBig(u.ab.pVar) ){
+    goto too_big;
   }
+  sqlite3VdbeMemShallowCopy(pOut, u.ab.pVar, MEM_Static);
+  UPDATE_MAX_BLOBSIZE(pOut);
   break;
 }
 
@@ -53721,6 +59269,10 @@
         break;
       }
     }
+#ifdef SQLITE_OMIT_FLOATING_POINT
+    pOut->u.i = u.af.rB;
+    MemSetTypeFlag(pOut, MEM_Int);
+#else
     if( sqlite3IsNaN(u.af.rB) ){
       goto arithmetic_result_is_null;
     }
@@ -53729,6 +59281,7 @@
     if( (u.af.flags & MEM_Real)==0 ){
       sqlite3VdbeIntegerAffinity(pOut);
     }
+#endif
   }
   break;
 
@@ -53788,7 +59341,7 @@
   for(u.ag.i=0; u.ag.i<u.ag.n; u.ag.i++, u.ag.pArg++){
     u.ag.apVal[u.ag.i] = u.ag.pArg;
     sqlite3VdbeMemStoreType(u.ag.pArg);
-    REGISTER_TRACE(pOp->p2, u.ag.pArg);
+    REGISTER_TRACE(pOp->p2+u.ag.i, u.ag.pArg);
   }
 
   assert( pOp->p4type==P4_FUNCDEF || pOp->p4type==P4_VDBEFUNC );
@@ -53951,6 +59504,7 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /* Opcode: RealAffinity P1 * * * *
 **
 ** If register P1 holds an integer convert it to a real value.
@@ -53967,6 +59521,7 @@
   }
   break;
 }
+#endif
 
 #ifndef SQLITE_OMIT_CAST
 /* Opcode: ToText P1 * * * *
@@ -54050,7 +59605,7 @@
   break;
 }
 
-#ifndef SQLITE_OMIT_CAST
+#if !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT)
 /* Opcode: ToReal P1 * * * *
 **
 ** Force the value in register P1 to be a floating point number.
@@ -54067,7 +59622,7 @@
   }
   break;
 }
-#endif /* SQLITE_OMIT_CAST */
+#endif /* !defined(SQLITE_OMIT_CAST) && !defined(SQLITE_OMIT_FLOATING_POINT) */
 
 /* Opcode: Lt P1 P2 P3 P4 P5
 **
@@ -54150,10 +59705,14 @@
 #if 0  /* local variables moved into u.ai */
   int res;            /* Result of the comparison of pIn1 against pIn3 */
   char affinity;      /* Affinity to use for comparison */
+  u16 flags1;         /* Copy of initial value of pIn1->flags */
+  u16 flags3;         /* Copy of initial value of pIn3->flags */
 #endif /* local variables moved into u.ai */
 
   pIn1 = &aMem[pOp->p1];
   pIn3 = &aMem[pOp->p3];
+  u.ai.flags1 = pIn1->flags;
+  u.ai.flags3 = pIn3->flags;
   if( (pIn1->flags | pIn3->flags)&MEM_Null ){
     /* One or both operands are NULL */
     if( pOp->p5 & SQLITE_NULLEQ ){
@@ -54208,6 +59767,10 @@
   }else if( u.ai.res ){
     pc = pOp->p2-1;
   }
+
+  /* Undo any changes made by applyAffinity() to the input registers. */
+  pIn1->flags = (pIn1->flags&~MEM_TypeMask) | (u.ai.flags1&MEM_TypeMask);
+  pIn3->flags = (pIn3->flags&~MEM_TypeMask) | (u.ai.flags3&MEM_TypeMask);
   break;
 }
 
@@ -55495,10 +61058,10 @@
 **
 ** Open a new cursor P1 to a transient table.
 ** The cursor is always opened read/write even if 
-** the main database is read-only.  The transient or virtual
+** the main database is read-only.  The ephemeral
 ** table is deleted automatically when the cursor is closed.
 **
-** P2 is the number of columns in the virtual table.
+** P2 is the number of columns in the ephemeral table.
 ** The cursor points to a BTree table if P4==0 and to a BTree index
 ** if P4 is not 0.  If P4 is not NULL, it points to a KeyInfo structure
 ** that defines the format of keys in the index.
@@ -55509,6 +61072,14 @@
 ** this opcode.  Then this opcode was call OpenVirtual.  But
 ** that created confusion with the whole virtual-table idea.
 */
+/* Opcode: OpenAutoindex P1 P2 * P4 *
+**
+** This opcode works the same as OP_OpenEphemeral.  It has a
+** different name to distinguish its use.  Tables created using
+** by this opcode will be used for automatically created transient
+** indices in joins.
+*/
+case OP_OpenAutoindex: 
 case OP_OpenEphemeral: {
 #if 0  /* local variables moved into u.ax */
   VdbeCursor *pCx;
@@ -55563,7 +61134,7 @@
 ** register P2.  In other words, cursor P1 becomes an alias for the 
 ** MEM_Blob content contained in register P2.
 **
-** A pseudo-table created by this opcode is used to hold the a single
+** A pseudo-table created by this opcode is used to hold a single
 ** row output from the sorter so that the row can be decomposed into
 ** individual columns using the OP_Column opcode.  The OP_Column opcode
 ** is the only cursor opcode that works with a pseudo-table.
@@ -56647,7 +62218,7 @@
   break;
 }
 
-/* Opcode: Next P1 P2 * * *
+/* Opcode: Next P1 P2 * * P5
 **
 ** Advance cursor P1 so that it points to the next key/data pair in its
 ** table or index.  If there are no more key/value pairs then fall through
@@ -56656,9 +62227,12 @@
 **
 ** The P1 cursor must be for a real table, not a pseudo-table.
 **
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
+**
 ** See also: Prev
 */
-/* Opcode: Prev P1 P2 * * *
+/* Opcode: Prev P1 P2 * * P5
 **
 ** Back up cursor P1 so that it points to the previous key/data pair in its
 ** table or index.  If there is no previous key/value pairs then fall through
@@ -56666,6 +62240,9 @@
 ** jump immediately to P2.
 **
 ** The P1 cursor must be for a real table, not a pseudo-table.
+**
+** If P5 is positive and the jump is taken, then event counter
+** number P5-1 in the prepared statement is incremented.
 */
 case OP_Prev:          /* jump */
 case OP_Next: {        /* jump */
@@ -56677,6 +62254,7 @@
 
   CHECK_FOR_INTERRUPT;
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+  assert( pOp->p5<=ArraySize(p->aCounter) );
   u.bm.pC = p->apCsr[pOp->p1];
   if( u.bm.pC==0 ){
     break;  /* See ticket #2273 */
@@ -57073,7 +62651,7 @@
     u.bu.initData.iDb = pOp->p1;
     u.bu.initData.pzErrMsg = &p->zErrMsg;
     u.bu.zSql = sqlite3MPrintf(db,
-       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s",
+       "SELECT name, rootpage, sql FROM '%q'.%s WHERE %s ORDER BY rowid",
        db->aDb[u.bu.iDb].zName, u.bu.zMaster, pOp->p4.z);
     if( u.bu.zSql==0 ){
       rc = SQLITE_NOMEM;
@@ -57662,6 +63240,144 @@
   break;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/* Opcode: Checkpoint P1 * * * *
+**
+** Checkpoint database P1. This is a no-op if P1 is not currently in
+** WAL mode.
+*/
+case OP_Checkpoint: {
+  rc = sqlite3Checkpoint(db, pOp->p1);
+  break;
+};  
+#endif
+
+/* Opcode: JournalMode P1 P2 P3 * P5
+**
+** Change the journal mode of database P1 to P3. P3 must be one of the
+** PAGER_JOURNALMODE_XXX values. If changing between the various rollback
+** modes (delete, truncate, persist, off and memory), this is a simple
+** operation. No IO is required.
+**
+** If changing into or out of WAL mode the procedure is more complicated.
+**
+** Write a string containing the final journal-mode to register P2.
+**
+** If an attempt to change in to or out of WAL mode fails because another
+** connection also has the same database open, then an SQLITE_BUSY error
+** is raised if P5==0, or of P5!=0 the journal mode changed is skipped
+** without signaling the error.
+*/
+case OP_JournalMode: {    /* out2-prerelease */
+#if 0  /* local variables moved into u.cd */
+  Btree *pBt;                     /* Btree to change journal mode of */
+  Pager *pPager;                  /* Pager associated with pBt */
+  int eNew;                       /* New journal mode */
+  int eOld;                       /* The old journal mode */
+  const char *zFilename;          /* Name of database file for pPager */
+#endif /* local variables moved into u.cd */
+
+  u.cd.eNew = pOp->p3;
+  assert( u.cd.eNew==PAGER_JOURNALMODE_DELETE
+       || u.cd.eNew==PAGER_JOURNALMODE_TRUNCATE
+       || u.cd.eNew==PAGER_JOURNALMODE_PERSIST
+       || u.cd.eNew==PAGER_JOURNALMODE_OFF
+       || u.cd.eNew==PAGER_JOURNALMODE_MEMORY
+       || u.cd.eNew==PAGER_JOURNALMODE_WAL
+       || u.cd.eNew==PAGER_JOURNALMODE_QUERY
+  );
+  assert( pOp->p1>=0 && pOp->p1<db->nDb );
+
+  /* This opcode is used in two places: PRAGMA journal_mode and ATTACH.
+  ** In PRAGMA journal_mode, the sqlite3VdbeUsesBtree() routine is called
+  ** when the statment is prepared and so p->aMutex.nMutex>0.  All mutexes
+  ** are already acquired.  But when used in ATTACH, sqlite3VdbeUsesBtree()
+  ** is not called when the statement is prepared because it requires the
+  ** iDb index of the database as a parameter, and the database has not
+  ** yet been attached so that index is unavailable.  We have to wait
+  ** until runtime (now) to get the mutex on the newly attached database.
+  ** No other mutexes are required by the ATTACH command so this is safe
+  ** to do.
+  */
+  assert( (p->btreeMask & (1<<pOp->p1))!=0 || p->aMutex.nMutex==0 );
+  if( p->aMutex.nMutex==0 ){
+    /* This occurs right after ATTACH.  Get a mutex on the newly ATTACHed
+    ** database. */
+    sqlite3VdbeUsesBtree(p, pOp->p1);
+    sqlite3VdbeMutexArrayEnter(p);
+  }
+
+  u.cd.pBt = db->aDb[pOp->p1].pBt;
+  u.cd.pPager = sqlite3BtreePager(u.cd.pBt);
+  u.cd.eOld = sqlite3PagerGetJournalMode(u.cd.pPager);
+  if( u.cd.eNew==PAGER_JOURNALMODE_QUERY ) u.cd.eNew = u.cd.eOld;
+  if( !sqlite3PagerOkToChangeJournalMode(u.cd.pPager) ) u.cd.eNew = u.cd.eOld;
+
+#ifndef SQLITE_OMIT_WAL
+  u.cd.zFilename = sqlite3PagerFilename(u.cd.pPager);
+
+  /* Do not allow a transition to journal_mode=WAL for a database
+  ** in temporary storage or if the VFS does not support xShmOpen.
+  */
+  if( u.cd.eNew==PAGER_JOURNALMODE_WAL
+   && (u.cd.zFilename[0]==0                         /* Temp file */
+       || !sqlite3PagerWalSupported(u.cd.pPager))   /* No xShmOpen support */
+  ){
+    u.cd.eNew = u.cd.eOld;
+  }
+
+  if( (u.cd.eNew!=u.cd.eOld)
+   && (u.cd.eOld==PAGER_JOURNALMODE_WAL || u.cd.eNew==PAGER_JOURNALMODE_WAL)
+  ){
+    if( !db->autoCommit || db->activeVdbeCnt>1 ){
+      rc = SQLITE_ERROR;
+      sqlite3SetString(&p->zErrMsg, db,
+          "cannot change %s wal mode from within a transaction",
+          (u.cd.eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
+      );
+      break;
+    }else{
+
+      if( u.cd.eOld==PAGER_JOURNALMODE_WAL ){
+        /* If leaving WAL mode, close the log file. If successful, the call
+        ** to PagerCloseWal() checkpoints and deletes the write-ahead-log
+        ** file. An EXCLUSIVE lock may still be held on the database file
+        ** after a successful return.
+        */
+        rc = sqlite3PagerCloseWal(u.cd.pPager);
+        if( rc==SQLITE_OK ){
+          sqlite3PagerSetJournalMode(u.cd.pPager, u.cd.eNew);
+        }else if( rc==SQLITE_BUSY && pOp->p5==0 ){
+          goto abort_due_to_error;
+        }
+      }
+
+      /* Open a transaction on the database file. Regardless of the journal
+      ** mode, this transaction always uses a rollback journal.
+      */
+      assert( sqlite3BtreeIsInTrans(u.cd.pBt)==0 );
+      if( rc==SQLITE_OK ){
+        rc = sqlite3BtreeSetVersion(u.cd.pBt, (u.cd.eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
+        if( rc==SQLITE_BUSY && pOp->p5==0 ) goto abort_due_to_error;
+      }
+      if( rc==SQLITE_BUSY ){
+        u.cd.eNew = u.cd.eOld;
+        rc = SQLITE_OK;
+      }
+    }
+  }
+#endif /* ifndef SQLITE_OMIT_WAL */
+
+  u.cd.eNew = sqlite3PagerSetJournalMode(u.cd.pPager, u.cd.eNew);
+
+  pOut = &aMem[pOp->p2];
+  pOut->flags = MEM_Str|MEM_Static|MEM_Term;
+  pOut->z = (char *)sqlite3JournalModename(u.cd.eNew);
+  pOut->n = sqlite3Strlen30(pOut->z);
+  pOut->enc = SQLITE_UTF8;
+  sqlite3VdbeChangeEncoding(pOut, encoding);
+  break;
+};  
 
 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
 /* Opcode: Vacuum * * * * *
@@ -57684,14 +63400,14 @@
 ** P2. Otherwise, fall through to the next instruction.
 */
 case OP_IncrVacuum: {        /* jump */
-#if 0  /* local variables moved into u.cd */
+#if 0  /* local variables moved into u.ce */
   Btree *pBt;
-#endif /* local variables moved into u.cd */
+#endif /* local variables moved into u.ce */
 
   assert( pOp->p1>=0 && pOp->p1<db->nDb );
   assert( (p->btreeMask & (1<<pOp->p1))!=0 );
-  u.cd.pBt = db->aDb[pOp->p1].pBt;
-  rc = sqlite3BtreeIncrVacuum(u.cd.pBt);
+  u.ce.pBt = db->aDb[pOp->p1].pBt;
+  rc = sqlite3BtreeIncrVacuum(u.ce.pBt);
   if( rc==SQLITE_DONE ){
     pc = pOp->p2 - 1;
     rc = SQLITE_OK;
@@ -57761,15 +63477,15 @@
 ** code will be set to SQLITE_LOCKED.
 */
 case OP_VBegin: {
-#if 0  /* local variables moved into u.ce */
+#if 0  /* local variables moved into u.cf */
   VTable *pVTab;
-#endif /* local variables moved into u.ce */
-  u.ce.pVTab = pOp->p4.pVtab;
-  rc = sqlite3VtabBegin(db, u.ce.pVTab);
-  if( u.ce.pVTab ){
+#endif /* local variables moved into u.cf */
+  u.cf.pVTab = pOp->p4.pVtab;
+  rc = sqlite3VtabBegin(db, u.cf.pVTab);
+  if( u.cf.pVTab ){
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.ce.pVTab->pVtab->zErrMsg;
-    u.ce.pVTab->pVtab->zErrMsg = 0;
+    p->zErrMsg = u.cf.pVTab->pVtab->zErrMsg;
+    u.cf.pVTab->pVtab->zErrMsg = 0;
   }
   break;
 }
@@ -57809,34 +63525,34 @@
 ** table and stores that cursor in P1.
 */
 case OP_VOpen: {
-#if 0  /* local variables moved into u.cf */
+#if 0  /* local variables moved into u.cg */
   VdbeCursor *pCur;
   sqlite3_vtab_cursor *pVtabCursor;
   sqlite3_vtab *pVtab;
   sqlite3_module *pModule;
-#endif /* local variables moved into u.cf */
+#endif /* local variables moved into u.cg */
 
-  u.cf.pCur = 0;
-  u.cf.pVtabCursor = 0;
-  u.cf.pVtab = pOp->p4.pVtab->pVtab;
-  u.cf.pModule = (sqlite3_module *)u.cf.pVtab->pModule;
-  assert(u.cf.pVtab && u.cf.pModule);
-  rc = u.cf.pModule->xOpen(u.cf.pVtab, &u.cf.pVtabCursor);
+  u.cg.pCur = 0;
+  u.cg.pVtabCursor = 0;
+  u.cg.pVtab = pOp->p4.pVtab->pVtab;
+  u.cg.pModule = (sqlite3_module *)u.cg.pVtab->pModule;
+  assert(u.cg.pVtab && u.cg.pModule);
+  rc = u.cg.pModule->xOpen(u.cg.pVtab, &u.cg.pVtabCursor);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.cf.pVtab->zErrMsg;
-  u.cf.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.cg.pVtab->zErrMsg;
+  u.cg.pVtab->zErrMsg = 0;
   if( SQLITE_OK==rc ){
     /* Initialize sqlite3_vtab_cursor base class */
-    u.cf.pVtabCursor->pVtab = u.cf.pVtab;
+    u.cg.pVtabCursor->pVtab = u.cg.pVtab;
 
     /* Initialise vdbe cursor object */
-    u.cf.pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
-    if( u.cf.pCur ){
-      u.cf.pCur->pVtabCursor = u.cf.pVtabCursor;
-      u.cf.pCur->pModule = u.cf.pVtabCursor->pVtab->pModule;
+    u.cg.pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
+    if( u.cg.pCur ){
+      u.cg.pCur->pVtabCursor = u.cg.pVtabCursor;
+      u.cg.pCur->pModule = u.cg.pVtabCursor->pVtab->pModule;
     }else{
       db->mallocFailed = 1;
-      u.cf.pModule->xClose(u.cf.pVtabCursor);
+      u.cg.pModule->xClose(u.cg.pVtabCursor);
     }
   }
   break;
@@ -57863,7 +63579,7 @@
 ** A jump is made to P2 if the result set after filtering would be empty.
 */
 case OP_VFilter: {   /* jump */
-#if 0  /* local variables moved into u.cg */
+#if 0  /* local variables moved into u.ch */
   int nArg;
   int iQuery;
   const sqlite3_module *pModule;
@@ -57875,46 +63591,46 @@
   int res;
   int i;
   Mem **apArg;
-#endif /* local variables moved into u.cg */
+#endif /* local variables moved into u.ch */
 
-  u.cg.pQuery = &aMem[pOp->p3];
-  u.cg.pArgc = &u.cg.pQuery[1];
-  u.cg.pCur = p->apCsr[pOp->p1];
-  REGISTER_TRACE(pOp->p3, u.cg.pQuery);
-  assert( u.cg.pCur->pVtabCursor );
-  u.cg.pVtabCursor = u.cg.pCur->pVtabCursor;
-  u.cg.pVtab = u.cg.pVtabCursor->pVtab;
-  u.cg.pModule = u.cg.pVtab->pModule;
+  u.ch.pQuery = &aMem[pOp->p3];
+  u.ch.pArgc = &u.ch.pQuery[1];
+  u.ch.pCur = p->apCsr[pOp->p1];
+  REGISTER_TRACE(pOp->p3, u.ch.pQuery);
+  assert( u.ch.pCur->pVtabCursor );
+  u.ch.pVtabCursor = u.ch.pCur->pVtabCursor;
+  u.ch.pVtab = u.ch.pVtabCursor->pVtab;
+  u.ch.pModule = u.ch.pVtab->pModule;
 
   /* Grab the index number and argc parameters */
-  assert( (u.cg.pQuery->flags&MEM_Int)!=0 && u.cg.pArgc->flags==MEM_Int );
-  u.cg.nArg = (int)u.cg.pArgc->u.i;
-  u.cg.iQuery = (int)u.cg.pQuery->u.i;
+  assert( (u.ch.pQuery->flags&MEM_Int)!=0 && u.ch.pArgc->flags==MEM_Int );
+  u.ch.nArg = (int)u.ch.pArgc->u.i;
+  u.ch.iQuery = (int)u.ch.pQuery->u.i;
 
   /* Invoke the xFilter method */
   {
-    u.cg.res = 0;
-    u.cg.apArg = p->apArg;
-    for(u.cg.i = 0; u.cg.i<u.cg.nArg; u.cg.i++){
-      u.cg.apArg[u.cg.i] = &u.cg.pArgc[u.cg.i+1];
-      sqlite3VdbeMemStoreType(u.cg.apArg[u.cg.i]);
+    u.ch.res = 0;
+    u.ch.apArg = p->apArg;
+    for(u.ch.i = 0; u.ch.i<u.ch.nArg; u.ch.i++){
+      u.ch.apArg[u.ch.i] = &u.ch.pArgc[u.ch.i+1];
+      sqlite3VdbeMemStoreType(u.ch.apArg[u.ch.i]);
     }
 
     p->inVtabMethod = 1;
-    rc = u.cg.pModule->xFilter(u.cg.pVtabCursor, u.cg.iQuery, pOp->p4.z, u.cg.nArg, u.cg.apArg);
+    rc = u.ch.pModule->xFilter(u.ch.pVtabCursor, u.ch.iQuery, pOp->p4.z, u.ch.nArg, u.ch.apArg);
     p->inVtabMethod = 0;
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.cg.pVtab->zErrMsg;
-    u.cg.pVtab->zErrMsg = 0;
+    p->zErrMsg = u.ch.pVtab->zErrMsg;
+    u.ch.pVtab->zErrMsg = 0;
     if( rc==SQLITE_OK ){
-      u.cg.res = u.cg.pModule->xEof(u.cg.pVtabCursor);
+      u.ch.res = u.ch.pModule->xEof(u.ch.pVtabCursor);
     }
 
-    if( u.cg.res ){
+    if( u.ch.res ){
       pc = pOp->p2 - 1;
     }
   }
-  u.cg.pCur->nullRow = 0;
+  u.ch.pCur->nullRow = 0;
 
   break;
 }
@@ -57928,52 +63644,52 @@
 ** P1 cursor is pointing to into register P3.
 */
 case OP_VColumn: {
-#if 0  /* local variables moved into u.ch */
+#if 0  /* local variables moved into u.ci */
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
   Mem *pDest;
   sqlite3_context sContext;
-#endif /* local variables moved into u.ch */
+#endif /* local variables moved into u.ci */
 
   VdbeCursor *pCur = p->apCsr[pOp->p1];
   assert( pCur->pVtabCursor );
   assert( pOp->p3>0 && pOp->p3<=p->nMem );
-  u.ch.pDest = &aMem[pOp->p3];
+  u.ci.pDest = &aMem[pOp->p3];
   if( pCur->nullRow ){
-    sqlite3VdbeMemSetNull(u.ch.pDest);
+    sqlite3VdbeMemSetNull(u.ci.pDest);
     break;
   }
-  u.ch.pVtab = pCur->pVtabCursor->pVtab;
-  u.ch.pModule = u.ch.pVtab->pModule;
-  assert( u.ch.pModule->xColumn );
-  memset(&u.ch.sContext, 0, sizeof(u.ch.sContext));
+  u.ci.pVtab = pCur->pVtabCursor->pVtab;
+  u.ci.pModule = u.ci.pVtab->pModule;
+  assert( u.ci.pModule->xColumn );
+  memset(&u.ci.sContext, 0, sizeof(u.ci.sContext));
 
   /* The output cell may already have a buffer allocated. Move
-  ** the current contents to u.ch.sContext.s so in case the user-function
+  ** the current contents to u.ci.sContext.s so in case the user-function
   ** can use the already allocated buffer instead of allocating a
   ** new one.
   */
-  sqlite3VdbeMemMove(&u.ch.sContext.s, u.ch.pDest);
-  MemSetTypeFlag(&u.ch.sContext.s, MEM_Null);
+  sqlite3VdbeMemMove(&u.ci.sContext.s, u.ci.pDest);
+  MemSetTypeFlag(&u.ci.sContext.s, MEM_Null);
 
-  rc = u.ch.pModule->xColumn(pCur->pVtabCursor, &u.ch.sContext, pOp->p2);
+  rc = u.ci.pModule->xColumn(pCur->pVtabCursor, &u.ci.sContext, pOp->p2);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.ch.pVtab->zErrMsg;
-  u.ch.pVtab->zErrMsg = 0;
-  if( u.ch.sContext.isError ){
-    rc = u.ch.sContext.isError;
+  p->zErrMsg = u.ci.pVtab->zErrMsg;
+  u.ci.pVtab->zErrMsg = 0;
+  if( u.ci.sContext.isError ){
+    rc = u.ci.sContext.isError;
   }
 
   /* Copy the result of the function to the P3 register. We
   ** do this regardless of whether or not an error occurred to ensure any
-  ** dynamic allocation in u.ch.sContext.s (a Mem struct) is  released.
+  ** dynamic allocation in u.ci.sContext.s (a Mem struct) is  released.
   */
-  sqlite3VdbeChangeEncoding(&u.ch.sContext.s, encoding);
-  sqlite3VdbeMemMove(u.ch.pDest, &u.ch.sContext.s);
-  REGISTER_TRACE(pOp->p3, u.ch.pDest);
-  UPDATE_MAX_BLOBSIZE(u.ch.pDest);
+  sqlite3VdbeChangeEncoding(&u.ci.sContext.s, encoding);
+  sqlite3VdbeMemMove(u.ci.pDest, &u.ci.sContext.s);
+  REGISTER_TRACE(pOp->p3, u.ci.pDest);
+  UPDATE_MAX_BLOBSIZE(u.ci.pDest);
 
-  if( sqlite3VdbeMemTooBig(u.ch.pDest) ){
+  if( sqlite3VdbeMemTooBig(u.ci.pDest) ){
     goto too_big;
   }
   break;
@@ -57988,22 +63704,22 @@
 ** the end of its result set, then fall through to the next instruction.
 */
 case OP_VNext: {   /* jump */
-#if 0  /* local variables moved into u.ci */
+#if 0  /* local variables moved into u.cj */
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
   int res;
   VdbeCursor *pCur;
-#endif /* local variables moved into u.ci */
+#endif /* local variables moved into u.cj */
 
-  u.ci.res = 0;
-  u.ci.pCur = p->apCsr[pOp->p1];
-  assert( u.ci.pCur->pVtabCursor );
-  if( u.ci.pCur->nullRow ){
+  u.cj.res = 0;
+  u.cj.pCur = p->apCsr[pOp->p1];
+  assert( u.cj.pCur->pVtabCursor );
+  if( u.cj.pCur->nullRow ){
     break;
   }
-  u.ci.pVtab = u.ci.pCur->pVtabCursor->pVtab;
-  u.ci.pModule = u.ci.pVtab->pModule;
-  assert( u.ci.pModule->xNext );
+  u.cj.pVtab = u.cj.pCur->pVtabCursor->pVtab;
+  u.cj.pModule = u.cj.pVtab->pModule;
+  assert( u.cj.pModule->xNext );
 
   /* Invoke the xNext() method of the module. There is no way for the
   ** underlying implementation to return an error if one occurs during
@@ -58012,16 +63728,16 @@
   ** some other method is next invoked on the save virtual table cursor.
   */
   p->inVtabMethod = 1;
-  rc = u.ci.pModule->xNext(u.ci.pCur->pVtabCursor);
+  rc = u.cj.pModule->xNext(u.cj.pCur->pVtabCursor);
   p->inVtabMethod = 0;
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.ci.pVtab->zErrMsg;
-  u.ci.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.cj.pVtab->zErrMsg;
+  u.cj.pVtab->zErrMsg = 0;
   if( rc==SQLITE_OK ){
-    u.ci.res = u.ci.pModule->xEof(u.ci.pCur->pVtabCursor);
+    u.cj.res = u.cj.pModule->xEof(u.cj.pCur->pVtabCursor);
   }
 
-  if( !u.ci.res ){
+  if( !u.cj.res ){
     /* If there is data, jump to P2 */
     pc = pOp->p2 - 1;
   }
@@ -58037,20 +63753,20 @@
 ** in register P1 is passed as the zName argument to the xRename method.
 */
 case OP_VRename: {
-#if 0  /* local variables moved into u.cj */
+#if 0  /* local variables moved into u.ck */
   sqlite3_vtab *pVtab;
   Mem *pName;
-#endif /* local variables moved into u.cj */
+#endif /* local variables moved into u.ck */
 
-  u.cj.pVtab = pOp->p4.pVtab->pVtab;
-  u.cj.pName = &aMem[pOp->p1];
-  assert( u.cj.pVtab->pModule->xRename );
-  REGISTER_TRACE(pOp->p1, u.cj.pName);
-  assert( u.cj.pName->flags & MEM_Str );
-  rc = u.cj.pVtab->pModule->xRename(u.cj.pVtab, u.cj.pName->z);
+  u.ck.pVtab = pOp->p4.pVtab->pVtab;
+  u.ck.pName = &aMem[pOp->p1];
+  assert( u.ck.pVtab->pModule->xRename );
+  REGISTER_TRACE(pOp->p1, u.ck.pName);
+  assert( u.ck.pName->flags & MEM_Str );
+  rc = u.ck.pVtab->pModule->xRename(u.ck.pVtab, u.ck.pName->z);
   sqlite3DbFree(db, p->zErrMsg);
-  p->zErrMsg = u.cj.pVtab->zErrMsg;
-  u.cj.pVtab->zErrMsg = 0;
+  p->zErrMsg = u.ck.pVtab->zErrMsg;
+  u.ck.pVtab->zErrMsg = 0;
 
   break;
 }
@@ -58081,7 +63797,7 @@
 ** is set to the value of the rowid for the row just inserted.
 */
 case OP_VUpdate: {
-#if 0  /* local variables moved into u.ck */
+#if 0  /* local variables moved into u.cl */
   sqlite3_vtab *pVtab;
   sqlite3_module *pModule;
   int nArg;
@@ -58089,27 +63805,27 @@
   sqlite_int64 rowid;
   Mem **apArg;
   Mem *pX;
-#endif /* local variables moved into u.ck */
+#endif /* local variables moved into u.cl */
 
-  u.ck.pVtab = pOp->p4.pVtab->pVtab;
-  u.ck.pModule = (sqlite3_module *)u.ck.pVtab->pModule;
-  u.ck.nArg = pOp->p2;
+  u.cl.pVtab = pOp->p4.pVtab->pVtab;
+  u.cl.pModule = (sqlite3_module *)u.cl.pVtab->pModule;
+  u.cl.nArg = pOp->p2;
   assert( pOp->p4type==P4_VTAB );
-  if( ALWAYS(u.ck.pModule->xUpdate) ){
-    u.ck.apArg = p->apArg;
-    u.ck.pX = &aMem[pOp->p3];
-    for(u.ck.i=0; u.ck.i<u.ck.nArg; u.ck.i++){
-      sqlite3VdbeMemStoreType(u.ck.pX);
-      u.ck.apArg[u.ck.i] = u.ck.pX;
-      u.ck.pX++;
+  if( ALWAYS(u.cl.pModule->xUpdate) ){
+    u.cl.apArg = p->apArg;
+    u.cl.pX = &aMem[pOp->p3];
+    for(u.cl.i=0; u.cl.i<u.cl.nArg; u.cl.i++){
+      sqlite3VdbeMemStoreType(u.cl.pX);
+      u.cl.apArg[u.cl.i] = u.cl.pX;
+      u.cl.pX++;
     }
-    rc = u.ck.pModule->xUpdate(u.ck.pVtab, u.ck.nArg, u.ck.apArg, &u.ck.rowid);
+    rc = u.cl.pModule->xUpdate(u.cl.pVtab, u.cl.nArg, u.cl.apArg, &u.cl.rowid);
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = u.ck.pVtab->zErrMsg;
-    u.ck.pVtab->zErrMsg = 0;
+    p->zErrMsg = u.cl.pVtab->zErrMsg;
+    u.cl.pVtab->zErrMsg = 0;
     if( rc==SQLITE_OK && pOp->p1 ){
-      assert( u.ck.nArg>1 && u.ck.apArg[0] && (u.ck.apArg[0]->flags&MEM_Null) );
-      db->lastRowid = u.ck.rowid;
+      assert( u.cl.nArg>1 && u.cl.apArg[0] && (u.cl.apArg[0]->flags&MEM_Null) );
+      db->lastRowid = u.cl.rowid;
     }
     p->nChange++;
   }
@@ -58123,21 +63839,7 @@
 ** Write the current number of pages in database P1 to memory cell P2.
 */
 case OP_Pagecount: {            /* out2-prerelease */
-#if 0  /* local variables moved into u.cl */
-  int p1;
-  int nPage;
-  Pager *pPager;
-#endif /* local variables moved into u.cl */
-
-  u.cl.p1 = pOp->p1;
-  u.cl.pPager = sqlite3BtreePager(db->aDb[u.cl.p1].pBt);
-  rc = sqlite3PagerPagecount(u.cl.pPager, &u.cl.nPage);
-  /* OP_Pagecount is always called from within a read transaction.  The
-  ** page count has already been successfully read and cached.  So the
-  ** sqlite3PagerPagecount() call above cannot fail. */
-  if( ALWAYS(rc==SQLITE_OK) ){
-    pOut->u.i = u.cl.nPage;
-  }
+  pOut->u.i = sqlite3BtreeLastPage(db->aDb[pOp->p1].pBt);
   break;
 }
 #endif
@@ -58183,6 +63885,7 @@
 ** the same as a no-op.  This opcodesnever appears in a real VM program.
 */
 default: {          /* This is really OP_Noop and OP_Explain */
+  assert( pOp->opcode==OP_Noop || pOp->opcode==OP_Explain );
   break;
 }
 
@@ -58234,7 +63937,9 @@
 vdbe_error_halt:
   assert( rc );
   p->rc = rc;
-  sqlite3_log(rc, "prepared statement aborts at %d: [%s]", pc, p->zSql);
+  testcase( sqlite3GlobalConfig.xLog!=0 );
+  sqlite3_log(rc, "statement aborts at %d: [%s] %s", 
+                   pc, p->zSql, p->zErrMsg);
   sqlite3VdbeHalt(p);
   if( rc==SQLITE_IOERR_NOMEM ) db->mallocFailed = 1;
   rc = SQLITE_ERROR;
@@ -59102,11 +64807,10 @@
 ** exists purely as a contingency, in case some malfunction in some other
 ** part of SQLite causes Sync to be called by mistake.
 */
-static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){   /*NO_TEST*/
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);                        /*NO_TEST*/
-  assert( 0 );                                                 /*NO_TEST*/
-  return SQLITE_OK;                                            /*NO_TEST*/
-}                                                              /*NO_TEST*/
+static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return SQLITE_OK;
+}
 
 /*
 ** Query the size of the file in bytes.
@@ -59120,7 +64824,7 @@
 /*
 ** Table of methods for MemJournal sqlite3_file object.
 */
-static struct sqlite3_io_methods MemJournalMethods = {
+static const struct sqlite3_io_methods MemJournalMethods = {
   1,                /* iVersion */
   memjrnlClose,     /* xClose */
   memjrnlRead,      /* xRead */
@@ -59143,7 +64847,7 @@
   MemJournal *p = (MemJournal *)pJfd;
   assert( EIGHT_BYTE_ALIGNMENT(p) );
   memset(p, 0, sqlite3MemJournalSize());
-  p->pMethod = &MemJournalMethods;
+  p->pMethod = (sqlite3_io_methods*)&MemJournalMethods;
 }
 
 /*
@@ -59702,7 +65406,7 @@
 
 /*
 ** Allocate and return a pointer to an expression to load the column iCol
-** from datasource iSrc datasource in SrcList pSrc.
+** from datasource iSrc in SrcList pSrc.
 */
 SQLITE_PRIVATE Expr *sqlite3CreateColumnExpr(sqlite3 *db, SrcList *pSrc, int iSrc, int iCol){
   Expr *p = sqlite3ExprAlloc(db, TK_COLUMN, 0, 0);
@@ -59714,6 +65418,8 @@
       p->iColumn = -1;
     }else{
       p->iColumn = (ynVar)iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
       pItem->colUsed |= ((Bitmask)1)<<(iCol>=BMS ? BMS-1 : iCol);
     }
     ExprSetProperty(p, EP_Resolved);
@@ -59990,7 +65696,7 @@
   ** result-set entry.
   */
   for(i=0; i<pEList->nExpr; i++){
-    if( sqlite3ExprCompare(pEList->a[i].pExpr, pE) ){
+    if( sqlite3ExprCompare(pEList->a[i].pExpr, pE)<2 ){
       return i+1;
     }
   }
@@ -60750,10 +66456,6 @@
   addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
                            (void*)p4, P4_COLLSEQ);
   sqlite3VdbeChangeP5(pParse->pVdbe, (u8)p5);
-  if( (p5 & SQLITE_AFF_MASK)!=SQLITE_AFF_NONE ){
-    sqlite3ExprCacheAffinityChange(pParse, in1, 1);
-    sqlite3ExprCacheAffinityChange(pParse, in2, 1);
-  }
   return addr;
 }
 
@@ -62384,6 +68086,7 @@
   return out;
 }
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Generate an instruction that will put the floating point
 ** value described by z[0..n-1] into register iMem.
@@ -62403,6 +68106,7 @@
     sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);
   }
 }
+#endif
 
 
 /*
@@ -62413,7 +68117,8 @@
 ** z[n] character is guaranteed to be something that does not look
 ** like the continuation of the number.
 */
-static void codeInteger(Vdbe *v, Expr *pExpr, int negFlag, int iMem){
+static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
+  Vdbe *v = pParse->pVdbe;
   if( pExpr->flags & EP_IntValue ){
     int i = pExpr->u.iValue;
     if( negFlag ) i = -i;
@@ -62429,7 +68134,11 @@
       zV = dup8bytes(v, (char*)&value);
       sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);
     }else{
+#ifdef SQLITE_OMIT_FLOATING_POINT
+      sqlite3ErrorMsg(pParse, "oversized integer: %s%s", negFlag ? "-" : "", z);
+#else
       codeReal(v, z, negFlag, iMem);
+#endif
     }
   }
 }
@@ -62582,6 +68291,27 @@
 }
 
 /*
+** Generate code to extract the value of the iCol-th column of a table.
+*/
+SQLITE_PRIVATE void sqlite3ExprCodeGetColumnOfTable(
+  Vdbe *v,        /* The VDBE under construction */
+  Table *pTab,    /* The table containing the value */
+  int iTabCur,    /* The cursor for this table */
+  int iCol,       /* Index of the column to extract */
+  int regOut      /* Extract the valud into this register */
+){
+  if( iCol<0 || iCol==pTab->iPKey ){
+    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
+  }else{
+    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
+    sqlite3VdbeAddOp3(v, op, iTabCur, iCol, regOut);
+  }
+  if( iCol>=0 ){
+    sqlite3ColumnDefault(v, pTab, iCol, regOut);
+  }
+}
+
+/*
 ** Generate code that will extract the iColumn-th column from
 ** table pTab and store the column value in a register.  An effort
 ** is made to store the column value in register iReg, but this is
@@ -62609,13 +68339,7 @@
     }
   }  
   assert( v!=0 );
-  if( iColumn<0 ){
-    sqlite3VdbeAddOp2(v, OP_Rowid, iTable, iReg);
-  }else if( ALWAYS(pTab!=0) ){
-    int op = IsVirtual(pTab) ? OP_VColumn : OP_Column;
-    sqlite3VdbeAddOp3(v, op, iTable, iColumn, iReg);
-    sqlite3ColumnDefault(v, pTab, iColumn, iReg);
-  }
+  sqlite3ExprCodeGetColumnOfTable(v, pTab, iTable, iColumn, iReg);
   sqlite3ExprCacheStore(pParse, iTable, iColumn, iReg);
   return iReg;
 }
@@ -62816,14 +68540,16 @@
       break;
     }
     case TK_INTEGER: {
-      codeInteger(v, pExpr, 0, target);
+      codeInteger(pParse, pExpr, 0, target);
       break;
     }
+#ifndef SQLITE_OMIT_FLOATING_POINT
     case TK_FLOAT: {
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       codeReal(v, pExpr->u.zToken, 0, target);
       break;
     }
+#endif
     case TK_STRING: {
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       sqlite3VdbeAddOp4(v, OP_String8, 0, target, 0, pExpr->u.zToken, 0);
@@ -62850,27 +68576,12 @@
     }
 #endif
     case TK_VARIABLE: {
-      VdbeOp *pOp;
       assert( !ExprHasProperty(pExpr, EP_IntValue) );
       assert( pExpr->u.zToken!=0 );
       assert( pExpr->u.zToken[0]!=0 );
-      if( pExpr->u.zToken[1]==0
-         && (pOp = sqlite3VdbeGetOp(v, -1))->opcode==OP_Variable
-         && pOp->p1+pOp->p3==pExpr->iColumn
-         && pOp->p2+pOp->p3==target
-         && pOp->p4.z==0
-      ){
-        /* If the previous instruction was a copy of the previous unnamed
-        ** parameter into the previous register, then simply increment the
-        ** repeat count on the prior instruction rather than making a new
-        ** instruction.
-        */
-        pOp->p3++;
-      }else{
-        sqlite3VdbeAddOp3(v, OP_Variable, pExpr->iColumn, target, 1);
-        if( pExpr->u.zToken[1]!=0 ){
-          sqlite3VdbeChangeP4(v, -1, pExpr->u.zToken, 0);
-        }
+      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iColumn, target);
+      if( pExpr->u.zToken[1]!=0 ){
+        sqlite3VdbeChangeP4(v, -1, pExpr->u.zToken, 0);
       }
       break;
     }
@@ -62993,11 +68704,13 @@
     case TK_UMINUS: {
       Expr *pLeft = pExpr->pLeft;
       assert( pLeft );
-      if( pLeft->op==TK_FLOAT ){
+      if( pLeft->op==TK_INTEGER ){
+        codeInteger(pParse, pLeft, 1, target);
+#ifndef SQLITE_OMIT_FLOATING_POINT
+      }else if( pLeft->op==TK_FLOAT ){
         assert( !ExprHasProperty(pExpr, EP_IntValue) );
         codeReal(v, pLeft->u.zToken, 1, target);
-      }else if( pLeft->op==TK_INTEGER ){
-        codeInteger(v, pLeft, 1, target);
+#endif
       }else{
         regFree1 = r1 = sqlite3GetTempReg(pParse);
         sqlite3VdbeAddOp2(v, OP_Integer, 0, r1);
@@ -63245,6 +68958,7 @@
         target
       ));
 
+#ifndef SQLITE_OMIT_FLOATING_POINT
       /* If the column has REAL affinity, it may currently be stored as an
       ** integer. Use OP_RealAffinity to make sure it is really real.  */
       if( pExpr->iColumn>=0 
@@ -63252,6 +68966,7 @@
       ){
         sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
       }
+#endif
       break;
     }
 
@@ -63917,59 +69632,76 @@
 }
 
 /*
-** Do a deep comparison of two expression trees.  Return TRUE (non-zero)
-** if they are identical and return FALSE if they differ in any way.
+** Do a deep comparison of two expression trees.  Return 0 if the two
+** expressions are completely identical.  Return 1 if they differ only
+** by a COLLATE operator at the top level.  Return 2 if there are differences
+** other than the top-level COLLATE operator.
 **
-** Sometimes this routine will return FALSE even if the two expressions
+** Sometimes this routine will return 2 even if the two expressions
 ** really are equivalent.  If we cannot prove that the expressions are
-** identical, we return FALSE just to be safe.  So if this routine
-** returns false, then you do not really know for certain if the two
-** expressions are the same.  But if you get a TRUE return, then you
+** identical, we return 2 just to be safe.  So if this routine
+** returns 2, then you do not really know for certain if the two
+** expressions are the same.  But if you get a 0 or 1 return, then you
 ** can be sure the expressions are the same.  In the places where
-** this routine is used, it does not hurt to get an extra FALSE - that
+** this routine is used, it does not hurt to get an extra 2 - that
 ** just might result in some slightly slower code.  But returning
-** an incorrect TRUE could lead to a malfunction.
+** an incorrect 0 or 1 could lead to a malfunction.
 */
 SQLITE_PRIVATE int sqlite3ExprCompare(Expr *pA, Expr *pB){
-  int i;
   if( pA==0||pB==0 ){
-    return pB==pA;
+    return pB==pA ? 0 : 2;
   }
   assert( !ExprHasAnyProperty(pA, EP_TokenOnly|EP_Reduced) );
   assert( !ExprHasAnyProperty(pB, EP_TokenOnly|EP_Reduced) );
   if( ExprHasProperty(pA, EP_xIsSelect) || ExprHasProperty(pB, EP_xIsSelect) ){
-    return 0;
+    return 2;
   }
-  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 0;
-  if( pA->op!=pB->op ) return 0;
-  if( !sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 0;
-  if( !sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 0;
-
-  if( pA->x.pList && pB->x.pList ){
-    if( pA->x.pList->nExpr!=pB->x.pList->nExpr ) return 0;
-    for(i=0; i<pA->x.pList->nExpr; i++){
-      Expr *pExprA = pA->x.pList->a[i].pExpr;
-      Expr *pExprB = pB->x.pList->a[i].pExpr;
-      if( !sqlite3ExprCompare(pExprA, pExprB) ) return 0;
-    }
-  }else if( pA->x.pList || pB->x.pList ){
-    return 0;
-  }
-
-  if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 0;
+  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
+  if( pA->op!=pB->op ) return 2;
+  if( sqlite3ExprCompare(pA->pLeft, pB->pLeft) ) return 2;
+  if( sqlite3ExprCompare(pA->pRight, pB->pRight) ) return 2;
+  if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList) ) return 2;
+  if( pA->iTable!=pB->iTable || pA->iColumn!=pB->iColumn ) return 2;
   if( ExprHasProperty(pA, EP_IntValue) ){
     if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
-      return 0;
+      return 2;
     }
   }else if( pA->op!=TK_COLUMN && pA->u.zToken ){
-    if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 0;
+    if( ExprHasProperty(pB, EP_IntValue) || NEVER(pB->u.zToken==0) ) return 2;
     if( sqlite3StrICmp(pA->u.zToken,pB->u.zToken)!=0 ){
-      return 0;
+      return 2;
     }
   }
-  return 1;
+  if( (pA->flags & EP_ExpCollate)!=(pB->flags & EP_ExpCollate) ) return 1;
+  if( (pA->flags & EP_ExpCollate)!=0 && pA->pColl!=pB->pColl ) return 2;
+  return 0;
 }
 
+/*
+** Compare two ExprList objects.  Return 0 if they are identical and 
+** non-zero if they differ in any way.
+**
+** This routine might return non-zero for equivalent ExprLists.  The
+** only consequence will be disabled optimizations.  But this routine
+** must never return 0 if the two ExprList objects are different, or
+** a malfunction will result.
+**
+** Two NULL pointers are considered to be the same.  But a NULL pointer
+** always differs from a non-NULL pointer.
+*/
+SQLITE_PRIVATE int sqlite3ExprListCompare(ExprList *pA, ExprList *pB){
+  int i;
+  if( pA==0 && pB==0 ) return 0;
+  if( pA==0 || pB==0 ) return 1;
+  if( pA->nExpr!=pB->nExpr ) return 1;
+  for(i=0; i<pA->nExpr; i++){
+    Expr *pExprA = pA->a[i].pExpr;
+    Expr *pExprB = pB->a[i].pExpr;
+    if( pA->a[i].sortOrder!=pB->a[i].sortOrder ) return 1;
+    if( sqlite3ExprCompare(pExprA, pExprB) ) return 1;
+  }
+  return 0;
+}
 
 /*
 ** Add a new element to the pAggInfo->aCol[] array.  Return the index of
@@ -64098,7 +69830,7 @@
         */
         struct AggInfo_func *pItem = pAggInfo->aFunc;
         for(i=0; i<pAggInfo->nFunc; i++, pItem++){
-          if( sqlite3ExprCompare(pItem->pExpr, pExpr) ){
+          if( sqlite3ExprCompare(pItem->pExpr, pExpr)==0 ){
             break;
           }
         }
@@ -64466,17 +70198,23 @@
 /*
 ** Register built-in functions used to help implement ALTER TABLE
 */
-SQLITE_PRIVATE void sqlite3AlterFunctions(sqlite3 *db){
-  sqlite3CreateFunc(db, "sqlite_rename_table", 2, SQLITE_UTF8, 0,
-                         renameTableFunc, 0, 0);
+SQLITE_PRIVATE void sqlite3AlterFunctions(void){
+  static SQLITE_WSD FuncDef aAlterTableFuncs[] = {
+    FUNCTION(sqlite_rename_table,   2, 0, 0, renameTableFunc),
 #ifndef SQLITE_OMIT_TRIGGER
-  sqlite3CreateFunc(db, "sqlite_rename_trigger", 2, SQLITE_UTF8, 0,
-                         renameTriggerFunc, 0, 0);
+    FUNCTION(sqlite_rename_trigger, 2, 0, 0, renameTriggerFunc),
 #endif
 #ifndef SQLITE_OMIT_FOREIGN_KEY
-  sqlite3CreateFunc(db, "sqlite_rename_parent", 3, SQLITE_UTF8, 0,
-                         renameParentFunc, 0, 0);
+    FUNCTION(sqlite_rename_parent,  3, 0, 0, renameParentFunc),
 #endif
+  };
+  int i;
+  FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+  FuncDef *aFunc = (FuncDef*)&GLOBAL(FuncDef, aAlterTableFuncs);
+
+  for(i=0; i<ArraySize(aAlterTableFuncs); i++){
+    sqlite3FuncDefInsert(pHash, &aFunc[i]);
+  }
 }
 
 /*
@@ -64620,7 +70358,9 @@
   char *zWhere = 0;         /* Where clause to locate temp triggers */
 #endif
   VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
-  
+  int savedDbFlags;         /* Saved value of db->flags */
+
+  savedDbFlags = db->flags;  
   if( NEVER(db->mallocFailed) ) goto exit_rename_table;
   assert( pSrc->nSrc==1 );
   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
@@ -64629,6 +70369,7 @@
   if( !pTab ) goto exit_rename_table;
   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
   zDb = db->aDb[iDb].zName;
+  db->flags |= SQLITE_PreferBuiltin;
 
   /* Get a NULL terminated version of the new table name. */
   zName = sqlite3NameFromToken(db, pName);
@@ -64719,9 +70460,9 @@
     ** for which the renamed table is the parent table.  */
     if( (zWhere=whereForeignKeys(pParse, pTab))!=0 ){
       sqlite3NestedParse(pParse, 
-          "UPDATE sqlite_master SET "
+          "UPDATE \"%w\".%s SET "
               "sql = sqlite_rename_parent(sql, %Q, %Q) "
-              "WHERE %s;", zTabName, zName, zWhere);
+              "WHERE %s;", zDb, SCHEMA_TABLE(iDb), zTabName, zName, zWhere);
       sqlite3DbFree(db, zWhere);
     }
   }
@@ -64796,6 +70537,7 @@
 exit_rename_table:
   sqlite3SrcListDelete(db, pSrc);
   sqlite3DbFree(db, zName);
+  db->flags = savedDbFlags;
 }
 
 
@@ -64915,9 +70657,11 @@
   zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
   if( zCol ){
     char *zEnd = &zCol[pColDef->n-1];
+    int savedDbFlags = db->flags;
     while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
       *zEnd-- = '\0';
     }
+    db->flags |= SQLITE_PreferBuiltin;
     sqlite3NestedParse(pParse, 
         "UPDATE \"%w\".%s SET "
           "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
@@ -64926,6 +70670,7 @@
       zTab
     );
     sqlite3DbFree(db, zCol);
+    db->flags = savedDbFlags;
   }
 
   /* If the default value of the new column is NULL, then set the file
@@ -65071,7 +70816,7 @@
   int iStatCur,           /* Open the sqlite_stat1 table on this cursor */
   const char *zWhere      /* Delete entries associated with this table */
 ){
-  static struct {
+  static const struct {
     const char *zName;
     const char *zCols;
   } aTable[] = {
@@ -65653,12 +71398,16 @@
                   n = 24;
                 }
                 pSample->nByte = (u8)n;
-                pSample->u.z = sqlite3DbMallocRaw(dbMem, n);
-                if( pSample->u.z ){
-                  memcpy(pSample->u.z, z, n);
+                if( n < 1){
+                  pSample->u.z = 0;
                 }else{
-                  db->mallocFailed = 1;
-                  break;
+                  pSample->u.z = sqlite3DbMallocRaw(dbMem, n);
+                  if( pSample->u.z ){
+                    memcpy(pSample->u.z, z, n);
+                  }else{
+                    db->mallocFailed = 1;
+                    break;
+                  }
                 }
               }
             }
@@ -65825,7 +71574,10 @@
     }
     pPager = sqlite3BtreePager(aNew->pBt);
     sqlite3PagerLockingMode(pPager, db->dfltLockMode);
-    sqlite3PagerJournalMode(pPager, db->dfltJournalMode);
+    /* journal_mode set by the OP_JournalMode opcode that will following
+    ** the OP_Function opcode that invoked this function. */
+    sqlite3BtreeSecureDelete(aNew->pBt,
+                             sqlite3BtreeSecureDelete(db->aDb[0].pBt,-1) );
   }
   aNew->safety_level = 3;
   aNew->zName = sqlite3DbStrDup(db, zName);
@@ -65834,7 +71586,7 @@
   }
 
 
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
   if( rc==SQLITE_OK ){
     extern int sqlite3CodecAttach(sqlite3*, int, const void*, int);
     extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
@@ -65968,7 +71720,7 @@
 static void codeAttach(
   Parse *pParse,       /* The parser context */
   int type,            /* Either SQLITE_ATTACH or SQLITE_DETACH */
-  FuncDef *pFunc,      /* FuncDef wrapper for detachFunc() or attachFunc() */
+  FuncDef const *pFunc,/* FuncDef wrapper for detachFunc() or attachFunc() */
   Expr *pAuthArg,      /* Expression to pass to authorization callback */
   Expr *pFilename,     /* Name of database file */
   Expr *pDbname,       /* Name of the database to use internally */
@@ -66019,6 +71771,17 @@
     sqlite3VdbeChangeP5(v, (u8)(pFunc->nArg));
     sqlite3VdbeChangeP4(v, -1, (char *)pFunc, P4_FUNCDEF);
 
+    if( type==SQLITE_ATTACH ){
+      /* On an attach, also set the journal mode.  Note that
+      ** sqlite3VdbeUsesBtree() is not call here since the iDb index
+      ** will be out of range prior to the new database being attached.
+      ** The OP_JournalMode opcode will all sqlite3VdbeUsesBtree() for us.
+      */
+      sqlite3VdbeAddOp3(v, OP_JournalMode, db->nDb, regArgs+3, 
+                           db->dfltJournalMode);
+      sqlite3VdbeChangeP5(v, 1);
+    }
+
     /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
     ** statement only). For DETACH, set it to false (expire all existing
     ** statements).
@@ -66038,7 +71801,7 @@
 **     DETACH pDbname
 */
 SQLITE_PRIVATE void sqlite3Detach(Parse *pParse, Expr *pDbname){
-  static FuncDef detach_func = {
+  static const FuncDef detach_func = {
     1,                /* nArg */
     SQLITE_UTF8,      /* iPrefEnc */
     0,                /* flags */
@@ -66059,7 +71822,7 @@
 **     ATTACH p AS pDbname KEY pKey
 */
 SQLITE_PRIVATE void sqlite3Attach(Parse *pParse, Expr *p, Expr *pDbname, Expr *pKey){
-  static FuncDef attach_func = {
+  static const FuncDef attach_func = {
     3,                /* nArg */
     SQLITE_UTF8,      /* iPrefEnc */
     0,                /* flags */
@@ -66674,7 +72437,7 @@
                          pParse->isMultiWrite && pParse->mayAbort);
     pParse->rc = SQLITE_DONE;
     pParse->colNamesSet = 0;
-  }else if( pParse->rc==SQLITE_OK ){
+  }else{
     pParse->rc = SQLITE_ERROR;
   }
   pParse->nTab = 0;
@@ -69854,7 +75617,7 @@
   if( zName ){
     Vdbe *v = sqlite3GetVdbe(pParse);
 #ifndef SQLITE_OMIT_AUTHORIZATION
-    static const char *az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
+    static const char * const az[] = { "BEGIN", "RELEASE", "ROLLBACK" };
     assert( !SAVEPOINT_BEGIN && SAVEPOINT_RELEASE==1 && SAVEPOINT_ROLLBACK==2 );
 #endif
     if( !v || sqlite3AuthCheck(pParse, SQLITE_SAVEPOINT, az[op], zName, 0) ){
@@ -69873,6 +75636,7 @@
   sqlite3 *db = pParse->db;
   if( db->aDb[1].pBt==0 && !pParse->explain ){
     int rc;
+    Btree *pBt;
     static const int flags = 
           SQLITE_OPEN_READWRITE |
           SQLITE_OPEN_CREATE |
@@ -69880,17 +75644,20 @@
           SQLITE_OPEN_DELETEONCLOSE |
           SQLITE_OPEN_TEMP_DB;
 
-    rc = sqlite3BtreeFactory(db, 0, 0, SQLITE_DEFAULT_CACHE_SIZE, flags,
-                                 &db->aDb[1].pBt);
+    rc = sqlite3BtreeFactory(db, 0, 0, SQLITE_DEFAULT_CACHE_SIZE, flags, &pBt);
     if( rc!=SQLITE_OK ){
       sqlite3ErrorMsg(pParse, "unable to open a temporary database "
         "file for storing temporary tables");
       pParse->rc = rc;
       return 1;
     }
+    db->aDb[1].pBt = pBt;
     assert( db->aDb[1].pSchema );
-    sqlite3PagerJournalMode(sqlite3BtreePager(db->aDb[1].pBt),
-                            db->dfltJournalMode);
+    if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
+      db->mallocFailed = 1;
+      return 1;
+    }
+    sqlite3PagerSetJournalMode(sqlite3BtreePager(pBt), db->dfltJournalMode);
   }
   return 0;
 }
@@ -70530,14 +76297,19 @@
 
   /* If no match is found, search the built-in functions.
   **
+  ** If the SQLITE_PreferBuiltin flag is set, then search the built-in
+  ** functions even if a prior app-defined function was found.  And give
+  ** priority to built-in functions.
+  **
   ** Except, if createFlag is true, that means that we are trying to
   ** install a new function.  Whatever FuncDef structure is returned will
   ** have fields overwritten with new information appropriate for the
   ** new function.  But the FuncDefs for built-in functions are read-only.
   ** So we must not search for built-ins when creating a new function.
   */ 
-  if( !createFlag && !pBest ){
+  if( !createFlag && (pBest==0 || (db->flags & SQLITE_PreferBuiltin)!=0) ){
     FuncDefHash *pHash = &GLOBAL(FuncDefHash, sqlite3GlobalFunctions);
+    bestScore = 0;
     p = functionSearch(pHash, h, zName, nName);
     while( p ){
       int score = matchQuality(p, nArg, enc);
@@ -71137,9 +76909,7 @@
     sqlite3VdbeAddOp2(v, OP_Copy, iRowid, iOld);
     for(iCol=0; iCol<pTab->nCol; iCol++){
       if( mask==0xffffffff || mask&(1<<iCol) ){
-        int iTarget = iOld + iCol + 1;
-        sqlite3VdbeAddOp3(v, OP_Column, iCur, iCol, iTarget);
-        sqlite3ColumnDefault(v, pTab, iCol, iTarget);
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol, iOld+iCol+1);
       }
     }
 
@@ -71535,14 +77305,24 @@
   }
   if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
   r = sqlite3_value_double(argv[0]);
-  zBuf = sqlite3_mprintf("%.*f",n,r);
-  if( zBuf==0 ){
-    sqlite3_result_error_nomem(context);
+  /* If Y==0 and X will fit in a 64-bit int,
+  ** handle the rounding directly,
+  ** otherwise use printf.
+  */
+  if( n==0 && r>=0 && r<LARGEST_INT64-1 ){
+    r = (double)((sqlite_int64)(r+0.5));
+  }else if( n==0 && r<0 && (-r)<LARGEST_INT64-1 ){
+    r = -(double)((sqlite_int64)((-r)+0.5));
   }else{
+    zBuf = sqlite3_mprintf("%.*f",n,r);
+    if( zBuf==0 ){
+      sqlite3_result_error_nomem(context);
+      return;
+    }
     sqlite3AtoF(zBuf, &r);
     sqlite3_free(zBuf);
-    sqlite3_result_double(context, r);
   }
+  sqlite3_result_double(context, r);
 }
 #endif
 
@@ -71704,12 +77484,18 @@
 ){
   sqlite3 *db = sqlite3_context_db_handle(context);
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-51513-12026 The last_insert_rowid() SQL function is a
+  ** wrapper around the sqlite3_last_insert_rowid() C/C++ interface
+  ** function. */
   sqlite3_result_int64(context, sqlite3_last_insert_rowid(db));
 }
 
 /*
-** Implementation of the changes() SQL function.  The return value is the
-** same as the sqlite3_changes() API function.
+** Implementation of the changes() SQL function.
+**
+** IMP: R-62073-11209 The changes() SQL function is a wrapper
+** around the sqlite3_changes() C/C++ function and hence follows the same
+** rules for counting changes.
 */
 static void changes(
   sqlite3_context *context,
@@ -71732,6 +77518,8 @@
 ){
   sqlite3 *db = sqlite3_context_db_handle(context);
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  /* IMP: R-52756-41993 This function is a wrapper around the
+  ** sqlite3_total_changes() C/C++ interface. */
   sqlite3_result_int(context, sqlite3_total_changes(db));
 }
 
@@ -71999,7 +77787,9 @@
   sqlite3_value **NotUsed2
 ){
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  sqlite3_result_text(context, sqlite3_version, -1, SQLITE_STATIC);
+  /* IMP: R-48699-48617 This function is an SQL wrapper around the
+  ** sqlite3_libversion() C-interface. */
+  sqlite3_result_text(context, sqlite3_libversion(), -1, SQLITE_STATIC);
 }
 
 /*
@@ -72013,9 +77803,54 @@
   sqlite3_value **NotUsed2
 ){
   UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  sqlite3_result_text(context, SQLITE_SOURCE_ID, -1, SQLITE_STATIC);
+  /* IMP: R-24470-31136 This function is an SQL wrapper around the
+  ** sqlite3_sourceid() C interface. */
+  sqlite3_result_text(context, sqlite3_sourceid(), -1, SQLITE_STATIC);
 }
 
+/*
+** Implementation of the sqlite_compileoption_used() function.
+** The result is an integer that identifies if the compiler option
+** was used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptionusedFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zOptName;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-xxxx This function is an SQL wrapper around the
+  ** sqlite3_compileoption_used() C interface. */
+  if( (zOptName = (const char*)sqlite3_value_text(argv[0]))!=0 ){
+    sqlite3_result_int(context, sqlite3_compileoption_used(zOptName));
+  }
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+/*
+** Implementation of the sqlite_compileoption_get() function. 
+** The result is a string that identifies the compiler options 
+** used to build SQLite.
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+static void compileoptiongetFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  int n;
+  assert( argc==1 );
+  UNUSED_PARAMETER(argc);
+  /* IMP: R-xxxx This function is an SQL wrapper around the
+  ** sqlite3_compileoption_get() C interface. */
+  n = sqlite3_value_int(argv[0]);
+  sqlite3_result_text(context, sqlite3_compileoption_get(n), -1, SQLITE_STATIC);
+}
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
 /* Array for converting from half-bytes (nybbles) into ASCII hex
 ** digits. */
 static const char hexdigits[] = {
@@ -72142,7 +77977,7 @@
   if( n>db->aLimit[SQLITE_LIMIT_LENGTH] ){
     sqlite3_result_error_toobig(context);
   }else{
-    sqlite3_result_zeroblob(context, (int)n);
+    sqlite3_result_zeroblob(context, (int)n); /* IMP: R-00293-64994 */
   }
 }
 
@@ -72610,20 +78445,15 @@
 }
 
 /*
-** This function registered all of the above C functions as SQL
-** functions.  This should be the only routine in this file with
-** external linkage.
+** This routine does per-connection function registration.  Most
+** of the built-in functions above are part of the global function set.
+** This routine only deals with those that are not global.
 */
 SQLITE_PRIVATE void sqlite3RegisterBuiltinFunctions(sqlite3 *db){
-#ifndef SQLITE_OMIT_ALTERTABLE
-  sqlite3AlterFunctions(db);
-#endif
-  if( !db->mallocFailed ){
-    int rc = sqlite3_overload_function(db, "MATCH", 2);
-    assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
-    if( rc==SQLITE_NOMEM ){
-      db->mallocFailed = 1;
-    }
+  int rc = sqlite3_overload_function(db, "MATCH", 2);
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    db->mallocFailed = 1;
   }
 }
 
@@ -72747,6 +78577,10 @@
     FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
     FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
     FUNCTION(sqlite_source_id,   0, 0, 0, sourceidFunc     ),
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+    FUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
+    FUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
     FUNCTION(quote,              1, 0, 0, quoteFunc        ),
     FUNCTION(last_insert_rowid,  0, 0, 0, last_insert_rowid),
     FUNCTION(changes,            0, 0, 0, changes          ),
@@ -72787,6 +78621,9 @@
     sqlite3FuncDefInsert(pHash, &aFunc[i]);
   }
   sqlite3RegisterDateTimeFunctions();
+#ifndef SQLITE_OMIT_ALTERTABLE
+  sqlite3AlterFunctions();
+#endif
 }
 
 /************** End of func.c ************************************************/
@@ -74831,7 +80668,7 @@
           if( pColumn->a[j].idx==i ) break;
         }
       }
-      if( pColumn && j>=pColumn->nId ){
+      if( (!useTempTable && !pList) || (pColumn && j>=pColumn->nId) ){
         sqlite3ExprCode(pParse, pTab->aCol[i].pDflt, regCols+i+1);
       }else if( useTempTable ){
         sqlite3VdbeAddOp3(v, OP_Column, srcTab, j, regCols+i+1); 
@@ -75246,19 +81083,33 @@
         ** the triggers and remove both the table and index b-tree entries.
         **
         ** Otherwise, if there are no triggers or the recursive-triggers
-        ** flag is not set, call GenerateRowIndexDelete(). This removes
-        ** the index b-tree entries only. The table b-tree entry will be 
-        ** replaced by the new entry when it is inserted.  */
+        ** flag is not set, but the table has one or more indexes, call 
+        ** GenerateRowIndexDelete(). This removes the index b-tree entries 
+        ** only. The table b-tree entry will be replaced by the new entry 
+        ** when it is inserted.  
+        **
+        ** If either GenerateRowDelete() or GenerateRowIndexDelete() is called,
+        ** also invoke MultiWrite() to indicate that this VDBE may require
+        ** statement rollback (if the statement is aborted after the delete
+        ** takes place). Earlier versions called sqlite3MultiWrite() regardless,
+        ** but being more selective here allows statements like:
+        **
+        **   REPLACE INTO t(rowid) VALUES($newrowid)
+        **
+        ** to run without a statement journal if there are no indexes on the
+        ** table.
+        */
         Trigger *pTrigger = 0;
         if( pParse->db->flags&SQLITE_RecTriggers ){
           pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
         }
-        sqlite3MultiWrite(pParse);
         if( pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0) ){
+          sqlite3MultiWrite(pParse);
           sqlite3GenerateRowDelete(
               pParse, pTab, baseCur, regRowid, 0, pTrigger, OE_Replace
           );
-        }else{
+        }else if( pTab->pIndex ){
+          sqlite3MultiWrite(pParse);
           sqlite3GenerateRowIndexDelete(pParse, pTab, baseCur, 0);
         }
         seenReplace = 1;
@@ -75700,7 +81551,7 @@
     }
   }
 #ifndef SQLITE_OMIT_CHECK
-  if( pDest->pCheck && !sqlite3ExprCompare(pSrc->pCheck, pDest->pCheck) ){
+  if( pDest->pCheck && sqlite3ExprCompare(pSrc->pCheck, pDest->pCheck) ){
     return 0;   /* Tables have different CHECK constraints.  Ticket #2252 */
   }
 #endif
@@ -75843,6 +81694,7 @@
   int nRetry = 0;             /* Number of retry attempts */
   int callbackIsInit;         /* True if callback data is initialized */
 
+  if( !sqlite3SafetyCheckOk(db) ) return SQLITE_MISUSE_BKPT;
   if( zSql==0 ) zSql = "";
 
   sqlite3_mutex_enter(db->mutex);
@@ -77112,6 +82964,9 @@
     { "legacy_file_format",       SQLITE_LegacyFileFmt },
     { "fullfsync",                SQLITE_FullFSync     },
     { "reverse_unordered_selects", SQLITE_ReverseOrder  },
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    { "automatic_index",          SQLITE_AutoIndex     },
+#endif
 #ifdef SQLITE_DEBUG
     { "sql_trace",                SQLITE_SqlTrace      },
     { "vdbe_listing",             SQLITE_VdbeListing   },
@@ -77193,6 +83048,31 @@
 }
 #endif
 
+
+/*
+** Parameter eMode must be one of the PAGER_JOURNALMODE_XXX constants
+** defined in pager.h. This function returns the associated lowercase
+** journal-mode name.
+*/
+SQLITE_PRIVATE const char *sqlite3JournalModename(int eMode){
+  static char * const azModeName[] = {
+    "delete", "persist", "off", "truncate", "memory"
+#ifndef SQLITE_OMIT_WAL
+     , "wal"
+#endif
+  };
+  assert( PAGER_JOURNALMODE_DELETE==0 );
+  assert( PAGER_JOURNALMODE_PERSIST==1 );
+  assert( PAGER_JOURNALMODE_OFF==2 );
+  assert( PAGER_JOURNALMODE_TRUNCATE==3 );
+  assert( PAGER_JOURNALMODE_MEMORY==4 );
+  assert( PAGER_JOURNALMODE_WAL==5 );
+  assert( eMode>=0 && eMode<=ArraySize(azModeName) );
+
+  if( eMode==ArraySize(azModeName) ) return 0;
+  return azModeName[eMode];
+}
+
 /*
 ** Process a pragma statement.  
 **
@@ -77265,11 +83145,11 @@
   ** page cache size value and the persistent page cache size value
   ** stored in the database file.
   **
-  ** The default cache size is stored in meta-value 2 of page 1 of the
-  ** database file.  The cache size is actually the absolute value of
-  ** this memory location.  The sign of meta-value 2 determines the
-  ** synchronous setting.  A negative value means synchronous is off
-  ** and a positive value means synchronous is on.
+  ** Older versions of SQLite would set the default cache size to a
+  ** negative number to indicate synchronous=OFF.  These days, synchronous
+  ** is always on by default regardless of the sign of the default cache
+  ** size.  But continue to take the absolute value of the default cache
+  ** size of historical compatibility.
   */
   if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){
     static const VdbeOpList getCacheSize[] = {
@@ -77298,10 +83178,6 @@
       if( size<0 ) size = -size;
       sqlite3BeginWriteOperation(pParse, 0, iDb);
       sqlite3VdbeAddOp2(v, OP_Integer, size, 1);
-      sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, 2, BTREE_DEFAULT_CACHE_SIZE);
-      addr = sqlite3VdbeAddOp2(v, OP_IfPos, 2, 0);
-      sqlite3VdbeAddOp2(v, OP_Integer, -size, 1);
-      sqlite3VdbeJumpHere(v, addr);
       sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_DEFAULT_CACHE_SIZE, 1);
       pDb->pSchema->cache_size = size;
       sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
@@ -77357,6 +83233,31 @@
   }else
 
   /*
+  **  PRAGMA [database.]secure_delete
+  **  PRAGMA [database.]secure_delete=ON/OFF
+  **
+  ** The first form reports the current setting for the
+  ** secure_delete flag.  The second form changes the secure_delete
+  ** flag setting and reports thenew value.
+  */
+  if( sqlite3StrICmp(zLeft,"secure_delete")==0 ){
+    Btree *pBt = pDb->pBt;
+    int b = -1;
+    assert( pBt!=0 );
+    if( zRight ){
+      b = getBoolean(zRight);
+    }
+    if( pId2->n==0 && b>=0 ){
+      int ii;
+      for(ii=0; ii<db->nDb; ii++){
+        sqlite3BtreeSecureDelete(db->aDb[ii].pBt, b);
+      }
+    }
+    b = sqlite3BtreeSecureDelete(pBt, b);
+    returnSingleInt(pParse, "secure_delete", b);
+  }else
+
+  /*
   **  PRAGMA [database.]page_count
   **
   ** Return the number of pages in the specified database.
@@ -77421,21 +83322,25 @@
 
   /*
   **  PRAGMA [database.]journal_mode
-  **  PRAGMA [database.]journal_mode = (delete|persist|off|truncate|memory)
+  **  PRAGMA [database.]journal_mode =
+  **                      (delete|persist|off|truncate|memory|wal|off)
   */
   if( sqlite3StrICmp(zLeft,"journal_mode")==0 ){
-    int eMode;
-    static char * const azModeName[] = {
-      "delete", "persist", "off", "truncate", "memory"
-    };
+    int eMode;                    /* One of the PAGER_JOURNALMODE_XXX symbols */
+
+    sqlite3VdbeSetNumCols(v, 1);
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "journal_mode", SQLITE_STATIC);
 
     if( zRight==0 ){
       eMode = PAGER_JOURNALMODE_QUERY;
     }else{
+      const char *zMode;
       int n = sqlite3Strlen30(zRight);
-      eMode = sizeof(azModeName)/sizeof(azModeName[0]) - 1;
-      while( eMode>=0 && sqlite3StrNICmp(zRight, azModeName[eMode], n)!=0 ){
-        eMode--;
+      for(eMode=0; (zMode = sqlite3JournalModename(eMode)); eMode++){
+        if( sqlite3StrNICmp(zRight, zMode, n)==0 ) break;
+      }
+      if( !zMode ){
+        eMode = PAGER_JOURNALMODE_QUERY;
       }
     }
     if( pId2->n==0 && eMode==PAGER_JOURNALMODE_QUERY ){
@@ -77444,39 +83349,31 @@
       ** the journal-mode of the main database).
       */
       eMode = db->dfltJournalMode;
+      sqlite3VdbeAddOp2(v, OP_String8, 0, 1);
+      sqlite3VdbeChangeP4(v, -1, sqlite3JournalModename(eMode), P4_STATIC);
     }else{
-      Pager *pPager;
+      int ii;
+
       if( pId2->n==0 ){
-        /* This indicates that no database name was specified as part
-        ** of the PRAGMA command. In this case the journal-mode must be
-        ** set on all attached databases, as well as the main db file.
+        /* When there is no database name before the "journal_mode" keyword
+        ** in the PRAGMA, then the journal-mode will be set on
+        ** all attached databases, as well as the main db file.
         **
         ** Also, the sqlite3.dfltJournalMode variable is set so that
         ** any subsequently attached databases also use the specified
         ** journal mode.
         */
-        int ii;
-        assert(pDb==&db->aDb[0]);
-        for(ii=1; ii<db->nDb; ii++){
-          if( db->aDb[ii].pBt ){
-            pPager = sqlite3BtreePager(db->aDb[ii].pBt);
-            sqlite3PagerJournalMode(pPager, eMode);
-          }
-        }
         db->dfltJournalMode = (u8)eMode;
       }
-      pPager = sqlite3BtreePager(pDb->pBt);
-      eMode = sqlite3PagerJournalMode(pPager, eMode);
+
+      for(ii=db->nDb-1; ii>=0; ii--){
+        if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
+          sqlite3VdbeUsesBtree(v, ii);
+          sqlite3VdbeAddOp3(v, OP_JournalMode, ii, 1, eMode);
+        }
+      }
     }
-    assert( eMode==PAGER_JOURNALMODE_DELETE
-              || eMode==PAGER_JOURNALMODE_TRUNCATE
-              || eMode==PAGER_JOURNALMODE_PERSIST
-              || eMode==PAGER_JOURNALMODE_OFF
-              || eMode==PAGER_JOURNALMODE_MEMORY );
-    sqlite3VdbeSetNumCols(v, 1);
-    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "journal_mode", SQLITE_STATIC);
-    sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, 
-           azModeName[eMode], P4_STATIC);
+
     sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
   }else
 
@@ -78274,6 +84171,56 @@
   }else
 #endif /* SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS */
 
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+  /*
+  **   PRAGMA compile_options
+  **
+  ** Return the names of all compile-time options used in this build,
+  ** one option per row.
+  */
+  if( sqlite3StrICmp(zLeft, "compile_options")==0 ){
+    int i = 0;
+    const char *zOpt;
+    sqlite3VdbeSetNumCols(v, 1);
+    pParse->nMem = 1;
+    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "compile_option", SQLITE_STATIC);
+    while( (zOpt = sqlite3_compileoption_get(i++))!=0 ){
+      sqlite3VdbeAddOp4(v, OP_String8, 0, 1, 0, zOpt, 0);
+      sqlite3VdbeAddOp2(v, OP_ResultRow, 1, 1);
+    }
+  }else
+#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
+
+#ifndef SQLITE_OMIT_WAL
+  /*
+  **   PRAGMA [database.]wal_checkpoint
+  **
+  ** Checkpoint the database.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_checkpoint")==0 ){
+    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    sqlite3VdbeAddOp3(v, OP_Checkpoint, pId2->z?iDb:SQLITE_MAX_ATTACHED, 0, 0);
+  }else
+
+  /*
+  **   PRAGMA wal_autocheckpoint
+  **   PRAGMA wal_autocheckpoint = N
+  **
+  ** Configure a database connection to automatically checkpoint a database
+  ** after accumulating N frames in the log. Or query for the current value
+  ** of N.
+  */
+  if( sqlite3StrICmp(zLeft, "wal_autocheckpoint")==0 ){
+    if( zRight ){
+      int nAuto = atoi(zRight);
+      sqlite3_wal_autocheckpoint(db, nAuto);
+    }
+    returnSingleInt(pParse, "wal_autocheckpoint", 
+       db->xWalCallback==sqlite3WalDefaultHook ? 
+           SQLITE_PTR_TO_INT(db->pWalArg) : 0);
+  }else
+#endif
+
 #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
   /*
   ** Report the current state of file logs for all databases
@@ -78308,7 +84255,7 @@
   }else
 #endif
 
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
   if( sqlite3StrICmp(zLeft, "key")==0 && zRight ){
     sqlite3_key(db, zRight, sqlite3Strlen30(zRight));
   }else
@@ -78331,17 +84278,15 @@
     }
   }else
 #endif
-#if SQLITE_HAS_CODEC || defined(SQLITE_ENABLE_CEROD)
+#if defined(SQLITE_HAS_CODEC) || defined(SQLITE_ENABLE_CEROD)
   if( sqlite3StrICmp(zLeft, "activate_extensions")==0 ){
-#if SQLITE_HAS_CODEC
+#ifdef SQLITE_HAS_CODEC
     if( sqlite3StrNICmp(zRight, "see-", 4)==0 ){
-      extern void sqlite3_activate_see(const char*);
       sqlite3_activate_see(&zRight[4]);
     }
 #endif
 #ifdef SQLITE_ENABLE_CEROD
     if( sqlite3StrNICmp(zRight, "cerod-", 6)==0 ){
-      extern void sqlite3_activate_cerod(const char*);
       sqlite3_activate_cerod(&zRight[6]);
     }
 #endif
@@ -78444,15 +84389,15 @@
     ** or executed.  All the parser does is build the internal data
     ** structures that describe the table, index, or view.
     */
-    char *zErr;
     int rc;
+    sqlite3_stmt *pStmt;
+
     assert( db->init.busy );
     db->init.iDb = iDb;
     db->init.newTnum = atoi(argv[1]);
     db->init.orphanTrigger = 0;
-    rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
+    rc = sqlite3_prepare(db, argv[2], -1, &pStmt, 0);
     db->init.iDb = 0;
-    assert( rc!=SQLITE_OK || zErr==0 );
     if( SQLITE_OK!=rc ){
       if( db->init.orphanTrigger ){
         assert( iDb==1 );
@@ -78461,11 +84406,11 @@
         if( rc==SQLITE_NOMEM ){
           db->mallocFailed = 1;
         }else if( rc!=SQLITE_INTERRUPT && rc!=SQLITE_LOCKED ){
-          corruptSchema(pData, argv[0], zErr);
+          corruptSchema(pData, argv[0], sqlite3_errmsg(db));
         }
       }
-      sqlite3DbFree(db, zErr);
     }
+    sqlite3_finalize(pStmt);
   }else if( argv[0]==0 ){
     corruptSchema(pData, 0, 0);
   }else{
@@ -78684,7 +84629,7 @@
   {
     char *zSql;
     zSql = sqlite3MPrintf(db, 
-        "SELECT name, rootpage, sql FROM '%q'.%s",
+        "SELECT name, rootpage, sql FROM '%q'.%s ORDER BY rowid",
         db->aDb[iDb].zName, zMasterName);
 #ifndef SQLITE_OMIT_AUTHORIZATION
     {
@@ -78950,6 +84895,7 @@
   sqlite3VtabUnlockList(db);
 
   pParse->db = db;
+  pParse->nQueryLoop = (double)1;
   if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
     char *zSqlCopy;
     int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
@@ -78971,6 +84917,7 @@
   }else{
     sqlite3RunParser(pParse, zSql, &zErrMsg);
   }
+  assert( 1==(int)pParse->nQueryLoop );
 
   if( db->mallocFailed ){
     pParse->rc = SQLITE_NOMEM;
@@ -79171,7 +85118,7 @@
     return SQLITE_MISUSE_BKPT;
   }
   sqlite3_mutex_enter(db->mutex);
-  zSql8 = sqlite3Utf16to8(db, zSql, nBytes);
+  zSql8 = sqlite3Utf16to8(db, zSql, nBytes, SQLITE_UTF16NATIVE);
   if( zSql8 ){
     rc = sqlite3LockAndPrepare(db, zSql8, -1, saveSqlFlag, 0, ppStmt, &zTail8);
   }
@@ -81755,8 +87702,8 @@
 **  (14)  The subquery does not use OFFSET
 **
 **  (15)  The outer query is not part of a compound select or the
-**        subquery does not have both an ORDER BY and a LIMIT clause.
-**        (See ticket #2339)
+**        subquery does not have a LIMIT clause.
+**        (See ticket #2339 and ticket [02a8e81d44]).
 **
 **  (16)  The outer query is not an aggregate or the subquery does
 **        not contain ORDER BY.  (Ticket #2942)  This used to not matter
@@ -81839,7 +87786,7 @@
   ** and (14). */
   if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
   if( pSub->pOffset ) return 0;                          /* Restriction (14) */
-  if( p->pRightmost && pSub->pLimit && pSub->pOrderBy ){
+  if( p->pRightmost && pSub->pLimit ){
     return 0;                                            /* Restriction (15) */
   }
   if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
@@ -82556,18 +88503,19 @@
   struct SrcList_item *pFrom;
 
   assert( p->selFlags & SF_Resolved );
-  assert( (p->selFlags & SF_HasTypeInfo)==0 );
-  p->selFlags |= SF_HasTypeInfo;
-  pParse = pWalker->pParse;
-  pTabList = p->pSrc;
-  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
-    Table *pTab = pFrom->pTab;
-    if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
-      /* A sub-query in the FROM clause of a SELECT */
-      Select *pSel = pFrom->pSelect;
-      assert( pSel );
-      while( pSel->pPrior ) pSel = pSel->pPrior;
-      selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+  if( (p->selFlags & SF_HasTypeInfo)==0 ){
+    p->selFlags |= SF_HasTypeInfo;
+    pParse = pWalker->pParse;
+    pTabList = p->pSrc;
+    for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+      Table *pTab = pFrom->pTab;
+      if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
+        /* A sub-query in the FROM clause of a SELECT */
+        Select *pSel = pFrom->pSelect;
+        assert( pSel );
+        while( pSel->pPrior ) pSel = pSel->pPrior;
+        selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
+      }
     }
   }
   return WRC_Continue;
@@ -82726,6 +88674,18 @@
       sqlite3ExprCacheClear(pParse);
     }
   }
+
+  /* Before populating the accumulator registers, clear the column cache.
+  ** Otherwise, if any of the required column values are already present 
+  ** in registers, sqlite3ExprCode() may use OP_SCopy to copy the value
+  ** to pC->iMem. But by the time the value is used, the original register
+  ** may have been used, invalidating the underlying buffer holding the
+  ** text or blob value. See ticket [883034dcb5].
+  **
+  ** Another solution would be to change the OP_SCopy used to copy cached
+  ** values to an OP_Copy.
+  */
+  sqlite3ExprCacheClear(pParse);
   for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
     sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
   }
@@ -82934,6 +88894,18 @@
     isDistinct = 0;
   }
 
+  /* If there is both a GROUP BY and an ORDER BY clause and they are
+  ** identical, then disable the ORDER BY clause since the GROUP BY
+  ** will cause elements to come out in the correct order.  This is
+  ** an optimization - the correct answer should result regardless.
+  ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
+  ** to disable this optimization for testing purposes.
+  */
+  if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy)==0
+         && (db->flags & SQLITE_GroupByOrder)==0 ){
+    pOrderBy = 0;
+  }
+
   /* If there is an ORDER BY clause, then this sorting
   ** index might end up being unused if the data can be 
   ** extracted in pre-sorted order.  If that is the case, then the
@@ -83839,7 +89811,8 @@
     goto trigger_cleanup;
   }
   pTab = sqlite3SrcListLookup(pParse, pTableName);
-  if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){
+  if( db->init.busy==0 && pName2->n==0 && pTab
+        && pTab->pSchema==db->aDb[1].pSchema ){
     iDb = 1;
   }
 
@@ -83967,12 +89940,12 @@
   TriggerStep *pStepList, /* The triggered program */
   Token *pAll             /* Token that describes the complete CREATE TRIGGER */
 ){
-  Trigger *pTrig = pParse->pNewTrigger;    /* Trigger being finished */
-  char *zName;                             /* Name of trigger */
-  sqlite3 *db = pParse->db;                /* The database */
-  DbFixer sFix;
-  int iDb;                                 /* Database containing the trigger */
-  Token nameToken;           /* Trigger name for error reporting */
+  Trigger *pTrig = pParse->pNewTrigger;   /* Trigger being finished */
+  char *zName;                            /* Name of trigger */
+  sqlite3 *db = pParse->db;               /* The database */
+  DbFixer sFix;                           /* Fixer object */
+  int iDb;                                /* Database containing the trigger */
+  Token nameToken;                        /* Trigger name for error reporting */
 
   pTrig = pParse->pNewTrigger;
   pParse->pNewTrigger = 0;
@@ -83991,7 +89964,7 @@
     goto triggerfinish_cleanup;
   }
 
-  /* if we are not initializing, and this trigger is not on a TEMP table, 
+  /* if we are not initializing,
   ** build the sqlite_master entry
   */
   if( !db->init.busy ){
@@ -84538,6 +90511,7 @@
   pSubParse->pToplevel = pTop;
   pSubParse->zAuthContext = pTrigger->zName;
   pSubParse->eTriggerOp = pTrigger->op;
+  pSubParse->nQueryLoop = pParse->nQueryLoop;
 
   v = sqlite3GetVdbe(pSubParse);
   if( v ){
@@ -84814,7 +90788,7 @@
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
-*************************************************************************
+sqlite*************************************************************************
 ** This file contains C code routines that are called by the parser
 ** to handle UPDATE statements.
 */
@@ -85201,8 +91175,7 @@
     );
     for(i=0; i<pTab->nCol; i++){
       if( aXRef[i]<0 || oldmask==0xffffffff || (oldmask & (1<<i)) ){
-        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regOld+i);
-        sqlite3ColumnDefault(v, pTab, i, regOld+i);
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOld+i);
       }else{
         sqlite3VdbeAddOp2(v, OP_Null, 0, regOld+i);
       }
@@ -85575,7 +91548,8 @@
   void (*saved_xTrace)(void*,const char*);  /* Saved db->xTrace */
   Db *pDb = 0;            /* Database to detach at end of vacuum */
   int isMemDb;            /* True if vacuuming a :memory: database */
-  int nRes;
+  int nRes;               /* Bytes of reserved space at the end of each page */
+  int nDb;                /* Number of attached databases */
 
   if( !db->autoCommit ){
     sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
@@ -85589,8 +91563,8 @@
   saved_nChange = db->nChange;
   saved_nTotalChange = db->nTotalChange;
   saved_xTrace = db->xTrace;
-  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
-  db->flags &= ~SQLITE_ForeignKeys;
+  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin;
+  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder);
   db->xTrace = 0;
 
   pMain = db->aDb[0].pBt;
@@ -85610,15 +91584,18 @@
   ** time to parse and run the PRAGMA to turn journalling off than it does
   ** to write the journal header file.
   */
+  nDb = db->nDb;
   if( sqlite3TempInMemory(db) ){
     zSql = "ATTACH ':memory:' AS vacuum_db;";
   }else{
     zSql = "ATTACH '' AS vacuum_db;";
   }
   rc = execSql(db, pzErrMsg, zSql);
+  if( db->nDb>nDb ){
+    pDb = &db->aDb[db->nDb-1];
+    assert( strcmp(pDb->zName,"vacuum_db")==0 );
+  }
   if( rc!=SQLITE_OK ) goto end_of_vacuum;
-  pDb = &db->aDb[db->nDb-1];
-  assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
   pTemp = db->aDb[db->nDb-1].pBt;
 
   /* The call to execSql() to attach the temp database has left the file
@@ -85640,6 +91617,12 @@
   }
 #endif
 
+  /* Do not attempt to change the page size for a WAL database */
+  if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+                                               ==PAGER_JOURNALMODE_WAL ){
+    db->nextPagesize = 0;
+  }
+
   if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
    || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
    || NEVER(db->mallocFailed)
@@ -85776,6 +91759,7 @@
   db->nChange = saved_nChange;
   db->nTotalChange = saved_nTotalChange;
   db->xTrace = saved_xTrace;
+  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
 
   /* Currently there is an SQL level transaction open on the vacuum
   ** database. No locks are held on any other files (since the main file
@@ -86458,6 +92442,7 @@
   }else{
     pParse->declareVtab = 1;
     pParse->db = db;
+    pParse->nQueryLoop = 1;
   
     if( SQLITE_OK==sqlite3RunParser(pParse, zCreateTable, &zErr) 
      && pParse->pNewTable
@@ -86978,6 +92963,7 @@
 #define WHERE_COLUMN_IN    0x00040000  /* x IN (...) */
 #define WHERE_COLUMN_NULL  0x00080000  /* x IS NULL */
 #define WHERE_INDEXED      0x000f0000  /* Anything that uses an index */
+#define WHERE_NOT_FULLSCAN 0x000f3000  /* Does not do a full table scan */
 #define WHERE_IN_ABLE      0x000f1000  /* Able to support an IN operator */
 #define WHERE_TOP_LIMIT    0x00100000  /* x<EXPR or x<=EXPR constraint */
 #define WHERE_BTM_LIMIT    0x00200000  /* x>EXPR or x>=EXPR constraint */
@@ -86987,6 +92973,7 @@
 #define WHERE_UNIQUE       0x04000000  /* Selects no more than one row */
 #define WHERE_VIRTUALTABLE 0x08000000  /* Use virtual-table processing */
 #define WHERE_MULTI_OR     0x10000000  /* OR using multiple indices */
+#define WHERE_TEMP_INDEX   0x20000000  /* Uses an ephemeral index */
 
 /*
 ** Initialize a preallocated WhereClause structure.
@@ -87396,7 +93383,7 @@
   }
   assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
   pColl = sqlite3ExprCollSeq(pParse, pLeft);
-  assert( pColl!=0 );  /* Every non-IPK column has a collating sequence */
+  if( pColl==0 ) return 0;  /* Happens when LHS has an undefined collation */
   if( (pColl->type!=SQLITE_COLL_BINARY || *pnoCase) &&
       (pColl->type!=SQLITE_COLL_NOCASE || !*pnoCase) ){
     /* IMP: R-09003-32046 For the GLOB operator, the column must use the
@@ -87839,7 +93826,7 @@
   Expr *pExpr;                     /* The expression to be analyzed */
   Bitmask prereqLeft;              /* Prerequesites of the pExpr->pLeft */
   Bitmask prereqAll;               /* Prerequesites of pExpr */
-  Bitmask extraRight = 0;          /* */
+  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
   Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
   int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
   int noCase = 0;                  /* LIKE/GLOB distinguishes case */
@@ -87911,7 +93898,8 @@
       pLeft = pDup->pLeft;
       pNew->leftCursor = pLeft->iTable;
       pNew->u.leftColumn = pLeft->iColumn;
-      pNew->prereqRight = prereqLeft;
+      testcase( (prereqLeft | extraRight) != prereqLeft );
+      pNew->prereqRight = prereqLeft | extraRight;
       pNew->prereqAll = prereqAll;
       pNew->eOperator = operatorMask(pDup->op);
     }
@@ -88315,6 +94303,11 @@
   WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm];        /* End of pWC->a[] */
   WhereTerm *pTerm;                 /* A single term of the WHERE clause */
 
+  /* No OR-clause optimization allowed if the NOT INDEXED clause is used */
+  if( pSrc->notIndexed ){
+    return;
+  }
+
   /* Search the WHERE clause terms for a usable WO_OR term. */
   for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
     if( pTerm->eOperator==WO_OR 
@@ -88357,8 +94350,9 @@
       /* If there is an ORDER BY clause, increase the scan cost to account 
       ** for the cost of the sort. */
       if( pOrderBy!=0 ){
+        WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
+                    rTotal, rTotal+nRow*estLog(nRow)));
         rTotal += nRow*estLog(nRow);
-        WHERETRACE(("... sorting increases OR cost to %.9g\n", rTotal));
       }
 
       /* If the cost of scanning using this OR term for optimization is
@@ -88377,6 +94371,247 @@
 #endif /* SQLITE_OMIT_OR_OPTIMIZATION */
 }
 
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Return TRUE if the WHERE clause term pTerm is of a form where it
+** could be used with an index to access pSrc, assuming an appropriate
+** index existed.
+*/
+static int termCanDriveIndex(
+  WhereTerm *pTerm,              /* WHERE clause term to check */
+  struct SrcList_item *pSrc,     /* Table we are trying to access */
+  Bitmask notReady               /* Tables in outer loops of the join */
+){
+  char aff;
+  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
+  if( pTerm->eOperator!=WO_EQ ) return 0;
+  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
+  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
+  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  return 1;
+}
+#endif
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** If the query plan for pSrc specified in pCost is a full table scan
+** and indexing is allows (if there is no NOT INDEXED clause) and it
+** possible to construct a transient index that would perform better
+** than a full table scan even when the cost of constructing the index
+** is taken into account, then alter the query plan to use the
+** transient index.
+*/
+static void bestAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to search */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereCost *pCost            /* Lowest cost query plan */
+){
+  double nTableRow;           /* Rows in the input table */
+  double logN;                /* log(nTableRow) */
+  double costTempIdx;         /* per-query cost of the transient index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  Table *pTable;              /* Table tht might be indexed */
+
+  if( (pParse->db->flags & SQLITE_AutoIndex)==0 ){
+    /* Automatic indices are disabled at run-time */
+    return;
+  }
+  if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
+    /* We already have some kind of index in use for this query. */
+    return;
+  }
+  if( pSrc->notIndexed ){
+    /* The NOT INDEXED clause appears in the SQL. */
+    return;
+  }
+
+  assert( pParse->nQueryLoop >= (double)1 );
+  pTable = pSrc->pTab;
+  nTableRow = pTable->pIndex ? pTable->pIndex->aiRowEst[0] : 1000000;
+  logN = estLog(nTableRow);
+  costTempIdx = 2*logN*(nTableRow/pParse->nQueryLoop + 1);
+  if( costTempIdx>=pCost->rCost ){
+    /* The cost of creating the transient table would be greater than
+    ** doing the full table scan */
+    return;
+  }
+
+  /* Search for any equality comparison term */
+  pWCEnd = &pWC->a[pWC->nTerm];
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      WHERETRACE(("auto-index reduces cost from %.2f to %.2f\n",
+                    pCost->rCost, costTempIdx));
+      pCost->rCost = costTempIdx;
+      pCost->nRow = logN + 1;
+      pCost->plan.wsFlags = WHERE_TEMP_INDEX;
+      pCost->used = pTerm->prereqRight;
+      break;
+    }
+  }
+}
+#else
+# define bestAutomaticIndex(A,B,C,D,E)  /* no-op */
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
+
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+/*
+** Generate code to construct the Index object for an automatic index
+** and to set up the WhereLevel object pLevel so that the code generator
+** makes use of the automatic index.
+*/
+static void constructAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to get the next index */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereLevel *pLevel          /* Write new index here */
+){
+  int nColumn;                /* Number of columns in the constructed index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  int nByte;                  /* Byte of memory needed for pIdx */
+  Index *pIdx;                /* Object describing the transient index */
+  Vdbe *v;                    /* Prepared statement under construction */
+  int regIsInit;              /* Register set by initialization */
+  int addrInit;               /* Address of the initialization bypass jump */
+  Table *pTable;              /* The table being indexed */
+  KeyInfo *pKeyinfo;          /* Key information for the index */   
+  int addrTop;                /* Top of the index fill loop */
+  int regRecord;              /* Register holding an index record */
+  int n;                      /* Column counter */
+  int i;                      /* Loop counter */
+  int mxBitCol;               /* Maximum column in pSrc->colUsed */
+  CollSeq *pColl;             /* Collating sequence to on a column */
+  Bitmask idxCols;            /* Bitmap of columns used for indexing */
+  Bitmask extraCols;          /* Bitmap of additional columns */
+
+  /* Generate code to skip over the creation and initialization of the
+  ** transient index on 2nd and subsequent iterations of the loop. */
+  v = pParse->pVdbe;
+  assert( v!=0 );
+  regIsInit = ++pParse->nMem;
+  addrInit = sqlite3VdbeAddOp1(v, OP_If, regIsInit);
+  sqlite3VdbeAddOp2(v, OP_Integer, 1, regIsInit);
+
+  /* Count the number of columns that will be added to the index
+  ** and used to match WHERE clause constraints */
+  nColumn = 0;
+  pTable = pSrc->pTab;
+  pWCEnd = &pWC->a[pWC->nTerm];
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      if( (idxCols & cMask)==0 ){
+        nColumn++;
+        idxCols |= cMask;
+      }
+    }
+  }
+  assert( nColumn>0 );
+  pLevel->plan.nEq = nColumn;
+
+  /* Count the number of additional columns needed to create a
+  ** covering index.  A "covering index" is an index that contains all
+  ** columns that are needed by the query.  With a covering index, the
+  ** original table never needs to be accessed.  Automatic indices must
+  ** be a covering index because the index will not be updated if the
+  ** original table changes and the index and table cannot both be used
+  ** if they go out of sync.
+  */
+  extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
+  mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
+  testcase( pTable->nCol==BMS-1 );
+  testcase( pTable->nCol==BMS-2 );
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ) nColumn++;
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    nColumn += pTable->nCol - BMS + 1;
+  }
+  pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
+
+  /* Construct the Index object to describe this index */
+  nByte = sizeof(Index);
+  nByte += nColumn*sizeof(int);     /* Index.aiColumn */
+  nByte += nColumn*sizeof(char*);   /* Index.azColl */
+  nByte += nColumn;                 /* Index.aSortOrder */
+  pIdx = sqlite3DbMallocZero(pParse->db, nByte);
+  if( pIdx==0 ) return;
+  pLevel->plan.u.pIdx = pIdx;
+  pIdx->azColl = (char**)&pIdx[1];
+  pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
+  pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
+  pIdx->zName = "auto-index";
+  pIdx->nColumn = nColumn;
+  pIdx->pTable = pTable;
+  n = 0;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
+      if( (idxCols & cMask)==0 ){
+        Expr *pX = pTerm->pExpr;
+        idxCols |= cMask;
+        pIdx->aiColumn[n] = pTerm->u.leftColumn;
+        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+        pIdx->azColl[n] = pColl->zName;
+        n++;
+      }
+    }
+  }
+  assert( n==pLevel->plan.nEq );
+
+  /* Add additional columns needed to make the automatic index into
+  ** a covering index */
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & (((Bitmask)1)<<i) ){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
+    for(i=BMS-1; i<pTable->nCol; i++){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  assert( n==nColumn );
+
+  /* Create the automatic index */
+  pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
+  assert( pLevel->iIdxCur>=0 );
+  sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
+                    (char*)pKeyinfo, P4_KEYINFO_HANDOFF);
+  VdbeComment((v, "for %s", pTable->zName));
+
+  /* Fill the automatic index with content */
+  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
+  regRecord = sqlite3GetTempReg(pParse);
+  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
+  sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
+  sqlite3VdbeJumpHere(v, addrTop);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  
+  /* Jump here when skipping the initialization */
+  sqlite3VdbeJumpHere(v, addrInit);
+}
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
+
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 /*
 ** Allocate and populate an sqlite3_index_info structure. It is the 
@@ -88561,6 +94796,7 @@
   WhereTerm *pTerm;
   int i, j;
   int nOrderBy;
+  double rCost;
 
   /* Make sure wsFlags is initialized to some sane value. Otherwise, if the 
   ** malloc in allocateIndexInfo() fails and this function returns leaving
@@ -88647,6 +94883,15 @@
     }
   }
 
+  /* If there is an ORDER BY clause, and the selected virtual table index
+  ** does not satisfy it, increase the cost of the scan accordingly. This
+  ** matches the processing for non-virtual tables in bestBtreeIndex().
+  */
+  rCost = pIdxInfo->estimatedCost;
+  if( pOrderBy && pIdxInfo->orderByConsumed==0 ){
+    rCost += estLog(rCost)*rCost;
+  }
+
   /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
   ** inital value of lowestCost in this loop. If it is, then the
   ** (cost<lowestCost) test below will never be true.
@@ -88654,10 +94899,10 @@
   ** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT 
   ** is defined.
   */
-  if( (SQLITE_BIG_DBL/((double)2))<pIdxInfo->estimatedCost ){
+  if( (SQLITE_BIG_DBL/((double)2))<rCost ){
     pCost->rCost = (SQLITE_BIG_DBL/((double)2));
   }else{
-    pCost->rCost = pIdxInfo->estimatedCost;
+    pCost->rCost = rCost;
   }
   pCost->plan.u.pVtabIdx = pIdxInfo;
   if( pIdxInfo->orderByConsumed ){
@@ -89058,14 +95303,14 @@
     **    Set to true if there was at least one "x IN (SELECT ...)" term used 
     **    in determining the value of nInMul.
     **
-    **  nBound:
+    **  estBound:
     **    An estimate on the amount of the table that must be searched.  A
     **    value of 100 means the entire table is searched.  Range constraints
     **    might reduce this to a value less than 100 to indicate that only
     **    a fraction of the table needs searching.  In the absence of
     **    sqlite_stat2 ANALYZE data, a single inequality reduces the search
     **    space to 1/3rd its original size.  So an x>? constraint reduces
-    **    nBound to 33.  Two constraints (x>? AND x<?) reduce nBound to 11.
+    **    estBound to 33.  Two constraints (x>? AND x<?) reduce estBound to 11.
     **
     **  bSort:   
     **    Boolean. True if there is an ORDER BY clause that will require an 
@@ -89087,13 +95332,14 @@
     int nEq;
     int bInEst = 0;
     int nInMul = 1;
-    int nBound = 100;
+    int estBound = 100;
+    int nBound = 0;             /* Number of range constraints seen */
     int bSort = 0;
     int bLookup = 0;
+    WhereTerm *pTerm;           /* A single term of the WHERE clause */
 
     /* Determine the values of nEq and nInMul */
     for(nEq=0; nEq<pProbe->nColumn; nEq++){
-      WhereTerm *pTerm;           /* A single term of the WHERE clause */
       int j = pProbe->aiColumn[nEq];
       pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
       if( pTerm==0 ) break;
@@ -89113,18 +95359,20 @@
       used |= pTerm->prereqRight;
     }
 
-    /* Determine the value of nBound. */
+    /* Determine the value of estBound. */
     if( nEq<pProbe->nColumn ){
       int j = pProbe->aiColumn[nEq];
       if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
         WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
         WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
-        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &nBound);
+        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &estBound);
         if( pTop ){
+          nBound = 1;
           wsFlags |= WHERE_TOP_LIMIT;
           used |= pTop->prereqRight;
         }
         if( pBtm ){
+          nBound++;
           wsFlags |= WHERE_BTM_LIMIT;
           used |= pBtm->prereqRight;
         }
@@ -89155,7 +95403,7 @@
 
     /* If currently calculating the cost of using an index (not the IPK
     ** index), determine if all required column data may be obtained without 
-    ** seeking to entries in the main table (i.e. if the index is a covering
+    ** using the main table (i.e. if the index is a covering
     ** index for this query). If it is, set the WHERE_IDX_ONLY flag in
     ** wsFlags. Otherwise, set the bLookup variable to true.  */
     if( pIdx && wsFlags ){
@@ -89174,8 +95422,7 @@
       }
     }
 
-    /**** Begin adding up the cost of using this index (Needs improvements)
-    **
+    /*
     ** Estimate the number of rows of output.  For an IN operator,
     ** do not let the estimate exceed half the rows in the table.
     */
@@ -89194,8 +95441,8 @@
     /* Adjust the number of rows and the cost downward to reflect rows
     ** that are excluded by range constraints.
     */
-    nRow = (nRow * (double)nBound) / (double)100;
-    cost = (cost * (double)nBound) / (double)100;
+    nRow = (nRow * (double)estBound) / (double)100;
+    cost = (cost * (double)estBound) / (double)100;
 
     /* Add in the estimated cost of sorting the result
     */
@@ -89212,17 +95459,75 @@
     }
     /**** Cost of using this index has now been computed ****/
 
+    /* If there are additional constraints on this table that cannot
+    ** be used with the current index, but which might lower the number
+    ** of output rows, adjust the nRow value accordingly.  This only 
+    ** matters if the current index is the least costly, so do not bother
+    ** with this step if we already know this index will not be chosen.
+    ** Also, never reduce the output row count below 2 using this step.
+    **
+    ** Do not reduce the output row count if pSrc is the only table that
+    ** is notReady; if notReady is a power of two.  This will be the case
+    ** when the main sqlite3WhereBegin() loop is scanning for a table with
+    ** and "optimal" index, and on such a scan the output row count
+    ** reduction is not valid because it does not update the "pCost->used"
+    ** bitmap.  The notReady bitmap will also be a power of two when we
+    ** are scanning for the last table in a 64-way join.  We are willing
+    ** to bypass this optimization in that corner case.
+    */
+    if( nRow>2 && cost<=pCost->rCost && (notReady & (notReady-1))!=0 ){
+      int k;                       /* Loop counter */
+      int nSkipEq = nEq;           /* Number of == constraints to skip */
+      int nSkipRange = nBound;     /* Number of < constraints to skip */
+      Bitmask thisTab;             /* Bitmap for pSrc */
+
+      thisTab = getMask(pWC->pMaskSet, iCur);
+      for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
+        if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
+        if( (pTerm->prereqAll & notReady)!=thisTab ) continue;
+        if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
+          if( nSkipEq ){
+            /* Ignore the first nEq equality matches since the index
+            ** has already accounted for these */
+            nSkipEq--;
+          }else{
+            /* Assume each additional equality match reduces the result
+            ** set size by a factor of 10 */
+            nRow /= 10;
+          }
+        }else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
+          if( nSkipRange ){
+            /* Ignore the first nBound range constraints since the index
+            ** has already accounted for these */
+            nSkipRange--;
+          }else{
+            /* Assume each additional range constraint reduces the result
+            ** set size by a factor of 3 */
+            nRow /= 3;
+          }
+        }else{
+          /* Any other expression lowers the output row count by half */
+          nRow /= 2;
+        }
+      }
+      if( nRow<2 ) nRow = 2;
+    }
+
+
     WHERETRACE((
-      "tbl=%s idx=%s nEq=%d nInMul=%d nBound=%d bSort=%d bLookup=%d"
-      " wsFlags=%d   (nRow=%.2f cost=%.2f)\n",
+      "%s(%s): nEq=%d nInMul=%d estBound=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
+      "         notReady=0x%llx nRow=%.2f cost=%.2f used=0x%llx\n",
       pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"), 
-      nEq, nInMul, nBound, bSort, bLookup, wsFlags, nRow, cost
+      nEq, nInMul, estBound, bSort, bLookup, wsFlags,
+      notReady, nRow, cost, used
     ));
 
     /* If this index is the best we have seen so far, then record this
     ** index and its cost in the pCost structure.
     */
-    if( (!pIdx || wsFlags) && cost<pCost->rCost ){
+    if( (!pIdx || wsFlags)
+     && (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->nRow))
+    ){
       pCost->rCost = cost;
       pCost->nRow = nRow;
       pCost->used = used;
@@ -89257,10 +95562,12 @@
   );
 
   WHERETRACE(("best index is: %s\n", 
-    (pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
+    ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" : 
+         pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
   ));
   
   bestOrClauseIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
+  bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
   pCost->plan.wsFlags |= eqTermMask;
 }
 
@@ -89318,7 +95625,7 @@
 */
 static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
   if( pTerm
-      && ALWAYS((pTerm->wtFlags & TERM_CODED)==0)
+      && (pTerm->wtFlags & TERM_CODED)==0
       && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
   ){
     pTerm->wtFlags |= TERM_CODED;
@@ -89516,7 +95823,9 @@
     int k = pIdx->aiColumn[j];
     pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
     if( NEVER(pTerm==0) ) break;
-    assert( (pTerm->wtFlags & TERM_CODED)==0 );
+    /* The following true for indices with redundant columns. 
+    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
+    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
     r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
     if( r1!=regBase+j ){
       if( nReg==1 ){
@@ -89730,7 +96039,11 @@
     pLevel->op = bRev ? OP_Prev : OP_Next;
     pLevel->p1 = iCur;
     pLevel->p2 = start;
-    pLevel->p5 = (pStart==0 && pEnd==0) ?1:0;
+    if( pStart==0 && pEnd==0 ){
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }else{
+      assert( pLevel->p5==0 );
+    }
     if( testOp!=OP_Noop ){
       iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
       sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
@@ -89799,7 +96112,8 @@
     int iIdxCur;         /* The VDBE cursor for the index */
     int nExtraReg = 0;   /* Number of extra registers needed */
     int op;              /* Instruction opcode */
-    char *zAff;
+    char *zStartAff;             /* Affinity for start of range constraint */
+    char *zEndAff;               /* Affinity for end of range constraint */
 
     pIdx = pLevel->plan.u.pIdx;
     iIdxCur = pLevel->iIdxCur;
@@ -89840,8 +96154,9 @@
     ** starting at regBase.
     */
     regBase = codeAllEqualityTerms(
-        pParse, pLevel, pWC, notReady, nExtraReg, &zAff
+        pParse, pLevel, pWC, notReady, nExtraReg, &zStartAff
     );
+    zEndAff = sqlite3DbStrDup(pParse->db, zStartAff);
     addrNxt = pLevel->addrNxt;
 
     /* If we are doing a reverse order scan on an ascending index, or
@@ -89866,15 +96181,15 @@
       Expr *pRight = pRangeStart->pExpr->pRight;
       sqlite3ExprCode(pParse, pRight, regBase+nEq);
       sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE){
+      if( zStartAff ){
+        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
           /* Since the comparison is to be performed with no conversions
           ** applied to the operands, set the affinity to apply to pRight to 
           ** SQLITE_AFF_NONE.  */
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+          zStartAff[nEq] = SQLITE_AFF_NONE;
         }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[nConstraint]) ){
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
+          zStartAff[nEq] = SQLITE_AFF_NONE;
         }
       }  
       nConstraint++;
@@ -89884,7 +96199,7 @@
       startEq = 0;
       start_constraints = 1;
     }
-    codeApplyAffinity(pParse, regBase, nConstraint, zAff);
+    codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
     op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
     assert( op!=0 );
     testcase( op==OP_Rewind );
@@ -89904,21 +96219,22 @@
       sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
       sqlite3ExprCode(pParse, pRight, regBase+nEq);
       sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE){
+      if( zEndAff ){
+        if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
           /* Since the comparison is to be performed with no conversions
           ** applied to the operands, set the affinity to apply to pRight to 
           ** SQLITE_AFF_NONE.  */
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+          zEndAff[nEq] = SQLITE_AFF_NONE;
         }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[nConstraint]) ){
-          zAff[nConstraint] = SQLITE_AFF_NONE;
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
+          zEndAff[nEq] = SQLITE_AFF_NONE;
         }
       }  
-      codeApplyAffinity(pParse, regBase, nEq+1, zAff);
+      codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
       nConstraint++;
     }
-    sqlite3DbFree(pParse->db, zAff);
+    sqlite3DbFree(pParse->db, zStartAff);
+    sqlite3DbFree(pParse->db, zEndAff);
 
     /* Top of the loop body */
     pLevel->p2 = sqlite3VdbeCurrentAddr(v);
@@ -90188,7 +96504,7 @@
 ** Free a WhereInfo structure
 */
 static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
-  if( pWInfo ){
+  if( ALWAYS(pWInfo) ){
     int i;
     for(i=0; i<pWInfo->nLevel; i++){
       sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
@@ -90199,6 +96515,13 @@
         }
         sqlite3DbFree(db, pInfo);
       }
+      if( pWInfo->a[i].plan.wsFlags & WHERE_TEMP_INDEX ){
+        Index *pIdx = pWInfo->a[i].plan.u.pIdx;
+        if( pIdx ){
+          sqlite3DbFree(db, pIdx->zColAff);
+          sqlite3DbFree(db, pIdx);
+        }
+      }
     }
     whereClauseClear(pWInfo->pWC);
     sqlite3DbFree(db, pWInfo);
@@ -90318,6 +96641,7 @@
   /* The number of tables in the FROM clause is limited by the number of
   ** bits in a Bitmask 
   */
+  testcase( pTabList->nSrc==BMS );
   if( pTabList->nSrc>BMS ){
     sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
     return 0;
@@ -90345,6 +96669,8 @@
       sizeof(WhereMaskSet)
   );
   if( db->mallocFailed ){
+    sqlite3DbFree(db, pWInfo);
+    pWInfo = 0;
     goto whereBeginError;
   }
   pWInfo->nLevel = nTabList;
@@ -90353,6 +96679,7 @@
   pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
   pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
   pWInfo->wctrlFlags = wctrlFlags;
+  pWInfo->savedNQueryLoop = pParse->nQueryLoop;
   pMaskSet = (WhereMaskSet*)&pWC[1];
 
   /* Split the WHERE clause into separate subexpressions where each
@@ -90454,20 +96781,25 @@
     bestPlan.rCost = SQLITE_BIG_DBL;
 
     /* Loop through the remaining entries in the FROM clause to find the
-    ** next nested loop. The FROM clause entries may be iterated through
+    ** next nested loop. The loop tests all FROM clause entries
     ** either once or twice. 
     **
-    ** The first iteration, which is always performed, searches for the
-    ** FROM clause entry that permits the lowest-cost, "optimal" scan. In
+    ** The first test is always performed if there are two or more entries
+    ** remaining and never performed if there is only one FROM clause entry
+    ** to choose from.  The first test looks for an "optimal" scan.  In
     ** this context an optimal scan is one that uses the same strategy
     ** for the given FROM clause entry as would be selected if the entry
     ** were used as the innermost nested loop.  In other words, a table
     ** is chosen such that the cost of running that table cannot be reduced
-    ** by waiting for other tables to run first.
+    ** by waiting for other tables to run first.  This "optimal" test works
+    ** by first assuming that the FROM clause is on the inner loop and finding
+    ** its query plan, then checking to see if that query plan uses any
+    ** other FROM clause terms that are notReady.  If no notReady terms are
+    ** used then the "optimal" query plan works.
     **
-    ** The second iteration is only performed if no optimal scan strategies
-    ** were found by the first. This iteration is used to search for the
-    ** lowest cost scan overall.
+    ** The second loop iteration is only performed if no optimal scan
+    ** strategies were found by the first loop. This 2nd iteration is used to
+    ** search for the lowest cost scan overall.
     **
     ** Previous versions of SQLite performed only the second iteration -
     ** the next outermost loop was always that with the lowest overall
@@ -90485,9 +96817,8 @@
     ** algorithm may choose to use t2 for the outer loop, which is a much
     ** costlier approach.
     */
-    for(isOptimal=1; isOptimal>=0 && bestJ<0; isOptimal--){
-      Bitmask mask = (isOptimal ? 0 : notReady);
-      assert( (nTabList-iFrom)>1 || isOptimal );
+    for(isOptimal=(iFrom<nTabList-1); isOptimal>=0; isOptimal--){
+      Bitmask mask;  /* Mask of tables not yet ready */
       for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
         int doNotReorder;    /* True if this table should not be reordered */
         WhereCost sCost;     /* Cost information from best[Virtual]Index() */
@@ -90500,6 +96831,7 @@
           if( j==iFrom ) iFrom++;
           continue;
         }
+        mask = (isOptimal ? m : notReady);
         pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
   
         assert( pTabItem->pTab );
@@ -90515,8 +96847,11 @@
         assert( isOptimal || (sCost.used&notReady)==0 );
 
         if( (sCost.used&notReady)==0
-         && (j==iFrom || sCost.rCost<bestPlan.rCost) 
+         && (bestJ<0 || sCost.rCost<bestPlan.rCost
+             || (sCost.rCost<=bestPlan.rCost && sCost.nRow<bestPlan.nRow))
         ){
+          WHERETRACE(("... best so far with cost=%g and nRow=%g\n",
+                      sCost.rCost, sCost.nRow));
           bestPlan = sCost;
           bestJ = j;
         }
@@ -90532,13 +96867,16 @@
     }
     andFlags &= bestPlan.plan.wsFlags;
     pLevel->plan = bestPlan.plan;
-    if( bestPlan.plan.wsFlags & WHERE_INDEXED ){
+    testcase( bestPlan.plan.wsFlags & WHERE_INDEXED );
+    testcase( bestPlan.plan.wsFlags & WHERE_TEMP_INDEX );
+    if( bestPlan.plan.wsFlags & (WHERE_INDEXED|WHERE_TEMP_INDEX) ){
       pLevel->iIdxCur = pParse->nTab++;
     }else{
       pLevel->iIdxCur = -1;
     }
     notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
     pLevel->iFrom = (u8)bestJ;
+    if( bestPlan.nRow>=(double)1 ) pParse->nQueryLoop *= bestPlan.nRow;
 
     /* Check that if the table scanned by this loop iteration had an
     ** INDEXED BY clause attached to it, that the named index is being
@@ -90585,6 +96923,7 @@
   ** searching those tables.
   */
   sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
+  notReady = ~(Bitmask)0;
   for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
     Table *pTab;     /* Table to open */
     int iDb;         /* Index of database containing table/index */
@@ -90597,7 +96936,9 @@
       if( pItem->zAlias ){
         zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
       }
-      if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
+        zMsg = sqlite3MAppendf(db, zMsg, "%s WITH AUTOMATIC INDEX", zMsg);
+      }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
         zMsg = sqlite3MAppendf(db, zMsg, "%s WITH INDEX %s",
            zMsg, pLevel->plan.u.pIdx->zName);
       }else if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
@@ -90620,8 +96961,11 @@
 #endif /* SQLITE_OMIT_EXPLAIN */
     pTabItem = &pTabList->a[pLevel->iFrom];
     pTab = pTabItem->pTab;
+    pLevel->iTabCur = pTabItem->iCursor;
     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
-    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
+      /* Do nothing */
+    }else
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
       const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
@@ -90633,6 +96977,8 @@
          && (wctrlFlags & WHERE_OMIT_OPEN)==0 ){
       int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
       sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
+      testcase( pTab->nCol==BMS-1 );
+      testcase( pTab->nCol==BMS );
       if( !pWInfo->okOnePass && pTab->nCol<BMS ){
         Bitmask b = pTabItem->colUsed;
         int n = 0;
@@ -90644,7 +96990,11 @@
     }else{
       sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
     }
-    pLevel->iTabCur = pTabItem->iCursor;
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
+    if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
+      constructAutomaticIndex(pParse, pWC, pTabItem, notReady, pLevel);
+    }else
+#endif
     if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
       Index *pIx = pLevel->plan.u.pIdx;
       KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
@@ -90656,8 +97006,10 @@
       VdbeComment((v, "%s", pIx->zName));
     }
     sqlite3CodeVerifySchema(pParse, iDb);
+    notReady &= ~getMask(pWC->pMaskSet, pTabItem->iCursor);
   }
   pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
+  if( db->mallocFailed ) goto whereBeginError;
 
   /* Generate the code to do the search.  Each iteration of the for
   ** loop below generates code for a single nested loop of the VM
@@ -90725,7 +97077,10 @@
 
   /* Jump here if malloc fails */
 whereBeginError:
-  whereInfoFree(db, pWInfo);
+  if( pWInfo ){
+    pParse->nQueryLoop = pWInfo->savedNQueryLoop;
+    whereInfoFree(db, pWInfo);
+  }
   return 0;
 }
 
@@ -90795,12 +97150,15 @@
     struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
     Table *pTab = pTabItem->pTab;
     assert( pTab!=0 );
-    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
-    if( (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0 ){
-      if( !pWInfo->okOnePass && (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
+    if( (pTab->tabFlags & TF_Ephemeral)==0
+     && pTab->pSelect==0
+     && (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0
+    ){
+      int ws = pLevel->plan.wsFlags;
+      if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
         sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
       }
-      if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
+      if( (ws & WHERE_INDEXED)!=0 && (ws & WHERE_TEMP_INDEX)==0 ){
         sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
       }
     }
@@ -90848,6 +97206,7 @@
 
   /* Final cleanup
   */
+  pParse->nQueryLoop = pWInfo->savedNQueryLoop;
   whereInfoFree(db, pWInfo);
   return;
 }
@@ -91134,7 +97493,7 @@
 **                     shifting non-terminals after a reduce.
 **  yy_default[]       Default action for each state.
 */
-#define YY_ACTTAB_COUNT (1543)
+#define YY_ACTTAB_COUNT (1550)
 static const YYACTIONTYPE yy_action[] = {
  /*     0 */   313,   49,  556,   46,  147,  172,  628,  598,   55,   55,
  /*    10 */    55,   55,  302,   53,   53,   53,   53,   52,   52,   51,
@@ -91284,13 +97643,13 @@
  /*  1450 */   249,  389,  487,  486,  314,  164,  602,   79,  310,  240,
  /*  1460 */   414,  373,  480,  163,  262,  371,  414,  162,  369,  602,
  /*  1470 */    78,  212,  478,   26,  477,  602,    9,  161,  467,  363,
- /*  1480 */   141,  122,  339,  187,  119,  457,  348,  117,  347,  116,
- /*  1490 */   115,  114,  448,  112,  182,  320,   22,  433,   19,  432,
- /*  1500 */   431,   63,  428,  610,  193,  298,  597,  574,  572,  404,
- /*  1510 */   555,  552,  290,  281,  510,  499,  498,  497,  495,  380,
- /*  1520 */   356,  460,  256,  250,  345,  447,  306,    5,  570,  550,
- /*  1530 */   299,  211,  370,  401,  550,  508,  502,  501,  490,  527,
- /*  1540 */   525,  483,  238,
+ /*  1480 */   141,  122,  339,  187,  119,  457,  348,  347,  117,  116,
+ /*  1490 */   115,  112,  114,  448,  182,   22,  320,  433,  432,  431,
+ /*  1500 */    19,  428,  610,  597,  574,  193,  572,   63,  298,  404,
+ /*  1510 */   555,  552,  290,  281,  510,  460,  498,  499,  495,  447,
+ /*  1520 */   356,  497,  256,  380,  306,  570,    5,  250,  345,  238,
+ /*  1530 */   299,  550,  527,  490,  508,  525,  502,  401,  501,  963,
+ /*  1540 */   211,  963,  483,  963,  963,  963,  963,  963,  963,  370,
 };
 static const YYCODETYPE yy_lookahead[] = {
  /*     0 */    19,  222,  223,  224,  225,   24,    1,   26,   77,   78,
@@ -91441,18 +97800,18 @@
  /*  1450 */   107,  150,  176,  176,  111,  156,  174,  175,  179,  116,
  /*  1460 */   165,   18,  157,  156,  238,  157,  165,  156,   45,  174,
  /*  1470 */   175,  157,  157,  135,  239,  174,  175,  156,  189,  157,
- /*  1480 */    68,  189,  139,  219,   22,  199,  157,  192,   18,  192,
- /*  1490 */   192,  192,  199,  189,  219,  157,  243,   40,  243,  157,
- /*  1500 */   157,  246,   38,  153,  196,  198,  166,  233,  233,  228,
- /*  1510 */   177,  177,  209,  177,  182,  177,  166,  177,  166,  178,
- /*  1520 */   242,  199,  242,  209,  209,  199,  148,  196,  166,  208,
- /*  1530 */   195,  236,  237,  191,  208,  183,  183,  183,  186,  174,
- /*  1540 */   174,  186,   92,
+ /*  1480 */    68,  189,  139,  219,   22,  199,  157,   18,  192,  192,
+ /*  1490 */   192,  189,  192,  199,  219,  243,  157,   40,  157,  157,
+ /*  1500 */   243,   38,  153,  166,  233,  196,  233,  246,  198,  228,
+ /*  1510 */   177,  177,  209,  177,  182,  199,  166,  177,  166,  199,
+ /*  1520 */   242,  177,  242,  178,  148,  166,  196,  209,  209,   92,
+ /*  1530 */   195,  208,  174,  186,  183,  174,  183,  191,  183,  253,
+ /*  1540 */   236,  253,  186,  253,  253,  253,  253,  253,  253,  237,
 };
 #define YY_SHIFT_USE_DFLT (-90)
 #define YY_SHIFT_COUNT (418)
 #define YY_SHIFT_MIN   (-89)
-#define YY_SHIFT_MAX   (1470)
+#define YY_SHIFT_MAX   (1469)
 static const short yy_shift_ofst[] = {
  /*     0 */   993, 1114, 1343, 1114, 1213, 1213,   90,   90,    0,  -19,
  /*    10 */  1213, 1213, 1213, 1213, 1213,  352,  517,  721, 1091, 1213,
@@ -91467,7 +97826,7 @@
  /*   100 */  1017,  -69,  -69,  -69,  -69,   -1,   -1,   58,  138,  -44,
  /*   110 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
  /*   120 */   517,  517,  517,  517,  517,  517,  202,  579,  517,  517,
- /*   130 */   517,  517,  517,  382,  885, 1450,  -90,  -90,  -90, 1293,
+ /*   130 */   517,  517,  517,  382,  885, 1437,  -90,  -90,  -90, 1293,
  /*   140 */    73,  272,  272,  309,  311,  297,  282,  216,  602,  538,
  /*   150 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
  /*   160 */   517,  517,  517,  517,  517,  517,  517,  517,  517,  517,
@@ -91478,8 +97837,8 @@
  /*   210 */   149,  604,  516,  149,  149,  508,    3,  299,  677,  871,
  /*   220 */   613,  613,  879,  871,  879,  144,  382,  226,  382,  226,
  /*   230 */   564,  226,  613,  226,  226,  404,  625,  625,  382,  426,
- /*   240 */   -89,  801, 1464, 1244, 1244, 1457, 1457, 1244, 1462, 1412,
- /*   250 */  1188, 1470, 1470, 1470, 1470, 1244, 1188, 1462, 1412, 1412,
+ /*   240 */   -89,  801, 1463, 1244, 1244, 1457, 1457, 1244, 1462, 1412,
+ /*   250 */  1188, 1469, 1469, 1469, 1469, 1244, 1188, 1462, 1412, 1412,
  /*   260 */  1244, 1443, 1338, 1423, 1244, 1244, 1443, 1244, 1443, 1244,
  /*   270 */  1443, 1414, 1306, 1306, 1306, 1365, 1348, 1348, 1414, 1306,
  /*   280 */  1317, 1306, 1365, 1306, 1306, 1267, 1268, 1267, 1268, 1267,
@@ -91500,7 +97859,7 @@
 #define YY_REDUCE_USE_DFLT (-222)
 #define YY_REDUCE_COUNT (312)
 #define YY_REDUCE_MIN   (-221)
-#define YY_REDUCE_MAX   (1378)
+#define YY_REDUCE_MAX   (1376)
 static const short yy_reduce_ofst[] = {
  /*     0 */   310,  994, 1134,  221,  169,  157,   89,   18,   83,  301,
  /*    10 */   377,  316,  312,   16,  295,  238,  249,  391, 1301, 1295,
@@ -91521,13 +97880,13 @@
  /*   160 */  1084, 1066, 1049, 1011, 1010, 1006, 1002,  999,  998,  973,
  /*   170 */   972,  970,  966,  964,  895,  894,  892,  833,  822,  762,
  /*   180 */   761,  229,  811,  804,  803,  389,  688,  808,  807,  737,
- /*   190 */   460,  464,  572,  584, 1355, 1366, 1365, 1352, 1354, 1353,
- /*   200 */  1352, 1326, 1335, 1342, 1335, 1335, 1335, 1335, 1335, 1335,
- /*   210 */  1335, 1295, 1295, 1335, 1335, 1321, 1362, 1331, 1378, 1326,
- /*   220 */  1315, 1314, 1280, 1322, 1278, 1341, 1352, 1340, 1350, 1338,
- /*   230 */  1332, 1336, 1303, 1334, 1333, 1281, 1275, 1274, 1340, 1307,
- /*   240 */  1308, 1350, 1255, 1343, 1342, 1255, 1253, 1338, 1275, 1304,
- /*   250 */  1293, 1299, 1298, 1297, 1295, 1329, 1286, 1264, 1292, 1289,
+ /*   190 */   460,  464,  572,  584, 1356, 1361, 1358, 1347, 1355, 1353,
+ /*   200 */  1351, 1323, 1335, 1346, 1335, 1335, 1335, 1335, 1335, 1335,
+ /*   210 */  1335, 1312, 1304, 1335, 1335, 1323, 1359, 1330, 1376, 1320,
+ /*   220 */  1319, 1318, 1280, 1316, 1278, 1345, 1352, 1344, 1350, 1340,
+ /*   230 */  1332, 1336, 1303, 1334, 1333, 1281, 1273, 1271, 1337, 1310,
+ /*   240 */  1309, 1349, 1261, 1342, 1341, 1257, 1252, 1339, 1275, 1302,
+ /*   250 */  1294, 1300, 1298, 1297, 1296, 1329, 1286, 1264, 1292, 1289,
  /*   260 */  1322, 1321, 1235, 1226, 1315, 1314, 1311, 1308, 1307, 1305,
  /*   270 */  1299, 1279, 1277, 1276, 1270, 1258, 1211, 1209, 1250, 1259,
  /*   280 */  1255, 1242, 1243, 1241, 1201, 1200, 1184, 1186, 1182, 1178,
@@ -95827,7 +102186,12 @@
     ** NULL.
     */
     case SQLITE_CONFIG_LOG: {
-      sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      /* MSVC is picky about pulling func ptrs from va lists.
+      ** http://support.microsoft.com/kb/47961
+      ** sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
+      */
+      typedef void(*LOGFUNC_t)(void*,int,const char*);
+      sqlite3GlobalConfig.xLog = va_arg(ap, LOGFUNC_t);
       sqlite3GlobalConfig.pLogArg = va_arg(ap, void*);
       break;
     }
@@ -96214,7 +102578,7 @@
     /* SQLITE_NOTFOUND    */ 0,
     /* SQLITE_FULL        */ "database or disk is full",
     /* SQLITE_CANTOPEN    */ "unable to open database file",
-    /* SQLITE_PROTOCOL    */ 0,
+    /* SQLITE_PROTOCOL    */ "locking protocol",
     /* SQLITE_EMPTY       */ "table contains no data",
     /* SQLITE_SCHEMA      */ "database schema has changed",
     /* SQLITE_TOOBIG      */ "string or blob too big",
@@ -96488,7 +102852,7 @@
   char *zFunc8;
   sqlite3_mutex_enter(db->mutex);
   assert( !db->mallocFailed );
-  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1);
+  zFunc8 = sqlite3Utf16to8(db, zFunctionName, -1, SQLITE_UTF16NATIVE);
   rc = sqlite3CreateFunc(db, zFunc8, nArg, eTextRep, p, xFunc, xStep, xFinal);
   sqlite3DbFree(db, zFunc8);
   rc = sqlite3ApiExit(db, rc);
@@ -96624,6 +102988,145 @@
   return pRet;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/*
+** The sqlite3_wal_hook() callback registered by sqlite3_wal_autocheckpoint().
+** Invoke sqlite3_wal_checkpoint if the number of frames in the log file
+** is greater than sqlite3.pWalArg cast to an integer (the value configured by
+** wal_autocheckpoint()).
+*/ 
+SQLITE_PRIVATE int sqlite3WalDefaultHook(
+  void *pClientData,     /* Argument */
+  sqlite3 *db,           /* Connection */
+  const char *zDb,       /* Database */
+  int nFrame             /* Size of WAL */
+){
+  if( nFrame>=SQLITE_PTR_TO_INT(pClientData) ){
+    sqlite3BeginBenignMalloc();
+    sqlite3_wal_checkpoint(db, zDb);
+    sqlite3EndBenignMalloc();
+  }
+  return SQLITE_OK;
+}
+#endif /* SQLITE_OMIT_WAL */
+
+/*
+** Configure an sqlite3_wal_hook() callback to automatically checkpoint
+** a database after committing a transaction if there are nFrame or
+** more frames in the log file. Passing zero or a negative value as the
+** nFrame parameter disables automatic checkpoints entirely.
+**
+** The callback registered by this function replaces any existing callback
+** registered using sqlite3_wal_hook(). Likewise, registering a callback
+** using sqlite3_wal_hook() disables the automatic checkpoint mechanism
+** configured by this function.
+*/
+SQLITE_API int sqlite3_wal_autocheckpoint(sqlite3 *db, int nFrame){
+#ifndef SQLITE_OMIT_WAL
+  if( nFrame>0 ){
+    sqlite3_wal_hook(db, sqlite3WalDefaultHook, SQLITE_INT_TO_PTR(nFrame));
+  }else{
+    sqlite3_wal_hook(db, 0, 0);
+  }
+#endif
+  return SQLITE_OK;
+}
+
+/*
+** Register a callback to be invoked each time a transaction is written
+** into the write-ahead-log by this database connection.
+*/
+SQLITE_API void *sqlite3_wal_hook(
+  sqlite3 *db,                    /* Attach the hook to this db handle */
+  int(*xCallback)(void *, sqlite3*, const char*, int),
+  void *pArg                      /* First argument passed to xCallback() */
+){
+#ifndef SQLITE_OMIT_WAL
+  void *pRet;
+  sqlite3_mutex_enter(db->mutex);
+  pRet = db->pWalArg;
+  db->xWalCallback = xCallback;
+  db->pWalArg = pArg;
+  sqlite3_mutex_leave(db->mutex);
+  return pRet;
+#else
+  return 0;
+#endif
+}
+
+
+/*
+** Checkpoint database zDb. If zDb is NULL, or if the buffer zDb points
+** to contains a zero-length string, all attached databases are 
+** checkpointed.
+*/
+SQLITE_API int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb){
+#ifdef SQLITE_OMIT_WAL
+  return SQLITE_OK;
+#else
+  int rc;                         /* Return code */
+  int iDb = SQLITE_MAX_ATTACHED;  /* sqlite3.aDb[] index of db to checkpoint */
+
+  sqlite3_mutex_enter(db->mutex);
+  if( zDb && zDb[0] ){
+    iDb = sqlite3FindDbName(db, zDb);
+  }
+  if( iDb<0 ){
+    rc = SQLITE_ERROR;
+    sqlite3Error(db, SQLITE_ERROR, "unknown database: %s", zDb);
+  }else{
+    rc = sqlite3Checkpoint(db, iDb);
+    sqlite3Error(db, rc, 0);
+  }
+  rc = sqlite3ApiExit(db, rc);
+  sqlite3_mutex_leave(db->mutex);
+  return rc;
+#endif
+}
+
+#ifndef SQLITE_OMIT_WAL
+/*
+** Run a checkpoint on database iDb. This is a no-op if database iDb is
+** not currently open in WAL mode.
+**
+** If a transaction is open on the database being checkpointed, this 
+** function returns SQLITE_LOCKED and a checkpoint is not attempted. If 
+** an error occurs while running the checkpoint, an SQLite error code is 
+** returned (i.e. SQLITE_IOERR). Otherwise, SQLITE_OK.
+**
+** The mutex on database handle db should be held by the caller. The mutex
+** associated with the specific b-tree being checkpointed is taken by
+** this function while the checkpoint is running.
+**
+** If iDb is passed SQLITE_MAX_ATTACHED, then all attached databases are
+** checkpointed. If an error is encountered it is returned immediately -
+** no attempt is made to checkpoint any remaining databases.
+*/
+SQLITE_PRIVATE int sqlite3Checkpoint(sqlite3 *db, int iDb){
+  int rc = SQLITE_OK;             /* Return code */
+  int i;                          /* Used to iterate through attached dbs */
+
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  for(i=0; i<db->nDb && rc==SQLITE_OK; i++){
+    if( i==iDb || iDb==SQLITE_MAX_ATTACHED ){
+      Btree *pBt = db->aDb[i].pBt;
+      if( pBt ){
+        if( sqlite3BtreeIsInReadTrans(pBt) ){
+          rc = SQLITE_LOCKED;
+        }else{
+          sqlite3BtreeEnter(pBt);
+          rc = sqlite3PagerCheckpoint(sqlite3BtreePager(pBt));
+          sqlite3BtreeLeave(pBt);
+        }
+      }
+    }
+  }
+
+  return rc;
+}
+#endif /* SQLITE_OMIT_WAL */
+
 /*
 ** This function returns true if main-memory should be used instead of
 ** a temporary file for transient pager files and statement journals.
@@ -97046,7 +103549,7 @@
   db->autoCommit = 1;
   db->nextAutovac = -1;
   db->nextPagesize = 0;
-  db->flags |= SQLITE_ShortColNames
+  db->flags |= SQLITE_ShortColNames | SQLITE_AutoIndex
 #if SQLITE_DEFAULT_FILE_FORMAT<4
                  | SQLITE_LegacyFileFmt
 #endif
@@ -97184,6 +103687,8 @@
   setupLookaside(db, 0, sqlite3GlobalConfig.szLookaside,
                         sqlite3GlobalConfig.nLookaside);
 
+  sqlite3_wal_autocheckpoint(db, SQLITE_DEFAULT_WAL_AUTOCHECKPOINT);
+
 opendb_out:
   if( db ){
     assert( db->mutex!=0 || isThreadsafe==0 || sqlite3GlobalConfig.bFullMutex==0 );
@@ -97311,7 +103816,7 @@
   char *zName8;
   sqlite3_mutex_enter(db->mutex);
   assert( !db->mallocFailed );
-  zName8 = sqlite3Utf16to8(db, zName, -1);
+  zName8 = sqlite3Utf16to8(db, zName, -1, SQLITE_UTF16NATIVE);
   if( zName8 ){
     rc = createCollation(db, zName8, (u8)enc, SQLITE_COLL_USER, pCtx, xCompare, 0);
     sqlite3DbFree(db, zName8);
@@ -97678,9 +104183,13 @@
     ** dileterious behavior.
     */
     case SQLITE_TESTCTRL_PENDING_BYTE: {
-      unsigned int newVal = va_arg(ap, unsigned int);
-      rc = sqlite3PendingByte;
-      if( newVal ) sqlite3PendingByte = newVal;
+      rc = PENDING_BYTE;
+#ifndef SQLITE_OMIT_WSD
+      {
+        unsigned int newVal = va_arg(ap, unsigned int);
+        if( newVal ) sqlite3PendingByte = newVal;
+      }
+#endif
       break;
     }
 
@@ -97784,6 +104293,15 @@
     }
 #endif 
 
+    /* sqlite3_test_control(SQLITE_TESTCTRL_PGHDRSZ)
+    **
+    ** Return the size of a pcache header in bytes.
+    */
+    case SQLITE_TESTCTRL_PGHDRSZ: {
+      rc = sizeof(PgHdr);
+      break;
+    }
+
   }
   va_end(ap);
 #endif /* SQLITE_OMIT_BUILTIN_TEST */
@@ -97949,6 +104467,7 @@
 
   if( xNotify==0 ){
     removeFromBlockedList(db);
+    db->pBlockingConnection = 0;
     db->pUnlockConnection = 0;
     db->xUnlockNotify = 0;
     db->pUnlockArg = 0;
@@ -98149,9 +104668,6 @@
 **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
 */
 
-/* TODO(shess) Consider exporting this comment to an HTML file or the
-** wiki.
-*/
 /* The full-text index is stored in a series of b+tree (-like)
 ** structures called segments which map terms to doclists.  The
 ** structures are like b+trees in layout, but are constructed from the
@@ -98174,30 +104690,40 @@
 ** 21 bits - BBA
 ** and so on.
 **
-** This is identical to how sqlite encodes varints (see util.c).
+** This is similar in concept to how sqlite encodes "varints" but
+** the encoding is not the same.  SQLite varints are big-endian
+** are are limited to 9 bytes in length whereas FTS3 varints are
+** little-endian and can be up to 10 bytes in length (in theory).
+**
+** Example encodings:
+**
+**     1:    0x01
+**   127:    0x7f
+**   128:    0x81 0x00
 **
 **
 **** Document lists ****
 ** A doclist (document list) holds a docid-sorted list of hits for a
-** given term.  Doclists hold docids, and can optionally associate
-** token positions and offsets with docids.
+** given term.  Doclists hold docids and associated token positions.
+** A docid is the unique integer identifier for a single document.
+** A position is the index of a word within the document.  The first 
+** word of the document has a position of 0.
 **
-** A DL_POSITIONS_OFFSETS doclist is stored like this:
+** FTS3 used to optionally store character offsets using a compile-time
+** option.  But that functionality is no longer supported.
+**
+** A doclist is stored like this:
 **
 ** array {
 **   varint docid;
 **   array {                (position list for column 0)
-**     varint position;     (delta from previous position plus POS_BASE)
-**     varint startOffset;  (delta from previous startOffset)
-**     varint endOffset;    (delta from startOffset)
+**     varint position;     (2 more than the delta from previous position)
 **   }
 **   array {
 **     varint POS_COLUMN;   (marks start of position list for new column)
 **     varint column;       (index of new column)
 **     array {
-**       varint position;   (delta from previous position plus POS_BASE)
-**       varint startOffset;(delta from previous startOffset)
-**       varint endOffset;  (delta from startOffset)
+**       varint position;   (2 more than the delta from previous position)
 **     }
 **   }
 **   varint POS_END;        (marks end of positions for this document.
@@ -98205,19 +104731,32 @@
 **
 ** Here, array { X } means zero or more occurrences of X, adjacent in
 ** memory.  A "position" is an index of a token in the token stream
-** generated by the tokenizer, while an "offset" is a byte offset,
-** both based at 0.  Note that POS_END and POS_COLUMN occur in the
-** same logical place as the position element, and act as sentinals
-** ending a position list array.
+** generated by the tokenizer. Note that POS_END and POS_COLUMN occur 
+** in the same logical place as the position element, and act as sentinals
+** ending a position list array.  POS_END is 0.  POS_COLUMN is 1.
+** The positions numbers are not stored literally but rather as two more
+** than the difference from the prior position, or the just the position plus
+** 2 for the first position.  Example:
 **
-** A DL_POSITIONS doclist omits the startOffset and endOffset
-** information.  A DL_DOCIDS doclist omits both the position and
-** offset information, becoming an array of varint-encoded docids.
+**   label:       A B C D E  F  G H   I  J K
+**   value:     123 5 9 1 1 14 35 0 234 72 0
 **
-** On-disk data is stored as type DL_DEFAULT, so we don't serialize
-** the type.  Due to how deletion is implemented in the segmentation
-** system, on-disk doclists MUST store at least positions.
+** The 123 value is the first docid.  For column zero in this document
+** there are two matches at positions 3 and 10 (5-2 and 9-2+3).  The 1
+** at D signals the start of a new column; the 1 at E indicates that the
+** new column is column number 1.  There are two positions at 12 and 45
+** (14-2 and 35-2+12).  The 0 at H indicate the end-of-document.  The
+** 234 at I is the next docid.  It has one position 72 (72-2) and then
+** terminates with the 0 at K.
 **
+** A "position-list" is the list of positions for multiple columns for
+** a single docid.  A "column-list" is the set of positions for a single
+** column.  Hence, a position-list consists of one or more column-lists,
+** a document record consists of a docid followed by a position-list and
+** a doclist consists of one or more document records.
+**
+** A bare doclist omits the position information, becoming an 
+** array of varint-encoded docids.
 **
 **** Segment leaf nodes ****
 ** Segment leaf nodes store terms and doclists, ordered by term.  Leaf
@@ -98732,6 +105271,20 @@
 #define FTS3_VARINT_MAX 10
 
 /*
+** The testcase() macro is only used by the amalgamation.  If undefined,
+** make it a no-op.
+*/
+#ifndef testcase
+# define testcase(X)
+#endif
+
+/*
+** Terminator values for position-lists and column-lists.
+*/
+#define POS_COLUMN  (1)     /* Column-list terminator */
+#define POS_END     (0)     /* Position-list terminator */ 
+
+/*
 ** This section provides definitions to allow the
 ** FTS3 extension to be compiled outside of the 
 ** amalgamation.
@@ -98782,7 +105335,7 @@
   /* Precompiled statements used by the implementation. Each of these 
   ** statements is run and reset within a single virtual table API call. 
   */
-  sqlite3_stmt *aStmt[18];
+  sqlite3_stmt *aStmt[25];
 
   /* Pointer to string containing the SQL:
   **
@@ -98796,6 +105349,8 @@
   sqlite3_stmt **aLeavesStmt;     /* Array of prepared zSelectLeaves stmts */
 
   int nNodeSize;                  /* Soft limit for node size */
+  u8 bHasContent;                 /* True if %_content table exists */
+  u8 bHasDocsize;                 /* True if %_docsize table exists */
 
   /* The following hash table is used to buffer pending index updates during
   ** transactions. Variable nPendingData estimates the memory size of the 
@@ -98826,8 +105381,8 @@
   char *pNextId;                  /* Pointer into the body of aDoclist */
   char *aDoclist;                 /* List of docids for full-text queries */
   int nDoclist;                   /* Size of buffer at aDoclist */
-  int isMatchinfoOk;              /* True when aMatchinfo[] matches iPrevId */
-  u32 *aMatchinfo;
+  int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
+  u32 *aMatchinfo;                /* Information about most recent match */
 };
 
 /*
@@ -98933,6 +105488,8 @@
 );
 SQLITE_PRIVATE int sqlite3Fts3ReadBlock(Fts3Table*, sqlite3_int64, char const**, int*);
 SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(Fts3Table*, sqlite3_stmt **);
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeLocal(Fts3Cursor*, u32*);
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeGlobal(Fts3Cursor*, u32*);
 
 /* Flags allowed as part of the 4th argument to SegmentReaderIterate() */
 #define FTS3_SEGMENT_REQUIRE_POS   0x00000001
@@ -98957,6 +105514,7 @@
 
 SQLITE_PRIVATE char *sqlite3Fts3FindPositions(Fts3Expr *, sqlite3_int64, int);
 SQLITE_PRIVATE int sqlite3Fts3ExprLoadDoclist(Fts3Table *, Fts3Expr *);
+SQLITE_PRIVATE int sqlite3Fts3ExprNearTrim(Fts3Expr *, Fts3Expr *, int);
 
 /* fts3_tokenizer.c */
 SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *, int *);
@@ -98967,10 +105525,7 @@
 
 /* fts3_snippet.c */
 SQLITE_PRIVATE void sqlite3Fts3Offsets(sqlite3_context*, Fts3Cursor*);
-SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context*, Fts3Cursor*, 
-  const char *, const char *, const char *
-);
-SQLITE_PRIVATE void sqlite3Fts3Snippet2(sqlite3_context *, Fts3Cursor *, const char *,
+SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context *, Fts3Cursor *, const char *,
   const char *, const char *, int, int
 );
 SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *, Fts3Cursor *);
@@ -99040,8 +105595,7 @@
 }
 
 /*
-** Return the number of bytes required to store the value passed as the
-** first argument in varint form.
+** Return the number of bytes required to encode v as a varint
 */
 SQLITE_PRIVATE int sqlite3Fts3VarintLen(sqlite3_uint64 v){
   int i = 0;
@@ -99090,12 +105644,23 @@
   }
 }
 
+/*
+** Read a single varint from the doclist at *pp and advance *pp to point
+** to the first byte past the end of the varint.  Add the value of the varint
+** to *pVal.
+*/
 static void fts3GetDeltaVarint(char **pp, sqlite3_int64 *pVal){
   sqlite3_int64 iVal;
   *pp += sqlite3Fts3GetVarint(*pp, &iVal);
   *pVal += iVal;
 }
 
+/*
+** As long as *pp has not reached its end (pEnd), then do the same
+** as fts3GetDeltaVarint(): read a single varint and add it to *pVal.
+** But if we have reached the end of the varint, just set *pp=0 and
+** leave *pVal unchanged.
+*/
 static void fts3GetDeltaVarint2(char **pp, char *pEnd, sqlite3_int64 *pVal){
   if( *pp>=pEnd ){
     *pp = 0;
@@ -99131,29 +105696,46 @@
 }
 
 /*
+** Construct one or more SQL statements from the format string given
+** and then evaluate those statements.  The success code is writting
+** into *pRc.
+**
+** If *pRc is initially non-zero then this routine is a no-op.
+*/
+static void fts3DbExec(
+  int *pRc,              /* Success code */
+  sqlite3 *db,           /* Database in which to run SQL */
+  const char *zFormat,   /* Format string for SQL */
+  ...                    /* Arguments to the format string */
+){
+  va_list ap;
+  char *zSql;
+  if( *pRc ) return;
+  va_start(ap, zFormat);
+  zSql = sqlite3_vmprintf(zFormat, ap);
+  va_end(ap);
+  if( zSql==0 ){
+    *pRc = SQLITE_NOMEM;
+  }else{
+    *pRc = sqlite3_exec(db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
+  }
+}
+
+/*
 ** The xDestroy() virtual table method.
 */
 static int fts3DestroyMethod(sqlite3_vtab *pVtab){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;              /* Return code */
   Fts3Table *p = (Fts3Table *)pVtab;
+  sqlite3 *db = p->db;
 
-  /* Create a script to drop the underlying three storage tables. */
-  char *zSql = sqlite3_mprintf(
-      "DROP TABLE IF EXISTS %Q.'%q_content';"
-      "DROP TABLE IF EXISTS %Q.'%q_segments';"
-      "DROP TABLE IF EXISTS %Q.'%q_segdir';", 
-      p->zDb, p->zName, p->zDb, p->zName, p->zDb, p->zName
-  );
-
-  /* If malloc has failed, set rc to SQLITE_NOMEM. Otherwise, try to
-  ** execute the SQL script created above.
-  */
-  if( zSql ){
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
-    sqlite3_free(zSql);
-  }else{
-    rc = SQLITE_NOMEM;
-  }
+  /* Drop the shadow tables */
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_content'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segments'", p->zDb,p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_segdir'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_docsize'", p->zDb, p->zName);
+  fts3DbExec(&rc, db, "DROP TABLE IF EXISTS %Q.'%q_stat'", p->zDb, p->zName);
 
   /* If everything has worked, invoke fts3DisconnectMethod() to free the
   ** memory associated with the Fts3Table structure and return SQLITE_OK.
@@ -99200,24 +105782,39 @@
 ** Create the backing store tables (%_content, %_segments and %_segdir)
 ** required by the FTS3 table passed as the only argument. This is done
 ** as part of the vtab xCreate() method.
+**
+** If the p->bHasDocsize boolean is true (indicating that this is an
+** FTS4 table, not an FTS3 table) then also create the %_docsize and
+** %_stat tables required by FTS4.
 */
 static int fts3CreateTables(Fts3Table *p){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;             /* Return code */
   int i;                          /* Iterator variable */
   char *zContentCols;             /* Columns of %_content table */
-  char *zSql;                     /* SQL script to create required tables */
+  sqlite3 *db = p->db;            /* The database connection */
 
   /* Create a list of user columns for the content table */
-  zContentCols = sqlite3_mprintf("docid INTEGER PRIMARY KEY");
-  for(i=0; zContentCols && i<p->nColumn; i++){
-    char *z = p->azColumn[i];
-    zContentCols = sqlite3_mprintf("%z, 'c%d%q'", zContentCols, i, z);
-  }
+  if( p->bHasContent ){
+    zContentCols = sqlite3_mprintf("docid INTEGER PRIMARY KEY");
+    for(i=0; zContentCols && i<p->nColumn; i++){
+      char *z = p->azColumn[i];
+      zContentCols = sqlite3_mprintf("%z, 'c%d%q'", zContentCols, i, z);
+    }
+    if( zContentCols==0 ) rc = SQLITE_NOMEM;
 
-  /* Create the whole SQL script */
-  zSql = sqlite3_mprintf(
-      "CREATE TABLE %Q.'%q_content'(%s);"
-      "CREATE TABLE %Q.'%q_segments'(blockid INTEGER PRIMARY KEY, block BLOB);"
+    /* Create the content table */
+    fts3DbExec(&rc, db, 
+       "CREATE TABLE %Q.'%q_content'(%s)",
+       p->zDb, p->zName, zContentCols
+    );
+    sqlite3_free(zContentCols);
+  }
+  /* Create other tables */
+  fts3DbExec(&rc, db, 
+      "CREATE TABLE %Q.'%q_segments'(blockid INTEGER PRIMARY KEY, block BLOB);",
+      p->zDb, p->zName
+  );
+  fts3DbExec(&rc, db, 
       "CREATE TABLE %Q.'%q_segdir'("
         "level INTEGER,"
         "idx INTEGER,"
@@ -99227,30 +105824,61 @@
         "root BLOB,"
         "PRIMARY KEY(level, idx)"
       ");",
-      p->zDb, p->zName, zContentCols, p->zDb, p->zName, p->zDb, p->zName
+      p->zDb, p->zName
   );
-
-  /* Unless a malloc() failure has occurred, execute the SQL script to 
-  ** create the tables used to store data for this FTS3 virtual table.
-  */
-  if( zContentCols==0 || zSql==0 ){
-    rc = SQLITE_NOMEM;
-  }else{
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db, 
+        "CREATE TABLE %Q.'%q_docsize'(docid INTEGER PRIMARY KEY, size BLOB);",
+        p->zDb, p->zName
+    );
+    fts3DbExec(&rc, db, 
+        "CREATE TABLE %Q.'%q_stat'(id INTEGER PRIMARY KEY, value BLOB);",
+        p->zDb, p->zName
+    );
   }
-
-  sqlite3_free(zSql);
-  sqlite3_free(zContentCols);
   return rc;
 }
 
 /*
+** An sqlite3_exec() callback for fts3TableExists.
+*/
+static int fts3TableExistsCallback(void *pArg, int n, char **pp1, char **pp2){
+  *(int*)pArg = 1;
+  return 1;
+}
+
+/*
+** Determine if a table currently exists in the database.
+*/
+static void fts3TableExists(
+  int *pRc,             /* Success code */
+  sqlite3 *db,          /* The database connection to test */
+  const char *zDb,      /* ATTACHed database within the connection */
+  const char *zName,    /* Name of the FTS3 table */
+  const char *zSuffix,  /* Shadow table extension */
+  u8 *pResult           /* Write results here */
+){
+  int rc = SQLITE_OK;
+  int res = 0;
+  char *zSql;
+  if( *pRc ) return;
+  zSql = sqlite3_mprintf(
+    "SELECT 1 FROM %Q.sqlite_master WHERE name='%q%s'",
+    zDb, zName, zSuffix
+  );    
+  rc = sqlite3_exec(db, zSql, fts3TableExistsCallback, &res, 0);
+  sqlite3_free(zSql);
+  *pResult = res & 0xff;
+  if( rc!=SQLITE_ABORT ) *pRc = rc;
+}
+
+/*
 ** This function is the implementation of both the xConnect and xCreate
 ** methods of the FTS3 virtual table.
 **
 ** The argv[] array contains the following:
 **
-**   argv[0]   -> module name
+**   argv[0]   -> module name  ("fts3" or "fts4")
 **   argv[1]   -> database name
 **   argv[2]   -> table name
 **   argv[...] -> "column name" and other module argument fields.
@@ -99269,12 +105897,12 @@
   int rc;                         /* Return code */
   int i;                          /* Iterator variable */
   int nByte;                      /* Size of allocation used for *p */
-  int iCol;
-  int nString = 0;
-  int nCol = 0;
-  char *zCsr;
-  int nDb;
-  int nName;
+  int iCol;                       /* Column index */
+  int nString = 0;                /* Bytes required to hold all column names */
+  int nCol = 0;                   /* Number of columns in the FTS table */
+  char *zCsr;                     /* Space for holding column names */
+  int nDb;                        /* Bytes required to hold database name */
+  int nName;                      /* Bytes required to hold table name */
 
   const char *zTokenizer = 0;               /* Name of tokenizer to use */
   sqlite3_tokenizer *pTokenizer = 0;        /* Tokenizer for this table */
@@ -99360,9 +105988,15 @@
   ** database. TODO: For xConnect(), it could verify that said tables exist.
   */
   if( isCreate ){
+    p->bHasContent = 1;
+    p->bHasDocsize = argv[0][3]=='4';
     rc = fts3CreateTables(p);
-    if( rc!=SQLITE_OK ) goto fts3_init_out;
+  }else{
+    rc = SQLITE_OK;
+    fts3TableExists(&rc, db, argv[1], argv[2], "_content", &p->bHasContent);
+    fts3TableExists(&rc, db, argv[1], argv[2], "_docsize", &p->bHasDocsize);
   }
+  if( rc!=SQLITE_OK ) goto fts3_init_out;
 
   rc = fts3DeclareVtab(p);
   if( rc!=SQLITE_OK ) goto fts3_init_out;
@@ -99484,12 +106118,6 @@
   return SQLITE_OK;
 }
 
-/****************************************************************/
-/****************************************************************/
-/****************************************************************/
-/****************************************************************/
-
-
 /*
 ** Close the cursor.  For additional information see the documentation
 ** on the xClose method of the virtual table interface.
@@ -99504,6 +106132,11 @@
   return SQLITE_OK;
 }
 
+/*
+** Position the pCsr->pStmt statement so that it is on the row
+** of the %_content table that contains the last match.  Return
+** SQLITE_OK on success.  
+*/
 static int fts3CursorSeek(sqlite3_context *pContext, Fts3Cursor *pCsr){
   if( pCsr->isRequireSeek ){
     pCsr->isRequireSeek = 0;
@@ -99530,6 +106163,17 @@
   }
 }
 
+/*
+** Advance the cursor to the next row in the %_content table that
+** matches the search criteria.  For a MATCH search, this will be
+** the next row that matches.  For a full-table scan, this will be
+** simply the next row in the %_content table.  For a docid lookup,
+** this routine simply sets the EOF flag.
+**
+** Return SQLITE_OK if nothing goes wrong.  SQLITE_OK is returned
+** even if we reach end-of-file.  The fts3EofMethod() will be called
+** subsequently to determine whether or not an EOF was hit.
+*/
 static int fts3NextMethod(sqlite3_vtab_cursor *pCursor){
   int rc = SQLITE_OK;             /* Return code */
   Fts3Cursor *pCsr = (Fts3Cursor *)pCursor;
@@ -99545,7 +106189,7 @@
     sqlite3_reset(pCsr->pStmt);
     fts3GetDeltaVarint(&pCsr->pNextId, &pCsr->iPrevId);
     pCsr->isRequireSeek = 1;
-    pCsr->isMatchinfoOk = 1;
+    pCsr->isMatchinfoNeeded = 1;
   }
   return rc;
 }
@@ -99663,24 +106307,37 @@
 
 /*
 ** When this function is called, *ppPoslist is assumed to point to the 
-** start of a position-list.
+** start of a position-list. After it returns, *ppPoslist points to the
+** first byte after the position-list.
+**
+** A position list is list of positions (delta encoded) and columns for 
+** a single document record of a doclist.  So, in other words, this
+** routine advances *ppPoslist so that it points to the next docid in
+** the doclist, or to the first byte past the end of the doclist.
+**
+** If pp is not NULL, then the contents of the position list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.
 */
 static void fts3PoslistCopy(char **pp, char **ppPoslist){
   char *pEnd = *ppPoslist;
   char c = 0;
 
   /* The end of a position list is marked by a zero encoded as an FTS3 
-  ** varint. A single 0x00 byte. Except, if the 0x00 byte is preceded by
+  ** varint. A single POS_END (0) byte. Except, if the 0 byte is preceded by
   ** a byte with the 0x80 bit set, then it is not a varint 0, but the tail
   ** of some other, multi-byte, value.
   **
-  ** The following block moves pEnd to point to the first byte that is not 
+  ** The following while-loop moves pEnd to point to the first byte that is not 
   ** immediately preceded by a byte with the 0x80 bit set. Then increments
   ** pEnd once more so that it points to the byte immediately following the
   ** last byte in the position-list.
   */
-  while( *pEnd | c ) c = *pEnd++ & 0x80;
-  pEnd++;
+  while( *pEnd | c ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && (*pEnd)==0 );
+  }
+  pEnd++;  /* Advance past the POS_END terminator byte */
 
   if( pp ){
     int n = (int)(pEnd - *ppPoslist);
@@ -99692,12 +106349,34 @@
   *ppPoslist = pEnd;
 }
 
+/*
+** When this function is called, *ppPoslist is assumed to point to the 
+** start of a column-list. After it returns, *ppPoslist points to the
+** to the terminator (POS_COLUMN or POS_END) byte of the column-list.
+**
+** A column-list is list of delta-encoded positions for a single column
+** within a single document within a doclist.
+**
+** The column-list is terminated either by a POS_COLUMN varint (1) or
+** a POS_END varint (0).  This routine leaves *ppPoslist pointing to
+** the POS_COLUMN or POS_END that terminates the column-list.
+**
+** If pp is not NULL, then the contents of the column-list are copied
+** to *pp. *pp is set to point to the first byte past the last byte copied
+** before this function returns.  The POS_COLUMN or POS_END terminator
+** is not copied into *pp.
+*/
 static void fts3ColumnlistCopy(char **pp, char **ppPoslist){
   char *pEnd = *ppPoslist;
   char c = 0;
 
-  /* A column-list is terminated by either a 0x01 or 0x00. */
-  while( 0xFE & (*pEnd | c) ) c = *pEnd++ & 0x80;
+  /* A column-list is terminated by either a 0x01 or 0x00 byte that is
+  ** not part of a multi-byte varint.
+  */
+  while( 0xFE & (*pEnd | c) ){
+    c = *pEnd++ & 0x80;
+    testcase( c!=0 && ((*pEnd)&0xfe)==0 );
+  }
   if( pp ){
     int n = (int)(pEnd - *ppPoslist);
     char *p = *pp;
@@ -99709,37 +106388,45 @@
 }
 
 /*
-** Value used to signify the end of an offset-list. This is safe because
+** Value used to signify the end of an position-list. This is safe because
 ** it is not possible to have a document with 2^31 terms.
 */
-#define OFFSET_LIST_END 0x7fffffff
+#define POSITION_LIST_END 0x7fffffff
 
 /*
-** This function is used to help parse offset-lists. When this function is
-** called, *pp may point to the start of the next varint in the offset-list
-** being parsed, or it may point to 1 byte past the end of the offset-list
-** (in which case **pp will be 0x00 or 0x01).
+** This function is used to help parse position-lists. When this function is
+** called, *pp may point to the start of the next varint in the position-list
+** being parsed, or it may point to 1 byte past the end of the position-list
+** (in which case **pp will be a terminator bytes POS_END (0) or
+** (1)).
 **
-** If *pp points past the end of the current offset list, set *pi to 
-** OFFSET_LIST_END and return. Otherwise, read the next varint from *pp,
+** If *pp points past the end of the current position-list, set *pi to 
+** POSITION_LIST_END and return. Otherwise, read the next varint from *pp,
 ** increment the current value of *pi by the value read, and set *pp to
 ** point to the next value before returning.
+**
+** Before calling this routine *pi must be initialized to the value of
+** the previous position, or zero if we are reading the first position
+** in the position-list.  Because positions are delta-encoded, the value
+** of the previous position is needed in order to compute the value of
+** the next position.
 */
 static void fts3ReadNextPos(
-  char **pp,                      /* IN/OUT: Pointer into offset-list buffer */
-  sqlite3_int64 *pi               /* IN/OUT: Value read from offset-list */
+  char **pp,                    /* IN/OUT: Pointer into position-list buffer */
+  sqlite3_int64 *pi             /* IN/OUT: Value read from position-list */
 ){
-  if( **pp&0xFE ){
+  if( (**pp)&0xFE ){
     fts3GetDeltaVarint(pp, pi);
     *pi -= 2;
   }else{
-    *pi = OFFSET_LIST_END;
+    *pi = POSITION_LIST_END;
   }
 }
 
 /*
-** If parameter iCol is not 0, write an 0x01 byte followed by the value of
-** iCol encoded as a varint to *pp. 
+** If parameter iCol is not 0, write an POS_COLUMN (1) byte followed by
+** the value of iCol encoded as a varint to *pp.   This will start a new
+** column list.
 **
 ** Set *pp to point to the byte just after the last byte written before 
 ** returning (do not modify it if iCol==0). Return the total number of bytes
@@ -99757,7 +106444,11 @@
 }
 
 /*
-**
+** Compute the union of two position lists.  The output written
+** into *pp contains all positions of both *pp1 and *pp2 in sorted
+** order and with any duplicates removed.  All pointers are
+** updated appropriately.   The caller is responsible for insuring
+** that there is enough space in *pp to hold the complete output.
 */
 static void fts3PoslistMerge(
   char **pp,                      /* Output buffer */
@@ -99769,32 +106460,33 @@
   char *p2 = *pp2;
 
   while( *p1 || *p2 ){
-    int iCol1;
-    int iCol2;
+    int iCol1;         /* The current column index in pp1 */
+    int iCol2;         /* The current column index in pp2 */
 
-    if( *p1==0x01 ) sqlite3Fts3GetVarint32(&p1[1], &iCol1);
-    else if( *p1==0x00 ) iCol1 = OFFSET_LIST_END;
+    if( *p1==POS_COLUMN ) sqlite3Fts3GetVarint32(&p1[1], &iCol1);
+    else if( *p1==POS_END ) iCol1 = POSITION_LIST_END;
     else iCol1 = 0;
 
-    if( *p2==0x01 ) sqlite3Fts3GetVarint32(&p2[1], &iCol2);
-    else if( *p2==0x00 ) iCol2 = OFFSET_LIST_END;
+    if( *p2==POS_COLUMN ) sqlite3Fts3GetVarint32(&p2[1], &iCol2);
+    else if( *p2==POS_END ) iCol2 = POSITION_LIST_END;
     else iCol2 = 0;
 
     if( iCol1==iCol2 ){
-      sqlite3_int64 i1 = 0;
-      sqlite3_int64 i2 = 0;
+      sqlite3_int64 i1 = 0;       /* Last position from pp1 */
+      sqlite3_int64 i2 = 0;       /* Last position from pp2 */
       sqlite3_int64 iPrev = 0;
       int n = fts3PutColNumber(&p, iCol1);
       p1 += n;
       p2 += n;
 
-      /* At this point, both p1 and p2 point to the start of offset-lists.
-      ** An offset-list is a list of non-negative delta-encoded varints, each 
-      ** incremented by 2 before being stored. Each list is terminated by a 0 
-      ** or 1 value (0x00 or 0x01). The following block merges the two lists
+      /* At this point, both p1 and p2 point to the start of column-lists
+      ** for the same column (the column with index iCol1 and iCol2).
+      ** A column-list is a list of non-negative delta-encoded varints, each 
+      ** incremented by 2 before being stored. Each list is terminated by a
+      ** POS_END (0) or POS_COLUMN (1). The following block merges the two lists
       ** and writes the results to buffer p. p is left pointing to the byte
-      ** after the list written. No terminator (0x00 or 0x01) is written to
-      ** the output.
+      ** after the list written. No terminator (POS_END or POS_COLUMN) is
+      ** written to the output.
       */
       fts3GetDeltaVarint(&p1, &i1);
       fts3GetDeltaVarint(&p2, &i2);
@@ -99809,7 +106501,7 @@
         }else{
           fts3ReadNextPos(&p2, &i2);
         }
-      }while( i1!=OFFSET_LIST_END || i2!=OFFSET_LIST_END );
+      }while( i1!=POSITION_LIST_END || i2!=POSITION_LIST_END );
     }else if( iCol1<iCol2 ){
       p1 += fts3PutColNumber(&p, iCol1);
       fts3ColumnlistCopy(&p, &p1);
@@ -99819,7 +106511,7 @@
     }
   }
 
-  *p++ = '\0';
+  *p++ = POS_END;
   *pp = p;
   *pp1 = p1 + 1;
   *pp2 = p2 + 1;
@@ -99842,11 +106534,11 @@
   int iCol1 = 0;
   int iCol2 = 0;
   assert( *p1!=0 && *p2!=0 );
-  if( *p1==0x01 ){ 
+  if( *p1==POS_COLUMN ){ 
     p1++;
     p1 += sqlite3Fts3GetVarint32(p1, &iCol1);
   }
-  if( *p2==0x01 ){ 
+  if( *p2==POS_COLUMN ){ 
     p2++;
     p2 += sqlite3Fts3GetVarint32(p2, &iCol2);
   }
@@ -99859,11 +106551,12 @@
       sqlite3_int64 iPos2 = 0;
 
       if( pp && iCol1 ){
-        *p++ = 0x01;
+        *p++ = POS_COLUMN;
         p += sqlite3Fts3PutVarint(p, iCol1);
       }
 
-      assert( *p1!=0x00 && *p2!=0x00 && *p1!=0x01 && *p2!=0x01 );
+      assert( *p1!=POS_END && *p1!=POS_COLUMN );
+      assert( *p2!=POS_END && *p2!=POS_COLUMN );
       fts3GetDeltaVarint(&p1, &iPos1); iPos1 -= 2;
       fts3GetDeltaVarint(&p2, &iPos2); iPos2 -= 2;
 
@@ -100115,6 +106808,7 @@
     default: assert( mergetype==MERGE_POS_NEAR || mergetype==MERGE_NEAR ); {
       char *aTmp = 0;
       char **ppPos = 0;
+
       if( mergetype==MERGE_POS_NEAR ){
         ppPos = &p;
         aTmp = sqlite3_malloc(2*(n1+n2+1));
@@ -100219,9 +106913,9 @@
 **
 ** The returned doclist may be in one of two formats, depending on the 
 ** value of parameter isReqPos. If isReqPos is zero, then the doclist is
-** a sorted list of delta-compressed docids. If isReqPos is non-zero, 
-** then the returned list is in the same format as is stored in the
-** database without the found length specifier at the start of on-disk
+** a sorted list of delta-compressed docids (a bare doclist). If isReqPos
+** is non-zero, then the returned list is in the same format as is stored 
+** in the database without the found length specifier at the start of on-disk
 ** doclists.
 */
 static int fts3TermSelect(
@@ -100411,9 +107105,79 @@
   return rc;
 }
 
+static int fts3NearMerge(
+  int mergetype,                  /* MERGE_POS_NEAR or MERGE_NEAR */
+  int nNear,                      /* Parameter to NEAR operator */
+  int nTokenLeft,                 /* Number of tokens in LHS phrase arg */
+  char *aLeft,                    /* Doclist for LHS (incl. positions) */
+  int nLeft,                      /* Size of LHS doclist in bytes */
+  int nTokenRight,                /* As nTokenLeft */
+  char *aRight,                   /* As aLeft */
+  int nRight,                     /* As nRight */
+  char **paOut,                   /* OUT: Results of merge (malloced) */
+  int *pnOut                      /* OUT: Sized of output buffer */
+){
+  char *aOut;
+  int rc;
+
+  assert( mergetype==MERGE_POS_NEAR || MERGE_NEAR );
+
+  aOut = sqlite3_malloc(nLeft+nRight+1);
+  if( aOut==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = fts3DoclistMerge(mergetype, nNear+nTokenRight, nNear+nTokenLeft, 
+      aOut, pnOut, aLeft, nLeft, aRight, nRight
+    );
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(aOut);
+      aOut = 0;
+    }
+  }
+
+  *paOut = aOut;
+  return rc;
+}
+
+SQLITE_PRIVATE int sqlite3Fts3ExprNearTrim(Fts3Expr *pLeft, Fts3Expr *pRight, int nNear){
+  int rc;
+  if( pLeft->aDoclist==0 || pRight->aDoclist==0 ){
+    sqlite3_free(pLeft->aDoclist);
+    sqlite3_free(pRight->aDoclist);
+    pRight->aDoclist = 0;
+    pLeft->aDoclist = 0;
+    rc = SQLITE_OK;
+  }else{
+    char *aOut;
+    int nOut;
+
+    rc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
+        pLeft->pPhrase->nToken, pLeft->aDoclist, pLeft->nDoclist,
+        pRight->pPhrase->nToken, pRight->aDoclist, pRight->nDoclist,
+        &aOut, &nOut
+    );
+    if( rc!=SQLITE_OK ) return rc;
+    sqlite3_free(pRight->aDoclist);
+    pRight->aDoclist = aOut;
+    pRight->nDoclist = nOut;
+
+    rc = fts3NearMerge(MERGE_POS_NEAR, nNear, 
+        pRight->pPhrase->nToken, pRight->aDoclist, pRight->nDoclist,
+        pLeft->pPhrase->nToken, pLeft->aDoclist, pLeft->nDoclist,
+        &aOut, &nOut
+    );
+    sqlite3_free(pLeft->aDoclist);
+    pLeft->aDoclist = aOut;
+    pLeft->nDoclist = nOut;
+  }
+  return rc;
+}
+
 /*
 ** Evaluate the full-text expression pExpr against fts3 table pTab. Store
-** the resulting doclist in *paOut and *pnOut.
+** the resulting doclist in *paOut and *pnOut.  This routine mallocs for
+** the space needed to store the output.  The caller is responsible for
+** freeing the space when it has finished.
 */
 static int evalFts3Expr(
   Fts3Table *p,                   /* Virtual table handle */
@@ -100455,9 +107219,6 @@
             Fts3Expr *pLeft;
             Fts3Expr *pRight;
             int mergetype = isReqPos ? MERGE_POS_NEAR : MERGE_NEAR;
-            int nParam1;
-            int nParam2;
-            char *aBuffer;
            
             if( pExpr->pParent && pExpr->pParent->eType==FTSQUERY_NEAR ){
               mergetype = MERGE_POS_NEAR;
@@ -100470,17 +107231,11 @@
             assert( pRight->eType==FTSQUERY_PHRASE );
             assert( pLeft->eType==FTSQUERY_PHRASE );
 
-            nParam1 = pExpr->nNear+1;
-            nParam2 = nParam1+pLeft->pPhrase->nToken+pRight->pPhrase->nToken-2;
-            aBuffer = sqlite3_malloc(nLeft+nRight+1);
-            rc = fts3DoclistMerge(mergetype, nParam1, nParam2, aBuffer,
-                pnOut, aLeft, nLeft, aRight, nRight
+            rc = fts3NearMerge(mergetype, pExpr->nNear, 
+                pLeft->pPhrase->nToken, aLeft, nLeft,
+                pRight->pPhrase->nToken, aRight, nRight,
+                paOut, pnOut
             );
-            if( rc!=SQLITE_OK ){
-              sqlite3_free(aBuffer);
-            }else{
-              *paOut = aBuffer;
-            }
             sqlite3_free(aLeft);
             break;
           }
@@ -100595,7 +107350,13 @@
     rc = sqlite3Fts3ExprParse(p->pTokenizer, p->azColumn, p->nColumn, 
         iCol, zQuery, -1, &pCsr->pExpr
     );
-    if( rc!=SQLITE_OK ) return rc;
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_ERROR ){
+        p->base.zErrMsg = sqlite3_mprintf("malformed MATCH expression: [%s]",
+                                          zQuery);
+      }
+      return rc;
+    }
 
     rc = evalFts3Expr(p, pCsr->pExpr, &pCsr->aDoclist, &pCsr->nDoclist, 0);
     pCsr->pNextId = pCsr->aDoclist;
@@ -100731,7 +107492,7 @@
 
 /*
 ** After ExprLoadDoclist() (see above) has been called, this function is
-** used to iterate through the position lists that make up the doclist
+** used to iterate/search through the position lists that make up the doclist
 ** stored in pExpr->aDoclist.
 */
 SQLITE_PRIVATE char *sqlite3Fts3FindPositions(
@@ -100748,7 +107509,9 @@
     while( pCsr<pEnd ){
       if( pExpr->iCurrent<iDocid ){
         fts3PoslistCopy(0, &pCsr);
-        fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
+        if( pCsr<pEnd ){
+          fts3GetDeltaVarint(&pCsr, &pExpr->iCurrent);
+        }
         pExpr->pCurrent = pCsr;
       }else{
         if( pExpr->iCurrent==iDocid ){
@@ -100766,7 +107529,7 @@
             pCsr++;
             pCsr += sqlite3Fts3GetVarint32(pCsr, &iThis);
           }
-          if( iCol==iThis ) return pCsr;
+          if( iCol==iThis && (*pCsr&0xFE) ) return pCsr;
         }
         return 0;
       }
@@ -100818,45 +107581,8 @@
   const char *zStart = "<b>";
   const char *zEnd = "</b>";
   const char *zEllipsis = "<b>...</b>";
-
-  /* There must be at least one argument passed to this function (otherwise
-  ** the non-overloaded version would have been called instead of this one).
-  */
-  assert( nVal>=1 );
-
-  if( nVal>4 ){
-    sqlite3_result_error(pContext, 
-        "wrong number of arguments to function snippet()", -1);
-    return;
-  }
-  if( fts3FunctionArg(pContext, "snippet", apVal[0], &pCsr) ) return;
-
-  switch( nVal ){
-    case 4: zEllipsis = (const char*)sqlite3_value_text(apVal[3]);
-    case 3: zEnd = (const char*)sqlite3_value_text(apVal[2]);
-    case 2: zStart = (const char*)sqlite3_value_text(apVal[1]);
-  }
-  if( !zEllipsis || !zEnd || !zStart ){
-    sqlite3_result_error_nomem(pContext);
-  }else if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
-    sqlite3Fts3Snippet(pContext, pCsr, zStart, zEnd, zEllipsis);
-  }
-}
-
-/*
-** Implementation of the snippet2() function for FTS3
-*/
-static void fts3Snippet2Func(
-  sqlite3_context *pContext,      /* SQLite function call context */
-  int nVal,                       /* Size of apVal[] array */
-  sqlite3_value **apVal           /* Array of arguments */
-){
-  Fts3Cursor *pCsr;               /* Cursor handle passed through apVal[0] */
-  const char *zStart = "<b>";
-  const char *zEnd = "</b>";
-  const char *zEllipsis = "<b>...</b>";
   int iCol = -1;
-  int nToken = 10;
+  int nToken = 15;                /* Default number of tokens in snippet */
 
   /* There must be at least one argument passed to this function (otherwise
   ** the non-overloaded version would have been called instead of this one).
@@ -100880,7 +107606,7 @@
   if( !zEllipsis || !zEnd || !zStart ){
     sqlite3_result_error_nomem(pContext);
   }else if( SQLITE_OK==fts3CursorSeek(pContext, pCsr) ){
-    sqlite3Fts3Snippet2(pContext, pCsr, zStart, zEnd, zEllipsis, iCol, nToken);
+    sqlite3Fts3Snippet(pContext, pCsr, zStart, zEnd, zEllipsis, iCol, nToken);
   }
 }
 
@@ -100981,7 +107707,6 @@
     void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
   } aOverload[] = {
     { "snippet", fts3SnippetFunc },
-    { "snippet2", fts3Snippet2Func },
     { "offsets", fts3OffsetsFunc },
     { "optimize", fts3OptimizeFunc },
     { "matchinfo", fts3MatchinfoFunc },
@@ -101010,22 +107735,35 @@
   sqlite3_vtab *pVtab,            /* Virtual table handle */
   const char *zName               /* New name of table */
 ){
-  Fts3Table *p = (Fts3Table *)pVtab;     
-  int rc = SQLITE_NOMEM;          /* Return Code */
-  char *zSql;                     /* SQL script to run to rename tables */
+  Fts3Table *p = (Fts3Table *)pVtab;
+  sqlite3 *db;                    /* Database connection */
+  int rc;                         /* Return Code */
  
-  zSql = sqlite3_mprintf(
-    "ALTER TABLE %Q.'%q_content'  RENAME TO '%q_content';"
-    "ALTER TABLE %Q.'%q_segments' RENAME TO '%q_segments';"
-    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';"
-    , p->zDb, p->zName, zName 
-    , p->zDb, p->zName, zName 
-    , p->zDb, p->zName, zName
+  db = p->db;
+  rc = SQLITE_OK;
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_content'  RENAME TO '%q_content';",
+    p->zDb, p->zName, zName
   );
-  if( zSql ){
-    rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
-    sqlite3_free(zSql);
+  if( rc==SQLITE_ERROR ) rc = SQLITE_OK;
+  if( p->bHasDocsize ){
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_docsize'  RENAME TO '%q_docsize';",
+      p->zDb, p->zName, zName
+    );
+    fts3DbExec(&rc, db,
+      "ALTER TABLE %Q.'%q_stat'  RENAME TO '%q_stat';",
+      p->zDb, p->zName, zName
+    );
   }
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segments' RENAME TO '%q_segments';",
+    p->zDb, p->zName, zName
+  );
+  fts3DbExec(&rc, db,
+    "ALTER TABLE %Q.'%q_segdir'   RENAME TO '%q_segdir';",
+    p->zDb, p->zName, zName
+  );
   return rc;
 }
 
@@ -101131,14 +107869,19 @@
   if( SQLITE_OK==rc 
    && SQLITE_OK==(rc = sqlite3Fts3InitHashTable(db, pHash, "fts3_tokenizer"))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "snippet", -1))
-   && SQLITE_OK==(rc = sqlite3_overload_function(db, "snippet2", -1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "offsets", 1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "matchinfo", -1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "optimize", 1))
   ){
-    return sqlite3_create_module_v2(
+    rc = sqlite3_create_module_v2(
         db, "fts3", &fts3Module, (void *)pHash, hashDestroy
     );
+    if( rc==SQLITE_OK ){
+      rc = sqlite3_create_module_v2(
+          db, "fts4", &fts3Module, (void *)pHash, 0
+      );
+    }
+    return rc;
   }
 
   /* An error has occurred. Delete the hash table and return the error code. */
@@ -103068,9 +109811,11 @@
     if( c->iOffset>iStartOffset ){
       int n = c->iOffset-iStartOffset;
       if( n>c->nAllocated ){
+        char *pNew;
         c->nAllocated = n+20;
-        c->zToken = sqlite3_realloc(c->zToken, c->nAllocated);
-        if( c->zToken==NULL ) return SQLITE_NOMEM;
+        pNew = sqlite3_realloc(c->zToken, c->nAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->zToken = pNew;
       }
       porter_stemmer(&z[iStartOffset], n, c->zToken, pnBytes);
       *pzToken = c->zToken;
@@ -103781,9 +110526,11 @@
     if( c->iOffset>iStartOffset ){
       int i, n = c->iOffset-iStartOffset;
       if( n>c->nTokenAllocated ){
+        char *pNew;
         c->nTokenAllocated = n+20;
-        c->pToken = sqlite3_realloc(c->pToken, c->nTokenAllocated);
-        if( c->pToken==NULL ) return SQLITE_NOMEM;
+        pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->pToken = pNew;
       }
       for(i=0; i<n; i++){
         /* TODO(shess) This needs expansion to handle UTF-8
@@ -103967,19 +110714,26 @@
 #define SQL_DELETE_ALL_CONTENT         2 
 #define SQL_DELETE_ALL_SEGMENTS        3
 #define SQL_DELETE_ALL_SEGDIR          4
-#define SQL_SELECT_CONTENT_BY_ROWID    5
-#define SQL_NEXT_SEGMENT_INDEX         6
-#define SQL_INSERT_SEGMENTS            7
-#define SQL_NEXT_SEGMENTS_ID           8
-#define SQL_INSERT_SEGDIR              9
-#define SQL_SELECT_LEVEL              10
-#define SQL_SELECT_ALL_LEVEL          11
-#define SQL_SELECT_LEVEL_COUNT        12
-#define SQL_SELECT_SEGDIR_COUNT_MAX   13
-#define SQL_DELETE_SEGDIR_BY_LEVEL    14
-#define SQL_DELETE_SEGMENTS_RANGE     15
-#define SQL_CONTENT_INSERT            16
-#define SQL_GET_BLOCK                 17
+#define SQL_DELETE_ALL_DOCSIZE         5
+#define SQL_DELETE_ALL_STAT            6
+#define SQL_SELECT_CONTENT_BY_ROWID    7
+#define SQL_NEXT_SEGMENT_INDEX         8
+#define SQL_INSERT_SEGMENTS            9
+#define SQL_NEXT_SEGMENTS_ID          10
+#define SQL_INSERT_SEGDIR             11
+#define SQL_SELECT_LEVEL              12
+#define SQL_SELECT_ALL_LEVEL          13
+#define SQL_SELECT_LEVEL_COUNT        14
+#define SQL_SELECT_SEGDIR_COUNT_MAX   15
+#define SQL_DELETE_SEGDIR_BY_LEVEL    16
+#define SQL_DELETE_SEGMENTS_RANGE     17
+#define SQL_CONTENT_INSERT            18
+#define SQL_GET_BLOCK                 19
+#define SQL_DELETE_DOCSIZE            20
+#define SQL_REPLACE_DOCSIZE           21
+#define SQL_SELECT_DOCSIZE            22
+#define SQL_SELECT_DOCTOTAL           23
+#define SQL_REPLACE_DOCTOTAL          24
 
 /*
 ** This function is used to obtain an SQLite prepared statement handle
@@ -104004,25 +110758,32 @@
 /* 2  */  "DELETE FROM %Q.'%q_content'",
 /* 3  */  "DELETE FROM %Q.'%q_segments'",
 /* 4  */  "DELETE FROM %Q.'%q_segdir'",
-/* 5  */  "SELECT * FROM %Q.'%q_content' WHERE rowid=?",
-/* 6  */  "SELECT coalesce(max(idx)+1, 0) FROM %Q.'%q_segdir' WHERE level=?",
-/* 7  */  "INSERT INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
-/* 8  */  "SELECT coalesce(max(blockid)+1, 1) FROM %Q.'%q_segments'",
-/* 9  */  "INSERT INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
+/* 5  */  "DELETE FROM %Q.'%q_docsize'",
+/* 6  */  "DELETE FROM %Q.'%q_stat'",
+/* 7  */  "SELECT * FROM %Q.'%q_content' WHERE rowid=?",
+/* 8  */  "SELECT (SELECT max(idx) FROM %Q.'%q_segdir' WHERE level = ?) + 1",
+/* 9  */  "INSERT INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
+/* 10 */  "SELECT coalesce((SELECT max(blockid) FROM %Q.'%q_segments') + 1, 1)",
+/* 11 */  "INSERT INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
 
           /* Return segments in order from oldest to newest.*/ 
-/* 10 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+/* 12 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
             "FROM %Q.'%q_segdir' WHERE level = ? ORDER BY idx ASC",
-/* 11 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+/* 13 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
             "FROM %Q.'%q_segdir' ORDER BY level DESC, idx ASC",
 
-/* 12 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
-/* 13 */  "SELECT count(*), max(level) FROM %Q.'%q_segdir'",
+/* 14 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
+/* 15 */  "SELECT count(*), max(level) FROM %Q.'%q_segdir'",
 
-/* 14 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
-/* 15 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
-/* 16 */  "INSERT INTO %Q.'%q_content' VALUES(%z)",
-/* 17 */  "SELECT block FROM %Q.'%q_segments' WHERE blockid = ?",
+/* 16 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
+/* 17 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
+/* 18 */  "INSERT INTO %Q.'%q_content' VALUES(%z)",
+/* 19 */  "SELECT block FROM %Q.'%q_segments' WHERE blockid = ?",
+/* 20 */  "DELETE FROM %Q.'%q_docsize' WHERE docid = ?",
+/* 21 */  "REPLACE INTO %Q.'%q_docsize' VALUES(?,?)",
+/* 22 */  "SELECT size FROM %Q.'%q_docsize' WHERE docid=?",
+/* 23 */  "SELECT value FROM %Q.'%q_stat' WHERE id=0",
+/* 24 */  "REPLACE INTO %Q.'%q_stat' VALUES(0,?)",
   };
   int rc = SQLITE_OK;
   sqlite3_stmt *pStmt;
@@ -104079,14 +110840,21 @@
 ** Returns SQLITE_OK if the statement is successfully executed, or an
 ** SQLite error code otherwise.
 */
-static int fts3SqlExec(Fts3Table *p, int eStmt, sqlite3_value **apVal){
+static void fts3SqlExec(
+  int *pRC,                /* Result code */
+  Fts3Table *p,            /* The FTS3 table */
+  int eStmt,               /* Index of statement to evaluate */
+  sqlite3_value **apVal    /* Parameters to bind */
+){
   sqlite3_stmt *pStmt;
-  int rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
+  int rc;
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
   if( rc==SQLITE_OK ){
     sqlite3_step(pStmt);
     rc = sqlite3_reset(pStmt);
   }
-  return rc;
+  *pRC = rc;
 }
 
 
@@ -104266,11 +111034,17 @@
 **
 ** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
 */
-static int fts3PendingTermsAdd(Fts3Table *p, const char *zText, int iCol){
+static int fts3PendingTermsAdd(
+  Fts3Table *p,          /* FTS table into which text will be inserted */
+  const char *zText,     /* Text of document to be inseted */
+  int iCol,              /* Column number into which text is inserted */
+  u32 *pnWord            /* OUT: Number of tokens inserted */
+){
   int rc;
   int iStart;
   int iEnd;
   int iPos;
+  int nWord = 0;
 
   char const *zToken;
   int nToken;
@@ -104294,6 +111068,8 @@
       && SQLITE_OK==(rc = xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos))
   ){
     PendingList *pList;
+ 
+    if( iPos>=nWord ) nWord = iPos+1;
 
     /* Positions cannot be negative; we use -1 as a terminator internally.
     ** Tokens must have a non-zero length.
@@ -104323,6 +111099,7 @@
   }
 
   pModule->xClose(pCsr);
+  *pnWord = nWord;
   return (rc==SQLITE_DONE ? SQLITE_OK : rc);
 }
 
@@ -104363,12 +111140,12 @@
 ** Argument apVal is the same as the similarly named argument passed to
 ** fts3InsertData(). Parameter iDocid is the docid of the new row.
 */
-static int fts3InsertTerms(Fts3Table *p, sqlite3_value **apVal){
+static int fts3InsertTerms(Fts3Table *p, sqlite3_value **apVal, u32 *aSz){
   int i;                          /* Iterator variable */
   for(i=2; i<p->nColumn+2; i++){
     const char *zText = (const char *)sqlite3_value_text(apVal[i]);
     if( zText ){
-      int rc = fts3PendingTermsAdd(p, zText, i-2);
+      int rc = fts3PendingTermsAdd(p, zText, i-2, &aSz[i-2]);
       if( rc!=SQLITE_OK ){
         return rc;
       }
@@ -104449,18 +111226,18 @@
 ** pending terms.
 */
 static int fts3DeleteAll(Fts3Table *p){
-  int rc;                         /* Return code */
+  int rc = SQLITE_OK;             /* Return code */
 
   /* Discard the contents of the pending-terms hash table. */
   sqlite3Fts3PendingTermsClear(p);
 
   /* Delete everything from the %_content, %_segments and %_segdir tables. */
-  rc = fts3SqlExec(p, SQL_DELETE_ALL_CONTENT, 0);
-  if( rc==SQLITE_OK ){
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGMENTS, 0);
-  }
-  if( rc==SQLITE_OK ){
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGDIR, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_CONTENT, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGMENTS, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
+  if( p->bHasDocsize ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_DOCSIZE, 0);
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_STAT, 0);
   }
   return rc;
 }
@@ -104470,20 +111247,27 @@
 ** (an integer) of a row about to be deleted. Remove all terms from the
 ** full-text index.
 */
-static int fts3DeleteTerms(Fts3Table *p, sqlite3_value **apVal){
+static void fts3DeleteTerms(
+  int *pRC,               /* Result code */
+  Fts3Table *p,           /* The FTS table to delete from */
+  sqlite3_value **apVal,  /* apVal[] contains the docid to be deleted */
+  u32 *aSz                /* Sizes of deleted document written here */
+){
   int rc;
   sqlite3_stmt *pSelect;
 
+  if( *pRC ) return;
   rc = fts3SqlStmt(p, SQL_SELECT_CONTENT_BY_ROWID, &pSelect, apVal);
   if( rc==SQLITE_OK ){
     if( SQLITE_ROW==sqlite3_step(pSelect) ){
       int i;
       for(i=1; i<=p->nColumn; i++){
         const char *zText = (const char *)sqlite3_column_text(pSelect, i);
-        rc = fts3PendingTermsAdd(p, zText, -1);
+        rc = fts3PendingTermsAdd(p, zText, -1, &aSz[i-1]);
         if( rc!=SQLITE_OK ){
           sqlite3_reset(pSelect);
-          return rc;
+          *pRC = rc;
+          return;
         }
       }
     }
@@ -104491,7 +111275,7 @@
   }else{
     sqlite3_reset(pSelect);
   }
-  return rc;
+  *pRC = rc;
 }
 
 /*
@@ -105611,7 +112395,7 @@
       rc = sqlite3_reset(pDelete);
     }
   }else{
-    rc = fts3SqlExec(p, SQL_DELETE_ALL_SEGDIR, 0);
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
   }
 
   return rc;
@@ -106040,6 +112824,211 @@
 }
 
 /*
+** Encode N integers as varints into a blob.
+*/
+static void fts3EncodeIntArray(
+  int N,             /* The number of integers to encode */
+  u32 *a,            /* The integer values */
+  char *zBuf,        /* Write the BLOB here */
+  int *pNBuf         /* Write number of bytes if zBuf[] used here */
+){
+  int i, j;
+  for(i=j=0; i<N; i++){
+    j += sqlite3Fts3PutVarint(&zBuf[j], (sqlite3_int64)a[i]);
+  }
+  *pNBuf = j;
+}
+
+/*
+** Decode a blob of varints into N integers
+*/
+static void fts3DecodeIntArray(
+  int N,             /* The number of integers to decode */
+  u32 *a,            /* Write the integer values */
+  const char *zBuf,  /* The BLOB containing the varints */
+  int nBuf           /* size of the BLOB */
+){
+  int i, j;
+  UNUSED_PARAMETER(nBuf);
+  for(i=j=0; i<N; i++){
+    sqlite3_int64 x;
+    j += sqlite3Fts3GetVarint(&zBuf[j], &x);
+    assert(j<=nBuf);
+    a[i] = (u32)(x & 0xffffffff);
+  }
+}
+
+/*
+** Fill in the document size auxiliary information for the matchinfo
+** structure.  The auxiliary information is:
+**
+**    N     Total number of documents in the full-text index
+**    a0    Average length of column 0 over the whole index
+**    n0    Length of column 0 on the matching row
+**    ...
+**    aM    Average length of column M over the whole index
+**    nM    Length of column M on the matching row
+**
+** The fts3MatchinfoDocsizeLocal() routine fills in the nX values.
+** The fts3MatchinfoDocsizeGlobal() routine fills in N and the aX values.
+*/
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeLocal(Fts3Cursor *pCur, u32 *a){
+  const char *pBlob;       /* The BLOB holding %_docsize info */
+  int nBlob;               /* Size of the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i, j;                /* Loop counters */
+  sqlite3_int64 x;         /* Varint value */
+  int rc;                  /* Result code from subfunctions */
+  Fts3Table *p;            /* The FTS table */
+
+  p = (Fts3Table*)pCur->base.pVtab;
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    return rc;
+  }
+  sqlite3_bind_int64(pStmt, 1, pCur->iPrevId);
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    nBlob = sqlite3_column_bytes(pStmt, 0);
+    pBlob = (const char*)sqlite3_column_blob(pStmt, 0);
+    for(i=j=0; i<p->nColumn && j<nBlob; i++){
+      j = sqlite3Fts3GetVarint(&pBlob[j], &x);
+      a[2+i*2] = (u32)(x & 0xffffffff);
+    }
+  }
+  sqlite3_reset(pStmt);
+  return SQLITE_OK; 
+}
+SQLITE_PRIVATE int sqlite3Fts3MatchinfoDocsizeGlobal(Fts3Cursor *pCur, u32 *a){
+  const char *pBlob;       /* The BLOB holding %_stat info */
+  int nBlob;               /* Size of the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i, j;                /* Loop counters */
+  sqlite3_int64 x;         /* Varint value */
+  int nDoc;                /* Number of documents */
+  int rc;                  /* Result code from subfunctions */
+  Fts3Table *p;            /* The FTS table */
+
+  p = (Fts3Table*)pCur->base.pVtab;
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    return rc;
+  }
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    nBlob = sqlite3_column_bytes(pStmt, 0);
+    pBlob = (const char*)sqlite3_column_blob(pStmt, 0);
+    j = sqlite3Fts3GetVarint(pBlob, &x);
+    a[0] = nDoc = (u32)(x & 0xffffffff);
+    for(i=0; i<p->nColumn && j<nBlob; i++){
+      j = sqlite3Fts3GetVarint(&pBlob[j], &x);
+      a[1+i*2] = ((u32)(x & 0xffffffff) + nDoc/2)/nDoc;
+    }
+  }
+  sqlite3_reset(pStmt);
+  return SQLITE_OK; 
+}
+
+/*
+** Insert the sizes (in tokens) for each column of the document
+** with docid equal to p->iPrevDocid.  The sizes are encoded as
+** a blob of varints.
+*/
+static void fts3InsertDocsize(
+  int *pRC,         /* Result code */
+  Fts3Table *p,     /* Table into which to insert */
+  u32 *aSz          /* Sizes of each column */
+){
+  char *pBlob;             /* The BLOB encoding of the document size */
+  int nBlob;               /* Number of bytes in the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement used to insert the encoding */
+  int rc;                  /* Result code from subfunctions */
+
+  if( *pRC ) return;
+  pBlob = sqlite3_malloc( 10*p->nColumn );
+  if( pBlob==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  fts3EncodeIntArray(p->nColumn, aSz, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(pBlob);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int64(pStmt, 1, p->iPrevDocid);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, sqlite3_free);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+}
+
+/*
+** Update the 0 record of the %_stat table so that it holds a blob
+** which contains the document count followed by the cumulative
+** document sizes for all columns.
+*/
+static void fts3UpdateDocTotals(
+  int *pRC,       /* The result code */
+  Fts3Table *p,   /* Table being updated */
+  u32 *aSzIns,    /* Size increases */
+  u32 *aSzDel,    /* Size decreases */
+  int nChng       /* Change in the number of documents */
+){
+  char *pBlob;             /* Storage for BLOB written into %_stat */
+  int nBlob;               /* Size of BLOB written into %_stat */
+  u32 *a;                  /* Array of integers that becomes the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subfunctions */
+
+  if( *pRC ) return;
+  a = sqlite3_malloc( (sizeof(u32)+10)*(p->nColumn+1) );
+  if( a==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  pBlob = (char*)&a[p->nColumn+1];
+  rc = fts3SqlStmt(p, SQL_SELECT_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    fts3DecodeIntArray(p->nColumn+1, a,
+         sqlite3_column_blob(pStmt, 0),
+         sqlite3_column_bytes(pStmt, 0));
+  }else{
+    memset(a, 0, sizeof(u32)*(p->nColumn+1) );
+  }
+  sqlite3_reset(pStmt);
+  if( nChng<0 && a[0]<(u32)(-nChng) ){
+    a[0] = 0;
+  }else{
+    a[0] += nChng;
+  }
+  for(i=0; i<p->nColumn; i++){
+    u32 x = a[i+1];
+    if( x+aSzIns[i] < aSzDel[i] ){
+      x = 0;
+    }else{
+      x = x + aSzIns[i] - aSzDel[i];
+    }
+    a[i+1] = x;
+  }
+  fts3EncodeIntArray(p->nColumn+1, a, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCTOTAL, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_blob(pStmt, 1, pBlob, nBlob, SQLITE_STATIC);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+  sqlite3_free(a);
+}
+
+/*
 ** Handle a 'special' INSERT of the form:
 **
 **   "INSERT INTO tbl(tbl) VALUES(<expr>)"
@@ -106090,8 +113079,17 @@
   int rc = SQLITE_OK;             /* Return Code */
   int isRemove = 0;               /* True for an UPDATE or DELETE */
   sqlite3_int64 iRemove = 0;      /* Rowid removed by UPDATE or DELETE */
+  u32 *aSzIns;                    /* Sizes of inserted documents */
+  u32 *aSzDel;                    /* Sizes of deleted documents */
+  int nChng = 0;                  /* Net change in number of documents */
 
 
+  /* Allocate space to hold the change in document sizes */
+  aSzIns = sqlite3_malloc( sizeof(aSzIns[0])*p->nColumn*2 );
+  if( aSzIns==0 ) return SQLITE_NOMEM;
+  aSzDel = &aSzIns[p->nColumn];
+  memset(aSzIns, 0, sizeof(aSzIns[0])*p->nColumn*2);
+
   /* If this is a DELETE or UPDATE operation, remove the old record. */
   if( sqlite3_value_type(apVal[0])!=SQLITE_NULL ){
     int isEmpty;
@@ -106107,15 +113105,16 @@
         isRemove = 1;
         iRemove = sqlite3_value_int64(apVal[0]);
         rc = fts3PendingTermsDocid(p, iRemove);
-        if( rc==SQLITE_OK ){
-          rc = fts3DeleteTerms(p, apVal);
-          if( rc==SQLITE_OK ){
-            rc = fts3SqlExec(p, SQL_DELETE_CONTENT, apVal);
-          }
+        fts3DeleteTerms(&rc, p, apVal, aSzDel);
+        fts3SqlExec(&rc, p, SQL_DELETE_CONTENT, apVal);
+        if( p->bHasDocsize ){
+          fts3SqlExec(&rc, p, SQL_DELETE_DOCSIZE, apVal);
+          nChng--;
         }
       }
     }
   }else if( sqlite3_value_type(apVal[p->nColumn+2])!=SQLITE_NULL ){
+    sqlite3_free(aSzIns);
     return fts3SpecialInsert(p, apVal[p->nColumn+2]);
   }
   
@@ -106126,10 +113125,19 @@
       rc = fts3PendingTermsDocid(p, *pRowid);
     }
     if( rc==SQLITE_OK ){
-      rc = fts3InsertTerms(p, apVal);
+      rc = fts3InsertTerms(p, apVal, aSzIns);
+    }
+    if( p->bHasDocsize ){
+      nChng++;
+      fts3InsertDocsize(&rc, p, aSzIns);
     }
   }
 
+  if( p->bHasDocsize ){
+    fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nChng);
+  }
+
+  sqlite3_free(aSzIns);
   return rc;
 }
 
@@ -106176,727 +113184,97 @@
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 
-typedef struct Snippet Snippet;
 
 /*
-** An instance of the following structure keeps track of generated
-** matching-word offset information and snippets.
+** Used as an fts3ExprIterate() context when loading phrase doclists to
+** Fts3Expr.aDoclist[]/nDoclist.
 */
-struct Snippet {
-  int nMatch;                     /* Total number of matches */
-  int nAlloc;                     /* Space allocated for aMatch[] */
-  struct snippetMatch {  /* One entry for each matching term */
-    char snStatus;       /* Status flag for use while constructing snippets */
-    short int nByte;     /* Number of bytes in the term */
-    short int iCol;      /* The column that contains the match */
-    short int iTerm;     /* The index in Query.pTerms[] of the matching term */
-    int iToken;          /* The index of the matching document token */
-    int iStart;          /* The offset to the first character of the term */
-  } *aMatch;                      /* Points to space obtained from malloc */
-  char *zOffset;                  /* Text rendering of aMatch[] */
-  int nOffset;                    /* strlen(zOffset) */
-  char *zSnippet;                 /* Snippet text */
-  int nSnippet;                   /* strlen(zSnippet) */
+typedef struct LoadDoclistCtx LoadDoclistCtx;
+struct LoadDoclistCtx {
+  Fts3Table *pTab;                /* FTS3 Table */
+  int nPhrase;                    /* Number of phrases seen so far */
+  int nToken;                     /* Number of tokens seen so far */
+};
+
+/*
+** The following types are used as part of the implementation of the 
+** fts3BestSnippet() routine.
+*/
+typedef struct SnippetIter SnippetIter;
+typedef struct SnippetPhrase SnippetPhrase;
+typedef struct SnippetFragment SnippetFragment;
+
+struct SnippetIter {
+  Fts3Cursor *pCsr;               /* Cursor snippet is being generated from */
+  int iCol;                       /* Extract snippet from this column */
+  int nSnippet;                   /* Requested snippet length (in tokens) */
+  int nPhrase;                    /* Number of phrases in query */
+  SnippetPhrase *aPhrase;         /* Array of size nPhrase */
+  int iCurrent;                   /* First token of current snippet */
+};
+
+struct SnippetPhrase {
+  int nToken;                     /* Number of tokens in phrase */
+  char *pList;                    /* Pointer to start of phrase position list */
+  int iHead;                      /* Next value in position list */
+  char *pHead;                    /* Position list data following iHead */
+  int iTail;                      /* Next value in trailing position list */
+  char *pTail;                    /* Position list data following iTail */
+};
+
+struct SnippetFragment {
+  int iCol;                       /* Column snippet is extracted from */
+  int iPos;                       /* Index of first token in snippet */
+  u64 covered;                    /* Mask of query phrases covered */
+  u64 hlmask;                     /* Mask of snippet terms to highlight */
+};
+
+/*
+** This type is used as an fts3ExprIterate() context object while 
+** accumulating the data returned by the matchinfo() function.
+*/
+typedef struct MatchInfo MatchInfo;
+struct MatchInfo {
+  Fts3Cursor *pCursor;            /* FTS3 Cursor */
+  int nCol;                       /* Number of columns in table */
+  u32 *aMatchinfo;                /* Pre-allocated buffer */
 };
 
 
-/* It is not safe to call isspace(), tolower(), or isalnum() on
-** hi-bit-set characters.  This is the same solution used in the
-** tokenizer.
+
+/*
+** The snippet() and offsets() functions both return text values. An instance
+** of the following structure is used to accumulate those values while the
+** functions are running. See fts3StringAppend() for details.
 */
-static int fts3snippetIsspace(char c){
-  return (c&0x80)==0 ? isspace(c) : 0;
-}
+typedef struct StrBuffer StrBuffer;
+struct StrBuffer {
+  char *z;                        /* Pointer to buffer containing string */
+  int n;                          /* Length of z in bytes (excl. nul-term) */
+  int nAlloc;                     /* Allocated size of buffer z in bytes */
+};
 
 
 /*
-** A StringBuffer object holds a zero-terminated string that grows
-** arbitrarily by appending.  Space to hold the string is obtained
-** from sqlite3_malloc().  After any memory allocation failure, 
-** StringBuffer.z is set to NULL and no further allocation is attempted.
-*/
-typedef struct StringBuffer {
-  char *z;         /* Text of the string.  Space from malloc. */
-  int nUsed;       /* Number bytes of z[] used, not counting \000 terminator */
-  int nAlloc;      /* Bytes allocated for z[] */
-} StringBuffer;
-
-
-/*
-** Initialize a new StringBuffer.
-*/
-static void fts3SnippetSbInit(StringBuffer *p){
-  p->nAlloc = 100;
-  p->nUsed = 0;
-  p->z = sqlite3_malloc( p->nAlloc );
-}
-
-/*
-** Append text to the string buffer.
-*/
-static void fts3SnippetAppend(StringBuffer *p, const char *zNew, int nNew){
-  if( p->z==0 ) return;
-  if( nNew<0 ) nNew = (int)strlen(zNew);
-  if( p->nUsed + nNew >= p->nAlloc ){
-    int nAlloc;
-    char *zNew;
-
-    nAlloc = p->nUsed + nNew + p->nAlloc;
-    zNew = sqlite3_realloc(p->z, nAlloc);
-    if( zNew==0 ){
-      sqlite3_free(p->z);
-      p->z = 0;
-      return;
-    }
-    p->z = zNew;
-    p->nAlloc = nAlloc;
-  }
-  memcpy(&p->z[p->nUsed], zNew, nNew);
-  p->nUsed += nNew;
-  p->z[p->nUsed] = 0;
-}
-
-/* If the StringBuffer ends in something other than white space, add a
-** single space character to the end.
-*/
-static void fts3SnippetAppendWhiteSpace(StringBuffer *p){
-  if( p->z && p->nUsed && !fts3snippetIsspace(p->z[p->nUsed-1]) ){
-    fts3SnippetAppend(p, " ", 1);
-  }
-}
-
-/* Remove white space from the end of the StringBuffer */
-static void fts3SnippetTrimWhiteSpace(StringBuffer *p){
-  if( p->z ){
-    while( p->nUsed && fts3snippetIsspace(p->z[p->nUsed-1]) ){
-      p->nUsed--;
-    }
-    p->z[p->nUsed] = 0;
-  }
-}
-
-/* 
-** Release all memory associated with the Snippet structure passed as
-** an argument.
-*/
-static void fts3SnippetFree(Snippet *p){
-  if( p ){
-    sqlite3_free(p->aMatch);
-    sqlite3_free(p->zOffset);
-    sqlite3_free(p->zSnippet);
-    sqlite3_free(p);
-  }
-}
-
-/*
-** Append a single entry to the p->aMatch[] log.
-*/
-static int snippetAppendMatch(
-  Snippet *p,               /* Append the entry to this snippet */
-  int iCol, int iTerm,      /* The column and query term */
-  int iToken,               /* Matching token in document */
-  int iStart, int nByte     /* Offset and size of the match */
-){
-  int i;
-  struct snippetMatch *pMatch;
-  if( p->nMatch+1>=p->nAlloc ){
-    struct snippetMatch *pNew;
-    p->nAlloc = p->nAlloc*2 + 10;
-    pNew = sqlite3_realloc(p->aMatch, p->nAlloc*sizeof(p->aMatch[0]) );
-    if( pNew==0 ){
-      p->aMatch = 0;
-      p->nMatch = 0;
-      p->nAlloc = 0;
-      return SQLITE_NOMEM;
-    }
-    p->aMatch = pNew;
-  }
-  i = p->nMatch++;
-  pMatch = &p->aMatch[i];
-  pMatch->iCol = (short)iCol;
-  pMatch->iTerm = (short)iTerm;
-  pMatch->iToken = iToken;
-  pMatch->iStart = iStart;
-  pMatch->nByte = (short)nByte;
-  return SQLITE_OK;
-}
-
-/*
-** Sizing information for the circular buffer used in snippetOffsetsOfColumn()
-*/
-#define FTS3_ROTOR_SZ   (32)
-#define FTS3_ROTOR_MASK (FTS3_ROTOR_SZ-1)
-
-/*
-** Function to iterate through the tokens of a compiled expression.
+** This function is used to help iterate through a position-list. A position
+** list is a list of unique integers, sorted from smallest to largest. Each
+** element of the list is represented by an FTS3 varint that takes the value
+** of the difference between the current element and the previous one plus
+** two. For example, to store the position-list:
 **
-** Except, skip all tokens on the right-hand side of a NOT operator.
-** This function is used to find tokens as part of snippet and offset
-** generation and we do nt want snippets and offsets to report matches
-** for tokens on the RHS of a NOT.
-*/
-static int fts3NextExprToken(Fts3Expr **ppExpr, int *piToken){
-  Fts3Expr *p = *ppExpr;
-  int iToken = *piToken;
-  if( iToken<0 ){
-    /* In this case the expression p is the root of an expression tree.
-    ** Move to the first token in the expression tree.
-    */
-    while( p->pLeft ){
-      p = p->pLeft;
-    }
-    iToken = 0;
-  }else{
-    assert(p && p->eType==FTSQUERY_PHRASE );
-    if( iToken<(p->pPhrase->nToken-1) ){
-      iToken++;
-    }else{
-      iToken = 0;
-      while( p->pParent && p->pParent->pLeft!=p ){
-        assert( p->pParent->pRight==p );
-        p = p->pParent;
-      }
-      p = p->pParent;
-      if( p ){
-        assert( p->pRight!=0 );
-        p = p->pRight;
-        while( p->pLeft ){
-          p = p->pLeft;
-        }
-      }
-    }
-  }
-
-  *ppExpr = p;
-  *piToken = iToken;
-  return p?1:0;
-}
-
-/*
-** Return TRUE if the expression node pExpr is located beneath the
-** RHS of a NOT operator.
-*/
-static int fts3ExprBeneathNot(Fts3Expr *p){
-  Fts3Expr *pParent;
-  while( p ){
-    pParent = p->pParent;
-    if( pParent && pParent->eType==FTSQUERY_NOT && pParent->pRight==p ){
-      return 1;
-    }
-    p = pParent;
-  }
-  return 0;
-}
-
-/*
-** Add entries to pSnippet->aMatch[] for every match that occurs against
-** document zDoc[0..nDoc-1] which is stored in column iColumn.
-*/
-static int snippetOffsetsOfColumn(
-  Fts3Cursor *pCur,         /* The fulltest search cursor */
-  Snippet *pSnippet,             /* The Snippet object to be filled in */
-  int iColumn,                   /* Index of fulltext table column */
-  const char *zDoc,              /* Text of the fulltext table column */
-  int nDoc                       /* Length of zDoc in bytes */
-){
-  const sqlite3_tokenizer_module *pTModule;  /* The tokenizer module */
-  sqlite3_tokenizer *pTokenizer;             /* The specific tokenizer */
-  sqlite3_tokenizer_cursor *pTCursor;        /* Tokenizer cursor */
-  Fts3Table *pVtab;                /* The full text index */
-  int nColumn;                         /* Number of columns in the index */
-  int i, j;                            /* Loop counters */
-  int rc;                              /* Return code */
-  unsigned int match, prevMatch;       /* Phrase search bitmasks */
-  const char *zToken;                  /* Next token from the tokenizer */
-  int nToken;                          /* Size of zToken */
-  int iBegin, iEnd, iPos;              /* Offsets of beginning and end */
-
-  /* The following variables keep a circular buffer of the last
-  ** few tokens */
-  unsigned int iRotor = 0;             /* Index of current token */
-  int iRotorBegin[FTS3_ROTOR_SZ];      /* Beginning offset of token */
-  int iRotorLen[FTS3_ROTOR_SZ];        /* Length of token */
-
-  pVtab =  (Fts3Table *)pCur->base.pVtab;
-  nColumn = pVtab->nColumn;
-  pTokenizer = pVtab->pTokenizer;
-  pTModule = pTokenizer->pModule;
-  rc = pTModule->xOpen(pTokenizer, zDoc, nDoc, &pTCursor);
-  if( rc ) return rc;
-  pTCursor->pTokenizer = pTokenizer;
-
-  prevMatch = 0;
-  while( (rc = pTModule->xNext(pTCursor, &zToken, &nToken,
-                               &iBegin, &iEnd, &iPos))==SQLITE_OK ){
-    Fts3Expr *pIter = pCur->pExpr;
-    int iIter = -1;
-    iRotorBegin[iRotor&FTS3_ROTOR_MASK] = iBegin;
-    iRotorLen[iRotor&FTS3_ROTOR_MASK] = iEnd-iBegin;
-    match = 0;
-    for(i=0; i<(FTS3_ROTOR_SZ-1) && fts3NextExprToken(&pIter, &iIter); i++){
-      int nPhrase;                    /* Number of tokens in current phrase */
-      struct PhraseToken *pToken;     /* Current token */
-      int iCol;                       /* Column index */
-
-      if( fts3ExprBeneathNot(pIter) ) continue;
-      nPhrase = pIter->pPhrase->nToken;
-      pToken = &pIter->pPhrase->aToken[iIter];
-      iCol = pIter->pPhrase->iColumn;
-      if( iCol>=0 && iCol<nColumn && iCol!=iColumn ) continue;
-      if( pToken->n>nToken ) continue;
-      if( !pToken->isPrefix && pToken->n<nToken ) continue;
-      assert( pToken->n<=nToken );
-      if( memcmp(pToken->z, zToken, pToken->n) ) continue;
-      if( iIter>0 && (prevMatch & (1<<i))==0 ) continue;
-      match |= 1<<i;
-      if( i==(FTS3_ROTOR_SZ-2) || nPhrase==iIter+1 ){
-        for(j=nPhrase-1; j>=0; j--){
-          int k = (iRotor-j) & FTS3_ROTOR_MASK;
-          rc = snippetAppendMatch(pSnippet, iColumn, i-j, iPos-j,
-                                  iRotorBegin[k], iRotorLen[k]);
-          if( rc ) goto end_offsets_of_column;
-        }
-      }
-    }
-    prevMatch = match<<1;
-    iRotor++;
-  }
-end_offsets_of_column:
-  pTModule->xClose(pTCursor);  
-  return rc==SQLITE_DONE ? SQLITE_OK : rc;
-}
-
-/*
-** Remove entries from the pSnippet structure to account for the NEAR
-** operator. When this is called, pSnippet contains the list of token 
-** offsets produced by treating all NEAR operators as AND operators.
-** This function removes any entries that should not be present after
-** accounting for the NEAR restriction. For example, if the queried
-** document is:
+**     4 9 113
 **
-**     "A B C D E A"
+** the three varints:
 **
-** and the query is:
-** 
-**     A NEAR/0 E
+**     6 7 106
 **
-** then when this function is called the Snippet contains token offsets
-** 0, 4 and 5. This function removes the "0" entry (because the first A
-** is not near enough to an E).
+** are encoded.
 **
-** When this function is called, the value pointed to by parameter piLeft is
-** the integer id of the left-most token in the expression tree headed by
-** pExpr. This function increments *piLeft by the total number of tokens
-** in the expression tree headed by pExpr.
-**
-** Return 1 if any trimming occurs.  Return 0 if no trimming is required.
+** When this function is called, *pp points to the start of an element of
+** the list. *piPos contains the value of the previous entry in the list.
+** After it returns, *piPos contains the value of the next element of the
+** list and *pp is advanced to the following varint.
 */
-static int trimSnippetOffsets(
-  Fts3Expr *pExpr,      /* The search expression */
-  Snippet *pSnippet,    /* The set of snippet offsets to be trimmed */
-  int *piLeft           /* Index of left-most token in pExpr */
-){
-  if( pExpr ){
-    if( trimSnippetOffsets(pExpr->pLeft, pSnippet, piLeft) ){
-      return 1;
-    }
-
-    switch( pExpr->eType ){
-      case FTSQUERY_PHRASE:
-        *piLeft += pExpr->pPhrase->nToken;
-        break;
-      case FTSQUERY_NEAR: {
-        /* The right-hand-side of a NEAR operator is always a phrase. The
-        ** left-hand-side is either a phrase or an expression tree that is 
-        ** itself headed by a NEAR operator. The following initializations
-        ** set local variable iLeft to the token number of the left-most
-        ** token in the right-hand phrase, and iRight to the right most
-        ** token in the same phrase. For example, if we had:
-        **
-        **     <col> MATCH '"abc def" NEAR/2 "ghi jkl"'
-        **
-        ** then iLeft will be set to 2 (token number of ghi) and nToken will
-        ** be set to 4.
-        */
-        Fts3Expr *pLeft = pExpr->pLeft;
-        Fts3Expr *pRight = pExpr->pRight;
-        int iLeft = *piLeft;
-        int nNear = pExpr->nNear;
-        int nToken = pRight->pPhrase->nToken;
-        int jj, ii;
-        if( pLeft->eType==FTSQUERY_NEAR ){
-          pLeft = pLeft->pRight;
-        }
-        assert( pRight->eType==FTSQUERY_PHRASE );
-        assert( pLeft->eType==FTSQUERY_PHRASE );
-        nToken += pLeft->pPhrase->nToken;
-
-        for(ii=0; ii<pSnippet->nMatch; ii++){
-          struct snippetMatch *p = &pSnippet->aMatch[ii];
-          if( p->iTerm==iLeft ){
-            int isOk = 0;
-            /* Snippet ii is an occurence of query term iLeft in the document.
-            ** It occurs at position (p->iToken) of the document. We now
-            ** search for an instance of token (iLeft-1) somewhere in the 
-            ** range (p->iToken - nNear)...(p->iToken + nNear + nToken) within 
-            ** the set of snippetMatch structures. If one is found, proceed. 
-            ** If one cannot be found, then remove snippets ii..(ii+N-1) 
-            ** from the matching snippets, where N is the number of tokens 
-            ** in phrase pRight->pPhrase.
-            */
-            for(jj=0; isOk==0 && jj<pSnippet->nMatch; jj++){
-              struct snippetMatch *p2 = &pSnippet->aMatch[jj];
-              if( p2->iTerm==(iLeft-1) ){
-                if( p2->iToken>=(p->iToken-nNear-1) 
-                 && p2->iToken<(p->iToken+nNear+nToken) 
-                ){
-                  isOk = 1;
-                }
-              }
-            }
-            if( !isOk ){
-              int kk;
-              for(kk=0; kk<pRight->pPhrase->nToken; kk++){
-                pSnippet->aMatch[kk+ii].iTerm = -2;
-              }
-              return 1;
-            }
-          }
-          if( p->iTerm==(iLeft-1) ){
-            int isOk = 0;
-            for(jj=0; isOk==0 && jj<pSnippet->nMatch; jj++){
-              struct snippetMatch *p2 = &pSnippet->aMatch[jj];
-              if( p2->iTerm==iLeft ){
-                if( p2->iToken<=(p->iToken+nNear+1) 
-                 && p2->iToken>(p->iToken-nNear-nToken) 
-                ){
-                  isOk = 1;
-                }
-              }
-            }
-            if( !isOk ){
-              int kk;
-              for(kk=0; kk<pLeft->pPhrase->nToken; kk++){
-                pSnippet->aMatch[ii-kk].iTerm = -2;
-              }
-              return 1;
-            }
-          }
-        }
-        break;
-      }
-    }
-
-    if( trimSnippetOffsets(pExpr->pRight, pSnippet, piLeft) ){
-      return 1;
-    }
-  }
-  return 0;
-}
-
-/*
-** Compute all offsets for the current row of the query.  
-** If the offsets have already been computed, this routine is a no-op.
-*/
-static int snippetAllOffsets(Fts3Cursor *pCsr, Snippet **ppSnippet){
-  Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;  /* The FTS3 virtual table */
-  int nColumn;           /* Number of columns.  Docid does count */
-  int iColumn;           /* Index of of a column */
-  int i;                 /* Loop index */
-  int iFirst;            /* First column to search */
-  int iLast;             /* Last coumn to search */
-  int iTerm = 0;
-  Snippet *pSnippet;
-  int rc = SQLITE_OK;
-
-  if( pCsr->pExpr==0 ){
-    return SQLITE_OK;
-  }
-
-  pSnippet = (Snippet *)sqlite3_malloc(sizeof(Snippet));
-  *ppSnippet = pSnippet;
-  if( !pSnippet ){
-    return SQLITE_NOMEM;
-  }
-  memset(pSnippet, 0, sizeof(Snippet));
-
-  nColumn = p->nColumn;
-  iColumn = (pCsr->eSearch - 2);
-  if( iColumn<0 || iColumn>=nColumn ){
-    /* Look for matches over all columns of the full-text index */
-    iFirst = 0;
-    iLast = nColumn-1;
-  }else{
-    /* Look for matches in the iColumn-th column of the index only */
-    iFirst = iColumn;
-    iLast = iColumn;
-  }
-  for(i=iFirst; rc==SQLITE_OK && i<=iLast; i++){
-    const char *zDoc;
-    int nDoc;
-    zDoc = (const char*)sqlite3_column_text(pCsr->pStmt, i+1);
-    nDoc = sqlite3_column_bytes(pCsr->pStmt, i+1);
-    if( zDoc==0 && sqlite3_column_type(pCsr->pStmt, i+1)!=SQLITE_NULL ){
-      rc = SQLITE_NOMEM;
-    }else{
-      rc = snippetOffsetsOfColumn(pCsr, pSnippet, i, zDoc, nDoc);
-    }
-  }
-
-  while( trimSnippetOffsets(pCsr->pExpr, pSnippet, &iTerm) ){
-    iTerm = 0;
-  }
-
-  return rc;
-}
-
-/*
-** Convert the information in the aMatch[] array of the snippet
-** into the string zOffset[0..nOffset-1]. This string is used as
-** the return of the SQL offsets() function.
-*/
-static void snippetOffsetText(Snippet *p){
-  int i;
-  int cnt = 0;
-  StringBuffer sb;
-  char zBuf[200];
-  if( p->zOffset ) return;
-  fts3SnippetSbInit(&sb);
-  for(i=0; i<p->nMatch; i++){
-    struct snippetMatch *pMatch = &p->aMatch[i];
-    if( pMatch->iTerm>=0 ){
-      /* If snippetMatch.iTerm is less than 0, then the match was 
-      ** discarded as part of processing the NEAR operator (see the 
-      ** trimSnippetOffsetsForNear() function for details). Ignore 
-      ** it in this case
-      */
-      zBuf[0] = ' ';
-      sqlite3_snprintf(sizeof(zBuf)-1, &zBuf[cnt>0], "%d %d %d %d",
-          pMatch->iCol, pMatch->iTerm, pMatch->iStart, pMatch->nByte);
-      fts3SnippetAppend(&sb, zBuf, -1);
-      cnt++;
-    }
-  }
-  p->zOffset = sb.z;
-  p->nOffset = sb.z ? sb.nUsed : 0;
-}
-
-/*
-** zDoc[0..nDoc-1] is phrase of text.  aMatch[0..nMatch-1] are a set
-** of matching words some of which might be in zDoc.  zDoc is column
-** number iCol.
-**
-** iBreak is suggested spot in zDoc where we could begin or end an
-** excerpt.  Return a value similar to iBreak but possibly adjusted
-** to be a little left or right so that the break point is better.
-*/
-static int wordBoundary(
-  int iBreak,                   /* The suggested break point */
-  const char *zDoc,             /* Document text */
-  int nDoc,                     /* Number of bytes in zDoc[] */
-  struct snippetMatch *aMatch,  /* Matching words */
-  int nMatch,                   /* Number of entries in aMatch[] */
-  int iCol                      /* The column number for zDoc[] */
-){
-  int i;
-  if( iBreak<=10 ){
-    return 0;
-  }
-  if( iBreak>=nDoc-10 ){
-    return nDoc;
-  }
-  for(i=0; ALWAYS(i<nMatch) && aMatch[i].iCol<iCol; i++){}
-  while( i<nMatch && aMatch[i].iStart+aMatch[i].nByte<iBreak ){ i++; }
-  if( i<nMatch ){
-    if( aMatch[i].iStart<iBreak+10 ){
-      return aMatch[i].iStart;
-    }
-    if( i>0 && aMatch[i-1].iStart+aMatch[i-1].nByte>=iBreak ){
-      return aMatch[i-1].iStart;
-    }
-  }
-  for(i=1; i<=10; i++){
-    if( fts3snippetIsspace(zDoc[iBreak-i]) ){
-      return iBreak - i + 1;
-    }
-    if( fts3snippetIsspace(zDoc[iBreak+i]) ){
-      return iBreak + i + 1;
-    }
-  }
-  return iBreak;
-}
-
-
-
-/*
-** Allowed values for Snippet.aMatch[].snStatus
-*/
-#define SNIPPET_IGNORE  0   /* It is ok to omit this match from the snippet */
-#define SNIPPET_DESIRED 1   /* We want to include this match in the snippet */
-
-/*
-** Generate the text of a snippet.
-*/
-static void snippetText(
-  Fts3Cursor *pCursor,   /* The cursor we need the snippet for */
-  Snippet *pSnippet,
-  const char *zStartMark,     /* Markup to appear before each match */
-  const char *zEndMark,       /* Markup to appear after each match */
-  const char *zEllipsis       /* Ellipsis mark */
-){
-  int i, j;
-  struct snippetMatch *aMatch;
-  int nMatch;
-  int nDesired;
-  StringBuffer sb;
-  int tailCol;
-  int tailOffset;
-  int iCol;
-  int nDoc;
-  const char *zDoc;
-  int iStart, iEnd;
-  int tailEllipsis = 0;
-  int iMatch;
-  
-
-  sqlite3_free(pSnippet->zSnippet);
-  pSnippet->zSnippet = 0;
-  aMatch = pSnippet->aMatch;
-  nMatch = pSnippet->nMatch;
-  fts3SnippetSbInit(&sb);
-
-  for(i=0; i<nMatch; i++){
-    aMatch[i].snStatus = SNIPPET_IGNORE;
-  }
-  nDesired = 0;
-  for(i=0; i<FTS3_ROTOR_SZ; i++){
-    for(j=0; j<nMatch; j++){
-      if( aMatch[j].iTerm==i ){
-        aMatch[j].snStatus = SNIPPET_DESIRED;
-        nDesired++;
-        break;
-      }
-    }
-  }
-
-  iMatch = 0;
-  tailCol = -1;
-  tailOffset = 0;
-  for(i=0; i<nMatch && nDesired>0; i++){
-    if( aMatch[i].snStatus!=SNIPPET_DESIRED ) continue;
-    nDesired--;
-    iCol = aMatch[i].iCol;
-    zDoc = (const char*)sqlite3_column_text(pCursor->pStmt, iCol+1);
-    nDoc = sqlite3_column_bytes(pCursor->pStmt, iCol+1);
-    iStart = aMatch[i].iStart - 40;
-    iStart = wordBoundary(iStart, zDoc, nDoc, aMatch, nMatch, iCol);
-    if( iStart<=10 ){
-      iStart = 0;
-    }
-    if( iCol==tailCol && iStart<=tailOffset+20 ){
-      iStart = tailOffset;
-    }
-    if( (iCol!=tailCol && tailCol>=0) || iStart!=tailOffset ){
-      fts3SnippetTrimWhiteSpace(&sb);
-      fts3SnippetAppendWhiteSpace(&sb);
-      fts3SnippetAppend(&sb, zEllipsis, -1);
-      fts3SnippetAppendWhiteSpace(&sb);
-    }
-    iEnd = aMatch[i].iStart + aMatch[i].nByte + 40;
-    iEnd = wordBoundary(iEnd, zDoc, nDoc, aMatch, nMatch, iCol);
-    if( iEnd>=nDoc-10 ){
-      iEnd = nDoc;
-      tailEllipsis = 0;
-    }else{
-      tailEllipsis = 1;
-    }
-    while( iMatch<nMatch && aMatch[iMatch].iCol<iCol ){ iMatch++; }
-    while( iStart<iEnd ){
-      while( iMatch<nMatch && aMatch[iMatch].iStart<iStart
-             && aMatch[iMatch].iCol<=iCol ){
-        iMatch++;
-      }
-      if( iMatch<nMatch && aMatch[iMatch].iStart<iEnd
-             && aMatch[iMatch].iCol==iCol ){
-        fts3SnippetAppend(&sb, &zDoc[iStart], aMatch[iMatch].iStart - iStart);
-        iStart = aMatch[iMatch].iStart;
-        fts3SnippetAppend(&sb, zStartMark, -1);
-        fts3SnippetAppend(&sb, &zDoc[iStart], aMatch[iMatch].nByte);
-        fts3SnippetAppend(&sb, zEndMark, -1);
-        iStart += aMatch[iMatch].nByte;
-        for(j=iMatch+1; j<nMatch; j++){
-          if( aMatch[j].iTerm==aMatch[iMatch].iTerm
-              && aMatch[j].snStatus==SNIPPET_DESIRED ){
-            nDesired--;
-            aMatch[j].snStatus = SNIPPET_IGNORE;
-          }
-        }
-      }else{
-        fts3SnippetAppend(&sb, &zDoc[iStart], iEnd - iStart);
-        iStart = iEnd;
-      }
-    }
-    tailCol = iCol;
-    tailOffset = iEnd;
-  }
-  fts3SnippetTrimWhiteSpace(&sb);
-  if( tailEllipsis ){
-    fts3SnippetAppendWhiteSpace(&sb);
-    fts3SnippetAppend(&sb, zEllipsis, -1);
-  }
-  pSnippet->zSnippet = sb.z;
-  pSnippet->nSnippet = sb.z ? sb.nUsed : 0;
-}
-
-SQLITE_PRIVATE void sqlite3Fts3Offsets(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr                /* Cursor object */
-){
-  Snippet *p;                     /* Snippet structure */
-  int rc = snippetAllOffsets(pCsr, &p);
-  if( rc==SQLITE_OK ){
-    snippetOffsetText(p);
-    if( p->zOffset ){
-      sqlite3_result_text(pCtx, p->zOffset, p->nOffset, SQLITE_TRANSIENT);
-    }else{
-      sqlite3_result_error_nomem(pCtx);
-    }
-  }else{
-    sqlite3_result_error_nomem(pCtx);
-  }
-  fts3SnippetFree(p);
-}
-
-SQLITE_PRIVATE void sqlite3Fts3Snippet(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr,               /* Cursor object */
-  const char *zStart,             /* Snippet start text - "<b>" */
-  const char *zEnd,               /* Snippet end text - "</b>" */
-  const char *zEllipsis           /* Snippet ellipsis text - "<b>...</b>" */
-){
-  Snippet *p;                     /* Snippet structure */
-  int rc = snippetAllOffsets(pCsr, &p);
-  if( rc==SQLITE_OK ){
-    snippetText(pCsr, p, zStart, zEnd, zEllipsis);
-    if( p->zSnippet ){
-      sqlite3_result_text(pCtx, p->zSnippet, p->nSnippet, SQLITE_TRANSIENT);
-    }else{
-      sqlite3_result_error_nomem(pCtx);
-    }
-  }else{
-    sqlite3_result_error_nomem(pCtx);
-  }
-  fts3SnippetFree(p);
-}
-
-/*************************************************************************
-** Below this point is the alternative, experimental snippet() implementation.
-*/
-
-#define SNIPPET_BUFFER_CHUNK  64
-#define SNIPPET_BUFFER_SIZE   SNIPPET_BUFFER_CHUNK*4
-#define SNIPPET_BUFFER_MASK   (SNIPPET_BUFFER_SIZE-1)
-
 static void fts3GetDeltaPosition(char **pp, int *piPos){
   int iVal;
   *pp += sqlite3Fts3GetVarint32(*pp, &iVal);
@@ -106904,6 +113282,31 @@
 }
 
 /*
+** Helper function for fts3ExprIterate() (see below).
+*/
+static int fts3ExprIterate2(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int *piPhrase,                  /* Pointer to phrase counter */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
+){
+  int rc;                         /* Return code */
+  int eType = pExpr->eType;       /* Type of expression node pExpr */
+
+  if( eType!=FTSQUERY_PHRASE ){
+    assert( pExpr->pLeft && pExpr->pRight );
+    rc = fts3ExprIterate2(pExpr->pLeft, piPhrase, x, pCtx);
+    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
+      rc = fts3ExprIterate2(pExpr->pRight, piPhrase, x, pCtx);
+    }
+  }else{
+    rc = x(pExpr, *piPhrase, pCtx);
+    (*piPhrase)++;
+  }
+  return rc;
+}
+
+/*
 ** Iterate through all phrase nodes in an FTS3 query, except those that
 ** are part of a sub-tree that is the right-hand-side of a NOT operator.
 ** For each phrase node found, the supplied callback function is invoked.
@@ -106915,285 +113318,387 @@
 */
 static int fts3ExprIterate(
   Fts3Expr *pExpr,                /* Expression to iterate phrases of */
-  int (*x)(Fts3Expr *, void *),   /* Callback function to invoke for phrases */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
   void *pCtx                      /* Second argument to pass to callback */
 ){
-  int rc;
-  int eType = pExpr->eType;
-  if( eType==FTSQUERY_NOT ){
-    rc = SQLITE_OK;
-  }else if( eType!=FTSQUERY_PHRASE ){
-    assert( pExpr->pLeft && pExpr->pRight );
-    rc = fts3ExprIterate(pExpr->pLeft, x, pCtx);
-    if( rc==SQLITE_OK ){
-      rc = fts3ExprIterate(pExpr->pRight, x, pCtx);
-    }
-  }else{
-    rc = x(pExpr, pCtx);
-  }
-  return rc;
+  int iPhrase = 0;                /* Variable used as the phrase counter */
+  return fts3ExprIterate2(pExpr, &iPhrase, x, pCtx);
 }
 
-typedef struct LoadDoclistCtx LoadDoclistCtx;
-struct LoadDoclistCtx {
-  Fts3Table *pTab;                /* FTS3 Table */
-  int nPhrase;                    /* Number of phrases so far */
-};
-
-static int fts3ExprLoadDoclistsCb(Fts3Expr *pExpr, void *ctx){
+/*
+** The argument to this function is always a phrase node. Its doclist 
+** (Fts3Expr.aDoclist[]) and the doclists associated with all phrase nodes
+** to the left of this one in the query tree have already been loaded.
+**
+** If this phrase node is part of a series of phrase nodes joined by 
+** NEAR operators (and is not the left-most of said series), then elements are
+** removed from the phrases doclist consistent with the NEAR restriction. If
+** required, elements may be removed from the doclists of phrases to the
+** left of this one that are part of the same series of NEAR operator 
+** connected phrases.
+**
+** If an OOM error occurs, SQLITE_NOMEM is returned. Otherwise, SQLITE_OK.
+*/
+static int fts3ExprNearTrim(Fts3Expr *pExpr){
   int rc = SQLITE_OK;
-  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
-  p->nPhrase++;
-  if( pExpr->isLoaded==0 ){
-    rc = sqlite3Fts3ExprLoadDoclist(p->pTab, pExpr);
-    pExpr->isLoaded = 1;
-    if( rc==SQLITE_OK && pExpr->aDoclist ){
-      pExpr->pCurrent = pExpr->aDoclist;
-      pExpr->pCurrent += sqlite3Fts3GetVarint(pExpr->pCurrent,&pExpr->iCurrent);
-    }
-  }
-  return rc;
-}
+  Fts3Expr *pParent = pExpr->pParent;
 
-static int fts3ExprLoadDoclists(Fts3Cursor *pCsr, int *pnPhrase){
-  int rc;
-  LoadDoclistCtx sCtx = {0, 0};
-  sCtx.pTab = (Fts3Table *)pCsr->base.pVtab;
-  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb, (void *)&sCtx);
-  *pnPhrase = sCtx.nPhrase;
+  assert( pExpr->eType==FTSQUERY_PHRASE );
+  while( rc==SQLITE_OK
+   && pParent 
+   && pParent->eType==FTSQUERY_NEAR 
+   && pParent->pRight==pExpr 
+  ){
+    /* This expression (pExpr) is the right-hand-side of a NEAR operator. 
+    ** Find the expression to the left of the same operator.
+    */
+    int nNear = pParent->nNear;
+    Fts3Expr *pLeft = pParent->pLeft;
+
+    if( pLeft->eType!=FTSQUERY_PHRASE ){
+      assert( pLeft->eType==FTSQUERY_NEAR );
+      assert( pLeft->pRight->eType==FTSQUERY_PHRASE );
+      pLeft = pLeft->pRight;
+    }
+
+    rc = sqlite3Fts3ExprNearTrim(pLeft, pExpr, nNear);
+
+    pExpr = pLeft;
+    pParent = pExpr->pParent;
+  }
+
   return rc;
 }
 
 /*
-** Each call to this function populates a chunk of a snippet-buffer 
-** SNIPPET_BUFFER_CHUNK bytes in size.
-**
-** Return true if the end of the data has been reached (and all subsequent
-** calls to fts3LoadSnippetBuffer() with the same arguments will be no-ops), 
-** or false otherwise.
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
 */
-static int fts3LoadSnippetBuffer(
-  int iPos,                       /* Document token offset to load data for */
-  u8 *aBuffer,                    /* Circular snippet buffer to populate */
-  int nList,                      /* Number of position lists in appList */
-  char **apList,                  /* IN/OUT: nList position list pointers */
-  int *aiPrev                     /* IN/OUT: Previous positions read */
-){
-  int i;
-  int nFin = 0;
+static int fts3ExprLoadDoclistsCb1(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  int rc = SQLITE_OK;
+  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
 
-  assert( (iPos&(SNIPPET_BUFFER_CHUNK-1))==0 );
+  UNUSED_PARAMETER(iPhrase);
 
-  memset(&aBuffer[iPos&SNIPPET_BUFFER_MASK], 0, SNIPPET_BUFFER_CHUNK);
+  p->nPhrase++;
+  p->nToken += pExpr->pPhrase->nToken;
 
-  for(i=0; i<nList; i++){
-    int iPrev = aiPrev[i];
-    char *pList = apList[i];
-
-    if( !pList ){
-      nFin++;
-      continue;
+  if( pExpr->isLoaded==0 ){
+    rc = sqlite3Fts3ExprLoadDoclist(p->pTab, pExpr);
+    pExpr->isLoaded = 1;
+    if( rc==SQLITE_OK ){
+      rc = fts3ExprNearTrim(pExpr);
     }
-
-    while( iPrev<(iPos+SNIPPET_BUFFER_CHUNK) ){
-      if( iPrev>=iPos ){
-        aBuffer[iPrev&SNIPPET_BUFFER_MASK] = (u8)(i+1);
-      }
-      if( 0==((*pList)&0xFE) ){
-        nFin++;
-        break;
-      }
-      fts3GetDeltaPosition(&pList, &iPrev); 
-    }
-
-    aiPrev[i] = iPrev;
-    apList[i] = pList;
   }
 
-  return (nFin==nList);
+  return rc;
 }
 
-typedef struct SnippetCtx SnippetCtx;
-struct SnippetCtx {
-  Fts3Cursor *pCsr;
-  int iCol;
-  int iPhrase;
-  int *aiPrev;
-  int *anToken;
-  char **apList;
-};
-
-static int fts3SnippetFindPositions(Fts3Expr *pExpr, void *ctx){
-  SnippetCtx *p = (SnippetCtx *)ctx;
-  int iPhrase = p->iPhrase++;
-  char *pCsr;
-
-  p->anToken[iPhrase] = pExpr->pPhrase->nToken;
-  pCsr = sqlite3Fts3FindPositions(pExpr, p->pCsr->iPrevId, p->iCol);
-
-  if( pCsr ){
-    int iVal;
-    pCsr += sqlite3Fts3GetVarint32(pCsr, &iVal);
-    p->apList[iPhrase] = pCsr;
-    p->aiPrev[iPhrase] = iVal-2;
+/*
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
+*/
+static int fts3ExprLoadDoclistsCb2(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  UNUSED_PARAMETER(iPhrase);
+  UNUSED_PARAMETER(ctx);
+  if( pExpr->aDoclist ){
+    pExpr->pCurrent = pExpr->aDoclist;
+    pExpr->iCurrent = 0;
+    pExpr->pCurrent += sqlite3Fts3GetVarint(pExpr->pCurrent, &pExpr->iCurrent);
   }
   return SQLITE_OK;
 }
 
-static void fts3SnippetCnt(
-  int iIdx, 
-  int nSnippet, 
-  int *anCnt, 
-  u8 *aBuffer,
-  int *anToken,
-  u64 *pHlmask
+/*
+** Load the doclists for each phrase in the query associated with FTS3 cursor
+** pCsr. 
+**
+** If pnPhrase is not NULL, then *pnPhrase is set to the number of matchable 
+** phrases in the expression (all phrases except those directly or 
+** indirectly descended from the right-hand-side of a NOT operator). If 
+** pnToken is not NULL, then it is set to the number of tokens in all
+** matchable phrases of the expression.
+*/
+static int fts3ExprLoadDoclists(
+  Fts3Cursor *pCsr,               /* Fts3 cursor for current query */
+  int *pnPhrase,                  /* OUT: Number of phrases in query */
+  int *pnToken                    /* OUT: Number of tokens in query */
 ){
-  int iSub =  (iIdx-1)&SNIPPET_BUFFER_MASK;
-  int iAdd =  (iIdx+nSnippet-1)&SNIPPET_BUFFER_MASK;
-  int iSub2 = (iIdx+(nSnippet/3)-1)&SNIPPET_BUFFER_MASK;
-  int iAdd2 = (iIdx+(nSnippet*2/3)-1)&SNIPPET_BUFFER_MASK;
+  int rc;                         /* Return Code */
+  LoadDoclistCtx sCtx = {0,0,0};  /* Context for fts3ExprIterate() */
+  sCtx.pTab = (Fts3Table *)pCsr->base.pVtab;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb1, (void *)&sCtx);
+  if( rc==SQLITE_OK ){
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb2, 0);
+  }
+  if( pnPhrase ) *pnPhrase = sCtx.nPhrase;
+  if( pnToken ) *pnToken = sCtx.nToken;
+  return rc;
+}
 
-  u64 h = *pHlmask;
+/*
+** Advance the position list iterator specified by the first two 
+** arguments so that it points to the first element with a value greater
+** than or equal to parameter iNext.
+*/
+static void fts3SnippetAdvance(char **ppIter, int *piIter, int iNext){
+  char *pIter = *ppIter;
+  if( pIter ){
+    int iIter = *piIter;
 
-  anCnt[ aBuffer[iSub]  ]--;
-  anCnt[ aBuffer[iSub2] ]--;
-  anCnt[ aBuffer[iAdd]  ]++;
-  anCnt[ aBuffer[iAdd2] ]++;
+    while( iIter<iNext ){
+      if( 0==(*pIter & 0xFE) ){
+        iIter = -1;
+        pIter = 0;
+        break;
+      }
+      fts3GetDeltaPosition(&pIter, &iIter);
+    }
 
-  h = h >> 1;
-  if( aBuffer[iAdd] ){
-    int j;
-    for(j=anToken[aBuffer[iAdd]-1]; j>=1; j--){
-      h |= (u64)1 << (nSnippet-j);
+    *piIter = iIter;
+    *ppIter = pIter;
+  }
+}
+
+/*
+** Advance the snippet iterator to the next candidate snippet.
+*/
+static int fts3SnippetNextCandidate(SnippetIter *pIter){
+  int i;                          /* Loop counter */
+
+  if( pIter->iCurrent<0 ){
+    /* The SnippetIter object has just been initialized. The first snippet
+    ** candidate always starts at offset 0 (even if this candidate has a
+    ** score of 0.0).
+    */
+    pIter->iCurrent = 0;
+
+    /* Advance the 'head' iterator of each phrase to the first offset that
+    ** is greater than or equal to (iNext+nSnippet).
+    */
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, pIter->nSnippet);
+    }
+  }else{
+    int iStart;
+    int iEnd = 0x7FFFFFFF;
+
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      if( pPhrase->pHead && pPhrase->iHead<iEnd ){
+        iEnd = pPhrase->iHead;
+      }
+    }
+    if( iEnd==0x7FFFFFFF ){
+      return 1;
+    }
+
+    pIter->iCurrent = iStart = iEnd - pIter->nSnippet + 1;
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, iEnd+1);
+      fts3SnippetAdvance(&pPhrase->pTail, &pPhrase->iTail, iStart);
     }
   }
-  *pHlmask = h;
+
+  return 0;
 }
 
-static int fts3SnippetScore(int n, int *anCnt){
-  int j;
-  int iScore = 0;
-  for(j=1; j<=n; j++){
-    int nCnt = anCnt[j];
-    iScore += nCnt + (nCnt ? 1000 : 0);
+/*
+** Retrieve information about the current candidate snippet of snippet 
+** iterator pIter.
+*/
+static void fts3SnippetDetails(
+  SnippetIter *pIter,             /* Snippet iterator */
+  u64 mCovered,                   /* Bitmask of phrases already covered */
+  int *piToken,                   /* OUT: First token of proposed snippet */
+  int *piScore,                   /* OUT: "Score" for this snippet */
+  u64 *pmCover,                   /* OUT: Bitmask of phrases covered */
+  u64 *pmHighlight                /* OUT: Bitmask of terms to highlight */
+){
+  int iStart = pIter->iCurrent;   /* First token of snippet */
+  int iScore = 0;                 /* Score of this snippet */
+  int i;                          /* Loop counter */
+  u64 mCover = 0;                 /* Mask of phrases covered by this snippet */
+  u64 mHighlight = 0;             /* Mask of tokens to highlight in snippet */
+
+  for(i=0; i<pIter->nPhrase; i++){
+    SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+    if( pPhrase->pTail ){
+      char *pCsr = pPhrase->pTail;
+      int iCsr = pPhrase->iTail;
+
+      while( iCsr<(iStart+pIter->nSnippet) ){
+        int j;
+        u64 mPhrase = (u64)1 << i;
+        u64 mPos = (u64)1 << (iCsr - iStart);
+        assert( iCsr>=iStart );
+        if( (mCover|mCovered)&mPhrase ){
+          iScore++;
+        }else{
+          iScore += 1000;
+        }
+        mCover |= mPhrase;
+
+        for(j=0; j<pPhrase->nToken; j++){
+          mHighlight |= (mPos>>j);
+        }
+
+        if( 0==(*pCsr & 0x0FE) ) break;
+        fts3GetDeltaPosition(&pCsr, &iCsr);
+      }
+    }
   }
-  return iScore;
+
+  /* Set the output variables before returning. */
+  *piToken = iStart;
+  *piScore = iScore;
+  *pmCover = mCover;
+  *pmHighlight = mHighlight;
 }
 
+/*
+** This function is an fts3ExprIterate() callback used by fts3BestSnippet().
+** Each invocation populates an element of the SnippetIter.aPhrase[] array.
+*/
+static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  SnippetIter *p = (SnippetIter *)ctx;
+  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
+  char *pCsr;
+
+  pPhrase->nToken = pExpr->pPhrase->nToken;
+
+  pCsr = sqlite3Fts3FindPositions(pExpr, p->pCsr->iPrevId, p->iCol);
+  if( pCsr ){
+    int iFirst = 0;
+    pPhrase->pList = pCsr;
+    fts3GetDeltaPosition(&pCsr, &iFirst);
+    pPhrase->pHead = pCsr;
+    pPhrase->pTail = pCsr;
+    pPhrase->iHead = iFirst;
+    pPhrase->iTail = iFirst;
+  }else{
+    assert( pPhrase->pList==0 && pPhrase->pHead==0 && pPhrase->pTail==0 );
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Select the fragment of text consisting of nFragment contiguous tokens 
+** from column iCol that represent the "best" snippet. The best snippet
+** is the snippet with the highest score, where scores are calculated
+** by adding:
+**
+**   (a) +1 point for each occurence of a matchable phrase in the snippet.
+**
+**   (b) +1000 points for the first occurence of each matchable phrase in 
+**       the snippet for which the corresponding mCovered bit is not set.
+**
+** The selected snippet parameters are stored in structure *pFragment before
+** returning. The score of the selected snippet is stored in *piScore
+** before returning.
+*/
 static int fts3BestSnippet(
   int nSnippet,                   /* Desired snippet length */
   Fts3Cursor *pCsr,               /* Cursor to create snippet for */
   int iCol,                       /* Index of column to create snippet from */
-  int *piPos,                     /* OUT: Starting token for best snippet */
-  u64 *pHlmask                    /* OUT: Highlight mask for best snippet */
+  u64 mCovered,                   /* Mask of phrases already covered */
+  u64 *pmSeen,                    /* IN/OUT: Mask of phrases seen */
+  SnippetFragment *pFragment,     /* OUT: Best snippet found */
+  int *piScore                    /* OUT: Score of snippet pFragment */
 ){
   int rc;                         /* Return Code */
-  u8 aBuffer[SNIPPET_BUFFER_SIZE];/* Circular snippet buffer */
-  int *aiPrev;                    /* Used by fts3LoadSnippetBuffer() */
-  int *anToken;                   /* Number of tokens in each phrase */
-  char **apList;                  /* Array of position lists */
-  int *anCnt;                     /* Running totals of phrase occurences */
-  int nList;
+  int nList;                      /* Number of phrases in expression */
+  SnippetIter sIter;              /* Iterates through snippet candidates */
+  int nByte;                      /* Number of bytes of space to allocate */
+  int iBestScore = -1;            /* Best snippet score found so far */
+  int i;                          /* Loop counter */
 
-  int i;
-
-  u64 hlmask = 0;                 /* Current mask of highlighted terms */
-  u64 besthlmask = 0;             /* Mask of highlighted terms for iBestPos */
-  int iBestPos = 0;               /* Starting position of 'best' snippet */
-  int iBestScore = 0;             /* Score of best snippet higher->better */
-  SnippetCtx sCtx;
+  memset(&sIter, 0, sizeof(sIter));
 
   /* Iterate through the phrases in the expression to count them. The same
   ** callback makes sure the doclists are loaded for each phrase.
   */
-  rc = fts3ExprLoadDoclists(pCsr, &nList);
+  rc = fts3ExprLoadDoclists(pCsr, &nList, 0);
   if( rc!=SQLITE_OK ){
     return rc;
   }
 
   /* Now that it is known how many phrases there are, allocate and zero
-  ** the required arrays using malloc().
+  ** the required space using malloc().
   */
-  apList = sqlite3_malloc(
-      sizeof(u8*)*nList +         /* apList */
-      sizeof(int)*(nList) +       /* anToken */
-      sizeof(int)*nList +         /* aiPrev */
-      sizeof(int)*(nList+1)       /* anCnt */
-  );
-  if( !apList ){
+  nByte = sizeof(SnippetPhrase) * nList;
+  sIter.aPhrase = (SnippetPhrase *)sqlite3_malloc(nByte);
+  if( !sIter.aPhrase ){
     return SQLITE_NOMEM;
   }
-  memset(apList, 0, sizeof(u8*)*nList+sizeof(int)*nList+sizeof(int)*nList);
-  anToken = (int *)&apList[nList];
-  aiPrev = &anToken[nList];
-  anCnt = &aiPrev[nList];
+  memset(sIter.aPhrase, 0, nByte);
 
-  /* Initialize the contents of the aiPrev and aiList arrays. */
-  sCtx.pCsr = pCsr;
-  sCtx.iCol = iCol;
-  sCtx.apList = apList;
-  sCtx.aiPrev = aiPrev;
-  sCtx.anToken = anToken;
-  sCtx.iPhrase = 0;
-  (void)fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void *)&sCtx);
+  /* Initialize the contents of the SnippetIter object. Then iterate through
+  ** the set of phrases in the expression to populate the aPhrase[] array.
+  */
+  sIter.pCsr = pCsr;
+  sIter.iCol = iCol;
+  sIter.nSnippet = nSnippet;
+  sIter.nPhrase = nList;
+  sIter.iCurrent = -1;
+  (void)fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void *)&sIter);
 
-  /* Load the first two chunks of data into the buffer. */
-  memset(aBuffer, 0, SNIPPET_BUFFER_SIZE);
-  fts3LoadSnippetBuffer(0, aBuffer, nList, apList, aiPrev);
-  fts3LoadSnippetBuffer(SNIPPET_BUFFER_CHUNK, aBuffer, nList, apList, aiPrev);
-
-  /* Set the initial contents of the highlight-mask and anCnt[] array. */
-  for(i=1-nSnippet; i<=0; i++){
-    fts3SnippetCnt(i, nSnippet, anCnt, aBuffer, anToken, &hlmask);
+  /* Set the *pmSeen output variable. */
+  for(i=0; i<nList; i++){
+    if( sIter.aPhrase[i].pHead ){
+      *pmSeen |= (u64)1 << i;
+    }
   }
-  iBestScore = fts3SnippetScore(nList, anCnt);
-  besthlmask = hlmask;
-  iBestPos = 0;
 
-  for(i=1; 1; i++){
+  /* Loop through all candidate snippets. Store the best snippet in 
+  ** *pFragment. Store its associated 'score' in iBestScore.
+  */
+  pFragment->iCol = iCol;
+  while( !fts3SnippetNextCandidate(&sIter) ){
+    int iPos;
     int iScore;
-
-    if( 0==(i&(SNIPPET_BUFFER_CHUNK-1)) ){
-      int iLoad = i + SNIPPET_BUFFER_CHUNK;
-      if( fts3LoadSnippetBuffer(iLoad, aBuffer, nList, apList, aiPrev) ) break;
-    }
-
-    /* Figure out how highly a snippet starting at token offset i scores
-    ** according to fts3SnippetScore(). If it is higher than any previously
-    ** considered position, save the current position, score and hlmask as 
-    ** the best snippet candidate found so far.
-    */
-    fts3SnippetCnt(i, nSnippet, anCnt, aBuffer, anToken, &hlmask);
-    iScore = fts3SnippetScore(nList, anCnt);
+    u64 mCover;
+    u64 mHighlight;
+    fts3SnippetDetails(&sIter, mCovered, &iPos, &iScore, &mCover, &mHighlight);
+    assert( iScore>=0 );
     if( iScore>iBestScore ){
-      iBestPos = i;
+      pFragment->iPos = iPos;
+      pFragment->hlmask = mHighlight;
+      pFragment->covered = mCover;
       iBestScore = iScore;
-      besthlmask = hlmask;
     }
   }
 
-  sqlite3_free(apList);
-  *piPos = iBestPos;
-  *pHlmask = besthlmask;
+  sqlite3_free(sIter.aPhrase);
+  *piScore = iBestScore;
   return SQLITE_OK;
 }
 
-typedef struct StrBuffer StrBuffer;
-struct StrBuffer {
-  char *z;
-  int n;
-  int nAlloc;
-};
 
+/*
+** Append a string to the string-buffer passed as the first argument.
+**
+** If nAppend is negative, then the length of the string zAppend is
+** determined using strlen().
+*/
 static int fts3StringAppend(
-  StrBuffer *pStr, 
-  const char *zAppend, 
-  int nAppend
+  StrBuffer *pStr,                /* Buffer to append to */
+  const char *zAppend,            /* Pointer to data to append to buffer */
+  int nAppend                     /* Size of zAppend in bytes (or -1) */
 ){
   if( nAppend<0 ){
     nAppend = (int)strlen(zAppend);
   }
 
+  /* If there is insufficient space allocated at StrBuffer.z, use realloc()
+  ** to grow the buffer until so that it is big enough to accomadate the
+  ** appended data.
+  */
   if( pStr->n+nAppend+1>=pStr->nAlloc ){
     int nAlloc = pStr->nAlloc+nAppend+100;
     char *zNew = sqlite3_realloc(pStr->z, nAlloc);
@@ -107204,6 +113709,7 @@
     pStr->nAlloc = nAlloc;
   }
 
+  /* Append the data to the string buffer. */
   memcpy(&pStr->z[pStr->n], zAppend, nAppend);
   pStr->n += nAppend;
   pStr->z[pStr->n] = '\0';
@@ -107211,126 +113717,201 @@
   return SQLITE_OK;
 }
 
+/*
+** The fts3BestSnippet() function often selects snippets that end with a
+** query term. That is, the final term of the snippet is always a term
+** that requires highlighting. For example, if 'X' is a highlighted term
+** and '.' is a non-highlighted term, BestSnippet() may select:
+**
+**     ........X.....X
+**
+** This function "shifts" the beginning of the snippet forward in the 
+** document so that there are approximately the same number of 
+** non-highlighted terms to the right of the final highlighted term as there
+** are to the left of the first highlighted term. For example, to this:
+**
+**     ....X.....X....
+**
+** This is done as part of extracting the snippet text, not when selecting
+** the snippet. Snippet selection is done based on doclists only, so there
+** is no way for fts3BestSnippet() to know whether or not the document 
+** actually contains terms that follow the final highlighted term. 
+*/
+static int fts3SnippetShift(
+  Fts3Table *pTab,                /* FTS3 table snippet comes from */
+  int nSnippet,                   /* Number of tokens desired for snippet */
+  const char *zDoc,               /* Document text to extract snippet from */
+  int nDoc,                       /* Size of buffer zDoc in bytes */
+  int *piPos,                     /* IN/OUT: First token of snippet */
+  u64 *pHlmask                    /* IN/OUT: Mask of tokens to highlight */
+){
+  u64 hlmask = *pHlmask;          /* Local copy of initial highlight-mask */
+
+  if( hlmask ){
+    int nLeft;                    /* Tokens to the left of first highlight */
+    int nRight;                   /* Tokens to the right of last highlight */
+    int nDesired;                 /* Ideal number of tokens to shift forward */
+
+    for(nLeft=0; !(hlmask & ((u64)1 << nLeft)); nLeft++);
+    for(nRight=0; !(hlmask & ((u64)1 << (nSnippet-1-nRight))); nRight++);
+    nDesired = (nLeft-nRight)/2;
+
+    /* Ideally, the start of the snippet should be pushed forward in the
+    ** document nDesired tokens. This block checks if there are actually
+    ** nDesired tokens to the right of the snippet. If so, *piPos and
+    ** *pHlMask are updated to shift the snippet nDesired tokens to the
+    ** right. Otherwise, the snippet is shifted by the number of tokens
+    ** available.
+    */
+    if( nDesired>0 ){
+      int nShift;                 /* Number of tokens to shift snippet by */
+      int iCurrent = 0;           /* Token counter */
+      int rc;                     /* Return Code */
+      sqlite3_tokenizer_module *pMod;
+      sqlite3_tokenizer_cursor *pC;
+      pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+
+      /* Open a cursor on zDoc/nDoc. Check if there are (nSnippet+nDesired)
+      ** or more tokens in zDoc/nDoc.
+      */
+      rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      pC->pTokenizer = pTab->pTokenizer;
+      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
+        const char *ZDUMMY; int DUMMY1, DUMMY2, DUMMY3;
+        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
+      }
+      pMod->xClose(pC);
+      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }
+
+      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
+      assert( nShift<=nDesired );
+      if( nShift>0 ){
+        *piPos += nShift;
+        *pHlmask = hlmask >> nShift;
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/*
+** Extract the snippet text for fragment pFragment from cursor pCsr and
+** append it to string buffer pOut.
+*/
 static int fts3SnippetText(
   Fts3Cursor *pCsr,               /* FTS3 Cursor */
-  const char *zDoc,               /* Document to extract snippet from */
-  int nDoc,                       /* Size of zDoc in bytes */
+  SnippetFragment *pFragment,     /* Snippet to extract */
+  int iFragment,                  /* Fragment number */
+  int isLast,                     /* True for final fragment in snippet */
   int nSnippet,                   /* Number of tokens in extracted snippet */
-  int iPos,                       /* Index of first document token in snippet */
-  u64 hlmask,                     /* Bitmask of terms to highlight in snippet */
   const char *zOpen,              /* String inserted before highlighted term */
   const char *zClose,             /* String inserted after highlighted term */
-  const char *zEllipsis,
-  char **pzSnippet                /* OUT: Snippet text */
+  const char *zEllipsis,          /* String inserted between snippets */
+  StrBuffer *pOut                 /* Write output here */
 ){
   Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
   int rc;                         /* Return code */
-  int iCurrent = 0;
-  int iStart = 0;
-  int iEnd;
-
+  const char *zDoc;               /* Document text to extract snippet from */
+  int nDoc;                       /* Size of zDoc in bytes */
+  int iCurrent = 0;               /* Current token number of document */
+  int iEnd = 0;                   /* Byte offset of end of current token */
+  int isShiftDone = 0;            /* True after snippet is shifted */
+  int iPos = pFragment->iPos;     /* First token of snippet */
+  u64 hlmask = pFragment->hlmask; /* Highlight-mask for snippet */
+  int iCol = pFragment->iCol+1;   /* Query column to extract text from */
   sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
   sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
-  const char *ZDUMMY;             /* Dummy arguments used with tokenizer */
-  int DUMMY1, DUMMY2, DUMMY3;     /* Dummy arguments used with tokenizer */
+  const char *ZDUMMY;             /* Dummy argument used with tokenizer */
+  int DUMMY1;                     /* Dummy argument used with tokenizer */
+  
+  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol);
+  if( zDoc==0 ){
+    if( sqlite3_column_type(pCsr->pStmt, iCol)!=SQLITE_NULL ){
+      return SQLITE_NOMEM;
+    }
+    return SQLITE_OK;
+  }
+  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol);
 
-  StrBuffer res = {0, 0, 0};   /* Result string */
-
-  /* Open a token cursor on the document. Read all tokens up to and 
-  ** including token iPos (the first token of the snippet). Set variable
-  ** iStart to the byte offset in zDoc of the start of token iPos.
-  */
+  /* Open a token cursor on the document. */
   pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
   rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
-  while( rc==SQLITE_OK && iCurrent<iPos ){
-    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iStart, &DUMMY2, &iCurrent);
+  if( rc!=SQLITE_OK ){
+    return rc;
   }
-  iEnd = iStart;
-
-  if( rc==SQLITE_OK && iStart>0 ){
-    rc = fts3StringAppend(&res, zEllipsis, -1);
-  }
+  pC->pTokenizer = pTab->pTokenizer;
 
   while( rc==SQLITE_OK ){
-    int iBegin;
-    int iFin;
-    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    int iBegin;                   /* Offset in zDoc of start of token */
+    int iFin;                     /* Offset in zDoc of end of token */
+    int isHighlight;              /* True for highlighted terms */
 
-    if( rc==SQLITE_OK ){
-      if( iCurrent>=(iPos+nSnippet) ){
-        rc = SQLITE_DONE;
-      }else{
-        iEnd = iFin;
-        if( hlmask & ((u64)1 << (iCurrent-iPos)) ){
-          if( fts3StringAppend(&res, &zDoc[iStart], iBegin-iStart)
-           || fts3StringAppend(&res, zOpen, -1)
-           || fts3StringAppend(&res, &zDoc[iBegin], iEnd-iBegin)
-           || fts3StringAppend(&res, zClose, -1)
-          ){
-            rc = SQLITE_NOMEM;
-          }
-          iStart = iEnd;
-        }
+    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        /* Special case - the last token of the snippet is also the last token
+        ** of the column. Append any punctuation that occurred between the end
+        ** of the previous token and the end of the document to the output. 
+        ** Then break out of the loop. */
+        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);
       }
+      break;
     }
-  }
-  assert( rc!=SQLITE_OK );
-  if( rc==SQLITE_DONE ){
-    rc = fts3StringAppend(&res, &zDoc[iStart], iEnd-iStart);
-    if( rc==SQLITE_OK ){
-      rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
-      if( rc==SQLITE_OK ){
-        rc = fts3StringAppend(&res, zEllipsis, -1);
-      }else if( rc==SQLITE_DONE ){
-        rc = fts3StringAppend(&res, &zDoc[iEnd], -1);
+    if( iCurrent<iPos ){ continue; }
+
+    if( !isShiftDone ){
+      int n = nDoc - iBegin;
+      rc = fts3SnippetShift(pTab, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask);
+      isShiftDone = 1;
+
+      /* Now that the shift has been done, check if the initial "..." are
+      ** required. They are required if (a) this is not the first fragment,
+      ** or (b) this fragment does not begin at position 0 of its column. 
+      */
+      if( rc==SQLITE_OK && (iPos>0 || iFragment>0) ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
       }
+      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
     }
+
+    if( iCurrent>=(iPos+nSnippet) ){
+      if( isLast ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
+      }
+      break;
+    }
+
+    /* Set isHighlight to true if this term should be highlighted. */
+    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;
+
+    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
+    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);
+
+    iEnd = iFin;
   }
 
   pMod->xClose(pC);
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(res.z);
-  }else{
-    *pzSnippet = res.z;
-  }
   return rc;
 }
 
 
 /*
-** An instance of this structure is used to collect the 'global' part of
-** the matchinfo statistics. The 'global' part consists of the following:
+** This function is used to count the entries in a column-list (a 
+** delta-encoded list of term offsets within a single column of a single 
+** row). When this function is called, *ppCollist should point to the
+** beginning of the first varint in the column-list (the varint that
+** contains the position of the first matching term in the column data).
+** Before returning, *ppCollist is set to point to the first byte after
+** the last varint in the column-list (either the 0x00 signifying the end
+** of the position-list, or the 0x01 that precedes the column number of
+** the next column in the position-list).
 **
-**   1. The number of phrases in the query (nPhrase).
-**
-**   2. The number of columns in the FTS3 table (nCol).
-**
-**   3. A matrix of (nPhrase*nCol) integers containing the sum of the
-**      number of hits for each phrase in each column across all rows
-**      of the table.
-**
-** The total size of the global matchinfo array, assuming the number of
-** columns is N and the number of phrases is P is:
-**
-**   2 + P*(N+1)
-**
-** The number of hits for the 3rd phrase in the second column is found
-** using the expression:
-**
-**   aGlobal[2 + P*(1+2) + 1]
-*/
-typedef struct MatchInfo MatchInfo;
-struct MatchInfo {
-  Fts3Table *pTab;                /* FTS3 Table */
-  Fts3Cursor *pCursor;            /* FTS3 Cursor */
-  int iPhrase;                    /* Number of phrases so far */
-  int nCol;                       /* Number of columns in table */
-  u32 *aGlobal;                   /* Pre-allocated buffer */
-};
-
-/*
-** This function is used to count the entries in a column-list (delta-encoded
-** list of term offsets within a single column of a single row).
+** The number of elements in the column-list is returned.
 */
 static int fts3ColumnlistCount(char **ppCollist){
   char *pEnd = *ppCollist;
@@ -107347,15 +113928,21 @@
   return nEntry;
 }
 
-static void fts3LoadColumnlistCounts(char **pp, u32 *aOut){
+static void fts3LoadColumnlistCounts(char **pp, u32 *aOut, int isGlobal){
   char *pCsr = *pp;
   while( *pCsr ){
+    int nHit;
     sqlite3_int64 iCol = 0;
     if( *pCsr==0x01 ){
       pCsr++;
       pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
     }
-    aOut[iCol] += fts3ColumnlistCount(&pCsr);
+    nHit = fts3ColumnlistCount(&pCsr);
+    assert( nHit>0 );
+    if( isGlobal ){
+      aOut[iCol*3+1]++;
+    }
+    aOut[iCol*3] += nHit;
   }
   pCsr++;
   *pp = pCsr;
@@ -107363,16 +113950,18 @@
 
 /*
 ** fts3ExprIterate() callback used to collect the "global" matchinfo stats
-** for a single query.
+** for a single query. The "global" stats are those elements of the matchinfo
+** array that are constant for all rows returned by the current query.
 */
 static int fts3ExprGlobalMatchinfoCb(
   Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
   void *pCtx                      /* Pointer to MatchInfo structure */
 ){
   MatchInfo *p = (MatchInfo *)pCtx;
   char *pCsr;
   char *pEnd;
-  const int iStart = 2 + p->nCol*p->iPhrase;
+  const int iStart = 2 + (iPhrase * p->nCol * 3) + 1;
 
   assert( pExpr->isLoaded );
 
@@ -107380,84 +113969,108 @@
   pCsr = pExpr->aDoclist;
   pEnd = &pExpr->aDoclist[pExpr->nDoclist];
   while( pCsr<pEnd ){
-    while( *pCsr++ & 0x80 );
-    fts3LoadColumnlistCounts(&pCsr, &p->aGlobal[iStart]);
-  }
-
-  p->iPhrase++;
-  return SQLITE_OK;
-}
-
-static int fts3ExprLocalMatchinfoCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  void *pCtx                      /* Pointer to MatchInfo structure */
-){
-  MatchInfo *p = (MatchInfo *)pCtx;
-  int iPhrase = p->iPhrase++;
-
-  if( pExpr->aDoclist ){
-    char *pCsr;
-    int iOffset = 2 + p->nCol*(p->aGlobal[0]+iPhrase);
-
-    memset(&p->aGlobal[iOffset], 0, p->nCol*sizeof(u32));
-    pCsr = sqlite3Fts3FindPositions(pExpr, p->pCursor->iPrevId, -1);
-    if( pCsr ) fts3LoadColumnlistCounts(&pCsr, &p->aGlobal[iOffset]);
+    while( *pCsr++ & 0x80 );      /* Skip past docid. */
+    fts3LoadColumnlistCounts(&pCsr, &p->aMatchinfo[iStart], 1);
   }
 
   return SQLITE_OK;
 }
 
 /*
-** Populate pCsr->aMatchinfo[] with data for the current row. The 'matchinfo'
-** data is an array of 32-bit unsigned integers (C type u32).
+** fts3ExprIterate() callback used to collect the "local" matchinfo stats
+** for a single query. The "local" stats are those elements of the matchinfo
+** array that are different for each row returned by the query.
 */
-static int fts3GetMatchinfo(Fts3Cursor *pCsr){
-  MatchInfo g;
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  if( pCsr->aMatchinfo==0 ){
-    int rc;
-    int nPhrase;
-    int nMatchinfo;
+static int fts3ExprLocalMatchinfoCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  MatchInfo *p = (MatchInfo *)pCtx;
 
-    g.pTab = pTab;
-    g.nCol = pTab->nColumn;
-    g.iPhrase = 0;
-    rc = fts3ExprLoadDoclists(pCsr, &nPhrase);
-    if( rc!=SQLITE_OK ){
-      return rc;
+  if( pExpr->aDoclist ){
+    char *pCsr;
+    int iStart = 2 + (iPhrase * p->nCol * 3);
+    int i;
+
+    for(i=0; i<p->nCol; i++) p->aMatchinfo[iStart+i*3] = 0;
+
+    pCsr = sqlite3Fts3FindPositions(pExpr, p->pCursor->iPrevId, -1);
+    if( pCsr ){
+      fts3LoadColumnlistCounts(&pCsr, &p->aMatchinfo[iStart], 0);
     }
-
-    nMatchinfo = 2 + 2*g.nCol*nPhrase;
-
-    g.iPhrase = 0;
-    g.aGlobal = (u32 *)sqlite3_malloc(sizeof(u32)*nMatchinfo);
-    if( !g.aGlobal ){ 
-      return SQLITE_NOMEM;
-    }
-    memset(g.aGlobal, 0, sizeof(u32)*nMatchinfo);
-
-    g.aGlobal[0] = nPhrase;
-    g.aGlobal[1] = g.nCol;
-    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprGlobalMatchinfoCb, (void *)&g);
-
-    pCsr->aMatchinfo = g.aGlobal;
-  }
-
-  g.pTab = pTab;
-  g.pCursor = pCsr;
-  g.nCol = pTab->nColumn;
-  g.iPhrase = 0;
-  g.aGlobal = pCsr->aMatchinfo;
-
-  if( pCsr->isMatchinfoOk ){
-    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLocalMatchinfoCb, (void *)&g);
-    pCsr->isMatchinfoOk = 0;
   }
 
   return SQLITE_OK;
 }
 
-SQLITE_PRIVATE void sqlite3Fts3Snippet2(
+/*
+** Populate pCsr->aMatchinfo[] with data for the current row. The 
+** 'matchinfo' data is an array of 32-bit unsigned integers (C type u32).
+*/
+static int fts3GetMatchinfo(Fts3Cursor *pCsr){
+  MatchInfo sInfo;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+
+  sInfo.pCursor = pCsr;
+  sInfo.nCol = pTab->nColumn;
+
+  if( pCsr->aMatchinfo==0 ){
+    /* If Fts3Cursor.aMatchinfo[] is NULL, then this is the first time the
+    ** matchinfo function has been called for this query. In this case 
+    ** allocate the array used to accumulate the matchinfo data and
+    ** initialize those elements that are constant for every row.
+    */
+    int nPhrase;                  /* Number of phrases */
+    int nMatchinfo;               /* Number of u32 elements in match-info */
+
+    /* Load doclists for each phrase in the query. */
+    rc = fts3ExprLoadDoclists(pCsr, &nPhrase, 0);
+    if( rc!=SQLITE_OK ){
+      return rc;
+    }
+    nMatchinfo = 2 + 3*sInfo.nCol*nPhrase;
+    if( pTab->bHasDocsize ){
+      nMatchinfo += 1 + 2*pTab->nColumn;
+    }
+
+    sInfo.aMatchinfo = (u32 *)sqlite3_malloc(sizeof(u32)*nMatchinfo);
+    if( !sInfo.aMatchinfo ){ 
+      return SQLITE_NOMEM;
+    }
+    memset(sInfo.aMatchinfo, 0, sizeof(u32)*nMatchinfo);
+
+
+    /* First element of match-info is the number of phrases in the query */
+    sInfo.aMatchinfo[0] = nPhrase;
+    sInfo.aMatchinfo[1] = sInfo.nCol;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprGlobalMatchinfoCb,(void*)&sInfo);
+    if( pTab->bHasDocsize ){
+      int ofst = 2 + 3*sInfo.aMatchinfo[0]*sInfo.aMatchinfo[1];
+      rc = sqlite3Fts3MatchinfoDocsizeGlobal(pCsr, &sInfo.aMatchinfo[ofst]);
+    }
+    pCsr->aMatchinfo = sInfo.aMatchinfo;
+    pCsr->isMatchinfoNeeded = 1;
+  }
+
+  sInfo.aMatchinfo = pCsr->aMatchinfo;
+  if( rc==SQLITE_OK && pCsr->isMatchinfoNeeded ){
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLocalMatchinfoCb, (void*)&sInfo);
+    if( pTab->bHasDocsize ){
+      int ofst = 2 + 3*sInfo.aMatchinfo[0]*sInfo.aMatchinfo[1];
+      rc = sqlite3Fts3MatchinfoDocsizeLocal(pCsr, &sInfo.aMatchinfo[ofst]);
+    }
+    pCsr->isMatchinfoNeeded = 0;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of snippet() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Snippet(
   sqlite3_context *pCtx,          /* SQLite function call context */
   Fts3Cursor *pCsr,               /* Cursor object */
   const char *zStart,             /* Snippet start text - "<b>" */
@@ -107466,35 +114079,292 @@
   int iCol,                       /* Extract snippet from this column */
   int nToken                      /* Approximate number of tokens in snippet */
 ){
-  int rc;
-  int iPos = 0;
-  u64 hlmask = 0;
-  char *z = 0;
-  int nDoc;
-  const char *zDoc;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int i;
+  StrBuffer res = {0, 0, 0};
 
-  rc = fts3BestSnippet(nToken, pCsr, iCol, &iPos, &hlmask);
+  /* The returned text includes up to four fragments of text extracted from
+  ** the data in the current row. The first iteration of the for(...) loop
+  ** below attempts to locate a single fragment of text nToken tokens in 
+  ** size that contains at least one instance of all phrases in the query
+  ** expression that appear in the current row. If such a fragment of text
+  ** cannot be found, the second iteration of the loop attempts to locate
+  ** a pair of fragments, and so on.
+  */
+  int nSnippet = 0;               /* Number of fragments in this snippet */
+  SnippetFragment aSnippet[4];    /* Maximum of 4 fragments per snippet */
+  int nFToken = -1;               /* Number of tokens in each fragment */
 
-  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
-  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
-
-  if( rc==SQLITE_OK ){
-    rc = fts3SnippetText(
-        pCsr, zDoc, nDoc, nToken, iPos, hlmask, zStart, zEnd, zEllipsis, &z);
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
   }
+
+  for(nSnippet=1; 1; nSnippet++){
+
+    int iSnip;                    /* Loop counter 0..nSnippet-1 */
+    u64 mCovered = 0;             /* Bitmask of phrases covered by snippet */
+    u64 mSeen = 0;                /* Bitmask of phrases seen by BestSnippet() */
+
+    if( nToken>=0 ){
+      nFToken = (nToken+nSnippet-1) / nSnippet;
+    }else{
+      nFToken = -1 * nToken;
+    }
+
+    for(iSnip=0; iSnip<nSnippet; iSnip++){
+      int iBestScore = -1;        /* Best score of columns checked so far */
+      int iRead;                  /* Used to iterate through columns */
+      SnippetFragment *pFragment = &aSnippet[iSnip];
+
+      memset(pFragment, 0, sizeof(*pFragment));
+
+      /* Loop through all columns of the table being considered for snippets.
+      ** If the iCol argument to this function was negative, this means all
+      ** columns of the FTS3 table. Otherwise, only column iCol is considered.
+      */
+      for(iRead=0; iRead<pTab->nColumn; iRead++){
+        SnippetFragment sF;
+        int iS;
+        if( iCol>=0 && iRead!=iCol ) continue;
+
+        /* Find the best snippet of nFToken tokens in column iRead. */
+        rc = fts3BestSnippet(nFToken, pCsr, iRead, mCovered, &mSeen, &sF, &iS);
+        if( rc!=SQLITE_OK ){
+          goto snippet_out;
+        }
+        if( iS>iBestScore ){
+          *pFragment = sF;
+          iBestScore = iS;
+        }
+      }
+
+      mCovered |= pFragment->covered;
+    }
+
+    /* If all query phrases seen by fts3BestSnippet() are present in at least
+    ** one of the nSnippet snippet fragments, break out of the loop.
+    */
+    assert( (mCovered&mSeen)==mCovered );
+    if( mSeen==mCovered || nSnippet==SizeofArray(aSnippet) ) break;
+  }
+
+  assert( nFToken>0 );
+
+  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
+    rc = fts3SnippetText(pCsr, &aSnippet[i], 
+        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
+    );
+  }
+
+ snippet_out:
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pCtx, rc);
+    sqlite3_free(res.z);
   }else{
-    sqlite3_result_text(pCtx, z, -1, sqlite3_free);
+    sqlite3_result_text(pCtx, res.z, -1, sqlite3_free);
   }
 }
 
+
+typedef struct TermOffset TermOffset;
+typedef struct TermOffsetCtx TermOffsetCtx;
+
+struct TermOffset {
+  char *pList;                    /* Position-list */
+  int iPos;                       /* Position just read from pList */
+  int iOff;                       /* Offset of this term from read positions */
+};
+
+struct TermOffsetCtx {
+  int iCol;                       /* Column of table to populate aTerm for */
+  int iTerm;
+  sqlite3_int64 iDocid;
+  TermOffset *aTerm;
+};
+
+/*
+** This function is an fts3ExprIterate() callback used by sqlite3Fts3Offsets().
+*/
+static int fts3ExprTermOffsetInit(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
+  int nTerm;                      /* Number of tokens in phrase */
+  int iTerm;                      /* For looping through nTerm phrase terms */
+  char *pList;                    /* Pointer to position list for phrase */
+  int iPos = 0;                   /* First position in position-list */
+
+  UNUSED_PARAMETER(iPhrase);
+  pList = sqlite3Fts3FindPositions(pExpr, p->iDocid, p->iCol);
+  nTerm = pExpr->pPhrase->nToken;
+  if( pList ){
+    fts3GetDeltaPosition(&pList, &iPos);
+    assert( iPos>=0 );
+  }
+
+  for(iTerm=0; iTerm<nTerm; iTerm++){
+    TermOffset *pT = &p->aTerm[p->iTerm++];
+    pT->iOff = nTerm-iTerm-1;
+    pT->pList = pList;
+    pT->iPos = iPos;
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Implementation of offsets() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3Offsets(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr                /* Cursor object */
+){
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_tokenizer_module const *pMod = pTab->pTokenizer->pModule;
+  const char *ZDUMMY;             /* Dummy argument used with xNext() */
+  int NDUMMY;                     /* Dummy argument used with xNext() */
+  int rc;                         /* Return Code */
+  int nToken;                     /* Number of tokens in query */
+  int iCol;                       /* Column currently being processed */
+  StrBuffer res = {0, 0, 0};      /* Result string */
+  TermOffsetCtx sCtx;             /* Context for fts3ExprTermOffsetInit() */
+
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  memset(&sCtx, 0, sizeof(sCtx));
+  assert( pCsr->isRequireSeek==0 );
+
+  /* Count the number of terms in the query */
+  rc = fts3ExprLoadDoclists(pCsr, 0, &nToken);
+  if( rc!=SQLITE_OK ) goto offsets_out;
+
+  /* Allocate the array of TermOffset iterators. */
+  sCtx.aTerm = (TermOffset *)sqlite3_malloc(sizeof(TermOffset)*nToken);
+  if( 0==sCtx.aTerm ){
+    rc = SQLITE_NOMEM;
+    goto offsets_out;
+  }
+  sCtx.iDocid = pCsr->iPrevId;
+
+  /* Loop through the table columns, appending offset information to 
+  ** string-buffer res for each column.
+  */
+  for(iCol=0; iCol<pTab->nColumn; iCol++){
+    sqlite3_tokenizer_cursor *pC; /* Tokenizer cursor */
+    int iStart;
+    int iEnd;
+    int iCurrent;
+    const char *zDoc;
+    int nDoc;
+
+    /* Initialize the contents of sCtx.aTerm[] for column iCol. There is 
+    ** no way that this operation can fail, so the return code from
+    ** fts3ExprIterate() can be discarded.
+    */
+    sCtx.iCol = iCol;
+    sCtx.iTerm = 0;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprTermOffsetInit, (void *)&sCtx);
+
+    /* Retreive the text stored in column iCol. If an SQL NULL is stored 
+    ** in column iCol, jump immediately to the next iteration of the loop.
+    ** If an OOM occurs while retrieving the data (this can happen if SQLite
+    ** needs to transform the data from utf-16 to utf-8), return SQLITE_NOMEM 
+    ** to the caller. 
+    */
+    zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
+    nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
+    if( zDoc==0 ){
+      if( sqlite3_column_type(pCsr->pStmt, iCol+1)==SQLITE_NULL ){
+        continue;
+      }
+      rc = SQLITE_NOMEM;
+      goto offsets_out;
+    }
+
+    /* Initialize a tokenizer iterator to iterate through column iCol. */
+    rc = pMod->xOpen(pTab->pTokenizer, zDoc, nDoc, &pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
+    pC->pTokenizer = pTab->pTokenizer;
+
+    rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+    while( rc==SQLITE_OK ){
+      int i;                      /* Used to loop through terms */
+      int iMinPos = 0x7FFFFFFF;   /* Position of next token */
+      TermOffset *pTerm = 0;      /* TermOffset associated with next token */
+
+      for(i=0; i<nToken; i++){
+        TermOffset *pT = &sCtx.aTerm[i];
+        if( pT->pList && (pT->iPos-pT->iOff)<iMinPos ){
+          iMinPos = pT->iPos-pT->iOff;
+          pTerm = pT;
+        }
+      }
+
+      if( !pTerm ){
+        /* All offsets for this column have been gathered. */
+        break;
+      }else{
+        assert( iCurrent<=iMinPos );
+        if( 0==(0xFE&*pTerm->pList) ){
+          pTerm->pList = 0;
+        }else{
+          fts3GetDeltaPosition(&pTerm->pList, &pTerm->iPos);
+        }
+        while( rc==SQLITE_OK && iCurrent<iMinPos ){
+          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+        }
+        if( rc==SQLITE_OK ){
+          char aBuffer[64];
+          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
+              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
+          );
+          rc = fts3StringAppend(&res, aBuffer, -1);
+        }else if( rc==SQLITE_DONE ){
+          rc = SQLITE_CORRUPT;
+        }
+      }
+    }
+    if( rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
+    }
+
+    pMod->xClose(pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
+  }
+
+ offsets_out:
+  sqlite3_free(sCtx.aTerm);
+  assert( rc!=SQLITE_DONE );
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx,  rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, res.n-1, sqlite3_free);
+  }
+  return;
+}
+
+/*
+** Implementation of matchinfo() function.
+*/
 SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *pContext, Fts3Cursor *pCsr){
-  int rc = fts3GetMatchinfo(pCsr);
+  int rc;
+  if( !pCsr->pExpr ){
+    sqlite3_result_blob(pContext, "", 0, SQLITE_STATIC);
+    return;
+  }
+  rc = fts3GetMatchinfo(pCsr);
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pContext, rc);
   }else{
-    int n = sizeof(u32)*(2+pCsr->aMatchinfo[0]*pCsr->aMatchinfo[1]*2);
+    Fts3Table *pTab = (Fts3Table*)pCsr->base.pVtab;
+    int n = sizeof(u32)*(2+pCsr->aMatchinfo[0]*pCsr->aMatchinfo[1]*3);
+    if( pTab->bHasDocsize ){
+      n += sizeof(u32)*(1 + 2*pTab->nColumn);
+    }
     sqlite3_result_blob(pContext, pCsr->aMatchinfo, n, SQLITE_TRANSIENT);
   }
 }
@@ -107924,6 +114794,7 @@
   rc = sqlite3_step(pRtree->pReadNode);
   if( rc==SQLITE_ROW ){
     const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);
+    assert( sqlite3_column_bytes(pRtree->pReadNode, 0)==pRtree->iNodeSize );
     memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
     nodeReference(pParent);
   }else{
@@ -109983,6 +116854,7 @@
       }
       rc = sqlite3_reset(pRtree->pReadRowid);
     }
+    *pRowid = cell.iRowid;
 
     if( rc==SQLITE_OK ){
       rc = ChooseLeaf(pRtree, &cell, 0, &pLeaf);
@@ -110120,31 +116992,69 @@
 }
 
 /*
-** This routine queries database handle db for the page-size used by
-** database zDb. If successful, the page-size in bytes is written to
-** *piPageSize and SQLITE_OK returned. Otherwise, and an SQLite error 
-** code is returned.
+** The second argument to this function contains the text of an SQL statement
+** that returns a single integer value. The statement is compiled and executed
+** using database connection db. If successful, the integer value returned
+** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
+** code is returned and the value of *piVal after returning is not defined.
 */
-static int getPageSize(sqlite3 *db, const char *zDb, int *piPageSize){
+static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
   int rc = SQLITE_NOMEM;
+  if( zSql ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *piVal = sqlite3_column_int(pStmt, 0);
+      }
+      rc = sqlite3_finalize(pStmt);
+    }
+  }
+  return rc;
+}
+
+/*
+** This function is called from within the xConnect() or xCreate() method to
+** determine the node-size used by the rtree table being created or connected
+** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned.
+**
+** If this function is being called as part of an xConnect(), then the rtree
+** table already exists. In this case the node-size is determined by inspecting
+** the root node of the tree.
+**
+** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
+** This ensures that each node is stored on a single database page. If the 
+** database page-size is so large that more than RTREE_MAXCELLS entries 
+** would fit in a single node, use a smaller node-size.
+*/
+static int getNodeSize(
+  sqlite3 *db,                    /* Database handle */
+  Rtree *pRtree,                  /* Rtree handle */
+  int isCreate                    /* True for xCreate, false for xConnect */
+){
+  int rc;
   char *zSql;
-  sqlite3_stmt *pStmt = 0;
-
-  zSql = sqlite3_mprintf("PRAGMA %Q.page_size", zDb);
-  if( !zSql ){
-    return SQLITE_NOMEM;
+  if( isCreate ){
+    int iPageSize;
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
+    rc = getIntFromStmt(db, zSql, &iPageSize);
+    if( rc==SQLITE_OK ){
+      pRtree->iNodeSize = iPageSize-64;
+      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
+        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
+      }
+    }
+  }else{
+    zSql = sqlite3_mprintf(
+        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
+        pRtree->zDb, pRtree->zName
+    );
+    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
   }
 
-  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
   sqlite3_free(zSql);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    *piPageSize = sqlite3_column_int(pStmt, 0);
-  }
-  return sqlite3_finalize(pStmt);
+  return rc;
 }
 
 /* 
@@ -110165,7 +117075,6 @@
   int isCreate                        /* True for xCreate, false for xConnect */
 ){
   int rc = SQLITE_OK;
-  int iPageSize = 0;
   Rtree *pRtree;
   int nDb;              /* Length of string argv[1] */
   int nName;            /* Length of string argv[2] */
@@ -110184,11 +117093,6 @@
     return SQLITE_ERROR;
   }
 
-  rc = getPageSize(db, argv[1], &iPageSize);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
   /* Allocate the sqlite3_vtab structure */
   nDb = strlen(argv[1]);
   nName = strlen(argv[2]);
@@ -110207,44 +117111,37 @@
   memcpy(pRtree->zDb, argv[1], nDb);
   memcpy(pRtree->zName, argv[2], nName);
 
-  /* Figure out the node size to use. By default, use 64 bytes less than
-  ** the database page-size. This ensures that each node is stored on
-  ** a single database page.
-  **
-  ** If the databasd page-size is so large that more than RTREE_MAXCELLS
-  ** entries would fit in a single node, use a smaller node-size.
-  */
-  pRtree->iNodeSize = iPageSize-64;
-  if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
-    pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
-  }
+  /* Figure out the node size to use. */
+  rc = getNodeSize(db, pRtree, isCreate);
 
   /* Create/Connect to the underlying relational database schema. If
   ** that is successful, call sqlite3_declare_vtab() to configure
   ** the r-tree table schema.
   */
-  if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
-    *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
-  }else{
-    char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
-    char *zTmp;
-    int ii;
-    for(ii=4; zSql && ii<argc; ii++){
-      zTmp = zSql;
-      zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
-      sqlite3_free(zTmp);
-    }
-    if( zSql ){
-      zTmp = zSql;
-      zSql = sqlite3_mprintf("%s);", zTmp);
-      sqlite3_free(zTmp);
-    }
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-    }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+  if( rc==SQLITE_OK ){
+    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
       *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }else{
+      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
+      char *zTmp;
+      int ii;
+      for(ii=4; zSql && ii<argc; ii++){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
+        sqlite3_free(zTmp);
+      }
+      if( zSql ){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s);", zTmp);
+        sqlite3_free(zTmp);
+      }
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+      }
+      sqlite3_free(zSql);
     }
-    sqlite3_free(zSql);
   }
 
   if( rc==SQLITE_OK ){
diff --git a/dist/sqlite3.h b/dist/sqlite3.h
index a275b00..2fbdf2d 100644
--- a/dist/sqlite3.h
+++ b/dist/sqlite3.h
@@ -107,13 +107,13 @@
 ** [sqlite3_libversion_number()], [sqlite3_sourceid()],
 ** [sqlite_version()] and [sqlite_source_id()].
 */
-#define SQLITE_VERSION        "3.6.22"
-#define SQLITE_VERSION_NUMBER 3006022
-#define SQLITE_SOURCE_ID      "2010-03-22 23:55:10 82dd61fccff3e4c77e060e5734cd4b4e2eeb7c32"
+#define SQLITE_VERSION        "3.7.0"
+#define SQLITE_VERSION_NUMBER 3007000
+#define SQLITE_SOURCE_ID      "2010-06-19 15:10:10 2241788bc85fbc48e9cfecb95fe0a858338e37cb"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
-** KEYWORDS: sqlite3_version
+** KEYWORDS: sqlite3_version, sqlite3_sourceid
 **
 ** These interfaces provide the same information as the [SQLITE_VERSION],
 ** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
@@ -135,9 +135,9 @@
 ** function is provided for use in DLLs since DLL users usually do not have
 ** direct access to string constants within the DLL.  ^The
 ** sqlite3_libversion_number() function returns an integer equal to
-** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function a pointer
-** to a string constant whose value is the same as the [SQLITE_SOURCE_ID]
-** C preprocessor macro.
+** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function returns 
+** a pointer to a string constant whose value is the same as the 
+** [SQLITE_SOURCE_ID] C preprocessor macro.
 **
 ** See also: [sqlite_version()] and [sqlite_source_id()].
 */
@@ -147,6 +147,33 @@
 SQLITE_API int sqlite3_libversion_number(void);
 
 /*
+** CAPI3REF: Run-Time Library Compilation Options Diagnostics
+**
+** ^The sqlite3_compileoption_used() function returns 0 or 1 
+** indicating whether the specified option was defined at 
+** compile time.  ^The SQLITE_ prefix may be omitted from the 
+** option name passed to sqlite3_compileoption_used().  
+**
+** ^The sqlite3_compileoption_get() function allows interating
+** over the list of options that were defined at compile time by
+** returning the N-th compile time option string.  ^If N is out of range,
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_ 
+** prefix is omitted from any strings returned by 
+** sqlite3_compileoption_get().
+**
+** ^Support for the diagnostic functions sqlite3_compileoption_used()
+** and sqlite3_compileoption_get() may be omitted by specifing the 
+** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
+**
+** See also: SQL functions [sqlite_compileoption_used()] and
+** [sqlite_compileoption_get()] and the [compile_options pragma].
+*/
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
+SQLITE_API int sqlite3_compileoption_used(const char *zOptName);
+SQLITE_API const char *sqlite3_compileoption_get(int N);
+#endif
+
+/*
 ** CAPI3REF: Test To See If The Library Is Threadsafe
 **
 ** ^The sqlite3_threadsafe() function returns zero if and only if
@@ -366,7 +393,7 @@
 #define SQLITE_NOTFOUND    12   /* NOT USED. Table or record not found */
 #define SQLITE_FULL        13   /* Insertion failed because database is full */
 #define SQLITE_CANTOPEN    14   /* Unable to open the database file */
-#define SQLITE_PROTOCOL    15   /* NOT USED. Database lock protocol error */
+#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
 #define SQLITE_EMPTY       16   /* Database is empty */
 #define SQLITE_SCHEMA      17   /* The database schema changed */
 #define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
@@ -422,7 +449,12 @@
 #define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
 #define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
 #define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
-#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED | (1<<8) )
+#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
+#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
+#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
+#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
+#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
+#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
 
 /*
 ** CAPI3REF: Flags For File Open Operations
@@ -437,6 +469,7 @@
 #define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
 #define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
 #define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
+#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
 #define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
 #define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
 #define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
@@ -630,6 +663,13 @@
   int (*xFileControl)(sqlite3_file*, int op, void *pArg);
   int (*xSectorSize)(sqlite3_file*);
   int (*xDeviceCharacteristics)(sqlite3_file*);
+  /* Methods above are valid for version 1 */
+  int (*xShmOpen)(sqlite3_file*);
+  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
+  int (*xShmMap)(sqlite3_file*, int iPage, int pgsz, int, void volatile**);
+  void (*xShmBarrier)(sqlite3_file*);
+  int (*xShmClose)(sqlite3_file*, int deleteFlag);
+  /* Methods above are valid for version 2 */
   /* Additional methods may be added in future releases */
 };
 
@@ -647,11 +687,19 @@
 ** into an integer that the pArg argument points to. This capability
 ** is used during testing and only needs to be supported when SQLITE_TEST
 ** is defined.
+**
+** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
+** layer a hint of how large the database file will grow to be during the
+** current transaction.  This hint is not guaranteed to be accurate but it
+** is often close.  The underlying VFS might choose to preallocate database
+** file space based on this hint in order to help writes to the database
+** file run faster.
 */
 #define SQLITE_FCNTL_LOCKSTATE        1
 #define SQLITE_GET_LOCKPROXYFILE      2
 #define SQLITE_SET_LOCKPROXYFILE      3
 #define SQLITE_LAST_ERRNO             4
+#define SQLITE_FCNTL_SIZE_HINT        5
 
 /*
 ** CAPI3REF: Mutex Handle
@@ -796,7 +844,7 @@
 */
 typedef struct sqlite3_vfs sqlite3_vfs;
 struct sqlite3_vfs {
-  int iVersion;            /* Structure version number */
+  int iVersion;            /* Structure version number (currently 2) */
   int szOsFile;            /* Size of subclassed sqlite3_file */
   int mxPathname;          /* Maximum file pathname length */
   sqlite3_vfs *pNext;      /* Next registered VFS */
@@ -815,8 +863,17 @@
   int (*xSleep)(sqlite3_vfs*, int microseconds);
   int (*xCurrentTime)(sqlite3_vfs*, double*);
   int (*xGetLastError)(sqlite3_vfs*, int, char *);
-  /* New fields may be appended in figure versions.  The iVersion
-  ** value will increment whenever this happens. */
+  /*
+  ** The methods above are in version 1 of the sqlite_vfs object
+  ** definition.  Those that follow are added in version 2 or later
+  */
+  int (*xRename)(sqlite3_vfs*, const char *zOld, const char *zNew, int dirSync);
+  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
+  /*
+  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
+  ** New fields may be appended in figure versions.  The iVersion
+  ** value will increment whenever this happens. 
+  */
 };
 
 /*
@@ -837,6 +894,44 @@
 #define SQLITE_ACCESS_READ      2
 
 /*
+** CAPI3REF: Flags for the xShmLock VFS method
+**
+** These integer constants define the various locking operations
+** allowed by the xShmLock method of [sqlite3_io_methods].  The
+** following are the only legal combinations of flags to the
+** xShmLock method:
+**
+** <ul>
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
+** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
+** </ul>
+**
+** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
+** was given no the corresponding lock.  
+**
+** The xShmLock method can transition between unlocked and SHARED or
+** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
+** and EXCLUSIVE.
+*/
+#define SQLITE_SHM_UNLOCK       1
+#define SQLITE_SHM_LOCK         2
+#define SQLITE_SHM_SHARED       4
+#define SQLITE_SHM_EXCLUSIVE    8
+
+/*
+** CAPI3REF: Maximum xShmLock index
+**
+** The xShmLock method on [sqlite3_io_methods] may use values
+** between 0 and this upper bound as its "offset" argument.
+** The SQLite core will never attempt to acquire or release a
+** lock outside of this range
+*/
+#define SQLITE_SHM_NLOCK        8
+
+
+/*
 ** CAPI3REF: Initialize The SQLite Library
 **
 ** ^The sqlite3_initialize() routine initializes the
@@ -945,11 +1040,10 @@
 ** ^If the option is unknown or SQLite is unable to set the option
 ** then this routine returns a non-zero [error code].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_config(int, ...);
+SQLITE_API int sqlite3_config(int, ...);
 
 /*
 ** CAPI3REF: Configure database connections
-** EXPERIMENTAL
 **
 ** The sqlite3_db_config() interface is used to make configuration
 ** changes to a [database connection].  The interface is similar to
@@ -969,11 +1063,10 @@
 ** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
 ** the call is considered successful.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_config(sqlite3*, int op, ...);
+SQLITE_API int sqlite3_db_config(sqlite3*, int op, ...);
 
 /*
 ** CAPI3REF: Memory Allocation Routines
-** EXPERIMENTAL
 **
 ** An instance of this object defines the interface between SQLite
 ** and low-level memory allocation routines.
@@ -1055,7 +1148,6 @@
 
 /*
 ** CAPI3REF: Configuration Options
-** EXPERIMENTAL
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the first argument to the [sqlite3_config()] interface.
@@ -1241,6 +1333,24 @@
 ** [sqlite3_pcache_methods] object.  SQLite copies of the current
 ** page cache implementation into that object.)^ </dd>
 **
+** <dt>SQLITE_CONFIG_LOG</dt>
+** <dd> ^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
+** function with a call signature of void(*)(void*,int,const char*), 
+** and a pointer to void. ^If the function pointer is not NULL, it is
+** invoked by [sqlite3_log()] to process each logging event.  ^If the
+** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
+** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
+** passed through as the first parameter to the application-defined logger
+** function whenever that function is invoked.  ^The second parameter to
+** the logger function is a copy of the first parameter to the corresponding
+** [sqlite3_log()] call and is intended to be a [result code] or an
+** [extended result code].  ^The third parameter passed to the logger is
+** log message after formatting via [sqlite3_snprintf()].
+** The SQLite logging interface is not reentrant; the logger function
+** supplied by the application must not invoke any SQLite interface.
+** In a multi-threaded application, the application-defined logger
+** function must be threadsafe. </dd>
+**
 ** </dl>
 */
 #define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
@@ -1261,8 +1371,7 @@
 #define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
 
 /*
-** CAPI3REF: Configuration Options
-** EXPERIMENTAL
+** CAPI3REF: Database Connection Configuration Options
 **
 ** These constants are the available integer configuration options that
 ** can be passed as the second argument to the [sqlite3_db_config()] interface.
@@ -2038,7 +2147,6 @@
 
 /*
 ** CAPI3REF: Tracing And Profiling Functions
-** EXPERIMENTAL
 **
 ** These routines register callback functions that can be used for
 ** tracing and profiling the execution of SQL statements.
@@ -2056,7 +2164,7 @@
 ** the original statement text and an estimate of wall-clock time
 ** of how long that statement took to run.
 */
-SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
+SQLITE_API void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
 SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_profile(sqlite3*,
    void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
 
@@ -2849,6 +2957,14 @@
 ** be the case that the same database connection is being used by two or
 ** more threads at the same moment in time.
 **
+** For all versions of SQLite up to and including 3.6.23.1, it was required
+** after sqlite3_step() returned anything other than [SQLITE_ROW] that
+** [sqlite3_reset()] be called before any subsequent invocation of
+** sqlite3_step().  Failure to invoke [sqlite3_reset()] in this way would
+** result in an [SQLITE_MISUSE] return from sqlite3_step().  But after
+** version 3.6.23.1, sqlite3_step() began calling [sqlite3_reset()] 
+** automatically in this circumstance rather than returning [SQLITE_MISUSE].  
+**
 ** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
 ** API always returns a generic error code, [SQLITE_ERROR], following any
 ** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
@@ -3661,6 +3777,7 @@
   void(*)(void*,sqlite3*,int eTextRep,const void*)
 );
 
+#ifdef SQLITE_HAS_CODEC
 /*
 ** Specify the key for an encrypted database.  This routine should be
 ** called right after sqlite3_open().
@@ -3687,6 +3804,25 @@
 );
 
 /*
+** Specify the activation key for a SEE database.  Unless 
+** activated, none of the SEE routines will work.
+*/
+SQLITE_API void sqlite3_activate_see(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+#ifdef SQLITE_ENABLE_CEROD
+/*
+** Specify the activation key for a CEROD database.  Unless 
+** activated, none of the CEROD routines will work.
+*/
+SQLITE_API void sqlite3_activate_cerod(
+  const char *zPassPhrase        /* Activation phrase */
+);
+#endif
+
+/*
 ** CAPI3REF: Suspend Execution For A Short Time
 **
 ** ^The sqlite3_sleep() function causes the current thread to suspend execution
@@ -3824,8 +3960,6 @@
 ** an error or constraint causes an implicit rollback to occur.
 ** ^The rollback callback is not invoked if a transaction is
 ** automatically rolled back because the database connection is closed.
-** ^The rollback callback is not invoked if a transaction is
-** rolled back because a commit callback returned non-zero.
 **
 ** See also the [sqlite3_update_hook()] interface.
 */
@@ -4111,8 +4245,6 @@
 SQLITE_API void sqlite3_reset_auto_extension(void);
 
 /*
-****** EXPERIMENTAL - subject to change without notice **************
-**
 ** The interface to the virtual-table mechanism is currently considered
 ** to be experimental.  The interface might change in incompatible ways.
 ** If this is a problem for you, do not use the interface at this time.
@@ -4132,7 +4264,6 @@
 /*
 ** CAPI3REF: Virtual Table Object
 ** KEYWORDS: sqlite3_module {virtual table module}
-** EXPERIMENTAL
 **
 ** This structure, sometimes called a a "virtual table module", 
 ** defines the implementation of a [virtual tables].  
@@ -4179,7 +4310,6 @@
 /*
 ** CAPI3REF: Virtual Table Indexing Information
 ** KEYWORDS: sqlite3_index_info
-** EXPERIMENTAL
 **
 ** The sqlite3_index_info structure and its substructures is used to
 ** pass information into and receive the reply from the [xBestIndex]
@@ -4261,7 +4391,6 @@
 
 /*
 ** CAPI3REF: Register A Virtual Table Implementation
-** EXPERIMENTAL
 **
 ** ^These routines are used to register a new [virtual table module] name.
 ** ^Module names must be registered before
@@ -4283,13 +4412,13 @@
 ** interface is equivalent to sqlite3_create_module_v2() with a NULL
 ** destructor.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module(
+SQLITE_API int sqlite3_create_module(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
   void *pClientData          /* Client data for xCreate/xConnect */
 );
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module_v2(
+SQLITE_API int sqlite3_create_module_v2(
   sqlite3 *db,               /* SQLite connection to register module with */
   const char *zName,         /* Name of the module */
   const sqlite3_module *p,   /* Methods for the module */
@@ -4300,7 +4429,6 @@
 /*
 ** CAPI3REF: Virtual Table Instance Object
 ** KEYWORDS: sqlite3_vtab
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass
 ** of this object to describe a particular instance
@@ -4326,7 +4454,6 @@
 /*
 ** CAPI3REF: Virtual Table Cursor Object
 ** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
-** EXPERIMENTAL
 **
 ** Every [virtual table module] implementation uses a subclass of the
 ** following structure to describe cursors that point into the
@@ -4348,18 +4475,16 @@
 
 /*
 ** CAPI3REF: Declare The Schema Of A Virtual Table
-** EXPERIMENTAL
 **
 ** ^The [xCreate] and [xConnect] methods of a
 ** [virtual table module] call this interface
 ** to declare the format (the names and datatypes of the columns) of
 ** the virtual tables they implement.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
+SQLITE_API int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
 
 /*
 ** CAPI3REF: Overload A Function For A Virtual Table
-** EXPERIMENTAL
 **
 ** ^(Virtual tables can provide alternative implementations of functions
 ** using the [xFindFunction] method of the [virtual table module].  
@@ -4374,7 +4499,7 @@
 ** purpose is to be a placeholder function that can be overloaded
 ** by a [virtual table].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
+SQLITE_API int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
 
 /*
 ** The interface to the virtual-table mechanism defined above (back up
@@ -4384,8 +4509,6 @@
 **
 ** When the virtual-table mechanism stabilizes, we will declare the
 ** interface fixed, support it indefinitely, and remove this comment.
-**
-****** EXPERIMENTAL - subject to change without notice **************
 */
 
 /*
@@ -4728,7 +4851,6 @@
 
 /*
 ** CAPI3REF: Mutex Methods Object
-** EXPERIMENTAL
 **
 ** An instance of this structure defines the low-level routines
 ** used to allocate and use mutexes.
@@ -4941,11 +5063,11 @@
 #define SQLITE_TESTCTRL_RESERVE                 14
 #define SQLITE_TESTCTRL_OPTIMIZATIONS           15
 #define SQLITE_TESTCTRL_ISKEYWORD               16
-#define SQLITE_TESTCTRL_LAST                    16
+#define SQLITE_TESTCTRL_PGHDRSZ                 17
+#define SQLITE_TESTCTRL_LAST                    17
 
 /*
 ** CAPI3REF: SQLite Runtime Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information
 ** about the preformance of SQLite, and optionally to reset various
@@ -4973,12 +5095,11 @@
 **
 ** See also: [sqlite3_db_status()]
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
+SQLITE_API int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
 
 
 /*
 ** CAPI3REF: Status Parameters
-** EXPERIMENTAL
 **
 ** These integer constants designate various run-time status parameters
 ** that can be returned by [sqlite3_status()].
@@ -5065,14 +5186,15 @@
 
 /*
 ** CAPI3REF: Database Connection Status
-** EXPERIMENTAL
 **
 ** ^This interface is used to retrieve runtime status information 
 ** about a single [database connection].  ^The first argument is the
 ** database connection object to be interrogated.  ^The second argument
-** is the parameter to interrogate.  ^Currently, the only allowed value
-** for the second parameter is [SQLITE_DBSTATUS_LOOKASIDE_USED].
-** Additional options will likely appear in future releases of SQLite.
+** is an integer constant, taken from the set of
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros, that
+** determiness the parameter to interrogate.  The set of 
+** [SQLITE_DBSTATUS_LOOKASIDE_USED | SQLITE_DBSTATUS_*] macros is likely
+** to grow in future releases of SQLite.
 **
 ** ^The current value of the requested parameter is written into *pCur
 ** and the highest instantaneous value is written into *pHiwtr.  ^If
@@ -5081,11 +5203,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
+SQLITE_API int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for database connections
-** EXPERIMENTAL
 **
 ** These constants are the available integer "verbs" that can be passed as
 ** the second argument to the [sqlite3_db_status()] interface.
@@ -5100,14 +5221,21 @@
 ** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
 ** <dd>This parameter returns the number of lookaside memory slots currently
 ** checked out.</dd>)^
+**
+** <dt>SQLITE_DBSTATUS_CACHE_USED</dt>
+** <dd>^This parameter returns the approximate number of of bytes of heap
+** memory used by all pager caches associated with the database connection.
+** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
+** checked out.</dd>)^
 ** </dl>
 */
 #define SQLITE_DBSTATUS_LOOKASIDE_USED     0
+#define SQLITE_DBSTATUS_CACHE_USED         1
+#define SQLITE_DBSTATUS_MAX                1   /* Largest defined DBSTATUS */
 
 
 /*
 ** CAPI3REF: Prepared Statement Status
-** EXPERIMENTAL
 **
 ** ^(Each prepared statement maintains various
 ** [SQLITE_STMTSTATUS_SORT | counters] that measure the number
@@ -5129,11 +5257,10 @@
 **
 ** See also: [sqlite3_status()] and [sqlite3_db_status()].
 */
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
+SQLITE_API int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
 
 /*
 ** CAPI3REF: Status Parameters for prepared statements
-** EXPERIMENTAL
 **
 ** These preprocessor macros define integer codes that name counter
 ** values associated with the [sqlite3_stmt_status()] interface.
@@ -5151,14 +5278,21 @@
 ** A non-zero value in this counter may indicate an opportunity to
 ** improvement performance through careful use of indices.</dd>
 **
+** <dt>SQLITE_STMTSTATUS_AUTOINDEX</dt>
+** <dd>^This is the number of rows inserted into transient indices that
+** were created automatically in order to help joins run faster.
+** A non-zero value in this counter may indicate an opportunity to
+** improvement performance by adding permanent indices that do not
+** need to be reinitialized each time the statement is run.</dd>
+**
 ** </dl>
 */
 #define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
 #define SQLITE_STMTSTATUS_SORT              2
+#define SQLITE_STMTSTATUS_AUTOINDEX         3
 
 /*
 ** CAPI3REF: Custom Page Cache Object
-** EXPERIMENTAL
 **
 ** The sqlite3_pcache type is opaque.  It is implemented by
 ** the pluggable module.  The SQLite core has no knowledge of
@@ -5173,7 +5307,6 @@
 /*
 ** CAPI3REF: Application Defined Page Cache.
 ** KEYWORDS: {page cache}
-** EXPERIMENTAL
 **
 ** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
 ** register an alternative page cache implementation by passing in an 
@@ -5315,7 +5448,6 @@
 
 /*
 ** CAPI3REF: Online Backup Object
-** EXPERIMENTAL
 **
 ** The sqlite3_backup object records state information about an ongoing
 ** online backup operation.  ^The sqlite3_backup object is created by
@@ -5328,7 +5460,6 @@
 
 /*
 ** CAPI3REF: Online Backup API.
-** EXPERIMENTAL
 **
 ** The backup API copies the content of one database into another.
 ** It is useful either for creating backups of databases or
@@ -5397,10 +5528,14 @@
 ** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
 ** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
 **
-** ^The sqlite3_backup_step() might return [SQLITE_READONLY] if the destination
-** database was opened read-only or if
-** the destination is an in-memory database with a different page size
-** from the source database.
+** ^(The sqlite3_backup_step() might return [SQLITE_READONLY] if
+** <ol>
+** <li> the destination database was opened read-only, or
+** <li> the destination database is using write-ahead-log journaling
+** and the destination and source page sizes differ, or
+** <li> The destination database is an in-memory database and the
+** destination and source page sizes differ.
+** </ol>)^
 **
 ** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
 ** the [sqlite3_busy_handler | busy-handler function]
@@ -5516,7 +5651,6 @@
 
 /*
 ** CAPI3REF: Unlock Notification
-** EXPERIMENTAL
 **
 ** ^When running in shared-cache mode, a database operation may fail with
 ** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
@@ -5638,7 +5772,6 @@
 
 /*
 ** CAPI3REF: String Comparison
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_strnicmp()] API allows applications and extensions to
 ** compare the contents of two buffers containing UTF-8 strings in a
@@ -5649,16 +5782,19 @@
 
 /*
 ** CAPI3REF: Error Logging Interface
-** EXPERIMENTAL
 **
 ** ^The [sqlite3_log()] interface writes a message into the error log
-** established by the [SQLITE_CONFIG_ERRORLOG] option to [sqlite3_config()].
+** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
+** ^If logging is enabled, the zFormat string and subsequent arguments are
+** used with [sqlite3_snprintf()] to generate the final output string.
 **
 ** The sqlite3_log() interface is intended for use by extensions such as
 ** virtual tables, collating functions, and SQL functions.  While there is
 ** nothing to prevent an application from calling sqlite3_log(), doing so
 ** is considered bad form.
 **
+** The zFormat string must not be NULL.
+**
 ** To avoid deadlocks and other threading problems, the sqlite3_log() routine
 ** will not use dynamically allocated memory.  The log message is stored in
 ** a fixed-length buffer on the stack.  If the log message is longer than
@@ -5667,16 +5803,89 @@
 */
 SQLITE_API void sqlite3_log(int iErrCode, const char *zFormat, ...);
 
-// Begin Android add
 /*
-** Android additional API.
+** CAPI3REF: Write-Ahead Log Commit Hook
 **
-** This function changes the default behavior of BEGIN to IMMEDIATE if called
-** with immediate=1.
-** Calling with immediate=0 will revert to DEFERRED.
+** ^The [sqlite3_wal_hook()] function is used to register a callback that
+** will be invoked each time a database connection commits data to a
+** [write-ahead log] (i.e. whenever a transaction is committed in
+** [journal_mode | journal_mode=WAL mode]). 
+**
+** ^The callback is invoked by SQLite after the commit has taken place and 
+** the associated write-lock on the database released, so the implementation 
+** may read, write or [checkpoint] the database as required.
+**
+** ^The first parameter passed to the callback function when it is invoked
+** is a copy of the third parameter passed to sqlite3_wal_hook() when
+** registering the callback. ^The second is a copy of the database handle.
+** ^The third parameter is the name of the database that was written to -
+** either "main" or the name of an [ATTACH]-ed database. ^The fourth parameter
+** is the number of pages currently in the write-ahead log file,
+** including those that were just committed.
+**
+** The callback function should normally return [SQLITE_OK].  ^If an error
+** code is returned, that error will propagate back up through the
+** SQLite code base to cause the statement that provoked the callback
+** to report an error, though the commit will have still occurred. If the
+** callback returns [SQLITE_ROW] or [SQLITE_DONE], or if it returns a value
+** that does not correspond to any valid SQLite error code, the results
+** are undefined.
+**
+** A single database handle may have at most a single write-ahead log callback 
+** registered at one time. ^Calling [sqlite3_wal_hook()] replaces any
+** previously registered write-ahead log callback. ^Note that the
+** [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] both invoke [sqlite3_wal_hook()] and will
+** those overwrite any prior [sqlite3_wal_hook()] settings.
 */
-int sqlite3_set_transaction_default_immediate(sqlite3*, int immediate);
-// End Android add
+SQLITE_API void *sqlite3_wal_hook(
+  sqlite3*, 
+  int(*)(void *,sqlite3*,const char*,int),
+  void*
+);
+
+/*
+** CAPI3REF: Configure an auto-checkpoint
+**
+** ^The [sqlite3_wal_autocheckpoint(D,N)] is a wrapper around
+** [sqlite3_wal_hook()] that causes any database on [database connection] D
+** to automatically [checkpoint]
+** after committing a transaction if there are N or
+** more frames in the [write-ahead log] file.  ^Passing zero or 
+** a negative value as the nFrame parameter disables automatic
+** checkpoints entirely.
+**
+** ^The callback registered by this function replaces any existing callback
+** registered using [sqlite3_wal_hook()].  ^Likewise, registering a callback
+** using [sqlite3_wal_hook()] disables the automatic checkpoint mechanism
+** configured by this function.
+**
+** ^The [wal_autocheckpoint pragma] can be used to invoke this interface
+** from SQL.
+**
+** ^Every new [database connection] defaults to having the auto-checkpoint
+** enabled with a threshold of 1000 pages.  The use of this interface
+** is only necessary if the default setting is found to be suboptimal
+** for a particular application.
+*/
+SQLITE_API int sqlite3_wal_autocheckpoint(sqlite3 *db, int N);
+
+/*
+** CAPI3REF: Checkpoint a database
+**
+** ^The [sqlite3_wal_checkpoint(D,X)] interface causes database named X
+** on [database connection] D to be [checkpointed].  ^If X is NULL or an
+** empty string, then a checkpoint is run on all databases of
+** connection D.  ^If the database connection D is not in
+** [WAL | write-ahead log mode] then this interface is a harmless no-op.
+**
+** ^The [wal_checkpoint pragma] can be used to invoke this interface
+** from SQL.  ^The [sqlite3_wal_autocheckpoint()] interface and the
+** [wal_autocheckpoint pragma] can be used to cause this interface to be
+** run whenever the WAL reaches a certain size threshold.
+*/
+SQLITE_API int sqlite3_wal_checkpoint(sqlite3 *db, const char *zDb);
+
 /*
 ** Undo the hack that converts floating point types to integer for
 ** builds on processors without floating point support.
diff --git a/dist/sqlite3.h.orig b/dist/sqlite3.h.orig
deleted file mode 100644
index 56efddd..0000000
--- a/dist/sqlite3.h.orig
+++ /dev/null
@@ -1,5682 +0,0 @@
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This header file defines the interface that the SQLite library
-** presents to client programs.  If a C-function, structure, datatype,
-** or constant definition does not appear in this file, then it is
-** not a published API of SQLite, is subject to change without
-** notice, and should not be referenced by programs that use SQLite.
-**
-** Some of the definitions that are in this file are marked as
-** "experimental".  Experimental interfaces are normally new
-** features recently added to SQLite.  We do not anticipate changes
-** to experimental interfaces but reserve the right to make minor changes
-** if experience from use "in the wild" suggest such changes are prudent.
-**
-** The official C-language API documentation for SQLite is derived
-** from comments in this file.  This file is the authoritative source
-** on how SQLite interfaces are suppose to operate.
-**
-** The name of this file under configuration management is "sqlite.h.in".
-** The makefile makes some minor changes to this file (such as inserting
-** the version number) and changes its name to "sqlite3.h" as
-** part of the build process.
-*/
-#ifndef _SQLITE3_H_
-#define _SQLITE3_H_
-#include <stdarg.h>     /* Needed for the definition of va_list */
-
-/*
-** Make sure we can call this stuff from C++.
-*/
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
-/*
-** Add the ability to override 'extern'
-*/
-#ifndef SQLITE_EXTERN
-# define SQLITE_EXTERN extern
-#endif
-
-#ifndef SQLITE_API
-# define SQLITE_API
-#endif
-
-
-/*
-** These no-op macros are used in front of interfaces to mark those
-** interfaces as either deprecated or experimental.  New applications
-** should not use deprecated interfaces - they are support for backwards
-** compatibility only.  Application writers should be aware that
-** experimental interfaces are subject to change in point releases.
-**
-** These macros used to resolve to various kinds of compiler magic that
-** would generate warning messages when they were used.  But that
-** compiler magic ended up generating such a flurry of bug reports
-** that we have taken it all out and gone back to using simple
-** noop macros.
-*/
-#define SQLITE_DEPRECATED
-#define SQLITE_EXPERIMENTAL
-
-/*
-** Ensure these symbols were not defined by some previous header file.
-*/
-#ifdef SQLITE_VERSION
-# undef SQLITE_VERSION
-#endif
-#ifdef SQLITE_VERSION_NUMBER
-# undef SQLITE_VERSION_NUMBER
-#endif
-
-/*
-** CAPI3REF: Compile-Time Library Version Numbers
-**
-** ^(The [SQLITE_VERSION] C preprocessor macro in the sqlite3.h header
-** evaluates to a string literal that is the SQLite version in the
-** format "X.Y.Z" where X is the major version number (always 3 for
-** SQLite3) and Y is the minor version number and Z is the release number.)^
-** ^(The [SQLITE_VERSION_NUMBER] C preprocessor macro resolves to an integer
-** with the value (X*1000000 + Y*1000 + Z) where X, Y, and Z are the same
-** numbers used in [SQLITE_VERSION].)^
-** The SQLITE_VERSION_NUMBER for any given release of SQLite will also
-** be larger than the release from which it is derived.  Either Y will
-** be held constant and Z will be incremented or else Y will be incremented
-** and Z will be reset to zero.
-**
-** Since version 3.6.18, SQLite source code has been stored in the
-** <a href="http://www.fossil-scm.org/">Fossil configuration management
-** system</a>.  ^The SQLITE_SOURCE_ID macro evalutes to
-** a string which identifies a particular check-in of SQLite
-** within its configuration management system.  ^The SQLITE_SOURCE_ID
-** string contains the date and time of the check-in (UTC) and an SHA1
-** hash of the entire source tree.
-**
-** See also: [sqlite3_libversion()],
-** [sqlite3_libversion_number()], [sqlite3_sourceid()],
-** [sqlite_version()] and [sqlite_source_id()].
-*/
-#define SQLITE_VERSION        "3.6.22"
-#define SQLITE_VERSION_NUMBER 3006022
-#define SQLITE_SOURCE_ID      "2010-03-22 23:55:10 82dd61fccff3e4c77e060e5734cd4b4e2eeb7c32"
-
-/*
-** CAPI3REF: Run-Time Library Version Numbers
-** KEYWORDS: sqlite3_version
-**
-** These interfaces provide the same information as the [SQLITE_VERSION],
-** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros
-** but are associated with the library instead of the header file.  ^(Cautious
-** programmers might include assert() statements in their application to
-** verify that values returned by these interfaces match the macros in
-** the header, and thus insure that the application is
-** compiled with matching library and header files.
-**
-** <blockquote><pre>
-** assert( sqlite3_libversion_number()==SQLITE_VERSION_NUMBER );
-** assert( strcmp(sqlite3_sourceid(),SQLITE_SOURCE_ID)==0 );
-** assert( strcmp(sqlite3_libversion(),SQLITE_VERSION)==0 );
-** </pre></blockquote>)^
-**
-** ^The sqlite3_version[] string constant contains the text of [SQLITE_VERSION]
-** macro.  ^The sqlite3_libversion() function returns a pointer to the
-** to the sqlite3_version[] string constant.  The sqlite3_libversion()
-** function is provided for use in DLLs since DLL users usually do not have
-** direct access to string constants within the DLL.  ^The
-** sqlite3_libversion_number() function returns an integer equal to
-** [SQLITE_VERSION_NUMBER].  ^The sqlite3_sourceid() function a pointer
-** to a string constant whose value is the same as the [SQLITE_SOURCE_ID]
-** C preprocessor macro.
-**
-** See also: [sqlite_version()] and [sqlite_source_id()].
-*/
-SQLITE_API SQLITE_EXTERN const char sqlite3_version[];
-SQLITE_API const char *sqlite3_libversion(void);
-SQLITE_API const char *sqlite3_sourceid(void);
-SQLITE_API int sqlite3_libversion_number(void);
-
-/*
-** CAPI3REF: Test To See If The Library Is Threadsafe
-**
-** ^The sqlite3_threadsafe() function returns zero if and only if
-** SQLite was compiled mutexing code omitted due to the
-** [SQLITE_THREADSAFE] compile-time option being set to 0.
-**
-** SQLite can be compiled with or without mutexes.  When
-** the [SQLITE_THREADSAFE] C preprocessor macro is 1 or 2, mutexes
-** are enabled and SQLite is threadsafe.  When the
-** [SQLITE_THREADSAFE] macro is 0, 
-** the mutexes are omitted.  Without the mutexes, it is not safe
-** to use SQLite concurrently from more than one thread.
-**
-** Enabling mutexes incurs a measurable performance penalty.
-** So if speed is of utmost importance, it makes sense to disable
-** the mutexes.  But for maximum safety, mutexes should be enabled.
-** ^The default behavior is for mutexes to be enabled.
-**
-** This interface can be used by an application to make sure that the
-** version of SQLite that it is linking against was compiled with
-** the desired setting of the [SQLITE_THREADSAFE] macro.
-**
-** This interface only reports on the compile-time mutex setting
-** of the [SQLITE_THREADSAFE] flag.  If SQLite is compiled with
-** SQLITE_THREADSAFE=1 or =2 then mutexes are enabled by default but
-** can be fully or partially disabled using a call to [sqlite3_config()]
-** with the verbs [SQLITE_CONFIG_SINGLETHREAD], [SQLITE_CONFIG_MULTITHREAD],
-** or [SQLITE_CONFIG_MUTEX].  ^(The return value of the
-** sqlite3_threadsafe() function shows only the compile-time setting of
-** thread safety, not any run-time changes to that setting made by
-** sqlite3_config(). In other words, the return value from sqlite3_threadsafe()
-** is unchanged by calls to sqlite3_config().)^
-**
-** See the [threading mode] documentation for additional information.
-*/
-SQLITE_API int sqlite3_threadsafe(void);
-
-/*
-** CAPI3REF: Database Connection Handle
-** KEYWORDS: {database connection} {database connections}
-**
-** Each open SQLite database is represented by a pointer to an instance of
-** the opaque structure named "sqlite3".  It is useful to think of an sqlite3
-** pointer as an object.  The [sqlite3_open()], [sqlite3_open16()], and
-** [sqlite3_open_v2()] interfaces are its constructors, and [sqlite3_close()]
-** is its destructor.  There are many other interfaces (such as
-** [sqlite3_prepare_v2()], [sqlite3_create_function()], and
-** [sqlite3_busy_timeout()] to name but three) that are methods on an
-** sqlite3 object.
-*/
-typedef struct sqlite3 sqlite3;
-
-/*
-** CAPI3REF: 64-Bit Integer Types
-** KEYWORDS: sqlite_int64 sqlite_uint64
-**
-** Because there is no cross-platform way to specify 64-bit integer types
-** SQLite includes typedefs for 64-bit signed and unsigned integers.
-**
-** The sqlite3_int64 and sqlite3_uint64 are the preferred type definitions.
-** The sqlite_int64 and sqlite_uint64 types are supported for backwards
-** compatibility only.
-**
-** ^The sqlite3_int64 and sqlite_int64 types can store integer values
-** between -9223372036854775808 and +9223372036854775807 inclusive.  ^The
-** sqlite3_uint64 and sqlite_uint64 types can store integer values 
-** between 0 and +18446744073709551615 inclusive.
-*/
-#ifdef SQLITE_INT64_TYPE
-  typedef SQLITE_INT64_TYPE sqlite_int64;
-  typedef unsigned SQLITE_INT64_TYPE sqlite_uint64;
-#elif defined(_MSC_VER) || defined(__BORLANDC__)
-  typedef __int64 sqlite_int64;
-  typedef unsigned __int64 sqlite_uint64;
-#else
-  typedef long long int sqlite_int64;
-  typedef unsigned long long int sqlite_uint64;
-#endif
-typedef sqlite_int64 sqlite3_int64;
-typedef sqlite_uint64 sqlite3_uint64;
-
-/*
-** If compiling for a processor that lacks floating point support,
-** substitute integer for floating-point.
-*/
-#ifdef SQLITE_OMIT_FLOATING_POINT
-# define double sqlite3_int64
-#endif
-
-/*
-** CAPI3REF: Closing A Database Connection
-**
-** ^The sqlite3_close() routine is the destructor for the [sqlite3] object.
-** ^Calls to sqlite3_close() return SQLITE_OK if the [sqlite3] object is
-** successfullly destroyed and all associated resources are deallocated.
-**
-** Applications must [sqlite3_finalize | finalize] all [prepared statements]
-** and [sqlite3_blob_close | close] all [BLOB handles] associated with
-** the [sqlite3] object prior to attempting to close the object.  ^If
-** sqlite3_close() is called on a [database connection] that still has
-** outstanding [prepared statements] or [BLOB handles], then it returns
-** SQLITE_BUSY.
-**
-** ^If [sqlite3_close()] is invoked while a transaction is open,
-** the transaction is automatically rolled back.
-**
-** The C parameter to [sqlite3_close(C)] must be either a NULL
-** pointer or an [sqlite3] object pointer obtained
-** from [sqlite3_open()], [sqlite3_open16()], or
-** [sqlite3_open_v2()], and not previously closed.
-** ^Calling sqlite3_close() with a NULL pointer argument is a 
-** harmless no-op.
-*/
-SQLITE_API int sqlite3_close(sqlite3 *);
-
-/*
-** The type for a callback function.
-** This is legacy and deprecated.  It is included for historical
-** compatibility and is not documented.
-*/
-typedef int (*sqlite3_callback)(void*,int,char**, char**);
-
-/*
-** CAPI3REF: One-Step Query Execution Interface
-**
-** The sqlite3_exec() interface is a convenience wrapper around
-** [sqlite3_prepare_v2()], [sqlite3_step()], and [sqlite3_finalize()],
-** that allows an application to run multiple statements of SQL
-** without having to use a lot of C code. 
-**
-** ^The sqlite3_exec() interface runs zero or more UTF-8 encoded,
-** semicolon-separate SQL statements passed into its 2nd argument,
-** in the context of the [database connection] passed in as its 1st
-** argument.  ^If the callback function of the 3rd argument to
-** sqlite3_exec() is not NULL, then it is invoked for each result row
-** coming out of the evaluated SQL statements.  ^The 4th argument to
-** to sqlite3_exec() is relayed through to the 1st argument of each
-** callback invocation.  ^If the callback pointer to sqlite3_exec()
-** is NULL, then no callback is ever invoked and result rows are
-** ignored.
-**
-** ^If an error occurs while evaluating the SQL statements passed into
-** sqlite3_exec(), then execution of the current statement stops and
-** subsequent statements are skipped.  ^If the 5th parameter to sqlite3_exec()
-** is not NULL then any error message is written into memory obtained
-** from [sqlite3_malloc()] and passed back through the 5th parameter.
-** To avoid memory leaks, the application should invoke [sqlite3_free()]
-** on error message strings returned through the 5th parameter of
-** of sqlite3_exec() after the error message string is no longer needed.
-** ^If the 5th parameter to sqlite3_exec() is not NULL and no errors
-** occur, then sqlite3_exec() sets the pointer in its 5th parameter to
-** NULL before returning.
-**
-** ^If an sqlite3_exec() callback returns non-zero, the sqlite3_exec()
-** routine returns SQLITE_ABORT without invoking the callback again and
-** without running any subsequent SQL statements.
-**
-** ^The 2nd argument to the sqlite3_exec() callback function is the
-** number of columns in the result.  ^The 3rd argument to the sqlite3_exec()
-** callback is an array of pointers to strings obtained as if from
-** [sqlite3_column_text()], one for each column.  ^If an element of a
-** result row is NULL then the corresponding string pointer for the
-** sqlite3_exec() callback is a NULL pointer.  ^The 4th argument to the
-** sqlite3_exec() callback is an array of pointers to strings where each
-** entry represents the name of corresponding result column as obtained
-** from [sqlite3_column_name()].
-**
-** ^If the 2nd parameter to sqlite3_exec() is a NULL pointer, a pointer
-** to an empty string, or a pointer that contains only whitespace and/or 
-** SQL comments, then no SQL statements are evaluated and the database
-** is not changed.
-**
-** Restrictions:
-**
-** <ul>
-** <li> The application must insure that the 1st parameter to sqlite3_exec()
-**      is a valid and open [database connection].
-** <li> The application must not close [database connection] specified by
-**      the 1st parameter to sqlite3_exec() while sqlite3_exec() is running.
-** <li> The application must not modify the SQL statement text passed into
-**      the 2nd parameter of sqlite3_exec() while sqlite3_exec() is running.
-** </ul>
-*/
-SQLITE_API int sqlite3_exec(
-  sqlite3*,                                  /* An open database */
-  const char *sql,                           /* SQL to be evaluated */
-  int (*callback)(void*,int,char**,char**),  /* Callback function */
-  void *,                                    /* 1st argument to callback */
-  char **errmsg                              /* Error msg written here */
-);
-
-/*
-** CAPI3REF: Result Codes
-** KEYWORDS: SQLITE_OK {error code} {error codes}
-** KEYWORDS: {result code} {result codes}
-**
-** Many SQLite functions return an integer result code from the set shown
-** here in order to indicates success or failure.
-**
-** New error codes may be added in future versions of SQLite.
-**
-** See also: [SQLITE_IOERR_READ | extended result codes]
-*/
-#define SQLITE_OK           0   /* Successful result */
-/* beginning-of-error-codes */
-#define SQLITE_ERROR        1   /* SQL error or missing database */
-#define SQLITE_INTERNAL     2   /* Internal logic error in SQLite */
-#define SQLITE_PERM         3   /* Access permission denied */
-#define SQLITE_ABORT        4   /* Callback routine requested an abort */
-#define SQLITE_BUSY         5   /* The database file is locked */
-#define SQLITE_LOCKED       6   /* A table in the database is locked */
-#define SQLITE_NOMEM        7   /* A malloc() failed */
-#define SQLITE_READONLY     8   /* Attempt to write a readonly database */
-#define SQLITE_INTERRUPT    9   /* Operation terminated by sqlite3_interrupt()*/
-#define SQLITE_IOERR       10   /* Some kind of disk I/O error occurred */
-#define SQLITE_CORRUPT     11   /* The database disk image is malformed */
-#define SQLITE_NOTFOUND    12   /* NOT USED. Table or record not found */
-#define SQLITE_FULL        13   /* Insertion failed because database is full */
-#define SQLITE_CANTOPEN    14   /* Unable to open the database file */
-#define SQLITE_PROTOCOL    15   /* NOT USED. Database lock protocol error */
-#define SQLITE_EMPTY       16   /* Database is empty */
-#define SQLITE_SCHEMA      17   /* The database schema changed */
-#define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
-#define SQLITE_CONSTRAINT  19   /* Abort due to constraint violation */
-#define SQLITE_MISMATCH    20   /* Data type mismatch */
-#define SQLITE_MISUSE      21   /* Library used incorrectly */
-#define SQLITE_NOLFS       22   /* Uses OS features not supported on host */
-#define SQLITE_AUTH        23   /* Authorization denied */
-#define SQLITE_FORMAT      24   /* Auxiliary database format error */
-#define SQLITE_RANGE       25   /* 2nd parameter to sqlite3_bind out of range */
-#define SQLITE_NOTADB      26   /* File opened that is not a database file */
-#define SQLITE_ROW         100  /* sqlite3_step() has another row ready */
-#define SQLITE_DONE        101  /* sqlite3_step() has finished executing */
-/* end-of-error-codes */
-
-/*
-** CAPI3REF: Extended Result Codes
-** KEYWORDS: {extended error code} {extended error codes}
-** KEYWORDS: {extended result code} {extended result codes}
-**
-** In its default configuration, SQLite API routines return one of 26 integer
-** [SQLITE_OK | result codes].  However, experience has shown that many of
-** these result codes are too coarse-grained.  They do not provide as
-** much information about problems as programmers might like.  In an effort to
-** address this, newer versions of SQLite (version 3.3.8 and later) include
-** support for additional result codes that provide more detailed information
-** about errors. The extended result codes are enabled or disabled
-** on a per database connection basis using the
-** [sqlite3_extended_result_codes()] API.
-**
-** Some of the available extended result codes are listed here.
-** One may expect the number of extended result codes will be expand
-** over time.  Software that uses extended result codes should expect
-** to see new result codes in future releases of SQLite.
-**
-** The SQLITE_OK result code will never be extended.  It will always
-** be exactly zero.
-*/
-#define SQLITE_IOERR_READ              (SQLITE_IOERR | (1<<8))
-#define SQLITE_IOERR_SHORT_READ        (SQLITE_IOERR | (2<<8))
-#define SQLITE_IOERR_WRITE             (SQLITE_IOERR | (3<<8))
-#define SQLITE_IOERR_FSYNC             (SQLITE_IOERR | (4<<8))
-#define SQLITE_IOERR_DIR_FSYNC         (SQLITE_IOERR | (5<<8))
-#define SQLITE_IOERR_TRUNCATE          (SQLITE_IOERR | (6<<8))
-#define SQLITE_IOERR_FSTAT             (SQLITE_IOERR | (7<<8))
-#define SQLITE_IOERR_UNLOCK            (SQLITE_IOERR | (8<<8))
-#define SQLITE_IOERR_RDLOCK            (SQLITE_IOERR | (9<<8))
-#define SQLITE_IOERR_DELETE            (SQLITE_IOERR | (10<<8))
-#define SQLITE_IOERR_BLOCKED           (SQLITE_IOERR | (11<<8))
-#define SQLITE_IOERR_NOMEM             (SQLITE_IOERR | (12<<8))
-#define SQLITE_IOERR_ACCESS            (SQLITE_IOERR | (13<<8))
-#define SQLITE_IOERR_CHECKRESERVEDLOCK (SQLITE_IOERR | (14<<8))
-#define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
-#define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
-#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
-#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED | (1<<8) )
-
-/*
-** CAPI3REF: Flags For File Open Operations
-**
-** These bit values are intended for use in the
-** 3rd parameter to the [sqlite3_open_v2()] interface and
-** in the 4th parameter to the xOpen method of the
-** [sqlite3_vfs] object.
-*/
-#define SQLITE_OPEN_READONLY         0x00000001  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_READWRITE        0x00000002  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
-#define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
-#define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
-#define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
-#define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
-#define SQLITE_OPEN_MAIN_JOURNAL     0x00000800  /* VFS only */
-#define SQLITE_OPEN_TEMP_JOURNAL     0x00001000  /* VFS only */
-#define SQLITE_OPEN_SUBJOURNAL       0x00002000  /* VFS only */
-#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */
-#define SQLITE_OPEN_NOMUTEX          0x00008000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_FULLMUTEX        0x00010000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */
-
-/*
-** CAPI3REF: Device Characteristics
-**
-** The xDeviceCapabilities method of the [sqlite3_io_methods]
-** object returns an integer which is a vector of the these
-** bit values expressing I/O characteristics of the mass storage
-** device that holds the file that the [sqlite3_io_methods]
-** refers to.
-**
-** The SQLITE_IOCAP_ATOMIC property means that all writes of
-** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
-** mean that writes of blocks that are nnn bytes in size and
-** are aligned to an address which is an integer multiple of
-** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
-** that when data is appended to a file, the data is appended
-** first then the size of the file is extended, never the other
-** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
-** information is written to disk in the same order as calls
-** to xWrite().
-*/
-#define SQLITE_IOCAP_ATOMIC          0x00000001
-#define SQLITE_IOCAP_ATOMIC512       0x00000002
-#define SQLITE_IOCAP_ATOMIC1K        0x00000004
-#define SQLITE_IOCAP_ATOMIC2K        0x00000008
-#define SQLITE_IOCAP_ATOMIC4K        0x00000010
-#define SQLITE_IOCAP_ATOMIC8K        0x00000020
-#define SQLITE_IOCAP_ATOMIC16K       0x00000040
-#define SQLITE_IOCAP_ATOMIC32K       0x00000080
-#define SQLITE_IOCAP_ATOMIC64K       0x00000100
-#define SQLITE_IOCAP_SAFE_APPEND     0x00000200
-#define SQLITE_IOCAP_SEQUENTIAL      0x00000400
-
-/*
-** CAPI3REF: File Locking Levels
-**
-** SQLite uses one of these integer values as the second
-** argument to calls it makes to the xLock() and xUnlock() methods
-** of an [sqlite3_io_methods] object.
-*/
-#define SQLITE_LOCK_NONE          0
-#define SQLITE_LOCK_SHARED        1
-#define SQLITE_LOCK_RESERVED      2
-#define SQLITE_LOCK_PENDING       3
-#define SQLITE_LOCK_EXCLUSIVE     4
-
-/*
-** CAPI3REF: Synchronization Type Flags
-**
-** When SQLite invokes the xSync() method of an
-** [sqlite3_io_methods] object it uses a combination of
-** these integer values as the second argument.
-**
-** When the SQLITE_SYNC_DATAONLY flag is used, it means that the
-** sync operation only needs to flush data to mass storage.  Inode
-** information need not be flushed. If the lower four bits of the flag
-** equal SQLITE_SYNC_NORMAL, that means to use normal fsync() semantics.
-** If the lower four bits equal SQLITE_SYNC_FULL, that means
-** to use Mac OS X style fullsync instead of fsync().
-*/
-#define SQLITE_SYNC_NORMAL        0x00002
-#define SQLITE_SYNC_FULL          0x00003
-#define SQLITE_SYNC_DATAONLY      0x00010
-
-/*
-** CAPI3REF: OS Interface Open File Handle
-**
-** An [sqlite3_file] object represents an open file in the 
-** [sqlite3_vfs | OS interface layer].  Individual OS interface
-** implementations will
-** want to subclass this object by appending additional fields
-** for their own use.  The pMethods entry is a pointer to an
-** [sqlite3_io_methods] object that defines methods for performing
-** I/O operations on the open file.
-*/
-typedef struct sqlite3_file sqlite3_file;
-struct sqlite3_file {
-  const struct sqlite3_io_methods *pMethods;  /* Methods for an open file */
-};
-
-/*
-** CAPI3REF: OS Interface File Virtual Methods Object
-**
-** Every file opened by the [sqlite3_vfs] xOpen method populates an
-** [sqlite3_file] object (or, more commonly, a subclass of the
-** [sqlite3_file] object) with a pointer to an instance of this object.
-** This object defines the methods used to perform various operations
-** against the open file represented by the [sqlite3_file] object.
-**
-** If the xOpen method sets the sqlite3_file.pMethods element 
-** to a non-NULL pointer, then the sqlite3_io_methods.xClose method
-** may be invoked even if the xOpen reported that it failed.  The
-** only way to prevent a call to xClose following a failed xOpen
-** is for the xOpen to set the sqlite3_file.pMethods element to NULL.
-**
-** The flags argument to xSync may be one of [SQLITE_SYNC_NORMAL] or
-** [SQLITE_SYNC_FULL].  The first choice is the normal fsync().
-** The second choice is a Mac OS X style fullsync.  The [SQLITE_SYNC_DATAONLY]
-** flag may be ORed in to indicate that only the data of the file
-** and not its inode needs to be synced.
-**
-** The integer values to xLock() and xUnlock() are one of
-** <ul>
-** <li> [SQLITE_LOCK_NONE],
-** <li> [SQLITE_LOCK_SHARED],
-** <li> [SQLITE_LOCK_RESERVED],
-** <li> [SQLITE_LOCK_PENDING], or
-** <li> [SQLITE_LOCK_EXCLUSIVE].
-** </ul>
-** xLock() increases the lock. xUnlock() decreases the lock.
-** The xCheckReservedLock() method checks whether any database connection,
-** either in this process or in some other process, is holding a RESERVED,
-** PENDING, or EXCLUSIVE lock on the file.  It returns true
-** if such a lock exists and false otherwise.
-**
-** The xFileControl() method is a generic interface that allows custom
-** VFS implementations to directly control an open file using the
-** [sqlite3_file_control()] interface.  The second "op" argument is an
-** integer opcode.  The third argument is a generic pointer intended to
-** point to a structure that may contain arguments or space in which to
-** write return values.  Potential uses for xFileControl() might be
-** functions to enable blocking locks with timeouts, to change the
-** locking strategy (for example to use dot-file locks), to inquire
-** about the status of a lock, or to break stale locks.  The SQLite
-** core reserves all opcodes less than 100 for its own use.
-** A [SQLITE_FCNTL_LOCKSTATE | list of opcodes] less than 100 is available.
-** Applications that define a custom xFileControl method should use opcodes
-** greater than 100 to avoid conflicts.
-**
-** The xSectorSize() method returns the sector size of the
-** device that underlies the file.  The sector size is the
-** minimum write that can be performed without disturbing
-** other bytes in the file.  The xDeviceCharacteristics()
-** method returns a bit vector describing behaviors of the
-** underlying device:
-**
-** <ul>
-** <li> [SQLITE_IOCAP_ATOMIC]
-** <li> [SQLITE_IOCAP_ATOMIC512]
-** <li> [SQLITE_IOCAP_ATOMIC1K]
-** <li> [SQLITE_IOCAP_ATOMIC2K]
-** <li> [SQLITE_IOCAP_ATOMIC4K]
-** <li> [SQLITE_IOCAP_ATOMIC8K]
-** <li> [SQLITE_IOCAP_ATOMIC16K]
-** <li> [SQLITE_IOCAP_ATOMIC32K]
-** <li> [SQLITE_IOCAP_ATOMIC64K]
-** <li> [SQLITE_IOCAP_SAFE_APPEND]
-** <li> [SQLITE_IOCAP_SEQUENTIAL]
-** </ul>
-**
-** The SQLITE_IOCAP_ATOMIC property means that all writes of
-** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
-** mean that writes of blocks that are nnn bytes in size and
-** are aligned to an address which is an integer multiple of
-** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
-** that when data is appended to a file, the data is appended
-** first then the size of the file is extended, never the other
-** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
-** information is written to disk in the same order as calls
-** to xWrite().
-**
-** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
-** in the unread portions of the buffer with zeros.  A VFS that
-** fails to zero-fill short reads might seem to work.  However,
-** failure to zero-fill short reads will eventually lead to
-** database corruption.
-*/
-typedef struct sqlite3_io_methods sqlite3_io_methods;
-struct sqlite3_io_methods {
-  int iVersion;
-  int (*xClose)(sqlite3_file*);
-  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
-  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
-  int (*xTruncate)(sqlite3_file*, sqlite3_int64 size);
-  int (*xSync)(sqlite3_file*, int flags);
-  int (*xFileSize)(sqlite3_file*, sqlite3_int64 *pSize);
-  int (*xLock)(sqlite3_file*, int);
-  int (*xUnlock)(sqlite3_file*, int);
-  int (*xCheckReservedLock)(sqlite3_file*, int *pResOut);
-  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
-  int (*xSectorSize)(sqlite3_file*);
-  int (*xDeviceCharacteristics)(sqlite3_file*);
-  /* Additional methods may be added in future releases */
-};
-
-/*
-** CAPI3REF: Standard File Control Opcodes
-**
-** These integer constants are opcodes for the xFileControl method
-** of the [sqlite3_io_methods] object and for the [sqlite3_file_control()]
-** interface.
-**
-** The [SQLITE_FCNTL_LOCKSTATE] opcode is used for debugging.  This
-** opcode causes the xFileControl method to write the current state of
-** the lock (one of [SQLITE_LOCK_NONE], [SQLITE_LOCK_SHARED],
-** [SQLITE_LOCK_RESERVED], [SQLITE_LOCK_PENDING], or [SQLITE_LOCK_EXCLUSIVE])
-** into an integer that the pArg argument points to. This capability
-** is used during testing and only needs to be supported when SQLITE_TEST
-** is defined.
-*/
-#define SQLITE_FCNTL_LOCKSTATE        1
-#define SQLITE_GET_LOCKPROXYFILE      2
-#define SQLITE_SET_LOCKPROXYFILE      3
-#define SQLITE_LAST_ERRNO             4
-
-/*
-** CAPI3REF: Mutex Handle
-**
-** The mutex module within SQLite defines [sqlite3_mutex] to be an
-** abstract type for a mutex object.  The SQLite core never looks
-** at the internal representation of an [sqlite3_mutex].  It only
-** deals with pointers to the [sqlite3_mutex] object.
-**
-** Mutexes are created using [sqlite3_mutex_alloc()].
-*/
-typedef struct sqlite3_mutex sqlite3_mutex;
-
-/*
-** CAPI3REF: OS Interface Object
-**
-** An instance of the sqlite3_vfs object defines the interface between
-** the SQLite core and the underlying operating system.  The "vfs"
-** in the name of the object stands for "virtual file system".
-**
-** The value of the iVersion field is initially 1 but may be larger in
-** future versions of SQLite.  Additional fields may be appended to this
-** object when the iVersion value is increased.  Note that the structure
-** of the sqlite3_vfs object changes in the transaction between
-** SQLite version 3.5.9 and 3.6.0 and yet the iVersion field was not
-** modified.
-**
-** The szOsFile field is the size of the subclassed [sqlite3_file]
-** structure used by this VFS.  mxPathname is the maximum length of
-** a pathname in this VFS.
-**
-** Registered sqlite3_vfs objects are kept on a linked list formed by
-** the pNext pointer.  The [sqlite3_vfs_register()]
-** and [sqlite3_vfs_unregister()] interfaces manage this list
-** in a thread-safe way.  The [sqlite3_vfs_find()] interface
-** searches the list.  Neither the application code nor the VFS
-** implementation should use the pNext pointer.
-**
-** The pNext field is the only field in the sqlite3_vfs
-** structure that SQLite will ever modify.  SQLite will only access
-** or modify this field while holding a particular static mutex.
-** The application should never modify anything within the sqlite3_vfs
-** object once the object has been registered.
-**
-** The zName field holds the name of the VFS module.  The name must
-** be unique across all VFS modules.
-**
-** SQLite will guarantee that the zFilename parameter to xOpen
-** is either a NULL pointer or string obtained
-** from xFullPathname().  SQLite further guarantees that
-** the string will be valid and unchanged until xClose() is
-** called. Because of the previous sentence,
-** the [sqlite3_file] can safely store a pointer to the
-** filename if it needs to remember the filename for some reason.
-** If the zFilename parameter is xOpen is a NULL pointer then xOpen
-** must invent its own temporary name for the file.  Whenever the 
-** xFilename parameter is NULL it will also be the case that the
-** flags parameter will include [SQLITE_OPEN_DELETEONCLOSE].
-**
-** The flags argument to xOpen() includes all bits set in
-** the flags argument to [sqlite3_open_v2()].  Or if [sqlite3_open()]
-** or [sqlite3_open16()] is used, then flags includes at least
-** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]. 
-** If xOpen() opens a file read-only then it sets *pOutFlags to
-** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be set.
-**
-** SQLite will also add one of the following flags to the xOpen()
-** call, depending on the object being opened:
-**
-** <ul>
-** <li>  [SQLITE_OPEN_MAIN_DB]
-** <li>  [SQLITE_OPEN_MAIN_JOURNAL]
-** <li>  [SQLITE_OPEN_TEMP_DB]
-** <li>  [SQLITE_OPEN_TEMP_JOURNAL]
-** <li>  [SQLITE_OPEN_TRANSIENT_DB]
-** <li>  [SQLITE_OPEN_SUBJOURNAL]
-** <li>  [SQLITE_OPEN_MASTER_JOURNAL]
-** </ul>
-**
-** The file I/O implementation can use the object type flags to
-** change the way it deals with files.  For example, an application
-** that does not care about crash recovery or rollback might make
-** the open of a journal file a no-op.  Writes to this journal would
-** also be no-ops, and any attempt to read the journal would return
-** SQLITE_IOERR.  Or the implementation might recognize that a database
-** file will be doing page-aligned sector reads and writes in a random
-** order and set up its I/O subsystem accordingly.
-**
-** SQLite might also add one of the following flags to the xOpen method:
-**
-** <ul>
-** <li> [SQLITE_OPEN_DELETEONCLOSE]
-** <li> [SQLITE_OPEN_EXCLUSIVE]
-** </ul>
-**
-** The [SQLITE_OPEN_DELETEONCLOSE] flag means the file should be
-** deleted when it is closed.  The [SQLITE_OPEN_DELETEONCLOSE]
-** will be set for TEMP  databases, journals and for subjournals.
-**
-** The [SQLITE_OPEN_EXCLUSIVE] flag is always used in conjunction
-** with the [SQLITE_OPEN_CREATE] flag, which are both directly
-** analogous to the O_EXCL and O_CREAT flags of the POSIX open()
-** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the 
-** SQLITE_OPEN_CREATE, is used to indicate that file should always
-** be created, and that it is an error if it already exists.
-** It is <i>not</i> used to indicate the file should be opened 
-** for exclusive access.
-**
-** At least szOsFile bytes of memory are allocated by SQLite
-** to hold the  [sqlite3_file] structure passed as the third
-** argument to xOpen.  The xOpen method does not have to
-** allocate the structure; it should just fill it in.  Note that
-** the xOpen method must set the sqlite3_file.pMethods to either
-** a valid [sqlite3_io_methods] object or to NULL.  xOpen must do
-** this even if the open fails.  SQLite expects that the sqlite3_file.pMethods
-** element will be valid after xOpen returns regardless of the success
-** or failure of the xOpen call.
-**
-** The flags argument to xAccess() may be [SQLITE_ACCESS_EXISTS]
-** to test for the existence of a file, or [SQLITE_ACCESS_READWRITE] to
-** test whether a file is readable and writable, or [SQLITE_ACCESS_READ]
-** to test whether a file is at least readable.   The file can be a
-** directory.
-**
-** SQLite will always allocate at least mxPathname+1 bytes for the
-** output buffer xFullPathname.  The exact size of the output buffer
-** is also passed as a parameter to both  methods. If the output buffer
-** is not large enough, [SQLITE_CANTOPEN] should be returned. Since this is
-** handled as a fatal error by SQLite, vfs implementations should endeavor
-** to prevent this by setting mxPathname to a sufficiently large value.
-**
-** The xRandomness(), xSleep(), and xCurrentTime() interfaces
-** are not strictly a part of the filesystem, but they are
-** included in the VFS structure for completeness.
-** The xRandomness() function attempts to return nBytes bytes
-** of good-quality randomness into zOut.  The return value is
-** the actual number of bytes of randomness obtained.
-** The xSleep() method causes the calling thread to sleep for at
-** least the number of microseconds given.  The xCurrentTime()
-** method returns a Julian Day Number for the current date and time.
-**
-*/
-typedef struct sqlite3_vfs sqlite3_vfs;
-struct sqlite3_vfs {
-  int iVersion;            /* Structure version number */
-  int szOsFile;            /* Size of subclassed sqlite3_file */
-  int mxPathname;          /* Maximum file pathname length */
-  sqlite3_vfs *pNext;      /* Next registered VFS */
-  const char *zName;       /* Name of this virtual file system */
-  void *pAppData;          /* Pointer to application-specific data */
-  int (*xOpen)(sqlite3_vfs*, const char *zName, sqlite3_file*,
-               int flags, int *pOutFlags);
-  int (*xDelete)(sqlite3_vfs*, const char *zName, int syncDir);
-  int (*xAccess)(sqlite3_vfs*, const char *zName, int flags, int *pResOut);
-  int (*xFullPathname)(sqlite3_vfs*, const char *zName, int nOut, char *zOut);
-  void *(*xDlOpen)(sqlite3_vfs*, const char *zFilename);
-  void (*xDlError)(sqlite3_vfs*, int nByte, char *zErrMsg);
-  void (*(*xDlSym)(sqlite3_vfs*,void*, const char *zSymbol))(void);
-  void (*xDlClose)(sqlite3_vfs*, void*);
-  int (*xRandomness)(sqlite3_vfs*, int nByte, char *zOut);
-  int (*xSleep)(sqlite3_vfs*, int microseconds);
-  int (*xCurrentTime)(sqlite3_vfs*, double*);
-  int (*xGetLastError)(sqlite3_vfs*, int, char *);
-  /* New fields may be appended in figure versions.  The iVersion
-  ** value will increment whenever this happens. */
-};
-
-/*
-** CAPI3REF: Flags for the xAccess VFS method
-**
-** These integer constants can be used as the third parameter to
-** the xAccess method of an [sqlite3_vfs] object.  They determine
-** what kind of permissions the xAccess method is looking for.
-** With SQLITE_ACCESS_EXISTS, the xAccess method
-** simply checks whether the file exists.
-** With SQLITE_ACCESS_READWRITE, the xAccess method
-** checks whether the file is both readable and writable.
-** With SQLITE_ACCESS_READ, the xAccess method
-** checks whether the file is readable.
-*/
-#define SQLITE_ACCESS_EXISTS    0
-#define SQLITE_ACCESS_READWRITE 1
-#define SQLITE_ACCESS_READ      2
-
-/*
-** CAPI3REF: Initialize The SQLite Library
-**
-** ^The sqlite3_initialize() routine initializes the
-** SQLite library.  ^The sqlite3_shutdown() routine
-** deallocates any resources that were allocated by sqlite3_initialize().
-** These routines are designed to aid in process initialization and
-** shutdown on embedded systems.  Workstation applications using
-** SQLite normally do not need to invoke either of these routines.
-**
-** A call to sqlite3_initialize() is an "effective" call if it is
-** the first time sqlite3_initialize() is invoked during the lifetime of
-** the process, or if it is the first time sqlite3_initialize() is invoked
-** following a call to sqlite3_shutdown().  ^(Only an effective call
-** of sqlite3_initialize() does any initialization.  All other calls
-** are harmless no-ops.)^
-**
-** A call to sqlite3_shutdown() is an "effective" call if it is the first
-** call to sqlite3_shutdown() since the last sqlite3_initialize().  ^(Only
-** an effective call to sqlite3_shutdown() does any deinitialization.
-** All other valid calls to sqlite3_shutdown() are harmless no-ops.)^
-**
-** The sqlite3_initialize() interface is threadsafe, but sqlite3_shutdown()
-** is not.  The sqlite3_shutdown() interface must only be called from a
-** single thread.  All open [database connections] must be closed and all
-** other SQLite resources must be deallocated prior to invoking
-** sqlite3_shutdown().
-**
-** Among other things, ^sqlite3_initialize() will invoke
-** sqlite3_os_init().  Similarly, ^sqlite3_shutdown()
-** will invoke sqlite3_os_end().
-**
-** ^The sqlite3_initialize() routine returns [SQLITE_OK] on success.
-** ^If for some reason, sqlite3_initialize() is unable to initialize
-** the library (perhaps it is unable to allocate a needed resource such
-** as a mutex) it returns an [error code] other than [SQLITE_OK].
-**
-** ^The sqlite3_initialize() routine is called internally by many other
-** SQLite interfaces so that an application usually does not need to
-** invoke sqlite3_initialize() directly.  For example, [sqlite3_open()]
-** calls sqlite3_initialize() so the SQLite library will be automatically
-** initialized when [sqlite3_open()] is called if it has not be initialized
-** already.  ^However, if SQLite is compiled with the [SQLITE_OMIT_AUTOINIT]
-** compile-time option, then the automatic calls to sqlite3_initialize()
-** are omitted and the application must call sqlite3_initialize() directly
-** prior to using any other SQLite interface.  For maximum portability,
-** it is recommended that applications always invoke sqlite3_initialize()
-** directly prior to using any other SQLite interface.  Future releases
-** of SQLite may require this.  In other words, the behavior exhibited
-** when SQLite is compiled with [SQLITE_OMIT_AUTOINIT] might become the
-** default behavior in some future release of SQLite.
-**
-** The sqlite3_os_init() routine does operating-system specific
-** initialization of the SQLite library.  The sqlite3_os_end()
-** routine undoes the effect of sqlite3_os_init().  Typical tasks
-** performed by these routines include allocation or deallocation
-** of static resources, initialization of global variables,
-** setting up a default [sqlite3_vfs] module, or setting up
-** a default configuration using [sqlite3_config()].
-**
-** The application should never invoke either sqlite3_os_init()
-** or sqlite3_os_end() directly.  The application should only invoke
-** sqlite3_initialize() and sqlite3_shutdown().  The sqlite3_os_init()
-** interface is called automatically by sqlite3_initialize() and
-** sqlite3_os_end() is called by sqlite3_shutdown().  Appropriate
-** implementations for sqlite3_os_init() and sqlite3_os_end()
-** are built into SQLite when it is compiled for Unix, Windows, or OS/2.
-** When [custom builds | built for other platforms]
-** (using the [SQLITE_OS_OTHER=1] compile-time
-** option) the application must supply a suitable implementation for
-** sqlite3_os_init() and sqlite3_os_end().  An application-supplied
-** implementation of sqlite3_os_init() or sqlite3_os_end()
-** must return [SQLITE_OK] on success and some other [error code] upon
-** failure.
-*/
-SQLITE_API int sqlite3_initialize(void);
-SQLITE_API int sqlite3_shutdown(void);
-SQLITE_API int sqlite3_os_init(void);
-SQLITE_API int sqlite3_os_end(void);
-
-/*
-** CAPI3REF: Configuring The SQLite Library
-**
-** The sqlite3_config() interface is used to make global configuration
-** changes to SQLite in order to tune SQLite to the specific needs of
-** the application.  The default configuration is recommended for most
-** applications and so this routine is usually not necessary.  It is
-** provided to support rare applications with unusual needs.
-**
-** The sqlite3_config() interface is not threadsafe.  The application
-** must insure that no other SQLite interfaces are invoked by other
-** threads while sqlite3_config() is running.  Furthermore, sqlite3_config()
-** may only be invoked prior to library initialization using
-** [sqlite3_initialize()] or after shutdown by [sqlite3_shutdown()].
-** ^If sqlite3_config() is called after [sqlite3_initialize()] and before
-** [sqlite3_shutdown()] then it will return SQLITE_MISUSE.
-** Note, however, that ^sqlite3_config() can be called as part of the
-** implementation of an application-defined [sqlite3_os_init()].
-**
-** The first argument to sqlite3_config() is an integer
-** [SQLITE_CONFIG_SINGLETHREAD | configuration option] that determines
-** what property of SQLite is to be configured.  Subsequent arguments
-** vary depending on the [SQLITE_CONFIG_SINGLETHREAD | configuration option]
-** in the first argument.
-**
-** ^When a configuration option is set, sqlite3_config() returns [SQLITE_OK].
-** ^If the option is unknown or SQLite is unable to set the option
-** then this routine returns a non-zero [error code].
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_config(int, ...);
-
-/*
-** CAPI3REF: Configure database connections
-** EXPERIMENTAL
-**
-** The sqlite3_db_config() interface is used to make configuration
-** changes to a [database connection].  The interface is similar to
-** [sqlite3_config()] except that the changes apply to a single
-** [database connection] (specified in the first argument).  The
-** sqlite3_db_config() interface should only be used immediately after
-** the database connection is created using [sqlite3_open()],
-** [sqlite3_open16()], or [sqlite3_open_v2()].  
-**
-** The second argument to sqlite3_db_config(D,V,...)  is the
-** configuration verb - an integer code that indicates what
-** aspect of the [database connection] is being configured.
-** The only choice for this value is [SQLITE_DBCONFIG_LOOKASIDE].
-** New verbs are likely to be added in future releases of SQLite.
-** Additional arguments depend on the verb.
-**
-** ^Calls to sqlite3_db_config() return SQLITE_OK if and only if
-** the call is considered successful.
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_config(sqlite3*, int op, ...);
-
-/*
-** CAPI3REF: Memory Allocation Routines
-** EXPERIMENTAL
-**
-** An instance of this object defines the interface between SQLite
-** and low-level memory allocation routines.
-**
-** This object is used in only one place in the SQLite interface.
-** A pointer to an instance of this object is the argument to
-** [sqlite3_config()] when the configuration option is
-** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].  
-** By creating an instance of this object
-** and passing it to [sqlite3_config]([SQLITE_CONFIG_MALLOC])
-** during configuration, an application can specify an alternative
-** memory allocation subsystem for SQLite to use for all of its
-** dynamic memory needs.
-**
-** Note that SQLite comes with several [built-in memory allocators]
-** that are perfectly adequate for the overwhelming majority of applications
-** and that this object is only useful to a tiny minority of applications
-** with specialized memory allocation requirements.  This object is
-** also used during testing of SQLite in order to specify an alternative
-** memory allocator that simulates memory out-of-memory conditions in
-** order to verify that SQLite recovers gracefully from such
-** conditions.
-**
-** The xMalloc and xFree methods must work like the
-** malloc() and free() functions from the standard C library.
-** The xRealloc method must work like realloc() from the standard C library
-** with the exception that if the second argument to xRealloc is zero,
-** xRealloc must be a no-op - it must not perform any allocation or
-** deallocation.  ^SQLite guarantees that the second argument to
-** xRealloc is always a value returned by a prior call to xRoundup.
-** And so in cases where xRoundup always returns a positive number,
-** xRealloc can perform exactly as the standard library realloc() and
-** still be in compliance with this specification.
-**
-** xSize should return the allocated size of a memory allocation
-** previously obtained from xMalloc or xRealloc.  The allocated size
-** is always at least as big as the requested size but may be larger.
-**
-** The xRoundup method returns what would be the allocated size of
-** a memory allocation given a particular requested size.  Most memory
-** allocators round up memory allocations at least to the next multiple
-** of 8.  Some allocators round up to a larger multiple or to a power of 2.
-** Every memory allocation request coming in through [sqlite3_malloc()]
-** or [sqlite3_realloc()] first calls xRoundup.  If xRoundup returns 0, 
-** that causes the corresponding memory allocation to fail.
-**
-** The xInit method initializes the memory allocator.  (For example,
-** it might allocate any require mutexes or initialize internal data
-** structures.  The xShutdown method is invoked (indirectly) by
-** [sqlite3_shutdown()] and should deallocate any resources acquired
-** by xInit.  The pAppData pointer is used as the only parameter to
-** xInit and xShutdown.
-**
-** SQLite holds the [SQLITE_MUTEX_STATIC_MASTER] mutex when it invokes
-** the xInit method, so the xInit method need not be threadsafe.  The
-** xShutdown method is only called from [sqlite3_shutdown()] so it does
-** not need to be threadsafe either.  For all other methods, SQLite
-** holds the [SQLITE_MUTEX_STATIC_MEM] mutex as long as the
-** [SQLITE_CONFIG_MEMSTATUS] configuration option is turned on (which
-** it is by default) and so the methods are automatically serialized.
-** However, if [SQLITE_CONFIG_MEMSTATUS] is disabled, then the other
-** methods must be threadsafe or else make their own arrangements for
-** serialization.
-**
-** SQLite will never invoke xInit() more than once without an intervening
-** call to xShutdown().
-*/
-typedef struct sqlite3_mem_methods sqlite3_mem_methods;
-struct sqlite3_mem_methods {
-  void *(*xMalloc)(int);         /* Memory allocation function */
-  void (*xFree)(void*);          /* Free a prior allocation */
-  void *(*xRealloc)(void*,int);  /* Resize an allocation */
-  int (*xSize)(void*);           /* Return the size of an allocation */
-  int (*xRoundup)(int);          /* Round up request size to allocation size */
-  int (*xInit)(void*);           /* Initialize the memory allocator */
-  void (*xShutdown)(void*);      /* Deinitialize the memory allocator */
-  void *pAppData;                /* Argument to xInit() and xShutdown() */
-};
-
-/*
-** CAPI3REF: Configuration Options
-** EXPERIMENTAL
-**
-** These constants are the available integer configuration options that
-** can be passed as the first argument to the [sqlite3_config()] interface.
-**
-** New configuration options may be added in future releases of SQLite.
-** Existing configuration options might be discontinued.  Applications
-** should check the return code from [sqlite3_config()] to make sure that
-** the call worked.  The [sqlite3_config()] interface will return a
-** non-zero [error code] if a discontinued or unsupported configuration option
-** is invoked.
-**
-** <dl>
-** <dt>SQLITE_CONFIG_SINGLETHREAD</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Single-thread.  In other words, it disables
-** all mutexing and puts SQLite into a mode where it can only be used
-** by a single thread.   ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to change the [threading mode] from its default
-** value of Single-thread and so [sqlite3_config()] will return 
-** [SQLITE_ERROR] if called with the SQLITE_CONFIG_SINGLETHREAD
-** configuration option.</dd>
-**
-** <dt>SQLITE_CONFIG_MULTITHREAD</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Multi-thread.  In other words, it disables
-** mutexing on [database connection] and [prepared statement] objects.
-** The application is responsible for serializing access to
-** [database connections] and [prepared statements].  But other mutexes
-** are enabled so that SQLite will be safe to use in a multi-threaded
-** environment as long as no two threads attempt to use the same
-** [database connection] at the same time.  ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to set the Multi-thread [threading mode] and
-** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
-** SQLITE_CONFIG_MULTITHREAD configuration option.</dd>
-**
-** <dt>SQLITE_CONFIG_SERIALIZED</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Serialized. In other words, this option enables
-** all mutexes including the recursive
-** mutexes on [database connection] and [prepared statement] objects.
-** In this mode (which is the default when SQLite is compiled with
-** [SQLITE_THREADSAFE=1]) the SQLite library will itself serialize access
-** to [database connections] and [prepared statements] so that the
-** application is free to use the same [database connection] or the
-** same [prepared statement] in different threads at the same time.
-** ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to set the Serialized [threading mode] and
-** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
-** SQLITE_CONFIG_SERIALIZED configuration option.</dd>
-**
-** <dt>SQLITE_CONFIG_MALLOC</dt>
-** <dd> ^(This option takes a single argument which is a pointer to an
-** instance of the [sqlite3_mem_methods] structure.  The argument specifies
-** alternative low-level memory allocation routines to be used in place of
-** the memory allocation routines built into SQLite.)^ ^SQLite makes
-** its own private copy of the content of the [sqlite3_mem_methods] structure
-** before the [sqlite3_config()] call returns.</dd>
-**
-** <dt>SQLITE_CONFIG_GETMALLOC</dt>
-** <dd> ^(This option takes a single argument which is a pointer to an
-** instance of the [sqlite3_mem_methods] structure.  The [sqlite3_mem_methods]
-** structure is filled with the currently defined memory allocation routines.)^
-** This option can be used to overload the default memory allocation
-** routines with a wrapper that simulations memory allocation failure or
-** tracks memory usage, for example. </dd>
-**
-** <dt>SQLITE_CONFIG_MEMSTATUS</dt>
-** <dd> ^This option takes single argument of type int, interpreted as a 
-** boolean, which enables or disables the collection of memory allocation 
-** statistics. ^(When memory allocation statistics are disabled, the 
-** following SQLite interfaces become non-operational:
-**   <ul>
-**   <li> [sqlite3_memory_used()]
-**   <li> [sqlite3_memory_highwater()]
-**   <li> [sqlite3_soft_heap_limit()]
-**   <li> [sqlite3_status()]
-**   </ul>)^
-** ^Memory allocation statistics are enabled by default unless SQLite is
-** compiled with [SQLITE_DEFAULT_MEMSTATUS]=0 in which case memory
-** allocation statistics are disabled by default.
-** </dd>
-**
-** <dt>SQLITE_CONFIG_SCRATCH</dt>
-** <dd> ^This option specifies a static memory buffer that SQLite can use for
-** scratch memory.  There are three arguments:  A pointer an 8-byte
-** aligned memory buffer from which the scrach allocations will be
-** drawn, the size of each scratch allocation (sz),
-** and the maximum number of scratch allocations (N).  The sz
-** argument must be a multiple of 16. The sz parameter should be a few bytes
-** larger than the actual scratch space required due to internal overhead.
-** The first argument must be a pointer to an 8-byte aligned buffer
-** of at least sz*N bytes of memory.
-** ^SQLite will use no more than one scratch buffer per thread.  So
-** N should be set to the expected maximum number of threads.  ^SQLite will
-** never require a scratch buffer that is more than 6 times the database
-** page size. ^If SQLite needs needs additional scratch memory beyond 
-** what is provided by this configuration option, then 
-** [sqlite3_malloc()] will be used to obtain the memory needed.</dd>
-**
-** <dt>SQLITE_CONFIG_PAGECACHE</dt>
-** <dd> ^This option specifies a static memory buffer that SQLite can use for
-** the database page cache with the default page cache implemenation.  
-** This configuration should not be used if an application-define page
-** cache implementation is loaded using the SQLITE_CONFIG_PCACHE option.
-** There are three arguments to this option: A pointer to 8-byte aligned
-** memory, the size of each page buffer (sz), and the number of pages (N).
-** The sz argument should be the size of the largest database page
-** (a power of two between 512 and 32768) plus a little extra for each
-** page header.  ^The page header size is 20 to 40 bytes depending on
-** the host architecture.  ^It is harmless, apart from the wasted memory,
-** to make sz a little too large.  The first
-** argument should point to an allocation of at least sz*N bytes of memory.
-** ^SQLite will use the memory provided by the first argument to satisfy its
-** memory needs for the first N pages that it adds to cache.  ^If additional
-** page cache memory is needed beyond what is provided by this option, then
-** SQLite goes to [sqlite3_malloc()] for the additional storage space.
-** ^The implementation might use one or more of the N buffers to hold 
-** memory accounting information. The pointer in the first argument must
-** be aligned to an 8-byte boundary or subsequent behavior of SQLite
-** will be undefined.</dd>
-**
-** <dt>SQLITE_CONFIG_HEAP</dt>
-** <dd> ^This option specifies a static memory buffer that SQLite will use
-** for all of its dynamic memory allocation needs beyond those provided
-** for by [SQLITE_CONFIG_SCRATCH] and [SQLITE_CONFIG_PAGECACHE].
-** There are three arguments: An 8-byte aligned pointer to the memory,
-** the number of bytes in the memory buffer, and the minimum allocation size.
-** ^If the first pointer (the memory pointer) is NULL, then SQLite reverts
-** to using its default memory allocator (the system malloc() implementation),
-** undoing any prior invocation of [SQLITE_CONFIG_MALLOC].  ^If the
-** memory pointer is not NULL and either [SQLITE_ENABLE_MEMSYS3] or
-** [SQLITE_ENABLE_MEMSYS5] are defined, then the alternative memory
-** allocator is engaged to handle all of SQLites memory allocation needs.
-** The first pointer (the memory pointer) must be aligned to an 8-byte
-** boundary or subsequent behavior of SQLite will be undefined.</dd>
-**
-** <dt>SQLITE_CONFIG_MUTEX</dt>
-** <dd> ^(This option takes a single argument which is a pointer to an
-** instance of the [sqlite3_mutex_methods] structure.  The argument specifies
-** alternative low-level mutex routines to be used in place
-** the mutex routines built into SQLite.)^  ^SQLite makes a copy of the
-** content of the [sqlite3_mutex_methods] structure before the call to
-** [sqlite3_config()] returns. ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** the entire mutexing subsystem is omitted from the build and hence calls to
-** [sqlite3_config()] with the SQLITE_CONFIG_MUTEX configuration option will
-** return [SQLITE_ERROR].</dd>
-**
-** <dt>SQLITE_CONFIG_GETMUTEX</dt>
-** <dd> ^(This option takes a single argument which is a pointer to an
-** instance of the [sqlite3_mutex_methods] structure.  The
-** [sqlite3_mutex_methods]
-** structure is filled with the currently defined mutex routines.)^
-** This option can be used to overload the default mutex allocation
-** routines with a wrapper used to track mutex usage for performance
-** profiling or testing, for example.   ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** the entire mutexing subsystem is omitted from the build and hence calls to
-** [sqlite3_config()] with the SQLITE_CONFIG_GETMUTEX configuration option will
-** return [SQLITE_ERROR].</dd>
-**
-** <dt>SQLITE_CONFIG_LOOKASIDE</dt>
-** <dd> ^(This option takes two arguments that determine the default
-** memory allocation for the lookaside memory allocator on each
-** [database connection].  The first argument is the
-** size of each lookaside buffer slot and the second is the number of
-** slots allocated to each database connection.)^  ^(This option sets the
-** <i>default</i> lookaside size. The [SQLITE_DBCONFIG_LOOKASIDE]
-** verb to [sqlite3_db_config()] can be used to change the lookaside
-** configuration on individual connections.)^ </dd>
-**
-** <dt>SQLITE_CONFIG_PCACHE</dt>
-** <dd> ^(This option takes a single argument which is a pointer to
-** an [sqlite3_pcache_methods] object.  This object specifies the interface
-** to a custom page cache implementation.)^  ^SQLite makes a copy of the
-** object and uses it for page cache memory allocations.</dd>
-**
-** <dt>SQLITE_CONFIG_GETPCACHE</dt>
-** <dd> ^(This option takes a single argument which is a pointer to an
-** [sqlite3_pcache_methods] object.  SQLite copies of the current
-** page cache implementation into that object.)^ </dd>
-**
-** </dl>
-*/
-#define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
-#define SQLITE_CONFIG_MULTITHREAD   2  /* nil */
-#define SQLITE_CONFIG_SERIALIZED    3  /* nil */
-#define SQLITE_CONFIG_MALLOC        4  /* sqlite3_mem_methods* */
-#define SQLITE_CONFIG_GETMALLOC     5  /* sqlite3_mem_methods* */
-#define SQLITE_CONFIG_SCRATCH       6  /* void*, int sz, int N */
-#define SQLITE_CONFIG_PAGECACHE     7  /* void*, int sz, int N */
-#define SQLITE_CONFIG_HEAP          8  /* void*, int nByte, int min */
-#define SQLITE_CONFIG_MEMSTATUS     9  /* boolean */
-#define SQLITE_CONFIG_MUTEX        10  /* sqlite3_mutex_methods* */
-#define SQLITE_CONFIG_GETMUTEX     11  /* sqlite3_mutex_methods* */
-/* previously SQLITE_CONFIG_CHUNKALLOC 12 which is now unused. */ 
-#define SQLITE_CONFIG_LOOKASIDE    13  /* int int */
-#define SQLITE_CONFIG_PCACHE       14  /* sqlite3_pcache_methods* */
-#define SQLITE_CONFIG_GETPCACHE    15  /* sqlite3_pcache_methods* */
-#define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
-
-/*
-** CAPI3REF: Configuration Options
-** EXPERIMENTAL
-**
-** These constants are the available integer configuration options that
-** can be passed as the second argument to the [sqlite3_db_config()] interface.
-**
-** New configuration options may be added in future releases of SQLite.
-** Existing configuration options might be discontinued.  Applications
-** should check the return code from [sqlite3_db_config()] to make sure that
-** the call worked.  ^The [sqlite3_db_config()] interface will return a
-** non-zero [error code] if a discontinued or unsupported configuration option
-** is invoked.
-**
-** <dl>
-** <dt>SQLITE_DBCONFIG_LOOKASIDE</dt>
-** <dd> ^This option takes three additional arguments that determine the 
-** [lookaside memory allocator] configuration for the [database connection].
-** ^The first argument (the third parameter to [sqlite3_db_config()] is a
-** pointer to an memory buffer to use for lookaside memory.
-** ^The first argument after the SQLITE_DBCONFIG_LOOKASIDE verb
-** may be NULL in which case SQLite will allocate the
-** lookaside buffer itself using [sqlite3_malloc()]. ^The second argument is the
-** size of each lookaside buffer slot.  ^The third argument is the number of
-** slots.  The size of the buffer in the first argument must be greater than
-** or equal to the product of the second and third arguments.  The buffer
-** must be aligned to an 8-byte boundary.  ^If the second argument to
-** SQLITE_DBCONFIG_LOOKASIDE is not a multiple of 8, it is internally
-** rounded down to the next smaller
-** multiple of 8.  See also: [SQLITE_CONFIG_LOOKASIDE]</dd>
-**
-** </dl>
-*/
-#define SQLITE_DBCONFIG_LOOKASIDE    1001  /* void* int int */
-
-
-/*
-** CAPI3REF: Enable Or Disable Extended Result Codes
-**
-** ^The sqlite3_extended_result_codes() routine enables or disables the
-** [extended result codes] feature of SQLite. ^The extended result
-** codes are disabled by default for historical compatibility.
-*/
-SQLITE_API int sqlite3_extended_result_codes(sqlite3*, int onoff);
-
-/*
-** CAPI3REF: Last Insert Rowid
-**
-** ^Each entry in an SQLite table has a unique 64-bit signed
-** integer key called the [ROWID | "rowid"]. ^The rowid is always available
-** as an undeclared column named ROWID, OID, or _ROWID_ as long as those
-** names are not also used by explicitly declared columns. ^If
-** the table has a column of type [INTEGER PRIMARY KEY] then that column
-** is another alias for the rowid.
-**
-** ^This routine returns the [rowid] of the most recent
-** successful [INSERT] into the database from the [database connection]
-** in the first argument.  ^If no successful [INSERT]s
-** have ever occurred on that database connection, zero is returned.
-**
-** ^(If an [INSERT] occurs within a trigger, then the [rowid] of the inserted
-** row is returned by this routine as long as the trigger is running.
-** But once the trigger terminates, the value returned by this routine
-** reverts to the last value inserted before the trigger fired.)^
-**
-** ^An [INSERT] that fails due to a constraint violation is not a
-** successful [INSERT] and does not change the value returned by this
-** routine.  ^Thus INSERT OR FAIL, INSERT OR IGNORE, INSERT OR ROLLBACK,
-** and INSERT OR ABORT make no changes to the return value of this
-** routine when their insertion fails.  ^(When INSERT OR REPLACE
-** encounters a constraint violation, it does not fail.  The
-** INSERT continues to completion after deleting rows that caused
-** the constraint problem so INSERT OR REPLACE will always change
-** the return value of this interface.)^
-**
-** ^For the purposes of this routine, an [INSERT] is considered to
-** be successful even if it is subsequently rolled back.
-**
-** This function is accessible to SQL statements via the
-** [last_insert_rowid() SQL function].
-**
-** If a separate thread performs a new [INSERT] on the same
-** database connection while the [sqlite3_last_insert_rowid()]
-** function is running and thus changes the last insert [rowid],
-** then the value returned by [sqlite3_last_insert_rowid()] is
-** unpredictable and might not equal either the old or the new
-** last insert [rowid].
-*/
-SQLITE_API sqlite3_int64 sqlite3_last_insert_rowid(sqlite3*);
-
-/*
-** CAPI3REF: Count The Number Of Rows Modified
-**
-** ^This function returns the number of database rows that were changed
-** or inserted or deleted by the most recently completed SQL statement
-** on the [database connection] specified by the first parameter.
-** ^(Only changes that are directly specified by the [INSERT], [UPDATE],
-** or [DELETE] statement are counted.  Auxiliary changes caused by
-** triggers or [foreign key actions] are not counted.)^ Use the
-** [sqlite3_total_changes()] function to find the total number of changes
-** including changes caused by triggers and foreign key actions.
-**
-** ^Changes to a view that are simulated by an [INSTEAD OF trigger]
-** are not counted.  Only real table changes are counted.
-**
-** ^(A "row change" is a change to a single row of a single table
-** caused by an INSERT, DELETE, or UPDATE statement.  Rows that
-** are changed as side effects of [REPLACE] constraint resolution,
-** rollback, ABORT processing, [DROP TABLE], or by any other
-** mechanisms do not count as direct row changes.)^
-**
-** A "trigger context" is a scope of execution that begins and
-** ends with the script of a [CREATE TRIGGER | trigger]. 
-** Most SQL statements are
-** evaluated outside of any trigger.  This is the "top level"
-** trigger context.  If a trigger fires from the top level, a
-** new trigger context is entered for the duration of that one
-** trigger.  Subtriggers create subcontexts for their duration.
-**
-** ^Calling [sqlite3_exec()] or [sqlite3_step()] recursively does
-** not create a new trigger context.
-**
-** ^This function returns the number of direct row changes in the
-** most recent INSERT, UPDATE, or DELETE statement within the same
-** trigger context.
-**
-** ^Thus, when called from the top level, this function returns the
-** number of changes in the most recent INSERT, UPDATE, or DELETE
-** that also occurred at the top level.  ^(Within the body of a trigger,
-** the sqlite3_changes() interface can be called to find the number of
-** changes in the most recently completed INSERT, UPDATE, or DELETE
-** statement within the body of the same trigger.
-** However, the number returned does not include changes
-** caused by subtriggers since those have their own context.)^
-**
-** See also the [sqlite3_total_changes()] interface, the
-** [count_changes pragma], and the [changes() SQL function].
-**
-** If a separate thread makes changes on the same database connection
-** while [sqlite3_changes()] is running then the value returned
-** is unpredictable and not meaningful.
-*/
-SQLITE_API int sqlite3_changes(sqlite3*);
-
-/*
-** CAPI3REF: Total Number Of Rows Modified
-**
-** ^This function returns the number of row changes caused by [INSERT],
-** [UPDATE] or [DELETE] statements since the [database connection] was opened.
-** ^(The count returned by sqlite3_total_changes() includes all changes
-** from all [CREATE TRIGGER | trigger] contexts and changes made by
-** [foreign key actions]. However,
-** the count does not include changes used to implement [REPLACE] constraints,
-** do rollbacks or ABORT processing, or [DROP TABLE] processing.  The
-** count does not include rows of views that fire an [INSTEAD OF trigger],
-** though if the INSTEAD OF trigger makes changes of its own, those changes 
-** are counted.)^
-** ^The sqlite3_total_changes() function counts the changes as soon as
-** the statement that makes them is completed (when the statement handle
-** is passed to [sqlite3_reset()] or [sqlite3_finalize()]).
-**
-** See also the [sqlite3_changes()] interface, the
-** [count_changes pragma], and the [total_changes() SQL function].
-**
-** If a separate thread makes changes on the same database connection
-** while [sqlite3_total_changes()] is running then the value
-** returned is unpredictable and not meaningful.
-*/
-SQLITE_API int sqlite3_total_changes(sqlite3*);
-
-/*
-** CAPI3REF: Interrupt A Long-Running Query
-**
-** ^This function causes any pending database operation to abort and
-** return at its earliest opportunity. This routine is typically
-** called in response to a user action such as pressing "Cancel"
-** or Ctrl-C where the user wants a long query operation to halt
-** immediately.
-**
-** ^It is safe to call this routine from a thread different from the
-** thread that is currently running the database operation.  But it
-** is not safe to call this routine with a [database connection] that
-** is closed or might close before sqlite3_interrupt() returns.
-**
-** ^If an SQL operation is very nearly finished at the time when
-** sqlite3_interrupt() is called, then it might not have an opportunity
-** to be interrupted and might continue to completion.
-**
-** ^An SQL operation that is interrupted will return [SQLITE_INTERRUPT].
-** ^If the interrupted SQL operation is an INSERT, UPDATE, or DELETE
-** that is inside an explicit transaction, then the entire transaction
-** will be rolled back automatically.
-**
-** ^The sqlite3_interrupt(D) call is in effect until all currently running
-** SQL statements on [database connection] D complete.  ^Any new SQL statements
-** that are started after the sqlite3_interrupt() call and before the 
-** running statements reaches zero are interrupted as if they had been
-** running prior to the sqlite3_interrupt() call.  ^New SQL statements
-** that are started after the running statement count reaches zero are
-** not effected by the sqlite3_interrupt().
-** ^A call to sqlite3_interrupt(D) that occurs when there are no running
-** SQL statements is a no-op and has no effect on SQL statements
-** that are started after the sqlite3_interrupt() call returns.
-**
-** If the database connection closes while [sqlite3_interrupt()]
-** is running then bad things will likely happen.
-*/
-SQLITE_API void sqlite3_interrupt(sqlite3*);
-
-/*
-** CAPI3REF: Determine If An SQL Statement Is Complete
-**
-** These routines are useful during command-line input to determine if the
-** currently entered text seems to form a complete SQL statement or
-** if additional input is needed before sending the text into
-** SQLite for parsing.  ^These routines return 1 if the input string
-** appears to be a complete SQL statement.  ^A statement is judged to be
-** complete if it ends with a semicolon token and is not a prefix of a
-** well-formed CREATE TRIGGER statement.  ^Semicolons that are embedded within
-** string literals or quoted identifier names or comments are not
-** independent tokens (they are part of the token in which they are
-** embedded) and thus do not count as a statement terminator.  ^Whitespace
-** and comments that follow the final semicolon are ignored.
-**
-** ^These routines return 0 if the statement is incomplete.  ^If a
-** memory allocation fails, then SQLITE_NOMEM is returned.
-**
-** ^These routines do not parse the SQL statements thus
-** will not detect syntactically incorrect SQL.
-**
-** ^(If SQLite has not been initialized using [sqlite3_initialize()] prior 
-** to invoking sqlite3_complete16() then sqlite3_initialize() is invoked
-** automatically by sqlite3_complete16().  If that initialization fails,
-** then the return value from sqlite3_complete16() will be non-zero
-** regardless of whether or not the input SQL is complete.)^
-**
-** The input to [sqlite3_complete()] must be a zero-terminated
-** UTF-8 string.
-**
-** The input to [sqlite3_complete16()] must be a zero-terminated
-** UTF-16 string in native byte order.
-*/
-SQLITE_API int sqlite3_complete(const char *sql);
-SQLITE_API int sqlite3_complete16(const void *sql);
-
-/*
-** CAPI3REF: Register A Callback To Handle SQLITE_BUSY Errors
-**
-** ^This routine sets a callback function that might be invoked whenever
-** an attempt is made to open a database table that another thread
-** or process has locked.
-**
-** ^If the busy callback is NULL, then [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED]
-** is returned immediately upon encountering the lock.  ^If the busy callback
-** is not NULL, then the callback might be invoked with two arguments.
-**
-** ^The first argument to the busy handler is a copy of the void* pointer which
-** is the third argument to sqlite3_busy_handler().  ^The second argument to
-** the busy handler callback is the number of times that the busy handler has
-** been invoked for this locking event.  ^If the
-** busy callback returns 0, then no additional attempts are made to
-** access the database and [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED] is returned.
-** ^If the callback returns non-zero, then another attempt
-** is made to open the database for reading and the cycle repeats.
-**
-** The presence of a busy handler does not guarantee that it will be invoked
-** when there is lock contention. ^If SQLite determines that invoking the busy
-** handler could result in a deadlock, it will go ahead and return [SQLITE_BUSY]
-** or [SQLITE_IOERR_BLOCKED] instead of invoking the busy handler.
-** Consider a scenario where one process is holding a read lock that
-** it is trying to promote to a reserved lock and
-** a second process is holding a reserved lock that it is trying
-** to promote to an exclusive lock.  The first process cannot proceed
-** because it is blocked by the second and the second process cannot
-** proceed because it is blocked by the first.  If both processes
-** invoke the busy handlers, neither will make any progress.  Therefore,
-** SQLite returns [SQLITE_BUSY] for the first process, hoping that this
-** will induce the first process to release its read lock and allow
-** the second process to proceed.
-**
-** ^The default busy callback is NULL.
-**
-** ^The [SQLITE_BUSY] error is converted to [SQLITE_IOERR_BLOCKED]
-** when SQLite is in the middle of a large transaction where all the
-** changes will not fit into the in-memory cache.  SQLite will
-** already hold a RESERVED lock on the database file, but it needs
-** to promote this lock to EXCLUSIVE so that it can spill cache
-** pages into the database file without harm to concurrent
-** readers.  ^If it is unable to promote the lock, then the in-memory
-** cache will be left in an inconsistent state and so the error
-** code is promoted from the relatively benign [SQLITE_BUSY] to
-** the more severe [SQLITE_IOERR_BLOCKED].  ^This error code promotion
-** forces an automatic rollback of the changes.  See the
-** <a href="/cvstrac/wiki?p=CorruptionFollowingBusyError">
-** CorruptionFollowingBusyError</a> wiki page for a discussion of why
-** this is important.
-**
-** ^(There can only be a single busy handler defined for each
-** [database connection].  Setting a new busy handler clears any
-** previously set handler.)^  ^Note that calling [sqlite3_busy_timeout()]
-** will also set or clear the busy handler.
-**
-** The busy callback should not take any actions which modify the
-** database connection that invoked the busy handler.  Any such actions
-** result in undefined behavior.
-** 
-** A busy handler must not close the database connection
-** or [prepared statement] that invoked the busy handler.
-*/
-SQLITE_API int sqlite3_busy_handler(sqlite3*, int(*)(void*,int), void*);
-
-/*
-** CAPI3REF: Set A Busy Timeout
-**
-** ^This routine sets a [sqlite3_busy_handler | busy handler] that sleeps
-** for a specified amount of time when a table is locked.  ^The handler
-** will sleep multiple times until at least "ms" milliseconds of sleeping
-** have accumulated.  ^After at least "ms" milliseconds of sleeping,
-** the handler returns 0 which causes [sqlite3_step()] to return
-** [SQLITE_BUSY] or [SQLITE_IOERR_BLOCKED].
-**
-** ^Calling this routine with an argument less than or equal to zero
-** turns off all busy handlers.
-**
-** ^(There can only be a single busy handler for a particular
-** [database connection] any any given moment.  If another busy handler
-** was defined  (using [sqlite3_busy_handler()]) prior to calling
-** this routine, that other busy handler is cleared.)^
-*/
-SQLITE_API int sqlite3_busy_timeout(sqlite3*, int ms);
-
-/*
-** CAPI3REF: Convenience Routines For Running Queries
-**
-** Definition: A <b>result table</b> is memory data structure created by the
-** [sqlite3_get_table()] interface.  A result table records the
-** complete query results from one or more queries.
-**
-** The table conceptually has a number of rows and columns.  But
-** these numbers are not part of the result table itself.  These
-** numbers are obtained separately.  Let N be the number of rows
-** and M be the number of columns.
-**
-** A result table is an array of pointers to zero-terminated UTF-8 strings.
-** There are (N+1)*M elements in the array.  The first M pointers point
-** to zero-terminated strings that  contain the names of the columns.
-** The remaining entries all point to query results.  NULL values result
-** in NULL pointers.  All other values are in their UTF-8 zero-terminated
-** string representation as returned by [sqlite3_column_text()].
-**
-** A result table might consist of one or more memory allocations.
-** It is not safe to pass a result table directly to [sqlite3_free()].
-** A result table should be deallocated using [sqlite3_free_table()].
-**
-** As an example of the result table format, suppose a query result
-** is as follows:
-**
-** <blockquote><pre>
-**        Name        | Age
-**        -----------------------
-**        Alice       | 43
-**        Bob         | 28
-**        Cindy       | 21
-** </pre></blockquote>
-**
-** There are two column (M==2) and three rows (N==3).  Thus the
-** result table has 8 entries.  Suppose the result table is stored
-** in an array names azResult.  Then azResult holds this content:
-**
-** <blockquote><pre>
-**        azResult&#91;0] = "Name";
-**        azResult&#91;1] = "Age";
-**        azResult&#91;2] = "Alice";
-**        azResult&#91;3] = "43";
-**        azResult&#91;4] = "Bob";
-**        azResult&#91;5] = "28";
-**        azResult&#91;6] = "Cindy";
-**        azResult&#91;7] = "21";
-** </pre></blockquote>
-**
-** ^The sqlite3_get_table() function evaluates one or more
-** semicolon-separated SQL statements in the zero-terminated UTF-8
-** string of its 2nd parameter and returns a result table to the
-** pointer given in its 3rd parameter.
-**
-** After the application has finished with the result from sqlite3_get_table(),
-** it should pass the result table pointer to sqlite3_free_table() in order to
-** release the memory that was malloced.  Because of the way the
-** [sqlite3_malloc()] happens within sqlite3_get_table(), the calling
-** function must not try to call [sqlite3_free()] directly.  Only
-** [sqlite3_free_table()] is able to release the memory properly and safely.
-**
-** ^(The sqlite3_get_table() interface is implemented as a wrapper around
-** [sqlite3_exec()].  The sqlite3_get_table() routine does not have access
-** to any internal data structures of SQLite.  It uses only the public
-** interface defined here.  As a consequence, errors that occur in the
-** wrapper layer outside of the internal [sqlite3_exec()] call are not
-** reflected in subsequent calls to [sqlite3_errcode()] or
-** [sqlite3_errmsg()].)^
-*/
-SQLITE_API int sqlite3_get_table(
-  sqlite3 *db,          /* An open database */
-  const char *zSql,     /* SQL to be evaluated */
-  char ***pazResult,    /* Results of the query */
-  int *pnRow,           /* Number of result rows written here */
-  int *pnColumn,        /* Number of result columns written here */
-  char **pzErrmsg       /* Error msg written here */
-);
-SQLITE_API void sqlite3_free_table(char **result);
-
-/*
-** CAPI3REF: Formatted String Printing Functions
-**
-** These routines are work-alikes of the "printf()" family of functions
-** from the standard C library.
-**
-** ^The sqlite3_mprintf() and sqlite3_vmprintf() routines write their
-** results into memory obtained from [sqlite3_malloc()].
-** The strings returned by these two routines should be
-** released by [sqlite3_free()].  ^Both routines return a
-** NULL pointer if [sqlite3_malloc()] is unable to allocate enough
-** memory to hold the resulting string.
-**
-** ^(In sqlite3_snprintf() routine is similar to "snprintf()" from
-** the standard C library.  The result is written into the
-** buffer supplied as the second parameter whose size is given by
-** the first parameter. Note that the order of the
-** first two parameters is reversed from snprintf().)^  This is an
-** historical accident that cannot be fixed without breaking
-** backwards compatibility.  ^(Note also that sqlite3_snprintf()
-** returns a pointer to its buffer instead of the number of
-** characters actually written into the buffer.)^  We admit that
-** the number of characters written would be a more useful return
-** value but we cannot change the implementation of sqlite3_snprintf()
-** now without breaking compatibility.
-**
-** ^As long as the buffer size is greater than zero, sqlite3_snprintf()
-** guarantees that the buffer is always zero-terminated.  ^The first
-** parameter "n" is the total size of the buffer, including space for
-** the zero terminator.  So the longest string that can be completely
-** written will be n-1 characters.
-**
-** These routines all implement some additional formatting
-** options that are useful for constructing SQL statements.
-** All of the usual printf() formatting options apply.  In addition, there
-** is are "%q", "%Q", and "%z" options.
-**
-** ^(The %q option works like %s in that it substitutes a null-terminated
-** string from the argument list.  But %q also doubles every '\'' character.
-** %q is designed for use inside a string literal.)^  By doubling each '\''
-** character it escapes that character and allows it to be inserted into
-** the string.
-**
-** For example, assume the string variable zText contains text as follows:
-**
-** <blockquote><pre>
-**  char *zText = "It's a happy day!";
-** </pre></blockquote>
-**
-** One can use this text in an SQL statement as follows:
-**
-** <blockquote><pre>
-**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES('%q')", zText);
-**  sqlite3_exec(db, zSQL, 0, 0, 0);
-**  sqlite3_free(zSQL);
-** </pre></blockquote>
-**
-** Because the %q format string is used, the '\'' character in zText
-** is escaped and the SQL generated is as follows:
-**
-** <blockquote><pre>
-**  INSERT INTO table1 VALUES('It''s a happy day!')
-** </pre></blockquote>
-**
-** This is correct.  Had we used %s instead of %q, the generated SQL
-** would have looked like this:
-**
-** <blockquote><pre>
-**  INSERT INTO table1 VALUES('It's a happy day!');
-** </pre></blockquote>
-**
-** This second example is an SQL syntax error.  As a general rule you should
-** always use %q instead of %s when inserting text into a string literal.
-**
-** ^(The %Q option works like %q except it also adds single quotes around
-** the outside of the total string.  Additionally, if the parameter in the
-** argument list is a NULL pointer, %Q substitutes the text "NULL" (without
-** single quotes).)^  So, for example, one could say:
-**
-** <blockquote><pre>
-**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES(%Q)", zText);
-**  sqlite3_exec(db, zSQL, 0, 0, 0);
-**  sqlite3_free(zSQL);
-** </pre></blockquote>
-**
-** The code above will render a correct SQL statement in the zSQL
-** variable even if the zText variable is a NULL pointer.
-**
-** ^(The "%z" formatting option works like "%s" but with the
-** addition that after the string has been read and copied into
-** the result, [sqlite3_free()] is called on the input string.)^
-*/
-SQLITE_API char *sqlite3_mprintf(const char*,...);
-SQLITE_API char *sqlite3_vmprintf(const char*, va_list);
-SQLITE_API char *sqlite3_snprintf(int,char*,const char*, ...);
-
-/*
-** CAPI3REF: Memory Allocation Subsystem
-**
-** The SQLite core uses these three routines for all of its own
-** internal memory allocation needs. "Core" in the previous sentence
-** does not include operating-system specific VFS implementation.  The
-** Windows VFS uses native malloc() and free() for some operations.
-**
-** ^The sqlite3_malloc() routine returns a pointer to a block
-** of memory at least N bytes in length, where N is the parameter.
-** ^If sqlite3_malloc() is unable to obtain sufficient free
-** memory, it returns a NULL pointer.  ^If the parameter N to
-** sqlite3_malloc() is zero or negative then sqlite3_malloc() returns
-** a NULL pointer.
-**
-** ^Calling sqlite3_free() with a pointer previously returned
-** by sqlite3_malloc() or sqlite3_realloc() releases that memory so
-** that it might be reused.  ^The sqlite3_free() routine is
-** a no-op if is called with a NULL pointer.  Passing a NULL pointer
-** to sqlite3_free() is harmless.  After being freed, memory
-** should neither be read nor written.  Even reading previously freed
-** memory might result in a segmentation fault or other severe error.
-** Memory corruption, a segmentation fault, or other severe error
-** might result if sqlite3_free() is called with a non-NULL pointer that
-** was not obtained from sqlite3_malloc() or sqlite3_realloc().
-**
-** ^(The sqlite3_realloc() interface attempts to resize a
-** prior memory allocation to be at least N bytes, where N is the
-** second parameter.  The memory allocation to be resized is the first
-** parameter.)^ ^ If the first parameter to sqlite3_realloc()
-** is a NULL pointer then its behavior is identical to calling
-** sqlite3_malloc(N) where N is the second parameter to sqlite3_realloc().
-** ^If the second parameter to sqlite3_realloc() is zero or
-** negative then the behavior is exactly the same as calling
-** sqlite3_free(P) where P is the first parameter to sqlite3_realloc().
-** ^sqlite3_realloc() returns a pointer to a memory allocation
-** of at least N bytes in size or NULL if sufficient memory is unavailable.
-** ^If M is the size of the prior allocation, then min(N,M) bytes
-** of the prior allocation are copied into the beginning of buffer returned
-** by sqlite3_realloc() and the prior allocation is freed.
-** ^If sqlite3_realloc() returns NULL, then the prior allocation
-** is not freed.
-**
-** ^The memory returned by sqlite3_malloc() and sqlite3_realloc()
-** is always aligned to at least an 8 byte boundary.
-**
-** In SQLite version 3.5.0 and 3.5.1, it was possible to define
-** the SQLITE_OMIT_MEMORY_ALLOCATION which would cause the built-in
-** implementation of these routines to be omitted.  That capability
-** is no longer provided.  Only built-in memory allocators can be used.
-**
-** The Windows OS interface layer calls
-** the system malloc() and free() directly when converting
-** filenames between the UTF-8 encoding used by SQLite
-** and whatever filename encoding is used by the particular Windows
-** installation.  Memory allocation errors are detected, but
-** they are reported back as [SQLITE_CANTOPEN] or
-** [SQLITE_IOERR] rather than [SQLITE_NOMEM].
-**
-** The pointer arguments to [sqlite3_free()] and [sqlite3_realloc()]
-** must be either NULL or else pointers obtained from a prior
-** invocation of [sqlite3_malloc()] or [sqlite3_realloc()] that have
-** not yet been released.
-**
-** The application must not read or write any part of
-** a block of memory after it has been released using
-** [sqlite3_free()] or [sqlite3_realloc()].
-*/
-SQLITE_API void *sqlite3_malloc(int);
-SQLITE_API void *sqlite3_realloc(void*, int);
-SQLITE_API void sqlite3_free(void*);
-
-/*
-** CAPI3REF: Memory Allocator Statistics
-**
-** SQLite provides these two interfaces for reporting on the status
-** of the [sqlite3_malloc()], [sqlite3_free()], and [sqlite3_realloc()]
-** routines, which form the built-in memory allocation subsystem.
-**
-** ^The [sqlite3_memory_used()] routine returns the number of bytes
-** of memory currently outstanding (malloced but not freed).
-** ^The [sqlite3_memory_highwater()] routine returns the maximum
-** value of [sqlite3_memory_used()] since the high-water mark
-** was last reset.  ^The values returned by [sqlite3_memory_used()] and
-** [sqlite3_memory_highwater()] include any overhead
-** added by SQLite in its implementation of [sqlite3_malloc()],
-** but not overhead added by the any underlying system library
-** routines that [sqlite3_malloc()] may call.
-**
-** ^The memory high-water mark is reset to the current value of
-** [sqlite3_memory_used()] if and only if the parameter to
-** [sqlite3_memory_highwater()] is true.  ^The value returned
-** by [sqlite3_memory_highwater(1)] is the high-water mark
-** prior to the reset.
-*/
-SQLITE_API sqlite3_int64 sqlite3_memory_used(void);
-SQLITE_API sqlite3_int64 sqlite3_memory_highwater(int resetFlag);
-
-/*
-** CAPI3REF: Pseudo-Random Number Generator
-**
-** SQLite contains a high-quality pseudo-random number generator (PRNG) used to
-** select random [ROWID | ROWIDs] when inserting new records into a table that
-** already uses the largest possible [ROWID].  The PRNG is also used for
-** the build-in random() and randomblob() SQL functions.  This interface allows
-** applications to access the same PRNG for other purposes.
-**
-** ^A call to this routine stores N bytes of randomness into buffer P.
-**
-** ^The first time this routine is invoked (either internally or by
-** the application) the PRNG is seeded using randomness obtained
-** from the xRandomness method of the default [sqlite3_vfs] object.
-** ^On all subsequent invocations, the pseudo-randomness is generated
-** internally and without recourse to the [sqlite3_vfs] xRandomness
-** method.
-*/
-SQLITE_API void sqlite3_randomness(int N, void *P);
-
-/*
-** CAPI3REF: Compile-Time Authorization Callbacks
-**
-** ^This routine registers a authorizer callback with a particular
-** [database connection], supplied in the first argument.
-** ^The authorizer callback is invoked as SQL statements are being compiled
-** by [sqlite3_prepare()] or its variants [sqlite3_prepare_v2()],
-** [sqlite3_prepare16()] and [sqlite3_prepare16_v2()].  ^At various
-** points during the compilation process, as logic is being created
-** to perform various actions, the authorizer callback is invoked to
-** see if those actions are allowed.  ^The authorizer callback should
-** return [SQLITE_OK] to allow the action, [SQLITE_IGNORE] to disallow the
-** specific action but allow the SQL statement to continue to be
-** compiled, or [SQLITE_DENY] to cause the entire SQL statement to be
-** rejected with an error.  ^If the authorizer callback returns
-** any value other than [SQLITE_IGNORE], [SQLITE_OK], or [SQLITE_DENY]
-** then the [sqlite3_prepare_v2()] or equivalent call that triggered
-** the authorizer will fail with an error message.
-**
-** When the callback returns [SQLITE_OK], that means the operation
-** requested is ok.  ^When the callback returns [SQLITE_DENY], the
-** [sqlite3_prepare_v2()] or equivalent call that triggered the
-** authorizer will fail with an error message explaining that
-** access is denied. 
-**
-** ^The first parameter to the authorizer callback is a copy of the third
-** parameter to the sqlite3_set_authorizer() interface. ^The second parameter
-** to the callback is an integer [SQLITE_COPY | action code] that specifies
-** the particular action to be authorized. ^The third through sixth parameters
-** to the callback are zero-terminated strings that contain additional
-** details about the action to be authorized.
-**
-** ^If the action code is [SQLITE_READ]
-** and the callback returns [SQLITE_IGNORE] then the
-** [prepared statement] statement is constructed to substitute
-** a NULL value in place of the table column that would have
-** been read if [SQLITE_OK] had been returned.  The [SQLITE_IGNORE]
-** return can be used to deny an untrusted user access to individual
-** columns of a table.
-** ^If the action code is [SQLITE_DELETE] and the callback returns
-** [SQLITE_IGNORE] then the [DELETE] operation proceeds but the
-** [truncate optimization] is disabled and all rows are deleted individually.
-**
-** An authorizer is used when [sqlite3_prepare | preparing]
-** SQL statements from an untrusted source, to ensure that the SQL statements
-** do not try to access data they are not allowed to see, or that they do not
-** try to execute malicious statements that damage the database.  For
-** example, an application may allow a user to enter arbitrary
-** SQL queries for evaluation by a database.  But the application does
-** not want the user to be able to make arbitrary changes to the
-** database.  An authorizer could then be put in place while the
-** user-entered SQL is being [sqlite3_prepare | prepared] that
-** disallows everything except [SELECT] statements.
-**
-** Applications that need to process SQL from untrusted sources
-** might also consider lowering resource limits using [sqlite3_limit()]
-** and limiting database size using the [max_page_count] [PRAGMA]
-** in addition to using an authorizer.
-**
-** ^(Only a single authorizer can be in place on a database connection
-** at a time.  Each call to sqlite3_set_authorizer overrides the
-** previous call.)^  ^Disable the authorizer by installing a NULL callback.
-** The authorizer is disabled by default.
-**
-** The authorizer callback must not do anything that will modify
-** the database connection that invoked the authorizer callback.
-** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
-** database connections for the meaning of "modify" in this paragraph.
-**
-** ^When [sqlite3_prepare_v2()] is used to prepare a statement, the
-** statement might be re-prepared during [sqlite3_step()] due to a 
-** schema change.  Hence, the application should ensure that the
-** correct authorizer callback remains in place during the [sqlite3_step()].
-**
-** ^Note that the authorizer callback is invoked only during
-** [sqlite3_prepare()] or its variants.  Authorization is not
-** performed during statement evaluation in [sqlite3_step()], unless
-** as stated in the previous paragraph, sqlite3_step() invokes
-** sqlite3_prepare_v2() to reprepare a statement after a schema change.
-*/
-SQLITE_API int sqlite3_set_authorizer(
-  sqlite3*,
-  int (*xAuth)(void*,int,const char*,const char*,const char*,const char*),
-  void *pUserData
-);
-
-/*
-** CAPI3REF: Authorizer Return Codes
-**
-** The [sqlite3_set_authorizer | authorizer callback function] must
-** return either [SQLITE_OK] or one of these two constants in order
-** to signal SQLite whether or not the action is permitted.  See the
-** [sqlite3_set_authorizer | authorizer documentation] for additional
-** information.
-*/
-#define SQLITE_DENY   1   /* Abort the SQL statement with an error */
-#define SQLITE_IGNORE 2   /* Don't allow access, but don't generate an error */
-
-/*
-** CAPI3REF: Authorizer Action Codes
-**
-** The [sqlite3_set_authorizer()] interface registers a callback function
-** that is invoked to authorize certain SQL statement actions.  The
-** second parameter to the callback is an integer code that specifies
-** what action is being authorized.  These are the integer action codes that
-** the authorizer callback may be passed.
-**
-** These action code values signify what kind of operation is to be
-** authorized.  The 3rd and 4th parameters to the authorization
-** callback function will be parameters or NULL depending on which of these
-** codes is used as the second parameter.  ^(The 5th parameter to the
-** authorizer callback is the name of the database ("main", "temp",
-** etc.) if applicable.)^  ^The 6th parameter to the authorizer callback
-** is the name of the inner-most trigger or view that is responsible for
-** the access attempt or NULL if this access attempt is directly from
-** top-level SQL code.
-*/
-/******************************************* 3rd ************ 4th ***********/
-#define SQLITE_CREATE_INDEX          1   /* Index Name      Table Name      */
-#define SQLITE_CREATE_TABLE          2   /* Table Name      NULL            */
-#define SQLITE_CREATE_TEMP_INDEX     3   /* Index Name      Table Name      */
-#define SQLITE_CREATE_TEMP_TABLE     4   /* Table Name      NULL            */
-#define SQLITE_CREATE_TEMP_TRIGGER   5   /* Trigger Name    Table Name      */
-#define SQLITE_CREATE_TEMP_VIEW      6   /* View Name       NULL            */
-#define SQLITE_CREATE_TRIGGER        7   /* Trigger Name    Table Name      */
-#define SQLITE_CREATE_VIEW           8   /* View Name       NULL            */
-#define SQLITE_DELETE                9   /* Table Name      NULL            */
-#define SQLITE_DROP_INDEX           10   /* Index Name      Table Name      */
-#define SQLITE_DROP_TABLE           11   /* Table Name      NULL            */
-#define SQLITE_DROP_TEMP_INDEX      12   /* Index Name      Table Name      */
-#define SQLITE_DROP_TEMP_TABLE      13   /* Table Name      NULL            */
-#define SQLITE_DROP_TEMP_TRIGGER    14   /* Trigger Name    Table Name      */
-#define SQLITE_DROP_TEMP_VIEW       15   /* View Name       NULL            */
-#define SQLITE_DROP_TRIGGER         16   /* Trigger Name    Table Name      */
-#define SQLITE_DROP_VIEW            17   /* View Name       NULL            */
-#define SQLITE_INSERT               18   /* Table Name      NULL            */
-#define SQLITE_PRAGMA               19   /* Pragma Name     1st arg or NULL */
-#define SQLITE_READ                 20   /* Table Name      Column Name     */
-#define SQLITE_SELECT               21   /* NULL            NULL            */
-#define SQLITE_TRANSACTION          22   /* Operation       NULL            */
-#define SQLITE_UPDATE               23   /* Table Name      Column Name     */
-#define SQLITE_ATTACH               24   /* Filename        NULL            */
-#define SQLITE_DETACH               25   /* Database Name   NULL            */
-#define SQLITE_ALTER_TABLE          26   /* Database Name   Table Name      */
-#define SQLITE_REINDEX              27   /* Index Name      NULL            */
-#define SQLITE_ANALYZE              28   /* Table Name      NULL            */
-#define SQLITE_CREATE_VTABLE        29   /* Table Name      Module Name     */
-#define SQLITE_DROP_VTABLE          30   /* Table Name      Module Name     */
-#define SQLITE_FUNCTION             31   /* NULL            Function Name   */
-#define SQLITE_SAVEPOINT            32   /* Operation       Savepoint Name  */
-#define SQLITE_COPY                  0   /* No longer used */
-
-/*
-** CAPI3REF: Tracing And Profiling Functions
-** EXPERIMENTAL
-**
-** These routines register callback functions that can be used for
-** tracing and profiling the execution of SQL statements.
-**
-** ^The callback function registered by sqlite3_trace() is invoked at
-** various times when an SQL statement is being run by [sqlite3_step()].
-** ^The sqlite3_trace() callback is invoked with a UTF-8 rendering of the
-** SQL statement text as the statement first begins executing.
-** ^(Additional sqlite3_trace() callbacks might occur
-** as each triggered subprogram is entered.  The callbacks for triggers
-** contain a UTF-8 SQL comment that identifies the trigger.)^
-**
-** ^The callback function registered by sqlite3_profile() is invoked
-** as each SQL statement finishes.  ^The profile callback contains
-** the original statement text and an estimate of wall-clock time
-** of how long that statement took to run.
-*/
-SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_trace(sqlite3*, void(*xTrace)(void*,const char*), void*);
-SQLITE_API SQLITE_EXPERIMENTAL void *sqlite3_profile(sqlite3*,
-   void(*xProfile)(void*,const char*,sqlite3_uint64), void*);
-
-/*
-** CAPI3REF: Query Progress Callbacks
-**
-** ^This routine configures a callback function - the
-** progress callback - that is invoked periodically during long
-** running calls to [sqlite3_exec()], [sqlite3_step()] and
-** [sqlite3_get_table()].  An example use for this
-** interface is to keep a GUI updated during a large query.
-**
-** ^If the progress callback returns non-zero, the operation is
-** interrupted.  This feature can be used to implement a
-** "Cancel" button on a GUI progress dialog box.
-**
-** The progress handler must not do anything that will modify
-** the database connection that invoked the progress handler.
-** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
-** database connections for the meaning of "modify" in this paragraph.
-**
-*/
-SQLITE_API void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);
-
-/*
-** CAPI3REF: Opening A New Database Connection
-**
-** ^These routines open an SQLite database file whose name is given by the
-** filename argument. ^The filename argument is interpreted as UTF-8 for
-** sqlite3_open() and sqlite3_open_v2() and as UTF-16 in the native byte
-** order for sqlite3_open16(). ^(A [database connection] handle is usually
-** returned in *ppDb, even if an error occurs.  The only exception is that
-** if SQLite is unable to allocate memory to hold the [sqlite3] object,
-** a NULL will be written into *ppDb instead of a pointer to the [sqlite3]
-** object.)^ ^(If the database is opened (and/or created) successfully, then
-** [SQLITE_OK] is returned.  Otherwise an [error code] is returned.)^ ^The
-** [sqlite3_errmsg()] or [sqlite3_errmsg16()] routines can be used to obtain
-** an English language description of the error following a failure of any
-** of the sqlite3_open() routines.
-**
-** ^The default encoding for the database will be UTF-8 if
-** sqlite3_open() or sqlite3_open_v2() is called and
-** UTF-16 in the native byte order if sqlite3_open16() is used.
-**
-** Whether or not an error occurs when it is opened, resources
-** associated with the [database connection] handle should be released by
-** passing it to [sqlite3_close()] when it is no longer required.
-**
-** The sqlite3_open_v2() interface works like sqlite3_open()
-** except that it accepts two additional parameters for additional control
-** over the new database connection.  ^(The flags parameter to
-** sqlite3_open_v2() can take one of
-** the following three values, optionally combined with the 
-** [SQLITE_OPEN_NOMUTEX], [SQLITE_OPEN_FULLMUTEX], [SQLITE_OPEN_SHAREDCACHE],
-** and/or [SQLITE_OPEN_PRIVATECACHE] flags:)^
-**
-** <dl>
-** ^(<dt>[SQLITE_OPEN_READONLY]</dt>
-** <dd>The database is opened in read-only mode.  If the database does not
-** already exist, an error is returned.</dd>)^
-**
-** ^(<dt>[SQLITE_OPEN_READWRITE]</dt>
-** <dd>The database is opened for reading and writing if possible, or reading
-** only if the file is write protected by the operating system.  In either
-** case the database must already exist, otherwise an error is returned.</dd>)^
-**
-** ^(<dt>[SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]</dt>
-** <dd>The database is opened for reading and writing, and is creates it if
-** it does not already exist. This is the behavior that is always used for
-** sqlite3_open() and sqlite3_open16().</dd>)^
-** </dl>
-**
-** If the 3rd parameter to sqlite3_open_v2() is not one of the
-** combinations shown above or one of the combinations shown above combined
-** with the [SQLITE_OPEN_NOMUTEX], [SQLITE_OPEN_FULLMUTEX],
-** [SQLITE_OPEN_SHAREDCACHE] and/or [SQLITE_OPEN_SHAREDCACHE] flags,
-** then the behavior is undefined.
-**
-** ^If the [SQLITE_OPEN_NOMUTEX] flag is set, then the database connection
-** opens in the multi-thread [threading mode] as long as the single-thread
-** mode has not been set at compile-time or start-time.  ^If the
-** [SQLITE_OPEN_FULLMUTEX] flag is set then the database connection opens
-** in the serialized [threading mode] unless single-thread was
-** previously selected at compile-time or start-time.
-** ^The [SQLITE_OPEN_SHAREDCACHE] flag causes the database connection to be
-** eligible to use [shared cache mode], regardless of whether or not shared
-** cache is enabled using [sqlite3_enable_shared_cache()].  ^The
-** [SQLITE_OPEN_PRIVATECACHE] flag causes the database connection to not
-** participate in [shared cache mode] even if it is enabled.
-**
-** ^If the filename is ":memory:", then a private, temporary in-memory database
-** is created for the connection.  ^This in-memory database will vanish when
-** the database connection is closed.  Future versions of SQLite might
-** make use of additional special filenames that begin with the ":" character.
-** It is recommended that when a database filename actually does begin with
-** a ":" character you should prefix the filename with a pathname such as
-** "./" to avoid ambiguity.
-**
-** ^If the filename is an empty string, then a private, temporary
-** on-disk database will be created.  ^This private database will be
-** automatically deleted as soon as the database connection is closed.
-**
-** ^The fourth parameter to sqlite3_open_v2() is the name of the
-** [sqlite3_vfs] object that defines the operating system interface that
-** the new database connection should use.  ^If the fourth parameter is
-** a NULL pointer then the default [sqlite3_vfs] object is used.
-**
-** <b>Note to Windows users:</b>  The encoding used for the filename argument
-** of sqlite3_open() and sqlite3_open_v2() must be UTF-8, not whatever
-** codepage is currently defined.  Filenames containing international
-** characters must be converted to UTF-8 prior to passing them into
-** sqlite3_open() or sqlite3_open_v2().
-*/
-SQLITE_API int sqlite3_open(
-  const char *filename,   /* Database filename (UTF-8) */
-  sqlite3 **ppDb          /* OUT: SQLite db handle */
-);
-SQLITE_API int sqlite3_open16(
-  const void *filename,   /* Database filename (UTF-16) */
-  sqlite3 **ppDb          /* OUT: SQLite db handle */
-);
-SQLITE_API int sqlite3_open_v2(
-  const char *filename,   /* Database filename (UTF-8) */
-  sqlite3 **ppDb,         /* OUT: SQLite db handle */
-  int flags,              /* Flags */
-  const char *zVfs        /* Name of VFS module to use */
-);
-
-/*
-** CAPI3REF: Error Codes And Messages
-**
-** ^The sqlite3_errcode() interface returns the numeric [result code] or
-** [extended result code] for the most recent failed sqlite3_* API call
-** associated with a [database connection]. If a prior API call failed
-** but the most recent API call succeeded, the return value from
-** sqlite3_errcode() is undefined.  ^The sqlite3_extended_errcode()
-** interface is the same except that it always returns the 
-** [extended result code] even when extended result codes are
-** disabled.
-**
-** ^The sqlite3_errmsg() and sqlite3_errmsg16() return English-language
-** text that describes the error, as either UTF-8 or UTF-16 respectively.
-** ^(Memory to hold the error message string is managed internally.
-** The application does not need to worry about freeing the result.
-** However, the error string might be overwritten or deallocated by
-** subsequent calls to other SQLite interface functions.)^
-**
-** When the serialized [threading mode] is in use, it might be the
-** case that a second error occurs on a separate thread in between
-** the time of the first error and the call to these interfaces.
-** When that happens, the second error will be reported since these
-** interfaces always report the most recent result.  To avoid
-** this, each thread can obtain exclusive use of the [database connection] D
-** by invoking [sqlite3_mutex_enter]([sqlite3_db_mutex](D)) before beginning
-** to use D and invoking [sqlite3_mutex_leave]([sqlite3_db_mutex](D)) after
-** all calls to the interfaces listed here are completed.
-**
-** If an interface fails with SQLITE_MISUSE, that means the interface
-** was invoked incorrectly by the application.  In that case, the
-** error code and message may or may not be set.
-*/
-SQLITE_API int sqlite3_errcode(sqlite3 *db);
-SQLITE_API int sqlite3_extended_errcode(sqlite3 *db);
-SQLITE_API const char *sqlite3_errmsg(sqlite3*);
-SQLITE_API const void *sqlite3_errmsg16(sqlite3*);
-
-/*
-** CAPI3REF: SQL Statement Object
-** KEYWORDS: {prepared statement} {prepared statements}
-**
-** An instance of this object represents a single SQL statement.
-** This object is variously known as a "prepared statement" or a
-** "compiled SQL statement" or simply as a "statement".
-**
-** The life of a statement object goes something like this:
-**
-** <ol>
-** <li> Create the object using [sqlite3_prepare_v2()] or a related
-**      function.
-** <li> Bind values to [host parameters] using the sqlite3_bind_*()
-**      interfaces.
-** <li> Run the SQL by calling [sqlite3_step()] one or more times.
-** <li> Reset the statement using [sqlite3_reset()] then go back
-**      to step 2.  Do this zero or more times.
-** <li> Destroy the object using [sqlite3_finalize()].
-** </ol>
-**
-** Refer to documentation on individual methods above for additional
-** information.
-*/
-typedef struct sqlite3_stmt sqlite3_stmt;
-
-/*
-** CAPI3REF: Run-time Limits
-**
-** ^(This interface allows the size of various constructs to be limited
-** on a connection by connection basis.  The first parameter is the
-** [database connection] whose limit is to be set or queried.  The
-** second parameter is one of the [limit categories] that define a
-** class of constructs to be size limited.  The third parameter is the
-** new limit for that construct.  The function returns the old limit.)^
-**
-** ^If the new limit is a negative number, the limit is unchanged.
-** ^(For the limit category of SQLITE_LIMIT_XYZ there is a 
-** [limits | hard upper bound]
-** set by a compile-time C preprocessor macro named 
-** [limits | SQLITE_MAX_XYZ].
-** (The "_LIMIT_" in the name is changed to "_MAX_".))^
-** ^Attempts to increase a limit above its hard upper bound are
-** silently truncated to the hard upper bound.
-**
-** Run-time limits are intended for use in applications that manage
-** both their own internal database and also databases that are controlled
-** by untrusted external sources.  An example application might be a
-** web browser that has its own databases for storing history and
-** separate databases controlled by JavaScript applications downloaded
-** off the Internet.  The internal databases can be given the
-** large, default limits.  Databases managed by external sources can
-** be given much smaller limits designed to prevent a denial of service
-** attack.  Developers might also want to use the [sqlite3_set_authorizer()]
-** interface to further control untrusted SQL.  The size of the database
-** created by an untrusted script can be contained using the
-** [max_page_count] [PRAGMA].
-**
-** New run-time limit categories may be added in future releases.
-*/
-SQLITE_API int sqlite3_limit(sqlite3*, int id, int newVal);
-
-/*
-** CAPI3REF: Run-Time Limit Categories
-** KEYWORDS: {limit category} {*limit categories}
-**
-** These constants define various performance limits
-** that can be lowered at run-time using [sqlite3_limit()].
-** The synopsis of the meanings of the various limits is shown below.
-** Additional information is available at [limits | Limits in SQLite].
-**
-** <dl>
-** ^(<dt>SQLITE_LIMIT_LENGTH</dt>
-** <dd>The maximum size of any string or BLOB or table row.<dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
-** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_COLUMN</dt>
-** <dd>The maximum number of columns in a table definition or in the
-** result set of a [SELECT] or the maximum number of columns in an index
-** or in an ORDER BY or GROUP BY clause.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_EXPR_DEPTH</dt>
-** <dd>The maximum depth of the parse tree on any expression.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_COMPOUND_SELECT</dt>
-** <dd>The maximum number of terms in a compound SELECT statement.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_VDBE_OP</dt>
-** <dd>The maximum number of instructions in a virtual machine program
-** used to implement an SQL statement.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_FUNCTION_ARG</dt>
-** <dd>The maximum number of arguments on a function.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_ATTACHED</dt>
-** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
-**
-** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
-** <dd>The maximum length of the pattern argument to the [LIKE] or
-** [GLOB] operators.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
-** <dd>The maximum number of variables in an SQL statement that can
-** be bound.</dd>)^
-**
-** ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
-** <dd>The maximum depth of recursion for triggers.</dd>)^
-** </dl>
-*/
-#define SQLITE_LIMIT_LENGTH                    0
-#define SQLITE_LIMIT_SQL_LENGTH                1
-#define SQLITE_LIMIT_COLUMN                    2
-#define SQLITE_LIMIT_EXPR_DEPTH                3
-#define SQLITE_LIMIT_COMPOUND_SELECT           4
-#define SQLITE_LIMIT_VDBE_OP                   5
-#define SQLITE_LIMIT_FUNCTION_ARG              6
-#define SQLITE_LIMIT_ATTACHED                  7
-#define SQLITE_LIMIT_LIKE_PATTERN_LENGTH       8
-#define SQLITE_LIMIT_VARIABLE_NUMBER           9
-#define SQLITE_LIMIT_TRIGGER_DEPTH            10
-
-/*
-** CAPI3REF: Compiling An SQL Statement
-** KEYWORDS: {SQL statement compiler}
-**
-** To execute an SQL query, it must first be compiled into a byte-code
-** program using one of these routines.
-**
-** The first argument, "db", is a [database connection] obtained from a
-** prior successful call to [sqlite3_open()], [sqlite3_open_v2()] or
-** [sqlite3_open16()].  The database connection must not have been closed.
-**
-** The second argument, "zSql", is the statement to be compiled, encoded
-** as either UTF-8 or UTF-16.  The sqlite3_prepare() and sqlite3_prepare_v2()
-** interfaces use UTF-8, and sqlite3_prepare16() and sqlite3_prepare16_v2()
-** use UTF-16.
-**
-** ^If the nByte argument is less than zero, then zSql is read up to the
-** first zero terminator. ^If nByte is non-negative, then it is the maximum
-** number of  bytes read from zSql.  ^When nByte is non-negative, the
-** zSql string ends at either the first '\000' or '\u0000' character or
-** the nByte-th byte, whichever comes first. If the caller knows
-** that the supplied string is nul-terminated, then there is a small
-** performance advantage to be gained by passing an nByte parameter that
-** is equal to the number of bytes in the input string <i>including</i>
-** the nul-terminator bytes.
-**
-** ^If pzTail is not NULL then *pzTail is made to point to the first byte
-** past the end of the first SQL statement in zSql.  These routines only
-** compile the first statement in zSql, so *pzTail is left pointing to
-** what remains uncompiled.
-**
-** ^*ppStmt is left pointing to a compiled [prepared statement] that can be
-** executed using [sqlite3_step()].  ^If there is an error, *ppStmt is set
-** to NULL.  ^If the input text contains no SQL (if the input is an empty
-** string or a comment) then *ppStmt is set to NULL.
-** The calling procedure is responsible for deleting the compiled
-** SQL statement using [sqlite3_finalize()] after it has finished with it.
-** ppStmt may not be NULL.
-**
-** ^On success, the sqlite3_prepare() family of routines return [SQLITE_OK];
-** otherwise an [error code] is returned.
-**
-** The sqlite3_prepare_v2() and sqlite3_prepare16_v2() interfaces are
-** recommended for all new programs. The two older interfaces are retained
-** for backwards compatibility, but their use is discouraged.
-** ^In the "v2" interfaces, the prepared statement
-** that is returned (the [sqlite3_stmt] object) contains a copy of the
-** original SQL text. This causes the [sqlite3_step()] interface to
-** behave differently in three ways:
-**
-** <ol>
-** <li>
-** ^If the database schema changes, instead of returning [SQLITE_SCHEMA] as it
-** always used to do, [sqlite3_step()] will automatically recompile the SQL
-** statement and try to run it again.  ^If the schema has changed in
-** a way that makes the statement no longer valid, [sqlite3_step()] will still
-** return [SQLITE_SCHEMA].  But unlike the legacy behavior, [SQLITE_SCHEMA] is
-** now a fatal error.  Calling [sqlite3_prepare_v2()] again will not make the
-** error go away.  Note: use [sqlite3_errmsg()] to find the text
-** of the parsing error that results in an [SQLITE_SCHEMA] return.
-** </li>
-**
-** <li>
-** ^When an error occurs, [sqlite3_step()] will return one of the detailed
-** [error codes] or [extended error codes].  ^The legacy behavior was that
-** [sqlite3_step()] would only return a generic [SQLITE_ERROR] result code
-** and the application would have to make a second call to [sqlite3_reset()]
-** in order to find the underlying cause of the problem. With the "v2" prepare
-** interfaces, the underlying reason for the error is returned immediately.
-** </li>
-**
-** <li>
-** ^If the value of a [parameter | host parameter] in the WHERE clause might
-** change the query plan for a statement, then the statement may be
-** automatically recompiled (as if there had been a schema change) on the first 
-** [sqlite3_step()] call following any change to the 
-** [sqlite3_bind_text | bindings] of the [parameter]. 
-** </li>
-** </ol>
-*/
-SQLITE_API int sqlite3_prepare(
-  sqlite3 *db,            /* Database handle */
-  const char *zSql,       /* SQL statement, UTF-8 encoded */
-  int nByte,              /* Maximum length of zSql in bytes. */
-  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
-  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
-);
-SQLITE_API int sqlite3_prepare_v2(
-  sqlite3 *db,            /* Database handle */
-  const char *zSql,       /* SQL statement, UTF-8 encoded */
-  int nByte,              /* Maximum length of zSql in bytes. */
-  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
-  const char **pzTail     /* OUT: Pointer to unused portion of zSql */
-);
-SQLITE_API int sqlite3_prepare16(
-  sqlite3 *db,            /* Database handle */
-  const void *zSql,       /* SQL statement, UTF-16 encoded */
-  int nByte,              /* Maximum length of zSql in bytes. */
-  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
-  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
-);
-SQLITE_API int sqlite3_prepare16_v2(
-  sqlite3 *db,            /* Database handle */
-  const void *zSql,       /* SQL statement, UTF-16 encoded */
-  int nByte,              /* Maximum length of zSql in bytes. */
-  sqlite3_stmt **ppStmt,  /* OUT: Statement handle */
-  const void **pzTail     /* OUT: Pointer to unused portion of zSql */
-);
-
-/*
-** CAPI3REF: Retrieving Statement SQL
-**
-** ^This interface can be used to retrieve a saved copy of the original
-** SQL text used to create a [prepared statement] if that statement was
-** compiled using either [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()].
-*/
-SQLITE_API const char *sqlite3_sql(sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Dynamically Typed Value Object
-** KEYWORDS: {protected sqlite3_value} {unprotected sqlite3_value}
-**
-** SQLite uses the sqlite3_value object to represent all values
-** that can be stored in a database table. SQLite uses dynamic typing
-** for the values it stores.  ^Values stored in sqlite3_value objects
-** can be integers, floating point values, strings, BLOBs, or NULL.
-**
-** An sqlite3_value object may be either "protected" or "unprotected".
-** Some interfaces require a protected sqlite3_value.  Other interfaces
-** will accept either a protected or an unprotected sqlite3_value.
-** Every interface that accepts sqlite3_value arguments specifies
-** whether or not it requires a protected sqlite3_value.
-**
-** The terms "protected" and "unprotected" refer to whether or not
-** a mutex is held.  A internal mutex is held for a protected
-** sqlite3_value object but no mutex is held for an unprotected
-** sqlite3_value object.  If SQLite is compiled to be single-threaded
-** (with [SQLITE_THREADSAFE=0] and with [sqlite3_threadsafe()] returning 0)
-** or if SQLite is run in one of reduced mutex modes 
-** [SQLITE_CONFIG_SINGLETHREAD] or [SQLITE_CONFIG_MULTITHREAD]
-** then there is no distinction between protected and unprotected
-** sqlite3_value objects and they can be used interchangeably.  However,
-** for maximum code portability it is recommended that applications
-** still make the distinction between between protected and unprotected
-** sqlite3_value objects even when not strictly required.
-**
-** ^The sqlite3_value objects that are passed as parameters into the
-** implementation of [application-defined SQL functions] are protected.
-** ^The sqlite3_value object returned by
-** [sqlite3_column_value()] is unprotected.
-** Unprotected sqlite3_value objects may only be used with
-** [sqlite3_result_value()] and [sqlite3_bind_value()].
-** The [sqlite3_value_blob | sqlite3_value_type()] family of
-** interfaces require protected sqlite3_value objects.
-*/
-typedef struct Mem sqlite3_value;
-
-/*
-** CAPI3REF: SQL Function Context Object
-**
-** The context in which an SQL function executes is stored in an
-** sqlite3_context object.  ^A pointer to an sqlite3_context object
-** is always first parameter to [application-defined SQL functions].
-** The application-defined SQL function implementation will pass this
-** pointer through into calls to [sqlite3_result_int | sqlite3_result()],
-** [sqlite3_aggregate_context()], [sqlite3_user_data()],
-** [sqlite3_context_db_handle()], [sqlite3_get_auxdata()],
-** and/or [sqlite3_set_auxdata()].
-*/
-typedef struct sqlite3_context sqlite3_context;
-
-/*
-** CAPI3REF: Binding Values To Prepared Statements
-** KEYWORDS: {host parameter} {host parameters} {host parameter name}
-** KEYWORDS: {SQL parameter} {SQL parameters} {parameter binding}
-**
-** ^(In the SQL statement text input to [sqlite3_prepare_v2()] and its variants,
-** literals may be replaced by a [parameter] that matches one of following
-** templates:
-**
-** <ul>
-** <li>  ?
-** <li>  ?NNN
-** <li>  :VVV
-** <li>  @VVV
-** <li>  $VVV
-** </ul>
-**
-** In the templates above, NNN represents an integer literal,
-** and VVV represents an alphanumeric identifer.)^  ^The values of these
-** parameters (also called "host parameter names" or "SQL parameters")
-** can be set using the sqlite3_bind_*() routines defined here.
-**
-** ^The first argument to the sqlite3_bind_*() routines is always
-** a pointer to the [sqlite3_stmt] object returned from
-** [sqlite3_prepare_v2()] or its variants.
-**
-** ^The second argument is the index of the SQL parameter to be set.
-** ^The leftmost SQL parameter has an index of 1.  ^When the same named
-** SQL parameter is used more than once, second and subsequent
-** occurrences have the same index as the first occurrence.
-** ^The index for named parameters can be looked up using the
-** [sqlite3_bind_parameter_index()] API if desired.  ^The index
-** for "?NNN" parameters is the value of NNN.
-** ^The NNN value must be between 1 and the [sqlite3_limit()]
-** parameter [SQLITE_LIMIT_VARIABLE_NUMBER] (default value: 999).
-**
-** ^The third argument is the value to bind to the parameter.
-**
-** ^(In those routines that have a fourth argument, its value is the
-** number of bytes in the parameter.  To be clear: the value is the
-** number of <u>bytes</u> in the value, not the number of characters.)^
-** ^If the fourth parameter is negative, the length of the string is
-** the number of bytes up to the first zero terminator.
-**
-** ^The fifth argument to sqlite3_bind_blob(), sqlite3_bind_text(), and
-** sqlite3_bind_text16() is a destructor used to dispose of the BLOB or
-** string after SQLite has finished with it. ^If the fifth argument is
-** the special value [SQLITE_STATIC], then SQLite assumes that the
-** information is in static, unmanaged space and does not need to be freed.
-** ^If the fifth argument has the value [SQLITE_TRANSIENT], then
-** SQLite makes its own private copy of the data immediately, before
-** the sqlite3_bind_*() routine returns.
-**
-** ^The sqlite3_bind_zeroblob() routine binds a BLOB of length N that
-** is filled with zeroes.  ^A zeroblob uses a fixed amount of memory
-** (just an integer to hold its size) while it is being processed.
-** Zeroblobs are intended to serve as placeholders for BLOBs whose
-** content is later written using
-** [sqlite3_blob_open | incremental BLOB I/O] routines.
-** ^A negative value for the zeroblob results in a zero-length BLOB.
-**
-** ^If any of the sqlite3_bind_*() routines are called with a NULL pointer
-** for the [prepared statement] or with a prepared statement for which
-** [sqlite3_step()] has been called more recently than [sqlite3_reset()],
-** then the call will return [SQLITE_MISUSE].  If any sqlite3_bind_()
-** routine is passed a [prepared statement] that has been finalized, the
-** result is undefined and probably harmful.
-**
-** ^Bindings are not cleared by the [sqlite3_reset()] routine.
-** ^Unbound parameters are interpreted as NULL.
-**
-** ^The sqlite3_bind_* routines return [SQLITE_OK] on success or an
-** [error code] if anything goes wrong.
-** ^[SQLITE_RANGE] is returned if the parameter
-** index is out of range.  ^[SQLITE_NOMEM] is returned if malloc() fails.
-**
-** See also: [sqlite3_bind_parameter_count()],
-** [sqlite3_bind_parameter_name()], and [sqlite3_bind_parameter_index()].
-*/
-SQLITE_API int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
-SQLITE_API int sqlite3_bind_double(sqlite3_stmt*, int, double);
-SQLITE_API int sqlite3_bind_int(sqlite3_stmt*, int, int);
-SQLITE_API int sqlite3_bind_int64(sqlite3_stmt*, int, sqlite3_int64);
-SQLITE_API int sqlite3_bind_null(sqlite3_stmt*, int);
-SQLITE_API int sqlite3_bind_text(sqlite3_stmt*, int, const char*, int n, void(*)(void*));
-SQLITE_API int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int, void(*)(void*));
-SQLITE_API int sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
-SQLITE_API int sqlite3_bind_zeroblob(sqlite3_stmt*, int, int n);
-
-/*
-** CAPI3REF: Number Of SQL Parameters
-**
-** ^This routine can be used to find the number of [SQL parameters]
-** in a [prepared statement].  SQL parameters are tokens of the
-** form "?", "?NNN", ":AAA", "$AAA", or "@AAA" that serve as
-** placeholders for values that are [sqlite3_bind_blob | bound]
-** to the parameters at a later time.
-**
-** ^(This routine actually returns the index of the largest (rightmost)
-** parameter. For all forms except ?NNN, this will correspond to the
-** number of unique parameters.  If parameters of the ?NNN form are used,
-** there may be gaps in the list.)^
-**
-** See also: [sqlite3_bind_blob|sqlite3_bind()],
-** [sqlite3_bind_parameter_name()], and
-** [sqlite3_bind_parameter_index()].
-*/
-SQLITE_API int sqlite3_bind_parameter_count(sqlite3_stmt*);
-
-/*
-** CAPI3REF: Name Of A Host Parameter
-**
-** ^The sqlite3_bind_parameter_name(P,N) interface returns
-** the name of the N-th [SQL parameter] in the [prepared statement] P.
-** ^(SQL parameters of the form "?NNN" or ":AAA" or "@AAA" or "$AAA"
-** have a name which is the string "?NNN" or ":AAA" or "@AAA" or "$AAA"
-** respectively.
-** In other words, the initial ":" or "$" or "@" or "?"
-** is included as part of the name.)^
-** ^Parameters of the form "?" without a following integer have no name
-** and are referred to as "nameless" or "anonymous parameters".
-**
-** ^The first host parameter has an index of 1, not 0.
-**
-** ^If the value N is out of range or if the N-th parameter is
-** nameless, then NULL is returned.  ^The returned string is
-** always in UTF-8 encoding even if the named parameter was
-** originally specified as UTF-16 in [sqlite3_prepare16()] or
-** [sqlite3_prepare16_v2()].
-**
-** See also: [sqlite3_bind_blob|sqlite3_bind()],
-** [sqlite3_bind_parameter_count()], and
-** [sqlite3_bind_parameter_index()].
-*/
-SQLITE_API const char *sqlite3_bind_parameter_name(sqlite3_stmt*, int);
-
-/*
-** CAPI3REF: Index Of A Parameter With A Given Name
-**
-** ^Return the index of an SQL parameter given its name.  ^The
-** index value returned is suitable for use as the second
-** parameter to [sqlite3_bind_blob|sqlite3_bind()].  ^A zero
-** is returned if no matching parameter is found.  ^The parameter
-** name must be given in UTF-8 even if the original statement
-** was prepared from UTF-16 text using [sqlite3_prepare16_v2()].
-**
-** See also: [sqlite3_bind_blob|sqlite3_bind()],
-** [sqlite3_bind_parameter_count()], and
-** [sqlite3_bind_parameter_index()].
-*/
-SQLITE_API int sqlite3_bind_parameter_index(sqlite3_stmt*, const char *zName);
-
-/*
-** CAPI3REF: Reset All Bindings On A Prepared Statement
-**
-** ^Contrary to the intuition of many, [sqlite3_reset()] does not reset
-** the [sqlite3_bind_blob | bindings] on a [prepared statement].
-** ^Use this routine to reset all host parameters to NULL.
-*/
-SQLITE_API int sqlite3_clear_bindings(sqlite3_stmt*);
-
-/*
-** CAPI3REF: Number Of Columns In A Result Set
-**
-** ^Return the number of columns in the result set returned by the
-** [prepared statement]. ^This routine returns 0 if pStmt is an SQL
-** statement that does not return data (for example an [UPDATE]).
-*/
-SQLITE_API int sqlite3_column_count(sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Column Names In A Result Set
-**
-** ^These routines return the name assigned to a particular column
-** in the result set of a [SELECT] statement.  ^The sqlite3_column_name()
-** interface returns a pointer to a zero-terminated UTF-8 string
-** and sqlite3_column_name16() returns a pointer to a zero-terminated
-** UTF-16 string.  ^The first parameter is the [prepared statement]
-** that implements the [SELECT] statement. ^The second parameter is the
-** column number.  ^The leftmost column is number 0.
-**
-** ^The returned string pointer is valid until either the [prepared statement]
-** is destroyed by [sqlite3_finalize()] or until the next call to
-** sqlite3_column_name() or sqlite3_column_name16() on the same column.
-**
-** ^If sqlite3_malloc() fails during the processing of either routine
-** (for example during a conversion from UTF-8 to UTF-16) then a
-** NULL pointer is returned.
-**
-** ^The name of a result column is the value of the "AS" clause for
-** that column, if there is an AS clause.  If there is no AS clause
-** then the name of the column is unspecified and may change from
-** one release of SQLite to the next.
-*/
-SQLITE_API const char *sqlite3_column_name(sqlite3_stmt*, int N);
-SQLITE_API const void *sqlite3_column_name16(sqlite3_stmt*, int N);
-
-/*
-** CAPI3REF: Source Of Data In A Query Result
-**
-** ^These routines provide a means to determine the database, table, and
-** table column that is the origin of a particular result column in
-** [SELECT] statement.
-** ^The name of the database or table or column can be returned as
-** either a UTF-8 or UTF-16 string.  ^The _database_ routines return
-** the database name, the _table_ routines return the table name, and
-** the origin_ routines return the column name.
-** ^The returned string is valid until the [prepared statement] is destroyed
-** using [sqlite3_finalize()] or until the same information is requested
-** again in a different encoding.
-**
-** ^The names returned are the original un-aliased names of the
-** database, table, and column.
-**
-** ^The first argument to these interfaces is a [prepared statement].
-** ^These functions return information about the Nth result column returned by
-** the statement, where N is the second function argument.
-** ^The left-most column is column 0 for these routines.
-**
-** ^If the Nth column returned by the statement is an expression or
-** subquery and is not a column value, then all of these functions return
-** NULL.  ^These routine might also return NULL if a memory allocation error
-** occurs.  ^Otherwise, they return the name of the attached database, table,
-** or column that query result column was extracted from.
-**
-** ^As with all other SQLite APIs, those whose names end with "16" return
-** UTF-16 encoded strings and the other functions return UTF-8.
-**
-** ^These APIs are only available if the library was compiled with the
-** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol.
-**
-** If two or more threads call one or more of these routines against the same
-** prepared statement and column at the same time then the results are
-** undefined.
-**
-** If two or more threads call one or more
-** [sqlite3_column_database_name | column metadata interfaces]
-** for the same [prepared statement] and result column
-** at the same time then the results are undefined.
-*/
-SQLITE_API const char *sqlite3_column_database_name(sqlite3_stmt*,int);
-SQLITE_API const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
-SQLITE_API const char *sqlite3_column_table_name(sqlite3_stmt*,int);
-SQLITE_API const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
-SQLITE_API const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
-SQLITE_API const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);
-
-/*
-** CAPI3REF: Declared Datatype Of A Query Result
-**
-** ^(The first parameter is a [prepared statement].
-** If this statement is a [SELECT] statement and the Nth column of the
-** returned result set of that [SELECT] is a table column (not an
-** expression or subquery) then the declared type of the table
-** column is returned.)^  ^If the Nth column of the result set is an
-** expression or subquery, then a NULL pointer is returned.
-** ^The returned string is always UTF-8 encoded.
-**
-** ^(For example, given the database schema:
-**
-** CREATE TABLE t1(c1 VARIANT);
-**
-** and the following statement to be compiled:
-**
-** SELECT c1 + 1, c1 FROM t1;
-**
-** this routine would return the string "VARIANT" for the second result
-** column (i==1), and a NULL pointer for the first result column (i==0).)^
-**
-** ^SQLite uses dynamic run-time typing.  ^So just because a column
-** is declared to contain a particular type does not mean that the
-** data stored in that column is of the declared type.  SQLite is
-** strongly typed, but the typing is dynamic not static.  ^Type
-** is associated with individual values, not with the containers
-** used to hold those values.
-*/
-SQLITE_API const char *sqlite3_column_decltype(sqlite3_stmt*,int);
-SQLITE_API const void *sqlite3_column_decltype16(sqlite3_stmt*,int);
-
-/*
-** CAPI3REF: Evaluate An SQL Statement
-**
-** After a [prepared statement] has been prepared using either
-** [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()] or one of the legacy
-** interfaces [sqlite3_prepare()] or [sqlite3_prepare16()], this function
-** must be called one or more times to evaluate the statement.
-**
-** The details of the behavior of the sqlite3_step() interface depend
-** on whether the statement was prepared using the newer "v2" interface
-** [sqlite3_prepare_v2()] and [sqlite3_prepare16_v2()] or the older legacy
-** interface [sqlite3_prepare()] and [sqlite3_prepare16()].  The use of the
-** new "v2" interface is recommended for new applications but the legacy
-** interface will continue to be supported.
-**
-** ^In the legacy interface, the return value will be either [SQLITE_BUSY],
-** [SQLITE_DONE], [SQLITE_ROW], [SQLITE_ERROR], or [SQLITE_MISUSE].
-** ^With the "v2" interface, any of the other [result codes] or
-** [extended result codes] might be returned as well.
-**
-** ^[SQLITE_BUSY] means that the database engine was unable to acquire the
-** database locks it needs to do its job.  ^If the statement is a [COMMIT]
-** or occurs outside of an explicit transaction, then you can retry the
-** statement.  If the statement is not a [COMMIT] and occurs within a
-** explicit transaction then you should rollback the transaction before
-** continuing.
-**
-** ^[SQLITE_DONE] means that the statement has finished executing
-** successfully.  sqlite3_step() should not be called again on this virtual
-** machine without first calling [sqlite3_reset()] to reset the virtual
-** machine back to its initial state.
-**
-** ^If the SQL statement being executed returns any data, then [SQLITE_ROW]
-** is returned each time a new row of data is ready for processing by the
-** caller. The values may be accessed using the [column access functions].
-** sqlite3_step() is called again to retrieve the next row of data.
-**
-** ^[SQLITE_ERROR] means that a run-time error (such as a constraint
-** violation) has occurred.  sqlite3_step() should not be called again on
-** the VM. More information may be found by calling [sqlite3_errmsg()].
-** ^With the legacy interface, a more specific error code (for example,
-** [SQLITE_INTERRUPT], [SQLITE_SCHEMA], [SQLITE_CORRUPT], and so forth)
-** can be obtained by calling [sqlite3_reset()] on the
-** [prepared statement].  ^In the "v2" interface,
-** the more specific error code is returned directly by sqlite3_step().
-**
-** [SQLITE_MISUSE] means that the this routine was called inappropriately.
-** Perhaps it was called on a [prepared statement] that has
-** already been [sqlite3_finalize | finalized] or on one that had
-** previously returned [SQLITE_ERROR] or [SQLITE_DONE].  Or it could
-** be the case that the same database connection is being used by two or
-** more threads at the same moment in time.
-**
-** <b>Goofy Interface Alert:</b> In the legacy interface, the sqlite3_step()
-** API always returns a generic error code, [SQLITE_ERROR], following any
-** error other than [SQLITE_BUSY] and [SQLITE_MISUSE].  You must call
-** [sqlite3_reset()] or [sqlite3_finalize()] in order to find one of the
-** specific [error codes] that better describes the error.
-** We admit that this is a goofy design.  The problem has been fixed
-** with the "v2" interface.  If you prepare all of your SQL statements
-** using either [sqlite3_prepare_v2()] or [sqlite3_prepare16_v2()] instead
-** of the legacy [sqlite3_prepare()] and [sqlite3_prepare16()] interfaces,
-** then the more specific [error codes] are returned directly
-** by sqlite3_step().  The use of the "v2" interface is recommended.
-*/
-SQLITE_API int sqlite3_step(sqlite3_stmt*);
-
-/*
-** CAPI3REF: Number of columns in a result set
-**
-** ^The sqlite3_data_count(P) the number of columns in the
-** of the result set of [prepared statement] P.
-*/
-SQLITE_API int sqlite3_data_count(sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Fundamental Datatypes
-** KEYWORDS: SQLITE_TEXT
-**
-** ^(Every value in SQLite has one of five fundamental datatypes:
-**
-** <ul>
-** <li> 64-bit signed integer
-** <li> 64-bit IEEE floating point number
-** <li> string
-** <li> BLOB
-** <li> NULL
-** </ul>)^
-**
-** These constants are codes for each of those types.
-**
-** Note that the SQLITE_TEXT constant was also used in SQLite version 2
-** for a completely different meaning.  Software that links against both
-** SQLite version 2 and SQLite version 3 should use SQLITE3_TEXT, not
-** SQLITE_TEXT.
-*/
-#define SQLITE_INTEGER  1
-#define SQLITE_FLOAT    2
-#define SQLITE_BLOB     4
-#define SQLITE_NULL     5
-#ifdef SQLITE_TEXT
-# undef SQLITE_TEXT
-#else
-# define SQLITE_TEXT     3
-#endif
-#define SQLITE3_TEXT     3
-
-/*
-** CAPI3REF: Result Values From A Query
-** KEYWORDS: {column access functions}
-**
-** These routines form the "result set" interface.
-**
-** ^These routines return information about a single column of the current
-** result row of a query.  ^In every case the first argument is a pointer
-** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
-** that was returned from [sqlite3_prepare_v2()] or one of its variants)
-** and the second argument is the index of the column for which information
-** should be returned. ^The leftmost column of the result set has the index 0.
-** ^The number of columns in the result can be determined using
-** [sqlite3_column_count()].
-**
-** If the SQL statement does not currently point to a valid row, or if the
-** column index is out of range, the result is undefined.
-** These routines may only be called when the most recent call to
-** [sqlite3_step()] has returned [SQLITE_ROW] and neither
-** [sqlite3_reset()] nor [sqlite3_finalize()] have been called subsequently.
-** If any of these routines are called after [sqlite3_reset()] or
-** [sqlite3_finalize()] or after [sqlite3_step()] has returned
-** something other than [SQLITE_ROW], the results are undefined.
-** If [sqlite3_step()] or [sqlite3_reset()] or [sqlite3_finalize()]
-** are called from a different thread while any of these routines
-** are pending, then the results are undefined.
-**
-** ^The sqlite3_column_type() routine returns the
-** [SQLITE_INTEGER | datatype code] for the initial data type
-** of the result column.  ^The returned value is one of [SQLITE_INTEGER],
-** [SQLITE_FLOAT], [SQLITE_TEXT], [SQLITE_BLOB], or [SQLITE_NULL].  The value
-** returned by sqlite3_column_type() is only meaningful if no type
-** conversions have occurred as described below.  After a type conversion,
-** the value returned by sqlite3_column_type() is undefined.  Future
-** versions of SQLite may change the behavior of sqlite3_column_type()
-** following a type conversion.
-**
-** ^If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
-** routine returns the number of bytes in that BLOB or string.
-** ^If the result is a UTF-16 string, then sqlite3_column_bytes() converts
-** the string to UTF-8 and then returns the number of bytes.
-** ^If the result is a numeric value then sqlite3_column_bytes() uses
-** [sqlite3_snprintf()] to convert that value to a UTF-8 string and returns
-** the number of bytes in that string.
-** ^The value returned does not include the zero terminator at the end
-** of the string.  ^For clarity: the value returned is the number of
-** bytes in the string, not the number of characters.
-**
-** ^Strings returned by sqlite3_column_text() and sqlite3_column_text16(),
-** even empty strings, are always zero terminated.  ^The return
-** value from sqlite3_column_blob() for a zero-length BLOB is an arbitrary
-** pointer, possibly even a NULL pointer.
-**
-** ^The sqlite3_column_bytes16() routine is similar to sqlite3_column_bytes()
-** but leaves the result in UTF-16 in native byte order instead of UTF-8.
-** ^The zero terminator is not included in this count.
-**
-** ^The object returned by [sqlite3_column_value()] is an
-** [unprotected sqlite3_value] object.  An unprotected sqlite3_value object
-** may only be used with [sqlite3_bind_value()] and [sqlite3_result_value()].
-** If the [unprotected sqlite3_value] object returned by
-** [sqlite3_column_value()] is used in any other way, including calls
-** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
-** or [sqlite3_value_bytes()], then the behavior is undefined.
-**
-** These routines attempt to convert the value where appropriate.  ^For
-** example, if the internal representation is FLOAT and a text result
-** is requested, [sqlite3_snprintf()] is used internally to perform the
-** conversion automatically.  ^(The following table details the conversions
-** that are applied:
-**
-** <blockquote>
-** <table border="1">
-** <tr><th> Internal<br>Type <th> Requested<br>Type <th>  Conversion
-**
-** <tr><td>  NULL    <td> INTEGER   <td> Result is 0
-** <tr><td>  NULL    <td>  FLOAT    <td> Result is 0.0
-** <tr><td>  NULL    <td>   TEXT    <td> Result is NULL pointer
-** <tr><td>  NULL    <td>   BLOB    <td> Result is NULL pointer
-** <tr><td> INTEGER  <td>  FLOAT    <td> Convert from integer to float
-** <tr><td> INTEGER  <td>   TEXT    <td> ASCII rendering of the integer
-** <tr><td> INTEGER  <td>   BLOB    <td> Same as INTEGER->TEXT
-** <tr><td>  FLOAT   <td> INTEGER   <td> Convert from float to integer
-** <tr><td>  FLOAT   <td>   TEXT    <td> ASCII rendering of the float
-** <tr><td>  FLOAT   <td>   BLOB    <td> Same as FLOAT->TEXT
-** <tr><td>  TEXT    <td> INTEGER   <td> Use atoi()
-** <tr><td>  TEXT    <td>  FLOAT    <td> Use atof()
-** <tr><td>  TEXT    <td>   BLOB    <td> No change
-** <tr><td>  BLOB    <td> INTEGER   <td> Convert to TEXT then use atoi()
-** <tr><td>  BLOB    <td>  FLOAT    <td> Convert to TEXT then use atof()
-** <tr><td>  BLOB    <td>   TEXT    <td> Add a zero terminator if needed
-** </table>
-** </blockquote>)^
-**
-** The table above makes reference to standard C library functions atoi()
-** and atof().  SQLite does not really use these functions.  It has its
-** own equivalent internal routines.  The atoi() and atof() names are
-** used in the table for brevity and because they are familiar to most
-** C programmers.
-**
-** ^Note that when type conversions occur, pointers returned by prior
-** calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
-** sqlite3_column_text16() may be invalidated.
-** ^(Type conversions and pointer invalidations might occur
-** in the following cases:
-**
-** <ul>
-** <li> The initial content is a BLOB and sqlite3_column_text() or
-**      sqlite3_column_text16() is called.  A zero-terminator might
-**      need to be added to the string.</li>
-** <li> The initial content is UTF-8 text and sqlite3_column_bytes16() or
-**      sqlite3_column_text16() is called.  The content must be converted
-**      to UTF-16.</li>
-** <li> The initial content is UTF-16 text and sqlite3_column_bytes() or
-**      sqlite3_column_text() is called.  The content must be converted
-**      to UTF-8.</li>
-** </ul>)^
-**
-** ^Conversions between UTF-16be and UTF-16le are always done in place and do
-** not invalidate a prior pointer, though of course the content of the buffer
-** that the prior pointer points to will have been modified.  Other kinds
-** of conversion are done in place when it is possible, but sometimes they
-** are not possible and in those cases prior pointers are invalidated.
-**
-** ^(The safest and easiest to remember policy is to invoke these routines
-** in one of the following ways:
-**
-** <ul>
-**  <li>sqlite3_column_text() followed by sqlite3_column_bytes()</li>
-**  <li>sqlite3_column_blob() followed by sqlite3_column_bytes()</li>
-**  <li>sqlite3_column_text16() followed by sqlite3_column_bytes16()</li>
-** </ul>)^
-**
-** In other words, you should call sqlite3_column_text(),
-** sqlite3_column_blob(), or sqlite3_column_text16() first to force the result
-** into the desired format, then invoke sqlite3_column_bytes() or
-** sqlite3_column_bytes16() to find the size of the result.  Do not mix calls
-** to sqlite3_column_text() or sqlite3_column_blob() with calls to
-** sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
-** with calls to sqlite3_column_bytes().
-**
-** ^The pointers returned are valid until a type conversion occurs as
-** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
-** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
-** and BLOBs is freed automatically.  Do <b>not</b> pass the pointers returned
-** [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
-** [sqlite3_free()].
-**
-** ^(If a memory allocation error occurs during the evaluation of any
-** of these routines, a default value is returned.  The default value
-** is either the integer 0, the floating point number 0.0, or a NULL
-** pointer.  Subsequent calls to [sqlite3_errcode()] will return
-** [SQLITE_NOMEM].)^
-*/
-SQLITE_API const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
-SQLITE_API int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
-SQLITE_API int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
-SQLITE_API double sqlite3_column_double(sqlite3_stmt*, int iCol);
-SQLITE_API int sqlite3_column_int(sqlite3_stmt*, int iCol);
-SQLITE_API sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
-SQLITE_API const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
-SQLITE_API const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
-SQLITE_API int sqlite3_column_type(sqlite3_stmt*, int iCol);
-SQLITE_API sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);
-
-/*
-** CAPI3REF: Destroy A Prepared Statement Object
-**
-** ^The sqlite3_finalize() function is called to delete a [prepared statement].
-** ^If the statement was executed successfully or not executed at all, then
-** SQLITE_OK is returned. ^If execution of the statement failed then an
-** [error code] or [extended error code] is returned.
-**
-** ^This routine can be called at any point during the execution of the
-** [prepared statement].  ^If the virtual machine has not
-** completed execution when this routine is called, that is like
-** encountering an error or an [sqlite3_interrupt | interrupt].
-** ^Incomplete updates may be rolled back and transactions canceled,
-** depending on the circumstances, and the
-** [error code] returned will be [SQLITE_ABORT].
-*/
-SQLITE_API int sqlite3_finalize(sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Reset A Prepared Statement Object
-**
-** The sqlite3_reset() function is called to reset a [prepared statement]
-** object back to its initial state, ready to be re-executed.
-** ^Any SQL statement variables that had values bound to them using
-** the [sqlite3_bind_blob | sqlite3_bind_*() API] retain their values.
-** Use [sqlite3_clear_bindings()] to reset the bindings.
-**
-** ^The [sqlite3_reset(S)] interface resets the [prepared statement] S
-** back to the beginning of its program.
-**
-** ^If the most recent call to [sqlite3_step(S)] for the
-** [prepared statement] S returned [SQLITE_ROW] or [SQLITE_DONE],
-** or if [sqlite3_step(S)] has never before been called on S,
-** then [sqlite3_reset(S)] returns [SQLITE_OK].
-**
-** ^If the most recent call to [sqlite3_step(S)] for the
-** [prepared statement] S indicated an error, then
-** [sqlite3_reset(S)] returns an appropriate [error code].
-**
-** ^The [sqlite3_reset(S)] interface does not change the values
-** of any [sqlite3_bind_blob|bindings] on the [prepared statement] S.
-*/
-SQLITE_API int sqlite3_reset(sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Create Or Redefine SQL Functions
-** KEYWORDS: {function creation routines}
-** KEYWORDS: {application-defined SQL function}
-** KEYWORDS: {application-defined SQL functions}
-**
-** ^These two functions (collectively known as "function creation routines")
-** are used to add SQL functions or aggregates or to redefine the behavior
-** of existing SQL functions or aggregates.  The only difference between the
-** two is that the second parameter, the name of the (scalar) function or
-** aggregate, is encoded in UTF-8 for sqlite3_create_function() and UTF-16
-** for sqlite3_create_function16().
-**
-** ^The first parameter is the [database connection] to which the SQL
-** function is to be added.  ^If an application uses more than one database
-** connection then application-defined SQL functions must be added
-** to each database connection separately.
-**
-** The second parameter is the name of the SQL function to be created or
-** redefined.  ^The length of the name is limited to 255 bytes, exclusive of
-** the zero-terminator.  Note that the name length limit is in bytes, not
-** characters.  ^Any attempt to create a function with a longer name
-** will result in [SQLITE_ERROR] being returned.
-**
-** ^The third parameter (nArg)
-** is the number of arguments that the SQL function or
-** aggregate takes. ^If this parameter is -1, then the SQL function or
-** aggregate may take any number of arguments between 0 and the limit
-** set by [sqlite3_limit]([SQLITE_LIMIT_FUNCTION_ARG]).  If the third
-** parameter is less than -1 or greater than 127 then the behavior is
-** undefined.
-**
-** The fourth parameter, eTextRep, specifies what
-** [SQLITE_UTF8 | text encoding] this SQL function prefers for
-** its parameters.  Any SQL function implementation should be able to work
-** work with UTF-8, UTF-16le, or UTF-16be.  But some implementations may be
-** more efficient with one encoding than another.  ^An application may
-** invoke sqlite3_create_function() or sqlite3_create_function16() multiple
-** times with the same function but with different values of eTextRep.
-** ^When multiple implementations of the same function are available, SQLite
-** will pick the one that involves the least amount of data conversion.
-** If there is only a single implementation which does not care what text
-** encoding is used, then the fourth argument should be [SQLITE_ANY].
-**
-** ^(The fifth parameter is an arbitrary pointer.  The implementation of the
-** function can gain access to this pointer using [sqlite3_user_data()].)^
-**
-** The seventh, eighth and ninth parameters, xFunc, xStep and xFinal, are
-** pointers to C-language functions that implement the SQL function or
-** aggregate. ^A scalar SQL function requires an implementation of the xFunc
-** callback only; NULL pointers should be passed as the xStep and xFinal
-** parameters. ^An aggregate SQL function requires an implementation of xStep
-** and xFinal and NULL should be passed for xFunc. ^To delete an existing
-** SQL function or aggregate, pass NULL for all three function callbacks.
-**
-** ^It is permitted to register multiple implementations of the same
-** functions with the same name but with either differing numbers of
-** arguments or differing preferred text encodings.  ^SQLite will use
-** the implementation that most closely matches the way in which the
-** SQL function is used.  ^A function implementation with a non-negative
-** nArg parameter is a better match than a function implementation with
-** a negative nArg.  ^A function where the preferred text encoding
-** matches the database encoding is a better
-** match than a function where the encoding is different.  
-** ^A function where the encoding difference is between UTF16le and UTF16be
-** is a closer match than a function where the encoding difference is
-** between UTF8 and UTF16.
-**
-** ^Built-in functions may be overloaded by new application-defined functions.
-** ^The first application-defined function with a given name overrides all
-** built-in functions in the same [database connection] with the same name.
-** ^Subsequent application-defined functions of the same name only override 
-** prior application-defined functions that are an exact match for the
-** number of parameters and preferred encoding.
-**
-** ^An application-defined function is permitted to call other
-** SQLite interfaces.  However, such calls must not
-** close the database connection nor finalize or reset the prepared
-** statement in which the function is running.
-*/
-SQLITE_API int sqlite3_create_function(
-  sqlite3 *db,
-  const char *zFunctionName,
-  int nArg,
-  int eTextRep,
-  void *pApp,
-  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
-  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
-  void (*xFinal)(sqlite3_context*)
-);
-SQLITE_API int sqlite3_create_function16(
-  sqlite3 *db,
-  const void *zFunctionName,
-  int nArg,
-  int eTextRep,
-  void *pApp,
-  void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
-  void (*xStep)(sqlite3_context*,int,sqlite3_value**),
-  void (*xFinal)(sqlite3_context*)
-);
-
-/*
-** CAPI3REF: Text Encodings
-**
-** These constant define integer codes that represent the various
-** text encodings supported by SQLite.
-*/
-#define SQLITE_UTF8           1
-#define SQLITE_UTF16LE        2
-#define SQLITE_UTF16BE        3
-#define SQLITE_UTF16          4    /* Use native byte order */
-#define SQLITE_ANY            5    /* sqlite3_create_function only */
-#define SQLITE_UTF16_ALIGNED  8    /* sqlite3_create_collation only */
-
-/*
-** CAPI3REF: Deprecated Functions
-** DEPRECATED
-**
-** These functions are [deprecated].  In order to maintain
-** backwards compatibility with older code, these functions continue 
-** to be supported.  However, new applications should avoid
-** the use of these functions.  To help encourage people to avoid
-** using these functions, we are not going to tell you what they do.
-*/
-#ifndef SQLITE_OMIT_DEPRECATED
-SQLITE_API SQLITE_DEPRECATED int sqlite3_aggregate_count(sqlite3_context*);
-SQLITE_API SQLITE_DEPRECATED int sqlite3_expired(sqlite3_stmt*);
-SQLITE_API SQLITE_DEPRECATED int sqlite3_transfer_bindings(sqlite3_stmt*, sqlite3_stmt*);
-SQLITE_API SQLITE_DEPRECATED int sqlite3_global_recover(void);
-SQLITE_API SQLITE_DEPRECATED void sqlite3_thread_cleanup(void);
-SQLITE_API SQLITE_DEPRECATED int sqlite3_memory_alarm(void(*)(void*,sqlite3_int64,int),void*,sqlite3_int64);
-#endif
-
-/*
-** CAPI3REF: Obtaining SQL Function Parameter Values
-**
-** The C-language implementation of SQL functions and aggregates uses
-** this set of interface routines to access the parameter values on
-** the function or aggregate.
-**
-** The xFunc (for scalar functions) or xStep (for aggregates) parameters
-** to [sqlite3_create_function()] and [sqlite3_create_function16()]
-** define callbacks that implement the SQL functions and aggregates.
-** The 4th parameter to these callbacks is an array of pointers to
-** [protected sqlite3_value] objects.  There is one [sqlite3_value] object for
-** each parameter to the SQL function.  These routines are used to
-** extract values from the [sqlite3_value] objects.
-**
-** These routines work only with [protected sqlite3_value] objects.
-** Any attempt to use these routines on an [unprotected sqlite3_value]
-** object results in undefined behavior.
-**
-** ^These routines work just like the corresponding [column access functions]
-** except that  these routines take a single [protected sqlite3_value] object
-** pointer instead of a [sqlite3_stmt*] pointer and an integer column number.
-**
-** ^The sqlite3_value_text16() interface extracts a UTF-16 string
-** in the native byte-order of the host machine.  ^The
-** sqlite3_value_text16be() and sqlite3_value_text16le() interfaces
-** extract UTF-16 strings as big-endian and little-endian respectively.
-**
-** ^(The sqlite3_value_numeric_type() interface attempts to apply
-** numeric affinity to the value.  This means that an attempt is
-** made to convert the value to an integer or floating point.  If
-** such a conversion is possible without loss of information (in other
-** words, if the value is a string that looks like a number)
-** then the conversion is performed.  Otherwise no conversion occurs.
-** The [SQLITE_INTEGER | datatype] after conversion is returned.)^
-**
-** Please pay particular attention to the fact that the pointer returned
-** from [sqlite3_value_blob()], [sqlite3_value_text()], or
-** [sqlite3_value_text16()] can be invalidated by a subsequent call to
-** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
-** or [sqlite3_value_text16()].
-**
-** These routines must be called from the same thread as
-** the SQL function that supplied the [sqlite3_value*] parameters.
-*/
-SQLITE_API const void *sqlite3_value_blob(sqlite3_value*);
-SQLITE_API int sqlite3_value_bytes(sqlite3_value*);
-SQLITE_API int sqlite3_value_bytes16(sqlite3_value*);
-SQLITE_API double sqlite3_value_double(sqlite3_value*);
-SQLITE_API int sqlite3_value_int(sqlite3_value*);
-SQLITE_API sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
-SQLITE_API const unsigned char *sqlite3_value_text(sqlite3_value*);
-SQLITE_API const void *sqlite3_value_text16(sqlite3_value*);
-SQLITE_API const void *sqlite3_value_text16le(sqlite3_value*);
-SQLITE_API const void *sqlite3_value_text16be(sqlite3_value*);
-SQLITE_API int sqlite3_value_type(sqlite3_value*);
-SQLITE_API int sqlite3_value_numeric_type(sqlite3_value*);
-
-/*
-** CAPI3REF: Obtain Aggregate Function Context
-**
-** Implementions of aggregate SQL functions use this
-** routine to allocate memory for storing their state.
-**
-** ^The first time the sqlite3_aggregate_context(C,N) routine is called 
-** for a particular aggregate function, SQLite
-** allocates N of memory, zeroes out that memory, and returns a pointer
-** to the new memory. ^On second and subsequent calls to
-** sqlite3_aggregate_context() for the same aggregate function instance,
-** the same buffer is returned.  Sqlite3_aggregate_context() is normally
-** called once for each invocation of the xStep callback and then one
-** last time when the xFinal callback is invoked.  ^(When no rows match
-** an aggregate query, the xStep() callback of the aggregate function
-** implementation is never called and xFinal() is called exactly once.
-** In those cases, sqlite3_aggregate_context() might be called for the
-** first time from within xFinal().)^
-**
-** ^The sqlite3_aggregate_context(C,N) routine returns a NULL pointer if N is
-** less than or equal to zero or if a memory allocate error occurs.
-**
-** ^(The amount of space allocated by sqlite3_aggregate_context(C,N) is
-** determined by the N parameter on first successful call.  Changing the
-** value of N in subsequent call to sqlite3_aggregate_context() within
-** the same aggregate function instance will not resize the memory
-** allocation.)^
-**
-** ^SQLite automatically frees the memory allocated by 
-** sqlite3_aggregate_context() when the aggregate query concludes.
-**
-** The first parameter must be a copy of the
-** [sqlite3_context | SQL function context] that is the first parameter
-** to the xStep or xFinal callback routine that implements the aggregate
-** function.
-**
-** This routine must be called from the same thread in which
-** the aggregate SQL function is running.
-*/
-SQLITE_API void *sqlite3_aggregate_context(sqlite3_context*, int nBytes);
-
-/*
-** CAPI3REF: User Data For Functions
-**
-** ^The sqlite3_user_data() interface returns a copy of
-** the pointer that was the pUserData parameter (the 5th parameter)
-** of the [sqlite3_create_function()]
-** and [sqlite3_create_function16()] routines that originally
-** registered the application defined function.
-**
-** This routine must be called from the same thread in which
-** the application-defined function is running.
-*/
-SQLITE_API void *sqlite3_user_data(sqlite3_context*);
-
-/*
-** CAPI3REF: Database Connection For Functions
-**
-** ^The sqlite3_context_db_handle() interface returns a copy of
-** the pointer to the [database connection] (the 1st parameter)
-** of the [sqlite3_create_function()]
-** and [sqlite3_create_function16()] routines that originally
-** registered the application defined function.
-*/
-SQLITE_API sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
-
-/*
-** CAPI3REF: Function Auxiliary Data
-**
-** The following two functions may be used by scalar SQL functions to
-** associate metadata with argument values. If the same value is passed to
-** multiple invocations of the same SQL function during query execution, under
-** some circumstances the associated metadata may be preserved. This may
-** be used, for example, to add a regular-expression matching scalar
-** function. The compiled version of the regular expression is stored as
-** metadata associated with the SQL value passed as the regular expression
-** pattern.  The compiled regular expression can be reused on multiple
-** invocations of the same function so that the original pattern string
-** does not need to be recompiled on each invocation.
-**
-** ^The sqlite3_get_auxdata() interface returns a pointer to the metadata
-** associated by the sqlite3_set_auxdata() function with the Nth argument
-** value to the application-defined function. ^If no metadata has been ever
-** been set for the Nth argument of the function, or if the corresponding
-** function parameter has changed since the meta-data was set,
-** then sqlite3_get_auxdata() returns a NULL pointer.
-**
-** ^The sqlite3_set_auxdata() interface saves the metadata
-** pointed to by its 3rd parameter as the metadata for the N-th
-** argument of the application-defined function.  Subsequent
-** calls to sqlite3_get_auxdata() might return this data, if it has
-** not been destroyed.
-** ^If it is not NULL, SQLite will invoke the destructor
-** function given by the 4th parameter to sqlite3_set_auxdata() on
-** the metadata when the corresponding function parameter changes
-** or when the SQL statement completes, whichever comes first.
-**
-** SQLite is free to call the destructor and drop metadata on any
-** parameter of any function at any time.  ^The only guarantee is that
-** the destructor will be called before the metadata is dropped.
-**
-** ^(In practice, metadata is preserved between function calls for
-** expressions that are constant at compile time. This includes literal
-** values and [parameters].)^
-**
-** These routines must be called from the same thread in which
-** the SQL function is running.
-*/
-SQLITE_API void *sqlite3_get_auxdata(sqlite3_context*, int N);
-SQLITE_API void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));
-
-
-/*
-** CAPI3REF: Constants Defining Special Destructor Behavior
-**
-** These are special values for the destructor that is passed in as the
-** final argument to routines like [sqlite3_result_blob()].  ^If the destructor
-** argument is SQLITE_STATIC, it means that the content pointer is constant
-** and will never change.  It does not need to be destroyed.  ^The
-** SQLITE_TRANSIENT value means that the content will likely change in
-** the near future and that SQLite should make its own private copy of
-** the content before returning.
-**
-** The typedef is necessary to work around problems in certain
-** C++ compilers.  See ticket #2191.
-*/
-typedef void (*sqlite3_destructor_type)(void*);
-#define SQLITE_STATIC      ((sqlite3_destructor_type)0)
-#define SQLITE_TRANSIENT   ((sqlite3_destructor_type)-1)
-
-/*
-** CAPI3REF: Setting The Result Of An SQL Function
-**
-** These routines are used by the xFunc or xFinal callbacks that
-** implement SQL functions and aggregates.  See
-** [sqlite3_create_function()] and [sqlite3_create_function16()]
-** for additional information.
-**
-** These functions work very much like the [parameter binding] family of
-** functions used to bind values to host parameters in prepared statements.
-** Refer to the [SQL parameter] documentation for additional information.
-**
-** ^The sqlite3_result_blob() interface sets the result from
-** an application-defined function to be the BLOB whose content is pointed
-** to by the second parameter and which is N bytes long where N is the
-** third parameter.
-**
-** ^The sqlite3_result_zeroblob() interfaces set the result of
-** the application-defined function to be a BLOB containing all zero
-** bytes and N bytes in size, where N is the value of the 2nd parameter.
-**
-** ^The sqlite3_result_double() interface sets the result from
-** an application-defined function to be a floating point value specified
-** by its 2nd argument.
-**
-** ^The sqlite3_result_error() and sqlite3_result_error16() functions
-** cause the implemented SQL function to throw an exception.
-** ^SQLite uses the string pointed to by the
-** 2nd parameter of sqlite3_result_error() or sqlite3_result_error16()
-** as the text of an error message.  ^SQLite interprets the error
-** message string from sqlite3_result_error() as UTF-8. ^SQLite
-** interprets the string from sqlite3_result_error16() as UTF-16 in native
-** byte order.  ^If the third parameter to sqlite3_result_error()
-** or sqlite3_result_error16() is negative then SQLite takes as the error
-** message all text up through the first zero character.
-** ^If the third parameter to sqlite3_result_error() or
-** sqlite3_result_error16() is non-negative then SQLite takes that many
-** bytes (not characters) from the 2nd parameter as the error message.
-** ^The sqlite3_result_error() and sqlite3_result_error16()
-** routines make a private copy of the error message text before
-** they return.  Hence, the calling function can deallocate or
-** modify the text after they return without harm.
-** ^The sqlite3_result_error_code() function changes the error code
-** returned by SQLite as a result of an error in a function.  ^By default,
-** the error code is SQLITE_ERROR.  ^A subsequent call to sqlite3_result_error()
-** or sqlite3_result_error16() resets the error code to SQLITE_ERROR.
-**
-** ^The sqlite3_result_toobig() interface causes SQLite to throw an error
-** indicating that a string or BLOB is too long to represent.
-**
-** ^The sqlite3_result_nomem() interface causes SQLite to throw an error
-** indicating that a memory allocation failed.
-**
-** ^The sqlite3_result_int() interface sets the return value
-** of the application-defined function to be the 32-bit signed integer
-** value given in the 2nd argument.
-** ^The sqlite3_result_int64() interface sets the return value
-** of the application-defined function to be the 64-bit signed integer
-** value given in the 2nd argument.
-**
-** ^The sqlite3_result_null() interface sets the return value
-** of the application-defined function to be NULL.
-**
-** ^The sqlite3_result_text(), sqlite3_result_text16(),
-** sqlite3_result_text16le(), and sqlite3_result_text16be() interfaces
-** set the return value of the application-defined function to be
-** a text string which is represented as UTF-8, UTF-16 native byte order,
-** UTF-16 little endian, or UTF-16 big endian, respectively.
-** ^SQLite takes the text result from the application from
-** the 2nd parameter of the sqlite3_result_text* interfaces.
-** ^If the 3rd parameter to the sqlite3_result_text* interfaces
-** is negative, then SQLite takes result text from the 2nd parameter
-** through the first zero character.
-** ^If the 3rd parameter to the sqlite3_result_text* interfaces
-** is non-negative, then as many bytes (not characters) of the text
-** pointed to by the 2nd parameter are taken as the application-defined
-** function result.
-** ^If the 4th parameter to the sqlite3_result_text* interfaces
-** or sqlite3_result_blob is a non-NULL pointer, then SQLite calls that
-** function as the destructor on the text or BLOB result when it has
-** finished using that result.
-** ^If the 4th parameter to the sqlite3_result_text* interfaces or to
-** sqlite3_result_blob is the special constant SQLITE_STATIC, then SQLite
-** assumes that the text or BLOB result is in constant space and does not
-** copy the content of the parameter nor call a destructor on the content
-** when it has finished using that result.
-** ^If the 4th parameter to the sqlite3_result_text* interfaces
-** or sqlite3_result_blob is the special constant SQLITE_TRANSIENT
-** then SQLite makes a copy of the result into space obtained from
-** from [sqlite3_malloc()] before it returns.
-**
-** ^The sqlite3_result_value() interface sets the result of
-** the application-defined function to be a copy the
-** [unprotected sqlite3_value] object specified by the 2nd parameter.  ^The
-** sqlite3_result_value() interface makes a copy of the [sqlite3_value]
-** so that the [sqlite3_value] specified in the parameter may change or
-** be deallocated after sqlite3_result_value() returns without harm.
-** ^A [protected sqlite3_value] object may always be used where an
-** [unprotected sqlite3_value] object is required, so either
-** kind of [sqlite3_value] object can be used with this interface.
-**
-** If these routines are called from within the different thread
-** than the one containing the application-defined function that received
-** the [sqlite3_context] pointer, the results are undefined.
-*/
-SQLITE_API void sqlite3_result_blob(sqlite3_context*, const void*, int, void(*)(void*));
-SQLITE_API void sqlite3_result_double(sqlite3_context*, double);
-SQLITE_API void sqlite3_result_error(sqlite3_context*, const char*, int);
-SQLITE_API void sqlite3_result_error16(sqlite3_context*, const void*, int);
-SQLITE_API void sqlite3_result_error_toobig(sqlite3_context*);
-SQLITE_API void sqlite3_result_error_nomem(sqlite3_context*);
-SQLITE_API void sqlite3_result_error_code(sqlite3_context*, int);
-SQLITE_API void sqlite3_result_int(sqlite3_context*, int);
-SQLITE_API void sqlite3_result_int64(sqlite3_context*, sqlite3_int64);
-SQLITE_API void sqlite3_result_null(sqlite3_context*);
-SQLITE_API void sqlite3_result_text(sqlite3_context*, const char*, int, void(*)(void*));
-SQLITE_API void sqlite3_result_text16(sqlite3_context*, const void*, int, void(*)(void*));
-SQLITE_API void sqlite3_result_text16le(sqlite3_context*, const void*, int,void(*)(void*));
-SQLITE_API void sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
-SQLITE_API void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
-SQLITE_API void sqlite3_result_zeroblob(sqlite3_context*, int n);
-
-/*
-** CAPI3REF: Define New Collating Sequences
-**
-** These functions are used to add new collation sequences to the
-** [database connection] specified as the first argument.
-**
-** ^The name of the new collation sequence is specified as a UTF-8 string
-** for sqlite3_create_collation() and sqlite3_create_collation_v2()
-** and a UTF-16 string for sqlite3_create_collation16(). ^In all cases
-** the name is passed as the second function argument.
-**
-** ^The third argument may be one of the constants [SQLITE_UTF8],
-** [SQLITE_UTF16LE], or [SQLITE_UTF16BE], indicating that the user-supplied
-** routine expects to be passed pointers to strings encoded using UTF-8,
-** UTF-16 little-endian, or UTF-16 big-endian, respectively. ^The
-** third argument might also be [SQLITE_UTF16] to indicate that the routine
-** expects pointers to be UTF-16 strings in the native byte order, or the
-** argument can be [SQLITE_UTF16_ALIGNED] if the
-** the routine expects pointers to 16-bit word aligned strings
-** of UTF-16 in the native byte order.
-**
-** A pointer to the user supplied routine must be passed as the fifth
-** argument.  ^If it is NULL, this is the same as deleting the collation
-** sequence (so that SQLite cannot call it anymore).
-** ^Each time the application supplied function is invoked, it is passed
-** as its first parameter a copy of the void* passed as the fourth argument
-** to sqlite3_create_collation() or sqlite3_create_collation16().
-**
-** ^The remaining arguments to the application-supplied routine are two strings,
-** each represented by a (length, data) pair and encoded in the encoding
-** that was passed as the third argument when the collation sequence was
-** registered.  The application defined collation routine should
-** return negative, zero or positive if the first string is less than,
-** equal to, or greater than the second string. i.e. (STRING1 - STRING2).
-**
-** ^The sqlite3_create_collation_v2() works like sqlite3_create_collation()
-** except that it takes an extra argument which is a destructor for
-** the collation.  ^The destructor is called when the collation is
-** destroyed and is passed a copy of the fourth parameter void* pointer
-** of the sqlite3_create_collation_v2().
-** ^Collations are destroyed when they are overridden by later calls to the
-** collation creation functions or when the [database connection] is closed
-** using [sqlite3_close()].
-**
-** See also:  [sqlite3_collation_needed()] and [sqlite3_collation_needed16()].
-*/
-SQLITE_API int sqlite3_create_collation(
-  sqlite3*, 
-  const char *zName, 
-  int eTextRep, 
-  void*,
-  int(*xCompare)(void*,int,const void*,int,const void*)
-);
-SQLITE_API int sqlite3_create_collation_v2(
-  sqlite3*, 
-  const char *zName, 
-  int eTextRep, 
-  void*,
-  int(*xCompare)(void*,int,const void*,int,const void*),
-  void(*xDestroy)(void*)
-);
-SQLITE_API int sqlite3_create_collation16(
-  sqlite3*, 
-  const void *zName,
-  int eTextRep, 
-  void*,
-  int(*xCompare)(void*,int,const void*,int,const void*)
-);
-
-/*
-** CAPI3REF: Collation Needed Callbacks
-**
-** ^To avoid having to register all collation sequences before a database
-** can be used, a single callback function may be registered with the
-** [database connection] to be invoked whenever an undefined collation
-** sequence is required.
-**
-** ^If the function is registered using the sqlite3_collation_needed() API,
-** then it is passed the names of undefined collation sequences as strings
-** encoded in UTF-8. ^If sqlite3_collation_needed16() is used,
-** the names are passed as UTF-16 in machine native byte order.
-** ^A call to either function replaces the existing collation-needed callback.
-**
-** ^(When the callback is invoked, the first argument passed is a copy
-** of the second argument to sqlite3_collation_needed() or
-** sqlite3_collation_needed16().  The second argument is the database
-** connection.  The third argument is one of [SQLITE_UTF8], [SQLITE_UTF16BE],
-** or [SQLITE_UTF16LE], indicating the most desirable form of the collation
-** sequence function required.  The fourth parameter is the name of the
-** required collation sequence.)^
-**
-** The callback function should register the desired collation using
-** [sqlite3_create_collation()], [sqlite3_create_collation16()], or
-** [sqlite3_create_collation_v2()].
-*/
-SQLITE_API int sqlite3_collation_needed(
-  sqlite3*, 
-  void*, 
-  void(*)(void*,sqlite3*,int eTextRep,const char*)
-);
-SQLITE_API int sqlite3_collation_needed16(
-  sqlite3*, 
-  void*,
-  void(*)(void*,sqlite3*,int eTextRep,const void*)
-);
-
-/*
-** Specify the key for an encrypted database.  This routine should be
-** called right after sqlite3_open().
-**
-** The code to implement this API is not available in the public release
-** of SQLite.
-*/
-SQLITE_API int sqlite3_key(
-  sqlite3 *db,                   /* Database to be rekeyed */
-  const void *pKey, int nKey     /* The key */
-);
-
-/*
-** Change the key on an open database.  If the current database is not
-** encrypted, this routine will encrypt it.  If pNew==0 or nNew==0, the
-** database is decrypted.
-**
-** The code to implement this API is not available in the public release
-** of SQLite.
-*/
-SQLITE_API int sqlite3_rekey(
-  sqlite3 *db,                   /* Database to be rekeyed */
-  const void *pKey, int nKey     /* The new key */
-);
-
-/*
-** CAPI3REF: Suspend Execution For A Short Time
-**
-** ^The sqlite3_sleep() function causes the current thread to suspend execution
-** for at least a number of milliseconds specified in its parameter.
-**
-** ^If the operating system does not support sleep requests with
-** millisecond time resolution, then the time will be rounded up to
-** the nearest second. ^The number of milliseconds of sleep actually
-** requested from the operating system is returned.
-**
-** ^SQLite implements this interface by calling the xSleep()
-** method of the default [sqlite3_vfs] object.
-*/
-SQLITE_API int sqlite3_sleep(int);
-
-/*
-** CAPI3REF: Name Of The Folder Holding Temporary Files
-**
-** ^(If this global variable is made to point to a string which is
-** the name of a folder (a.k.a. directory), then all temporary files
-** created by SQLite when using a built-in [sqlite3_vfs | VFS]
-** will be placed in that directory.)^  ^If this variable
-** is a NULL pointer, then SQLite performs a search for an appropriate
-** temporary file directory.
-**
-** It is not safe to read or modify this variable in more than one
-** thread at a time.  It is not safe to read or modify this variable
-** if a [database connection] is being used at the same time in a separate
-** thread.
-** It is intended that this variable be set once
-** as part of process initialization and before any SQLite interface
-** routines have been called and that this variable remain unchanged
-** thereafter.
-**
-** ^The [temp_store_directory pragma] may modify this variable and cause
-** it to point to memory obtained from [sqlite3_malloc].  ^Furthermore,
-** the [temp_store_directory pragma] always assumes that any string
-** that this variable points to is held in memory obtained from 
-** [sqlite3_malloc] and the pragma may attempt to free that memory
-** using [sqlite3_free].
-** Hence, if this variable is modified directly, either it should be
-** made NULL or made to point to memory obtained from [sqlite3_malloc]
-** or else the use of the [temp_store_directory pragma] should be avoided.
-*/
-SQLITE_API SQLITE_EXTERN char *sqlite3_temp_directory;
-
-/*
-** CAPI3REF: Test For Auto-Commit Mode
-** KEYWORDS: {autocommit mode}
-**
-** ^The sqlite3_get_autocommit() interface returns non-zero or
-** zero if the given database connection is or is not in autocommit mode,
-** respectively.  ^Autocommit mode is on by default.
-** ^Autocommit mode is disabled by a [BEGIN] statement.
-** ^Autocommit mode is re-enabled by a [COMMIT] or [ROLLBACK].
-**
-** If certain kinds of errors occur on a statement within a multi-statement
-** transaction (errors including [SQLITE_FULL], [SQLITE_IOERR],
-** [SQLITE_NOMEM], [SQLITE_BUSY], and [SQLITE_INTERRUPT]) then the
-** transaction might be rolled back automatically.  The only way to
-** find out whether SQLite automatically rolled back the transaction after
-** an error is to use this function.
-**
-** If another thread changes the autocommit status of the database
-** connection while this routine is running, then the return value
-** is undefined.
-*/
-SQLITE_API int sqlite3_get_autocommit(sqlite3*);
-
-/*
-** CAPI3REF: Find The Database Handle Of A Prepared Statement
-**
-** ^The sqlite3_db_handle interface returns the [database connection] handle
-** to which a [prepared statement] belongs.  ^The [database connection]
-** returned by sqlite3_db_handle is the same [database connection]
-** that was the first argument
-** to the [sqlite3_prepare_v2()] call (or its variants) that was used to
-** create the statement in the first place.
-*/
-SQLITE_API sqlite3 *sqlite3_db_handle(sqlite3_stmt*);
-
-/*
-** CAPI3REF: Find the next prepared statement
-**
-** ^This interface returns a pointer to the next [prepared statement] after
-** pStmt associated with the [database connection] pDb.  ^If pStmt is NULL
-** then this interface returns a pointer to the first prepared statement
-** associated with the database connection pDb.  ^If no prepared statement
-** satisfies the conditions of this routine, it returns NULL.
-**
-** The [database connection] pointer D in a call to
-** [sqlite3_next_stmt(D,S)] must refer to an open database
-** connection and in particular must not be a NULL pointer.
-*/
-SQLITE_API sqlite3_stmt *sqlite3_next_stmt(sqlite3 *pDb, sqlite3_stmt *pStmt);
-
-/*
-** CAPI3REF: Commit And Rollback Notification Callbacks
-**
-** ^The sqlite3_commit_hook() interface registers a callback
-** function to be invoked whenever a transaction is [COMMIT | committed].
-** ^Any callback set by a previous call to sqlite3_commit_hook()
-** for the same database connection is overridden.
-** ^The sqlite3_rollback_hook() interface registers a callback
-** function to be invoked whenever a transaction is [ROLLBACK | rolled back].
-** ^Any callback set by a previous call to sqlite3_rollback_hook()
-** for the same database connection is overridden.
-** ^The pArg argument is passed through to the callback.
-** ^If the callback on a commit hook function returns non-zero,
-** then the commit is converted into a rollback.
-**
-** ^The sqlite3_commit_hook(D,C,P) and sqlite3_rollback_hook(D,C,P) functions
-** return the P argument from the previous call of the same function
-** on the same [database connection] D, or NULL for
-** the first call for each function on D.
-**
-** The callback implementation must not do anything that will modify
-** the database connection that invoked the callback.  Any actions
-** to modify the database connection must be deferred until after the
-** completion of the [sqlite3_step()] call that triggered the commit
-** or rollback hook in the first place.
-** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
-** database connections for the meaning of "modify" in this paragraph.
-**
-** ^Registering a NULL function disables the callback.
-**
-** ^When the commit hook callback routine returns zero, the [COMMIT]
-** operation is allowed to continue normally.  ^If the commit hook
-** returns non-zero, then the [COMMIT] is converted into a [ROLLBACK].
-** ^The rollback hook is invoked on a rollback that results from a commit
-** hook returning non-zero, just as it would be with any other rollback.
-**
-** ^For the purposes of this API, a transaction is said to have been
-** rolled back if an explicit "ROLLBACK" statement is executed, or
-** an error or constraint causes an implicit rollback to occur.
-** ^The rollback callback is not invoked if a transaction is
-** automatically rolled back because the database connection is closed.
-** ^The rollback callback is not invoked if a transaction is
-** rolled back because a commit callback returned non-zero.
-**
-** See also the [sqlite3_update_hook()] interface.
-*/
-SQLITE_API void *sqlite3_commit_hook(sqlite3*, int(*)(void*), void*);
-SQLITE_API void *sqlite3_rollback_hook(sqlite3*, void(*)(void *), void*);
-
-/*
-** CAPI3REF: Data Change Notification Callbacks
-**
-** ^The sqlite3_update_hook() interface registers a callback function
-** with the [database connection] identified by the first argument
-** to be invoked whenever a row is updated, inserted or deleted.
-** ^Any callback set by a previous call to this function
-** for the same database connection is overridden.
-**
-** ^The second argument is a pointer to the function to invoke when a
-** row is updated, inserted or deleted.
-** ^The first argument to the callback is a copy of the third argument
-** to sqlite3_update_hook().
-** ^The second callback argument is one of [SQLITE_INSERT], [SQLITE_DELETE],
-** or [SQLITE_UPDATE], depending on the operation that caused the callback
-** to be invoked.
-** ^The third and fourth arguments to the callback contain pointers to the
-** database and table name containing the affected row.
-** ^The final callback parameter is the [rowid] of the row.
-** ^In the case of an update, this is the [rowid] after the update takes place.
-**
-** ^(The update hook is not invoked when internal system tables are
-** modified (i.e. sqlite_master and sqlite_sequence).)^
-**
-** ^In the current implementation, the update hook
-** is not invoked when duplication rows are deleted because of an
-** [ON CONFLICT | ON CONFLICT REPLACE] clause.  ^Nor is the update hook
-** invoked when rows are deleted using the [truncate optimization].
-** The exceptions defined in this paragraph might change in a future
-** release of SQLite.
-**
-** The update hook implementation must not do anything that will modify
-** the database connection that invoked the update hook.  Any actions
-** to modify the database connection must be deferred until after the
-** completion of the [sqlite3_step()] call that triggered the update hook.
-** Note that [sqlite3_prepare_v2()] and [sqlite3_step()] both modify their
-** database connections for the meaning of "modify" in this paragraph.
-**
-** ^The sqlite3_update_hook(D,C,P) function
-** returns the P argument from the previous call
-** on the same [database connection] D, or NULL for
-** the first call on D.
-**
-** See also the [sqlite3_commit_hook()] and [sqlite3_rollback_hook()]
-** interfaces.
-*/
-SQLITE_API void *sqlite3_update_hook(
-  sqlite3*, 
-  void(*)(void *,int ,char const *,char const *,sqlite3_int64),
-  void*
-);
-
-/*
-** CAPI3REF: Enable Or Disable Shared Pager Cache
-** KEYWORDS: {shared cache}
-**
-** ^(This routine enables or disables the sharing of the database cache
-** and schema data structures between [database connection | connections]
-** to the same database. Sharing is enabled if the argument is true
-** and disabled if the argument is false.)^
-**
-** ^Cache sharing is enabled and disabled for an entire process.
-** This is a change as of SQLite version 3.5.0. In prior versions of SQLite,
-** sharing was enabled or disabled for each thread separately.
-**
-** ^(The cache sharing mode set by this interface effects all subsequent
-** calls to [sqlite3_open()], [sqlite3_open_v2()], and [sqlite3_open16()].
-** Existing database connections continue use the sharing mode
-** that was in effect at the time they were opened.)^
-**
-** ^(This routine returns [SQLITE_OK] if shared cache was enabled or disabled
-** successfully.  An [error code] is returned otherwise.)^
-**
-** ^Shared cache is disabled by default. But this might change in
-** future releases of SQLite.  Applications that care about shared
-** cache setting should set it explicitly.
-**
-** See Also:  [SQLite Shared-Cache Mode]
-*/
-SQLITE_API int sqlite3_enable_shared_cache(int);
-
-/*
-** CAPI3REF: Attempt To Free Heap Memory
-**
-** ^The sqlite3_release_memory() interface attempts to free N bytes
-** of heap memory by deallocating non-essential memory allocations
-** held by the database library.   Memory used to cache database
-** pages to improve performance is an example of non-essential memory.
-** ^sqlite3_release_memory() returns the number of bytes actually freed,
-** which might be more or less than the amount requested.
-*/
-SQLITE_API int sqlite3_release_memory(int);
-
-/*
-** CAPI3REF: Impose A Limit On Heap Size
-**
-** ^The sqlite3_soft_heap_limit() interface places a "soft" limit
-** on the amount of heap memory that may be allocated by SQLite.
-** ^If an internal allocation is requested that would exceed the
-** soft heap limit, [sqlite3_release_memory()] is invoked one or
-** more times to free up some space before the allocation is performed.
-**
-** ^The limit is called "soft" because if [sqlite3_release_memory()]
-** cannot free sufficient memory to prevent the limit from being exceeded,
-** the memory is allocated anyway and the current operation proceeds.
-**
-** ^A negative or zero value for N means that there is no soft heap limit and
-** [sqlite3_release_memory()] will only be called when memory is exhausted.
-** ^The default value for the soft heap limit is zero.
-**
-** ^(SQLite makes a best effort to honor the soft heap limit.
-** But if the soft heap limit cannot be honored, execution will
-** continue without error or notification.)^  This is why the limit is
-** called a "soft" limit.  It is advisory only.
-**
-** Prior to SQLite version 3.5.0, this routine only constrained the memory
-** allocated by a single thread - the same thread in which this routine
-** runs.  Beginning with SQLite version 3.5.0, the soft heap limit is
-** applied to all threads. The value specified for the soft heap limit
-** is an upper bound on the total memory allocation for all threads. In
-** version 3.5.0 there is no mechanism for limiting the heap usage for
-** individual threads.
-*/
-SQLITE_API void sqlite3_soft_heap_limit(int);
-
-/*
-** CAPI3REF: Extract Metadata About A Column Of A Table
-**
-** ^This routine returns metadata about a specific column of a specific
-** database table accessible using the [database connection] handle
-** passed as the first function argument.
-**
-** ^The column is identified by the second, third and fourth parameters to
-** this function. ^The second parameter is either the name of the database
-** (i.e. "main", "temp", or an attached database) containing the specified
-** table or NULL. ^If it is NULL, then all attached databases are searched
-** for the table using the same algorithm used by the database engine to
-** resolve unqualified table references.
-**
-** ^The third and fourth parameters to this function are the table and column
-** name of the desired column, respectively. Neither of these parameters
-** may be NULL.
-**
-** ^Metadata is returned by writing to the memory locations passed as the 5th
-** and subsequent parameters to this function. ^Any of these arguments may be
-** NULL, in which case the corresponding element of metadata is omitted.
-**
-** ^(<blockquote>
-** <table border="1">
-** <tr><th> Parameter <th> Output<br>Type <th>  Description
-**
-** <tr><td> 5th <td> const char* <td> Data type
-** <tr><td> 6th <td> const char* <td> Name of default collation sequence
-** <tr><td> 7th <td> int         <td> True if column has a NOT NULL constraint
-** <tr><td> 8th <td> int         <td> True if column is part of the PRIMARY KEY
-** <tr><td> 9th <td> int         <td> True if column is [AUTOINCREMENT]
-** </table>
-** </blockquote>)^
-**
-** ^The memory pointed to by the character pointers returned for the
-** declaration type and collation sequence is valid only until the next
-** call to any SQLite API function.
-**
-** ^If the specified table is actually a view, an [error code] is returned.
-**
-** ^If the specified column is "rowid", "oid" or "_rowid_" and an
-** [INTEGER PRIMARY KEY] column has been explicitly declared, then the output
-** parameters are set for the explicitly declared column. ^(If there is no
-** explicitly declared [INTEGER PRIMARY KEY] column, then the output
-** parameters are set as follows:
-**
-** <pre>
-**     data type: "INTEGER"
-**     collation sequence: "BINARY"
-**     not null: 0
-**     primary key: 1
-**     auto increment: 0
-** </pre>)^
-**
-** ^(This function may load one or more schemas from database files. If an
-** error occurs during this process, or if the requested table or column
-** cannot be found, an [error code] is returned and an error message left
-** in the [database connection] (to be retrieved using sqlite3_errmsg()).)^
-**
-** ^This API is only available if the library was compiled with the
-** [SQLITE_ENABLE_COLUMN_METADATA] C-preprocessor symbol defined.
-*/
-SQLITE_API int sqlite3_table_column_metadata(
-  sqlite3 *db,                /* Connection handle */
-  const char *zDbName,        /* Database name or NULL */
-  const char *zTableName,     /* Table name */
-  const char *zColumnName,    /* Column name */
-  char const **pzDataType,    /* OUTPUT: Declared data type */
-  char const **pzCollSeq,     /* OUTPUT: Collation sequence name */
-  int *pNotNull,              /* OUTPUT: True if NOT NULL constraint exists */
-  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
-  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
-);
-
-/*
-** CAPI3REF: Load An Extension
-**
-** ^This interface loads an SQLite extension library from the named file.
-**
-** ^The sqlite3_load_extension() interface attempts to load an
-** SQLite extension library contained in the file zFile.
-**
-** ^The entry point is zProc.
-** ^zProc may be 0, in which case the name of the entry point
-** defaults to "sqlite3_extension_init".
-** ^The sqlite3_load_extension() interface returns
-** [SQLITE_OK] on success and [SQLITE_ERROR] if something goes wrong.
-** ^If an error occurs and pzErrMsg is not 0, then the
-** [sqlite3_load_extension()] interface shall attempt to
-** fill *pzErrMsg with error message text stored in memory
-** obtained from [sqlite3_malloc()]. The calling function
-** should free this memory by calling [sqlite3_free()].
-**
-** ^Extension loading must be enabled using
-** [sqlite3_enable_load_extension()] prior to calling this API,
-** otherwise an error will be returned.
-**
-** See also the [load_extension() SQL function].
-*/
-SQLITE_API int sqlite3_load_extension(
-  sqlite3 *db,          /* Load the extension into this database connection */
-  const char *zFile,    /* Name of the shared library containing extension */
-  const char *zProc,    /* Entry point.  Derived from zFile if 0 */
-  char **pzErrMsg       /* Put error message here if not 0 */
-);
-
-/*
-** CAPI3REF: Enable Or Disable Extension Loading
-**
-** ^So as not to open security holes in older applications that are
-** unprepared to deal with extension loading, and as a means of disabling
-** extension loading while evaluating user-entered SQL, the following API
-** is provided to turn the [sqlite3_load_extension()] mechanism on and off.
-**
-** ^Extension loading is off by default. See ticket #1863.
-** ^Call the sqlite3_enable_load_extension() routine with onoff==1
-** to turn extension loading on and call it with onoff==0 to turn
-** it back off again.
-*/
-SQLITE_API int sqlite3_enable_load_extension(sqlite3 *db, int onoff);
-
-/*
-** CAPI3REF: Automatically Load An Extensions
-**
-** ^This API can be invoked at program startup in order to register
-** one or more statically linked extensions that will be available
-** to all new [database connections].
-**
-** ^(This routine stores a pointer to the extension entry point
-** in an array that is obtained from [sqlite3_malloc()].  That memory
-** is deallocated by [sqlite3_reset_auto_extension()].)^
-**
-** ^This function registers an extension entry point that is
-** automatically invoked whenever a new [database connection]
-** is opened using [sqlite3_open()], [sqlite3_open16()],
-** or [sqlite3_open_v2()].
-** ^Duplicate extensions are detected so calling this routine
-** multiple times with the same extension is harmless.
-** ^Automatic extensions apply across all threads.
-*/
-SQLITE_API int sqlite3_auto_extension(void (*xEntryPoint)(void));
-
-/*
-** CAPI3REF: Reset Automatic Extension Loading
-**
-** ^(This function disables all previously registered automatic
-** extensions. It undoes the effect of all prior
-** [sqlite3_auto_extension()] calls.)^
-**
-** ^This function disables automatic extensions in all threads.
-*/
-SQLITE_API void sqlite3_reset_auto_extension(void);
-
-/*
-****** EXPERIMENTAL - subject to change without notice **************
-**
-** The interface to the virtual-table mechanism is currently considered
-** to be experimental.  The interface might change in incompatible ways.
-** If this is a problem for you, do not use the interface at this time.
-**
-** When the virtual-table mechanism stabilizes, we will declare the
-** interface fixed, support it indefinitely, and remove this comment.
-*/
-
-/*
-** Structures used by the virtual table interface
-*/
-typedef struct sqlite3_vtab sqlite3_vtab;
-typedef struct sqlite3_index_info sqlite3_index_info;
-typedef struct sqlite3_vtab_cursor sqlite3_vtab_cursor;
-typedef struct sqlite3_module sqlite3_module;
-
-/*
-** CAPI3REF: Virtual Table Object
-** KEYWORDS: sqlite3_module {virtual table module}
-** EXPERIMENTAL
-**
-** This structure, sometimes called a a "virtual table module", 
-** defines the implementation of a [virtual tables].  
-** This structure consists mostly of methods for the module.
-**
-** ^A virtual table module is created by filling in a persistent
-** instance of this structure and passing a pointer to that instance
-** to [sqlite3_create_module()] or [sqlite3_create_module_v2()].
-** ^The registration remains valid until it is replaced by a different
-** module or until the [database connection] closes.  The content
-** of this structure must not change while it is registered with
-** any database connection.
-*/
-struct sqlite3_module {
-  int iVersion;
-  int (*xCreate)(sqlite3*, void *pAux,
-               int argc, const char *const*argv,
-               sqlite3_vtab **ppVTab, char**);
-  int (*xConnect)(sqlite3*, void *pAux,
-               int argc, const char *const*argv,
-               sqlite3_vtab **ppVTab, char**);
-  int (*xBestIndex)(sqlite3_vtab *pVTab, sqlite3_index_info*);
-  int (*xDisconnect)(sqlite3_vtab *pVTab);
-  int (*xDestroy)(sqlite3_vtab *pVTab);
-  int (*xOpen)(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor);
-  int (*xClose)(sqlite3_vtab_cursor*);
-  int (*xFilter)(sqlite3_vtab_cursor*, int idxNum, const char *idxStr,
-                int argc, sqlite3_value **argv);
-  int (*xNext)(sqlite3_vtab_cursor*);
-  int (*xEof)(sqlite3_vtab_cursor*);
-  int (*xColumn)(sqlite3_vtab_cursor*, sqlite3_context*, int);
-  int (*xRowid)(sqlite3_vtab_cursor*, sqlite3_int64 *pRowid);
-  int (*xUpdate)(sqlite3_vtab *, int, sqlite3_value **, sqlite3_int64 *);
-  int (*xBegin)(sqlite3_vtab *pVTab);
-  int (*xSync)(sqlite3_vtab *pVTab);
-  int (*xCommit)(sqlite3_vtab *pVTab);
-  int (*xRollback)(sqlite3_vtab *pVTab);
-  int (*xFindFunction)(sqlite3_vtab *pVtab, int nArg, const char *zName,
-                       void (**pxFunc)(sqlite3_context*,int,sqlite3_value**),
-                       void **ppArg);
-  int (*xRename)(sqlite3_vtab *pVtab, const char *zNew);
-};
-
-/*
-** CAPI3REF: Virtual Table Indexing Information
-** KEYWORDS: sqlite3_index_info
-** EXPERIMENTAL
-**
-** The sqlite3_index_info structure and its substructures is used to
-** pass information into and receive the reply from the [xBestIndex]
-** method of a [virtual table module].  The fields under **Inputs** are the
-** inputs to xBestIndex and are read-only.  xBestIndex inserts its
-** results into the **Outputs** fields.
-**
-** ^(The aConstraint[] array records WHERE clause constraints of the form:
-**
-** <pre>column OP expr</pre>
-**
-** where OP is =, &lt;, &lt;=, &gt;, or &gt;=.)^  ^(The particular operator is
-** stored in aConstraint[].op.)^  ^(The index of the column is stored in
-** aConstraint[].iColumn.)^  ^(aConstraint[].usable is TRUE if the
-** expr on the right-hand side can be evaluated (and thus the constraint
-** is usable) and false if it cannot.)^
-**
-** ^The optimizer automatically inverts terms of the form "expr OP column"
-** and makes other simplifications to the WHERE clause in an attempt to
-** get as many WHERE clause terms into the form shown above as possible.
-** ^The aConstraint[] array only reports WHERE clause terms that are
-** relevant to the particular virtual table being queried.
-**
-** ^Information about the ORDER BY clause is stored in aOrderBy[].
-** ^Each term of aOrderBy records a column of the ORDER BY clause.
-**
-** The [xBestIndex] method must fill aConstraintUsage[] with information
-** about what parameters to pass to xFilter.  ^If argvIndex>0 then
-** the right-hand side of the corresponding aConstraint[] is evaluated
-** and becomes the argvIndex-th entry in argv.  ^(If aConstraintUsage[].omit
-** is true, then the constraint is assumed to be fully handled by the
-** virtual table and is not checked again by SQLite.)^
-**
-** ^The idxNum and idxPtr values are recorded and passed into the
-** [xFilter] method.
-** ^[sqlite3_free()] is used to free idxPtr if and only if
-** needToFreeIdxPtr is true.
-**
-** ^The orderByConsumed means that output from [xFilter]/[xNext] will occur in
-** the correct order to satisfy the ORDER BY clause so that no separate
-** sorting step is required.
-**
-** ^The estimatedCost value is an estimate of the cost of doing the
-** particular lookup.  A full scan of a table with N entries should have
-** a cost of N.  A binary search of a table of N entries should have a
-** cost of approximately log(N).
-*/
-struct sqlite3_index_info {
-  /* Inputs */
-  int nConstraint;           /* Number of entries in aConstraint */
-  struct sqlite3_index_constraint {
-     int iColumn;              /* Column on left-hand side of constraint */
-     unsigned char op;         /* Constraint operator */
-     unsigned char usable;     /* True if this constraint is usable */
-     int iTermOffset;          /* Used internally - xBestIndex should ignore */
-  } *aConstraint;            /* Table of WHERE clause constraints */
-  int nOrderBy;              /* Number of terms in the ORDER BY clause */
-  struct sqlite3_index_orderby {
-     int iColumn;              /* Column number */
-     unsigned char desc;       /* True for DESC.  False for ASC. */
-  } *aOrderBy;               /* The ORDER BY clause */
-  /* Outputs */
-  struct sqlite3_index_constraint_usage {
-    int argvIndex;           /* if >0, constraint is part of argv to xFilter */
-    unsigned char omit;      /* Do not code a test for this constraint */
-  } *aConstraintUsage;
-  int idxNum;                /* Number used to identify the index */
-  char *idxStr;              /* String, possibly obtained from sqlite3_malloc */
-  int needToFreeIdxStr;      /* Free idxStr using sqlite3_free() if true */
-  int orderByConsumed;       /* True if output is already ordered */
-  double estimatedCost;      /* Estimated cost of using this index */
-};
-#define SQLITE_INDEX_CONSTRAINT_EQ    2
-#define SQLITE_INDEX_CONSTRAINT_GT    4
-#define SQLITE_INDEX_CONSTRAINT_LE    8
-#define SQLITE_INDEX_CONSTRAINT_LT    16
-#define SQLITE_INDEX_CONSTRAINT_GE    32
-#define SQLITE_INDEX_CONSTRAINT_MATCH 64
-
-/*
-** CAPI3REF: Register A Virtual Table Implementation
-** EXPERIMENTAL
-**
-** ^These routines are used to register a new [virtual table module] name.
-** ^Module names must be registered before
-** creating a new [virtual table] using the module and before using a
-** preexisting [virtual table] for the module.
-**
-** ^The module name is registered on the [database connection] specified
-** by the first parameter.  ^The name of the module is given by the 
-** second parameter.  ^The third parameter is a pointer to
-** the implementation of the [virtual table module].   ^The fourth
-** parameter is an arbitrary client data pointer that is passed through
-** into the [xCreate] and [xConnect] methods of the virtual table module
-** when a new virtual table is be being created or reinitialized.
-**
-** ^The sqlite3_create_module_v2() interface has a fifth parameter which
-** is a pointer to a destructor for the pClientData.  ^SQLite will
-** invoke the destructor function (if it is not NULL) when SQLite
-** no longer needs the pClientData pointer.  ^The sqlite3_create_module()
-** interface is equivalent to sqlite3_create_module_v2() with a NULL
-** destructor.
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module(
-  sqlite3 *db,               /* SQLite connection to register module with */
-  const char *zName,         /* Name of the module */
-  const sqlite3_module *p,   /* Methods for the module */
-  void *pClientData          /* Client data for xCreate/xConnect */
-);
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_create_module_v2(
-  sqlite3 *db,               /* SQLite connection to register module with */
-  const char *zName,         /* Name of the module */
-  const sqlite3_module *p,   /* Methods for the module */
-  void *pClientData,         /* Client data for xCreate/xConnect */
-  void(*xDestroy)(void*)     /* Module destructor function */
-);
-
-/*
-** CAPI3REF: Virtual Table Instance Object
-** KEYWORDS: sqlite3_vtab
-** EXPERIMENTAL
-**
-** Every [virtual table module] implementation uses a subclass
-** of this object to describe a particular instance
-** of the [virtual table].  Each subclass will
-** be tailored to the specific needs of the module implementation.
-** The purpose of this superclass is to define certain fields that are
-** common to all module implementations.
-**
-** ^Virtual tables methods can set an error message by assigning a
-** string obtained from [sqlite3_mprintf()] to zErrMsg.  The method should
-** take care that any prior string is freed by a call to [sqlite3_free()]
-** prior to assigning a new string to zErrMsg.  ^After the error message
-** is delivered up to the client application, the string will be automatically
-** freed by sqlite3_free() and the zErrMsg field will be zeroed.
-*/
-struct sqlite3_vtab {
-  const sqlite3_module *pModule;  /* The module for this virtual table */
-  int nRef;                       /* NO LONGER USED */
-  char *zErrMsg;                  /* Error message from sqlite3_mprintf() */
-  /* Virtual table implementations will typically add additional fields */
-};
-
-/*
-** CAPI3REF: Virtual Table Cursor Object
-** KEYWORDS: sqlite3_vtab_cursor {virtual table cursor}
-** EXPERIMENTAL
-**
-** Every [virtual table module] implementation uses a subclass of the
-** following structure to describe cursors that point into the
-** [virtual table] and are used
-** to loop through the virtual table.  Cursors are created using the
-** [sqlite3_module.xOpen | xOpen] method of the module and are destroyed
-** by the [sqlite3_module.xClose | xClose] method.  Cursors are used
-** by the [xFilter], [xNext], [xEof], [xColumn], and [xRowid] methods
-** of the module.  Each module implementation will define
-** the content of a cursor structure to suit its own needs.
-**
-** This superclass exists in order to define fields of the cursor that
-** are common to all implementations.
-*/
-struct sqlite3_vtab_cursor {
-  sqlite3_vtab *pVtab;      /* Virtual table of this cursor */
-  /* Virtual table implementations will typically add additional fields */
-};
-
-/*
-** CAPI3REF: Declare The Schema Of A Virtual Table
-** EXPERIMENTAL
-**
-** ^The [xCreate] and [xConnect] methods of a
-** [virtual table module] call this interface
-** to declare the format (the names and datatypes of the columns) of
-** the virtual tables they implement.
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_declare_vtab(sqlite3*, const char *zSQL);
-
-/*
-** CAPI3REF: Overload A Function For A Virtual Table
-** EXPERIMENTAL
-**
-** ^(Virtual tables can provide alternative implementations of functions
-** using the [xFindFunction] method of the [virtual table module].  
-** But global versions of those functions
-** must exist in order to be overloaded.)^
-**
-** ^(This API makes sure a global version of a function with a particular
-** name and number of parameters exists.  If no such function exists
-** before this API is called, a new function is created.)^  ^The implementation
-** of the new function always causes an exception to be thrown.  So
-** the new function is not good for anything by itself.  Its only
-** purpose is to be a placeholder function that can be overloaded
-** by a [virtual table].
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_overload_function(sqlite3*, const char *zFuncName, int nArg);
-
-/*
-** The interface to the virtual-table mechanism defined above (back up
-** to a comment remarkably similar to this one) is currently considered
-** to be experimental.  The interface might change in incompatible ways.
-** If this is a problem for you, do not use the interface at this time.
-**
-** When the virtual-table mechanism stabilizes, we will declare the
-** interface fixed, support it indefinitely, and remove this comment.
-**
-****** EXPERIMENTAL - subject to change without notice **************
-*/
-
-/*
-** CAPI3REF: A Handle To An Open BLOB
-** KEYWORDS: {BLOB handle} {BLOB handles}
-**
-** An instance of this object represents an open BLOB on which
-** [sqlite3_blob_open | incremental BLOB I/O] can be performed.
-** ^Objects of this type are created by [sqlite3_blob_open()]
-** and destroyed by [sqlite3_blob_close()].
-** ^The [sqlite3_blob_read()] and [sqlite3_blob_write()] interfaces
-** can be used to read or write small subsections of the BLOB.
-** ^The [sqlite3_blob_bytes()] interface returns the size of the BLOB in bytes.
-*/
-typedef struct sqlite3_blob sqlite3_blob;
-
-/*
-** CAPI3REF: Open A BLOB For Incremental I/O
-**
-** ^(This interfaces opens a [BLOB handle | handle] to the BLOB located
-** in row iRow, column zColumn, table zTable in database zDb;
-** in other words, the same BLOB that would be selected by:
-**
-** <pre>
-**     SELECT zColumn FROM zDb.zTable WHERE [rowid] = iRow;
-** </pre>)^
-**
-** ^If the flags parameter is non-zero, then the BLOB is opened for read
-** and write access. ^If it is zero, the BLOB is opened for read access.
-** ^It is not possible to open a column that is part of an index or primary 
-** key for writing. ^If [foreign key constraints] are enabled, it is 
-** not possible to open a column that is part of a [child key] for writing.
-**
-** ^Note that the database name is not the filename that contains
-** the database but rather the symbolic name of the database that
-** appears after the AS keyword when the database is connected using [ATTACH].
-** ^For the main database file, the database name is "main".
-** ^For TEMP tables, the database name is "temp".
-**
-** ^(On success, [SQLITE_OK] is returned and the new [BLOB handle] is written
-** to *ppBlob. Otherwise an [error code] is returned and *ppBlob is set
-** to be a null pointer.)^
-** ^This function sets the [database connection] error code and message
-** accessible via [sqlite3_errcode()] and [sqlite3_errmsg()] and related
-** functions. ^Note that the *ppBlob variable is always initialized in a
-** way that makes it safe to invoke [sqlite3_blob_close()] on *ppBlob
-** regardless of the success or failure of this routine.
-**
-** ^(If the row that a BLOB handle points to is modified by an
-** [UPDATE], [DELETE], or by [ON CONFLICT] side-effects
-** then the BLOB handle is marked as "expired".
-** This is true if any column of the row is changed, even a column
-** other than the one the BLOB handle is open on.)^
-** ^Calls to [sqlite3_blob_read()] and [sqlite3_blob_write()] for
-** a expired BLOB handle fail with an return code of [SQLITE_ABORT].
-** ^(Changes written into a BLOB prior to the BLOB expiring are not
-** rolled back by the expiration of the BLOB.  Such changes will eventually
-** commit if the transaction continues to completion.)^
-**
-** ^Use the [sqlite3_blob_bytes()] interface to determine the size of
-** the opened blob.  ^The size of a blob may not be changed by this
-** interface.  Use the [UPDATE] SQL command to change the size of a
-** blob.
-**
-** ^The [sqlite3_bind_zeroblob()] and [sqlite3_result_zeroblob()] interfaces
-** and the built-in [zeroblob] SQL function can be used, if desired,
-** to create an empty, zero-filled blob in which to read or write using
-** this interface.
-**
-** To avoid a resource leak, every open [BLOB handle] should eventually
-** be released by a call to [sqlite3_blob_close()].
-*/
-SQLITE_API int sqlite3_blob_open(
-  sqlite3*,
-  const char *zDb,
-  const char *zTable,
-  const char *zColumn,
-  sqlite3_int64 iRow,
-  int flags,
-  sqlite3_blob **ppBlob
-);
-
-/*
-** CAPI3REF: Close A BLOB Handle
-**
-** ^Closes an open [BLOB handle].
-**
-** ^Closing a BLOB shall cause the current transaction to commit
-** if there are no other BLOBs, no pending prepared statements, and the
-** database connection is in [autocommit mode].
-** ^If any writes were made to the BLOB, they might be held in cache
-** until the close operation if they will fit.
-**
-** ^(Closing the BLOB often forces the changes
-** out to disk and so if any I/O errors occur, they will likely occur
-** at the time when the BLOB is closed.  Any errors that occur during
-** closing are reported as a non-zero return value.)^
-**
-** ^(The BLOB is closed unconditionally.  Even if this routine returns
-** an error code, the BLOB is still closed.)^
-**
-** ^Calling this routine with a null pointer (such as would be returned
-** by a failed call to [sqlite3_blob_open()]) is a harmless no-op.
-*/
-SQLITE_API int sqlite3_blob_close(sqlite3_blob *);
-
-/*
-** CAPI3REF: Return The Size Of An Open BLOB
-**
-** ^Returns the size in bytes of the BLOB accessible via the 
-** successfully opened [BLOB handle] in its only argument.  ^The
-** incremental blob I/O routines can only read or overwriting existing
-** blob content; they cannot change the size of a blob.
-**
-** This routine only works on a [BLOB handle] which has been created
-** by a prior successful call to [sqlite3_blob_open()] and which has not
-** been closed by [sqlite3_blob_close()].  Passing any other pointer in
-** to this routine results in undefined and probably undesirable behavior.
-*/
-SQLITE_API int sqlite3_blob_bytes(sqlite3_blob *);
-
-/*
-** CAPI3REF: Read Data From A BLOB Incrementally
-**
-** ^(This function is used to read data from an open [BLOB handle] into a
-** caller-supplied buffer. N bytes of data are copied into buffer Z
-** from the open BLOB, starting at offset iOffset.)^
-**
-** ^If offset iOffset is less than N bytes from the end of the BLOB,
-** [SQLITE_ERROR] is returned and no data is read.  ^If N or iOffset is
-** less than zero, [SQLITE_ERROR] is returned and no data is read.
-** ^The size of the blob (and hence the maximum value of N+iOffset)
-** can be determined using the [sqlite3_blob_bytes()] interface.
-**
-** ^An attempt to read from an expired [BLOB handle] fails with an
-** error code of [SQLITE_ABORT].
-**
-** ^(On success, sqlite3_blob_read() returns SQLITE_OK.
-** Otherwise, an [error code] or an [extended error code] is returned.)^
-**
-** This routine only works on a [BLOB handle] which has been created
-** by a prior successful call to [sqlite3_blob_open()] and which has not
-** been closed by [sqlite3_blob_close()].  Passing any other pointer in
-** to this routine results in undefined and probably undesirable behavior.
-**
-** See also: [sqlite3_blob_write()].
-*/
-SQLITE_API int sqlite3_blob_read(sqlite3_blob *, void *Z, int N, int iOffset);
-
-/*
-** CAPI3REF: Write Data Into A BLOB Incrementally
-**
-** ^This function is used to write data into an open [BLOB handle] from a
-** caller-supplied buffer. ^N bytes of data are copied from the buffer Z
-** into the open BLOB, starting at offset iOffset.
-**
-** ^If the [BLOB handle] passed as the first argument was not opened for
-** writing (the flags parameter to [sqlite3_blob_open()] was zero),
-** this function returns [SQLITE_READONLY].
-**
-** ^This function may only modify the contents of the BLOB; it is
-** not possible to increase the size of a BLOB using this API.
-** ^If offset iOffset is less than N bytes from the end of the BLOB,
-** [SQLITE_ERROR] is returned and no data is written.  ^If N is
-** less than zero [SQLITE_ERROR] is returned and no data is written.
-** The size of the BLOB (and hence the maximum value of N+iOffset)
-** can be determined using the [sqlite3_blob_bytes()] interface.
-**
-** ^An attempt to write to an expired [BLOB handle] fails with an
-** error code of [SQLITE_ABORT].  ^Writes to the BLOB that occurred
-** before the [BLOB handle] expired are not rolled back by the
-** expiration of the handle, though of course those changes might
-** have been overwritten by the statement that expired the BLOB handle
-** or by other independent statements.
-**
-** ^(On success, sqlite3_blob_write() returns SQLITE_OK.
-** Otherwise, an  [error code] or an [extended error code] is returned.)^
-**
-** This routine only works on a [BLOB handle] which has been created
-** by a prior successful call to [sqlite3_blob_open()] and which has not
-** been closed by [sqlite3_blob_close()].  Passing any other pointer in
-** to this routine results in undefined and probably undesirable behavior.
-**
-** See also: [sqlite3_blob_read()].
-*/
-SQLITE_API int sqlite3_blob_write(sqlite3_blob *, const void *z, int n, int iOffset);
-
-/*
-** CAPI3REF: Virtual File System Objects
-**
-** A virtual filesystem (VFS) is an [sqlite3_vfs] object
-** that SQLite uses to interact
-** with the underlying operating system.  Most SQLite builds come with a
-** single default VFS that is appropriate for the host computer.
-** New VFSes can be registered and existing VFSes can be unregistered.
-** The following interfaces are provided.
-**
-** ^The sqlite3_vfs_find() interface returns a pointer to a VFS given its name.
-** ^Names are case sensitive.
-** ^Names are zero-terminated UTF-8 strings.
-** ^If there is no match, a NULL pointer is returned.
-** ^If zVfsName is NULL then the default VFS is returned.
-**
-** ^New VFSes are registered with sqlite3_vfs_register().
-** ^Each new VFS becomes the default VFS if the makeDflt flag is set.
-** ^The same VFS can be registered multiple times without injury.
-** ^To make an existing VFS into the default VFS, register it again
-** with the makeDflt flag set.  If two different VFSes with the
-** same name are registered, the behavior is undefined.  If a
-** VFS is registered with a name that is NULL or an empty string,
-** then the behavior is undefined.
-**
-** ^Unregister a VFS with the sqlite3_vfs_unregister() interface.
-** ^(If the default VFS is unregistered, another VFS is chosen as
-** the default.  The choice for the new VFS is arbitrary.)^
-*/
-SQLITE_API sqlite3_vfs *sqlite3_vfs_find(const char *zVfsName);
-SQLITE_API int sqlite3_vfs_register(sqlite3_vfs*, int makeDflt);
-SQLITE_API int sqlite3_vfs_unregister(sqlite3_vfs*);
-
-/*
-** CAPI3REF: Mutexes
-**
-** The SQLite core uses these routines for thread
-** synchronization. Though they are intended for internal
-** use by SQLite, code that links against SQLite is
-** permitted to use any of these routines.
-**
-** The SQLite source code contains multiple implementations
-** of these mutex routines.  An appropriate implementation
-** is selected automatically at compile-time.  ^(The following
-** implementations are available in the SQLite core:
-**
-** <ul>
-** <li>   SQLITE_MUTEX_OS2
-** <li>   SQLITE_MUTEX_PTHREAD
-** <li>   SQLITE_MUTEX_W32
-** <li>   SQLITE_MUTEX_NOOP
-** </ul>)^
-**
-** ^The SQLITE_MUTEX_NOOP implementation is a set of routines
-** that does no real locking and is appropriate for use in
-** a single-threaded application.  ^The SQLITE_MUTEX_OS2,
-** SQLITE_MUTEX_PTHREAD, and SQLITE_MUTEX_W32 implementations
-** are appropriate for use on OS/2, Unix, and Windows.
-**
-** ^(If SQLite is compiled with the SQLITE_MUTEX_APPDEF preprocessor
-** macro defined (with "-DSQLITE_MUTEX_APPDEF=1"), then no mutex
-** implementation is included with the library. In this case the
-** application must supply a custom mutex implementation using the
-** [SQLITE_CONFIG_MUTEX] option of the sqlite3_config() function
-** before calling sqlite3_initialize() or any other public sqlite3_
-** function that calls sqlite3_initialize().)^
-**
-** ^The sqlite3_mutex_alloc() routine allocates a new
-** mutex and returns a pointer to it. ^If it returns NULL
-** that means that a mutex could not be allocated.  ^SQLite
-** will unwind its stack and return an error.  ^(The argument
-** to sqlite3_mutex_alloc() is one of these integer constants:
-**
-** <ul>
-** <li>  SQLITE_MUTEX_FAST
-** <li>  SQLITE_MUTEX_RECURSIVE
-** <li>  SQLITE_MUTEX_STATIC_MASTER
-** <li>  SQLITE_MUTEX_STATIC_MEM
-** <li>  SQLITE_MUTEX_STATIC_MEM2
-** <li>  SQLITE_MUTEX_STATIC_PRNG
-** <li>  SQLITE_MUTEX_STATIC_LRU
-** <li>  SQLITE_MUTEX_STATIC_LRU2
-** </ul>)^
-**
-** ^The first two constants (SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE)
-** cause sqlite3_mutex_alloc() to create
-** a new mutex.  ^The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
-** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
-** The mutex implementation does not need to make a distinction
-** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
-** not want to.  ^SQLite will only request a recursive mutex in
-** cases where it really needs one.  ^If a faster non-recursive mutex
-** implementation is available on the host platform, the mutex subsystem
-** might return such a mutex in response to SQLITE_MUTEX_FAST.
-**
-** ^The other allowed parameters to sqlite3_mutex_alloc() (anything other
-** than SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) each return
-** a pointer to a static preexisting mutex.  ^Six static mutexes are
-** used by the current version of SQLite.  Future versions of SQLite
-** may add additional static mutexes.  Static mutexes are for internal
-** use by SQLite only.  Applications that use SQLite mutexes should
-** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
-** SQLITE_MUTEX_RECURSIVE.
-**
-** ^Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
-** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
-** returns a different mutex on every call.  ^But for the static
-** mutex types, the same mutex is returned on every call that has
-** the same type number.
-**
-** ^The sqlite3_mutex_free() routine deallocates a previously
-** allocated dynamic mutex.  ^SQLite is careful to deallocate every
-** dynamic mutex that it allocates.  The dynamic mutexes must not be in
-** use when they are deallocated.  Attempting to deallocate a static
-** mutex results in undefined behavior.  ^SQLite never deallocates
-** a static mutex.
-**
-** ^The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
-** to enter a mutex.  ^If another thread is already within the mutex,
-** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
-** SQLITE_BUSY.  ^The sqlite3_mutex_try() interface returns [SQLITE_OK]
-** upon successful entry.  ^(Mutexes created using
-** SQLITE_MUTEX_RECURSIVE can be entered multiple times by the same thread.
-** In such cases the,
-** mutex must be exited an equal number of times before another thread
-** can enter.)^  ^(If the same thread tries to enter any other
-** kind of mutex more than once, the behavior is undefined.
-** SQLite will never exhibit
-** such behavior in its own use of mutexes.)^
-**
-** ^(Some systems (for example, Windows 95) do not support the operation
-** implemented by sqlite3_mutex_try().  On those systems, sqlite3_mutex_try()
-** will always return SQLITE_BUSY.  The SQLite core only ever uses
-** sqlite3_mutex_try() as an optimization so this is acceptable behavior.)^
-**
-** ^The sqlite3_mutex_leave() routine exits a mutex that was
-** previously entered by the same thread.   ^(The behavior
-** is undefined if the mutex is not currently entered by the
-** calling thread or is not currently allocated.  SQLite will
-** never do either.)^
-**
-** ^If the argument to sqlite3_mutex_enter(), sqlite3_mutex_try(), or
-** sqlite3_mutex_leave() is a NULL pointer, then all three routines
-** behave as no-ops.
-**
-** See also: [sqlite3_mutex_held()] and [sqlite3_mutex_notheld()].
-*/
-SQLITE_API sqlite3_mutex *sqlite3_mutex_alloc(int);
-SQLITE_API void sqlite3_mutex_free(sqlite3_mutex*);
-SQLITE_API void sqlite3_mutex_enter(sqlite3_mutex*);
-SQLITE_API int sqlite3_mutex_try(sqlite3_mutex*);
-SQLITE_API void sqlite3_mutex_leave(sqlite3_mutex*);
-
-/*
-** CAPI3REF: Mutex Methods Object
-** EXPERIMENTAL
-**
-** An instance of this structure defines the low-level routines
-** used to allocate and use mutexes.
-**
-** Usually, the default mutex implementations provided by SQLite are
-** sufficient, however the user has the option of substituting a custom
-** implementation for specialized deployments or systems for which SQLite
-** does not provide a suitable implementation. In this case, the user
-** creates and populates an instance of this structure to pass
-** to sqlite3_config() along with the [SQLITE_CONFIG_MUTEX] option.
-** Additionally, an instance of this structure can be used as an
-** output variable when querying the system for the current mutex
-** implementation, using the [SQLITE_CONFIG_GETMUTEX] option.
-**
-** ^The xMutexInit method defined by this structure is invoked as
-** part of system initialization by the sqlite3_initialize() function.
-** ^The xMutexInit routine is calle by SQLite exactly once for each
-** effective call to [sqlite3_initialize()].
-**
-** ^The xMutexEnd method defined by this structure is invoked as
-** part of system shutdown by the sqlite3_shutdown() function. The
-** implementation of this method is expected to release all outstanding
-** resources obtained by the mutex methods implementation, especially
-** those obtained by the xMutexInit method.  ^The xMutexEnd()
-** interface is invoked exactly once for each call to [sqlite3_shutdown()].
-**
-** ^(The remaining seven methods defined by this structure (xMutexAlloc,
-** xMutexFree, xMutexEnter, xMutexTry, xMutexLeave, xMutexHeld and
-** xMutexNotheld) implement the following interfaces (respectively):
-**
-** <ul>
-**   <li>  [sqlite3_mutex_alloc()] </li>
-**   <li>  [sqlite3_mutex_free()] </li>
-**   <li>  [sqlite3_mutex_enter()] </li>
-**   <li>  [sqlite3_mutex_try()] </li>
-**   <li>  [sqlite3_mutex_leave()] </li>
-**   <li>  [sqlite3_mutex_held()] </li>
-**   <li>  [sqlite3_mutex_notheld()] </li>
-** </ul>)^
-**
-** The only difference is that the public sqlite3_XXX functions enumerated
-** above silently ignore any invocations that pass a NULL pointer instead
-** of a valid mutex handle. The implementations of the methods defined
-** by this structure are not required to handle this case, the results
-** of passing a NULL pointer instead of a valid mutex handle are undefined
-** (i.e. it is acceptable to provide an implementation that segfaults if
-** it is passed a NULL pointer).
-**
-** The xMutexInit() method must be threadsafe.  ^It must be harmless to
-** invoke xMutexInit() mutiple times within the same process and without
-** intervening calls to xMutexEnd().  Second and subsequent calls to
-** xMutexInit() must be no-ops.
-**
-** ^xMutexInit() must not use SQLite memory allocation ([sqlite3_malloc()]
-** and its associates).  ^Similarly, xMutexAlloc() must not use SQLite memory
-** allocation for a static mutex.  ^However xMutexAlloc() may use SQLite
-** memory allocation for a fast or recursive mutex.
-**
-** ^SQLite will invoke the xMutexEnd() method when [sqlite3_shutdown()] is
-** called, but only if the prior call to xMutexInit returned SQLITE_OK.
-** If xMutexInit fails in any way, it is expected to clean up after itself
-** prior to returning.
-*/
-typedef struct sqlite3_mutex_methods sqlite3_mutex_methods;
-struct sqlite3_mutex_methods {
-  int (*xMutexInit)(void);
-  int (*xMutexEnd)(void);
-  sqlite3_mutex *(*xMutexAlloc)(int);
-  void (*xMutexFree)(sqlite3_mutex *);
-  void (*xMutexEnter)(sqlite3_mutex *);
-  int (*xMutexTry)(sqlite3_mutex *);
-  void (*xMutexLeave)(sqlite3_mutex *);
-  int (*xMutexHeld)(sqlite3_mutex *);
-  int (*xMutexNotheld)(sqlite3_mutex *);
-};
-
-/*
-** CAPI3REF: Mutex Verification Routines
-**
-** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routines
-** are intended for use inside assert() statements.  ^The SQLite core
-** never uses these routines except inside an assert() and applications
-** are advised to follow the lead of the core.  ^The SQLite core only
-** provides implementations for these routines when it is compiled
-** with the SQLITE_DEBUG flag.  ^External mutex implementations
-** are only required to provide these routines if SQLITE_DEBUG is
-** defined and if NDEBUG is not defined.
-**
-** ^These routines should return true if the mutex in their argument
-** is held or not held, respectively, by the calling thread.
-**
-** ^The implementation is not required to provided versions of these
-** routines that actually work. If the implementation does not provide working
-** versions of these routines, it should at least provide stubs that always
-** return true so that one does not get spurious assertion failures.
-**
-** ^If the argument to sqlite3_mutex_held() is a NULL pointer then
-** the routine should return 1.   This seems counter-intuitive since
-** clearly the mutex cannot be held if it does not exist.  But the
-** the reason the mutex does not exist is because the build is not
-** using mutexes.  And we do not want the assert() containing the
-** call to sqlite3_mutex_held() to fail, so a non-zero return is
-** the appropriate thing to do.  ^The sqlite3_mutex_notheld()
-** interface should also return 1 when given a NULL pointer.
-*/
-#ifndef NDEBUG
-SQLITE_API int sqlite3_mutex_held(sqlite3_mutex*);
-SQLITE_API int sqlite3_mutex_notheld(sqlite3_mutex*);
-#endif
-
-/*
-** CAPI3REF: Mutex Types
-**
-** The [sqlite3_mutex_alloc()] interface takes a single argument
-** which is one of these integer constants.
-**
-** The set of static mutexes may change from one SQLite release to the
-** next.  Applications that override the built-in mutex logic must be
-** prepared to accommodate additional static mutexes.
-*/
-#define SQLITE_MUTEX_FAST             0
-#define SQLITE_MUTEX_RECURSIVE        1
-#define SQLITE_MUTEX_STATIC_MASTER    2
-#define SQLITE_MUTEX_STATIC_MEM       3  /* sqlite3_malloc() */
-#define SQLITE_MUTEX_STATIC_MEM2      4  /* NOT USED */
-#define SQLITE_MUTEX_STATIC_OPEN      4  /* sqlite3BtreeOpen() */
-#define SQLITE_MUTEX_STATIC_PRNG      5  /* sqlite3_random() */
-#define SQLITE_MUTEX_STATIC_LRU       6  /* lru page list */
-#define SQLITE_MUTEX_STATIC_LRU2      7  /* lru page list */
-
-/*
-** CAPI3REF: Retrieve the mutex for a database connection
-**
-** ^This interface returns a pointer the [sqlite3_mutex] object that 
-** serializes access to the [database connection] given in the argument
-** when the [threading mode] is Serialized.
-** ^If the [threading mode] is Single-thread or Multi-thread then this
-** routine returns a NULL pointer.
-*/
-SQLITE_API sqlite3_mutex *sqlite3_db_mutex(sqlite3*);
-
-/*
-** CAPI3REF: Low-Level Control Of Database Files
-**
-** ^The [sqlite3_file_control()] interface makes a direct call to the
-** xFileControl method for the [sqlite3_io_methods] object associated
-** with a particular database identified by the second argument. ^The
-** name of the database "main" for the main database or "temp" for the
-** TEMP database, or the name that appears after the AS keyword for
-** databases that are added using the [ATTACH] SQL command.
-** ^A NULL pointer can be used in place of "main" to refer to the
-** main database file.
-** ^The third and fourth parameters to this routine
-** are passed directly through to the second and third parameters of
-** the xFileControl method.  ^The return value of the xFileControl
-** method becomes the return value of this routine.
-**
-** ^If the second parameter (zDbName) does not match the name of any
-** open database file, then SQLITE_ERROR is returned.  ^This error
-** code is not remembered and will not be recalled by [sqlite3_errcode()]
-** or [sqlite3_errmsg()].  The underlying xFileControl method might
-** also return SQLITE_ERROR.  There is no way to distinguish between
-** an incorrect zDbName and an SQLITE_ERROR return from the underlying
-** xFileControl method.
-**
-** See also: [SQLITE_FCNTL_LOCKSTATE]
-*/
-SQLITE_API int sqlite3_file_control(sqlite3*, const char *zDbName, int op, void*);
-
-/*
-** CAPI3REF: Testing Interface
-**
-** ^The sqlite3_test_control() interface is used to read out internal
-** state of SQLite and to inject faults into SQLite for testing
-** purposes.  ^The first parameter is an operation code that determines
-** the number, meaning, and operation of all subsequent parameters.
-**
-** This interface is not for use by applications.  It exists solely
-** for verifying the correct operation of the SQLite library.  Depending
-** on how the SQLite library is compiled, this interface might not exist.
-**
-** The details of the operation codes, their meanings, the parameters
-** they take, and what they do are all subject to change without notice.
-** Unlike most of the SQLite API, this function is not guaranteed to
-** operate consistently from one release to the next.
-*/
-SQLITE_API int sqlite3_test_control(int op, ...);
-
-/*
-** CAPI3REF: Testing Interface Operation Codes
-**
-** These constants are the valid operation code parameters used
-** as the first argument to [sqlite3_test_control()].
-**
-** These parameters and their meanings are subject to change
-** without notice.  These values are for testing purposes only.
-** Applications should not use any of these parameters or the
-** [sqlite3_test_control()] interface.
-*/
-#define SQLITE_TESTCTRL_FIRST                    5
-#define SQLITE_TESTCTRL_PRNG_SAVE                5
-#define SQLITE_TESTCTRL_PRNG_RESTORE             6
-#define SQLITE_TESTCTRL_PRNG_RESET               7
-#define SQLITE_TESTCTRL_BITVEC_TEST              8
-#define SQLITE_TESTCTRL_FAULT_INSTALL            9
-#define SQLITE_TESTCTRL_BENIGN_MALLOC_HOOKS     10
-#define SQLITE_TESTCTRL_PENDING_BYTE            11
-#define SQLITE_TESTCTRL_ASSERT                  12
-#define SQLITE_TESTCTRL_ALWAYS                  13
-#define SQLITE_TESTCTRL_RESERVE                 14
-#define SQLITE_TESTCTRL_OPTIMIZATIONS           15
-#define SQLITE_TESTCTRL_ISKEYWORD               16
-#define SQLITE_TESTCTRL_LAST                    16
-
-/*
-** CAPI3REF: SQLite Runtime Status
-** EXPERIMENTAL
-**
-** ^This interface is used to retrieve runtime status information
-** about the preformance of SQLite, and optionally to reset various
-** highwater marks.  ^The first argument is an integer code for
-** the specific parameter to measure.  ^(Recognized integer codes
-** are of the form [SQLITE_STATUS_MEMORY_USED | SQLITE_STATUS_...].)^
-** ^The current value of the parameter is returned into *pCurrent.
-** ^The highest recorded value is returned in *pHighwater.  ^If the
-** resetFlag is true, then the highest record value is reset after
-** *pHighwater is written.  ^(Some parameters do not record the highest
-** value.  For those parameters
-** nothing is written into *pHighwater and the resetFlag is ignored.)^
-** ^(Other parameters record only the highwater mark and not the current
-** value.  For these latter parameters nothing is written into *pCurrent.)^
-**
-** ^The sqlite3_db_status() routine returns SQLITE_OK on success and a
-** non-zero [error code] on failure.
-**
-** This routine is threadsafe but is not atomic.  This routine can be
-** called while other threads are running the same or different SQLite
-** interfaces.  However the values returned in *pCurrent and
-** *pHighwater reflect the status of SQLite at different points in time
-** and it is possible that another thread might change the parameter
-** in between the times when *pCurrent and *pHighwater are written.
-**
-** See also: [sqlite3_db_status()]
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_status(int op, int *pCurrent, int *pHighwater, int resetFlag);
-
-
-/*
-** CAPI3REF: Status Parameters
-** EXPERIMENTAL
-**
-** These integer constants designate various run-time status parameters
-** that can be returned by [sqlite3_status()].
-**
-** <dl>
-** ^(<dt>SQLITE_STATUS_MEMORY_USED</dt>
-** <dd>This parameter is the current amount of memory checked out
-** using [sqlite3_malloc()], either directly or indirectly.  The
-** figure includes calls made to [sqlite3_malloc()] by the application
-** and internal memory usage by the SQLite library.  Scratch memory
-** controlled by [SQLITE_CONFIG_SCRATCH] and auxiliary page-cache
-** memory controlled by [SQLITE_CONFIG_PAGECACHE] is not included in
-** this parameter.  The amount returned is the sum of the allocation
-** sizes as reported by the xSize method in [sqlite3_mem_methods].</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_MALLOC_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [sqlite3_malloc()] or [sqlite3_realloc()] (or their
-** internal equivalents).  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_PAGECACHE_USED</dt>
-** <dd>This parameter returns the number of pages used out of the
-** [pagecache memory allocator] that was configured using 
-** [SQLITE_CONFIG_PAGECACHE].  The
-** value returned is in pages, not in bytes.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_PAGECACHE_OVERFLOW</dt>
-** <dd>This parameter returns the number of bytes of page cache
-** allocation which could not be statisfied by the [SQLITE_CONFIG_PAGECACHE]
-** buffer and where forced to overflow to [sqlite3_malloc()].  The
-** returned value includes allocations that overflowed because they
-** where too large (they were larger than the "sz" parameter to
-** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
-** no space was left in the page cache.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [pagecache memory allocator].  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_SCRATCH_USED</dt>
-** <dd>This parameter returns the number of allocations used out of the
-** [scratch memory allocator] configured using
-** [SQLITE_CONFIG_SCRATCH].  The value returned is in allocations, not
-** in bytes.  Since a single thread may only have one scratch allocation
-** outstanding at time, this parameter also reports the number of threads
-** using scratch memory at the same time.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>
-** <dd>This parameter returns the number of bytes of scratch memory
-** allocation which could not be statisfied by the [SQLITE_CONFIG_SCRATCH]
-** buffer and where forced to overflow to [sqlite3_malloc()].  The values
-** returned include overflows because the requested allocation was too
-** larger (that is, because the requested allocation was larger than the
-** "sz" parameter to [SQLITE_CONFIG_SCRATCH]) and because no scratch buffer
-** slots were available.
-** </dd>)^
-**
-** ^(<dt>SQLITE_STATUS_SCRATCH_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [scratch memory allocator].  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** ^(<dt>SQLITE_STATUS_PARSER_STACK</dt>
-** <dd>This parameter records the deepest parser stack.  It is only
-** meaningful if SQLite is compiled with [YYTRACKMAXSTACKDEPTH].</dd>)^
-** </dl>
-**
-** New status parameters may be added from time to time.
-*/
-#define SQLITE_STATUS_MEMORY_USED          0
-#define SQLITE_STATUS_PAGECACHE_USED       1
-#define SQLITE_STATUS_PAGECACHE_OVERFLOW   2
-#define SQLITE_STATUS_SCRATCH_USED         3
-#define SQLITE_STATUS_SCRATCH_OVERFLOW     4
-#define SQLITE_STATUS_MALLOC_SIZE          5
-#define SQLITE_STATUS_PARSER_STACK         6
-#define SQLITE_STATUS_PAGECACHE_SIZE       7
-#define SQLITE_STATUS_SCRATCH_SIZE         8
-
-/*
-** CAPI3REF: Database Connection Status
-** EXPERIMENTAL
-**
-** ^This interface is used to retrieve runtime status information 
-** about a single [database connection].  ^The first argument is the
-** database connection object to be interrogated.  ^The second argument
-** is the parameter to interrogate.  ^Currently, the only allowed value
-** for the second parameter is [SQLITE_DBSTATUS_LOOKASIDE_USED].
-** Additional options will likely appear in future releases of SQLite.
-**
-** ^The current value of the requested parameter is written into *pCur
-** and the highest instantaneous value is written into *pHiwtr.  ^If
-** the resetFlg is true, then the highest instantaneous value is
-** reset back down to the current value.
-**
-** See also: [sqlite3_status()] and [sqlite3_stmt_status()].
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
-
-/*
-** CAPI3REF: Status Parameters for database connections
-** EXPERIMENTAL
-**
-** These constants are the available integer "verbs" that can be passed as
-** the second argument to the [sqlite3_db_status()] interface.
-**
-** New verbs may be added in future releases of SQLite. Existing verbs
-** might be discontinued. Applications should check the return code from
-** [sqlite3_db_status()] to make sure that the call worked.
-** The [sqlite3_db_status()] interface will return a non-zero error code
-** if a discontinued or unsupported verb is invoked.
-**
-** <dl>
-** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
-** <dd>This parameter returns the number of lookaside memory slots currently
-** checked out.</dd>)^
-** </dl>
-*/
-#define SQLITE_DBSTATUS_LOOKASIDE_USED     0
-
-
-/*
-** CAPI3REF: Prepared Statement Status
-** EXPERIMENTAL
-**
-** ^(Each prepared statement maintains various
-** [SQLITE_STMTSTATUS_SORT | counters] that measure the number
-** of times it has performed specific operations.)^  These counters can
-** be used to monitor the performance characteristics of the prepared
-** statements.  For example, if the number of table steps greatly exceeds
-** the number of table searches or result rows, that would tend to indicate
-** that the prepared statement is using a full table scan rather than
-** an index.  
-**
-** ^(This interface is used to retrieve and reset counter values from
-** a [prepared statement].  The first argument is the prepared statement
-** object to be interrogated.  The second argument
-** is an integer code for a specific [SQLITE_STMTSTATUS_SORT | counter]
-** to be interrogated.)^
-** ^The current value of the requested counter is returned.
-** ^If the resetFlg is true, then the counter is reset to zero after this
-** interface call returns.
-**
-** See also: [sqlite3_status()] and [sqlite3_db_status()].
-*/
-SQLITE_API SQLITE_EXPERIMENTAL int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
-
-/*
-** CAPI3REF: Status Parameters for prepared statements
-** EXPERIMENTAL
-**
-** These preprocessor macros define integer codes that name counter
-** values associated with the [sqlite3_stmt_status()] interface.
-** The meanings of the various counters are as follows:
-**
-** <dl>
-** <dt>SQLITE_STMTSTATUS_FULLSCAN_STEP</dt>
-** <dd>^This is the number of times that SQLite has stepped forward in
-** a table as part of a full table scan.  Large numbers for this counter
-** may indicate opportunities for performance improvement through 
-** careful use of indices.</dd>
-**
-** <dt>SQLITE_STMTSTATUS_SORT</dt>
-** <dd>^This is the number of sort operations that have occurred.
-** A non-zero value in this counter may indicate an opportunity to
-** improvement performance through careful use of indices.</dd>
-**
-** </dl>
-*/
-#define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
-#define SQLITE_STMTSTATUS_SORT              2
-
-/*
-** CAPI3REF: Custom Page Cache Object
-** EXPERIMENTAL
-**
-** The sqlite3_pcache type is opaque.  It is implemented by
-** the pluggable module.  The SQLite core has no knowledge of
-** its size or internal structure and never deals with the
-** sqlite3_pcache object except by holding and passing pointers
-** to the object.
-**
-** See [sqlite3_pcache_methods] for additional information.
-*/
-typedef struct sqlite3_pcache sqlite3_pcache;
-
-/*
-** CAPI3REF: Application Defined Page Cache.
-** KEYWORDS: {page cache}
-** EXPERIMENTAL
-**
-** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE], ...) interface can
-** register an alternative page cache implementation by passing in an 
-** instance of the sqlite3_pcache_methods structure.)^ The majority of the 
-** heap memory used by SQLite is used by the page cache to cache data read 
-** from, or ready to be written to, the database file. By implementing a 
-** custom page cache using this API, an application can control more 
-** precisely the amount of memory consumed by SQLite, the way in which 
-** that memory is allocated and released, and the policies used to 
-** determine exactly which parts of a database file are cached and for 
-** how long.
-**
-** ^(The contents of the sqlite3_pcache_methods structure are copied to an
-** internal buffer by SQLite within the call to [sqlite3_config].  Hence
-** the application may discard the parameter after the call to
-** [sqlite3_config()] returns.)^
-**
-** ^The xInit() method is called once for each call to [sqlite3_initialize()]
-** (usually only once during the lifetime of the process). ^(The xInit()
-** method is passed a copy of the sqlite3_pcache_methods.pArg value.)^
-** ^The xInit() method can set up up global structures and/or any mutexes
-** required by the custom page cache implementation. 
-**
-** ^The xShutdown() method is called from within [sqlite3_shutdown()], 
-** if the application invokes this API. It can be used to clean up 
-** any outstanding resources before process shutdown, if required.
-**
-** ^SQLite holds a [SQLITE_MUTEX_RECURSIVE] mutex when it invokes
-** the xInit method, so the xInit method need not be threadsafe.  ^The
-** xShutdown method is only called from [sqlite3_shutdown()] so it does
-** not need to be threadsafe either.  All other methods must be threadsafe
-** in multithreaded applications.
-**
-** ^SQLite will never invoke xInit() more than once without an intervening
-** call to xShutdown().
-**
-** ^The xCreate() method is used to construct a new cache instance.  SQLite
-** will typically create one cache instance for each open database file,
-** though this is not guaranteed. ^The
-** first parameter, szPage, is the size in bytes of the pages that must
-** be allocated by the cache.  ^szPage will not be a power of two.  ^szPage
-** will the page size of the database file that is to be cached plus an
-** increment (here called "R") of about 100 or 200.  ^SQLite will use the
-** extra R bytes on each page to store metadata about the underlying
-** database page on disk.  The value of R depends
-** on the SQLite version, the target platform, and how SQLite was compiled.
-** ^R is constant for a particular build of SQLite.  ^The second argument to
-** xCreate(), bPurgeable, is true if the cache being created will
-** be used to cache database pages of a file stored on disk, or
-** false if it is used for an in-memory database. ^The cache implementation
-** does not have to do anything special based with the value of bPurgeable;
-** it is purely advisory.  ^On a cache where bPurgeable is false, SQLite will
-** never invoke xUnpin() except to deliberately delete a page.
-** ^In other words, a cache created with bPurgeable set to false will
-** never contain any unpinned pages.
-**
-** ^(The xCachesize() method may be called at any time by SQLite to set the
-** suggested maximum cache-size (number of pages stored by) the cache
-** instance passed as the first argument. This is the value configured using
-** the SQLite "[PRAGMA cache_size]" command.)^  ^As with the bPurgeable
-** parameter, the implementation is not required to do anything with this
-** value; it is advisory only.
-**
-** ^The xPagecount() method should return the number of pages currently
-** stored in the cache.
-** 
-** ^The xFetch() method is used to fetch a page and return a pointer to it. 
-** ^A 'page', in this context, is a buffer of szPage bytes aligned at an
-** 8-byte boundary. ^The page to be fetched is determined by the key. ^The
-** mimimum key value is 1. After it has been retrieved using xFetch, the page 
-** is considered to be "pinned".
-**
-** ^If the requested page is already in the page cache, then the page cache
-** implementation must return a pointer to the page buffer with its content
-** intact.  ^(If the requested page is not already in the cache, then the
-** behavior of the cache implementation is determined by the value of the
-** createFlag parameter passed to xFetch, according to the following table:
-**
-** <table border=1 width=85% align=center>
-** <tr><th> createFlag <th> Behaviour when page is not already in cache
-** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
-** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
-**                 Otherwise return NULL.
-** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
-**                 NULL if allocating a new page is effectively impossible.
-** </table>)^
-**
-** SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  If
-** a call to xFetch() with createFlag==1 returns NULL, then SQLite will
-** attempt to unpin one or more cache pages by spilling the content of
-** pinned pages to disk and synching the operating system disk cache. After
-** attempting to unpin pages, the xFetch() method will be invoked again with
-** a createFlag of 2.
-**
-** ^xUnpin() is called by SQLite with a pointer to a currently pinned page
-** as its second argument. ^(If the third parameter, discard, is non-zero,
-** then the page should be evicted from the cache. In this case SQLite 
-** assumes that the next time the page is retrieved from the cache using
-** the xFetch() method, it will be zeroed.)^ ^If the discard parameter is
-** zero, then the page is considered to be unpinned. ^The cache implementation
-** may choose to evict unpinned pages at any time.
-**
-** ^(The cache is not required to perform any reference counting. A single 
-** call to xUnpin() unpins the page regardless of the number of prior calls 
-** to xFetch().)^
-**
-** ^The xRekey() method is used to change the key value associated with the
-** page passed as the second argument from oldKey to newKey. ^If the cache
-** previously contains an entry associated with newKey, it should be
-** discarded. ^Any prior cache entry associated with newKey is guaranteed not
-** to be pinned.
-**
-** ^When SQLite calls the xTruncate() method, the cache must discard all
-** existing cache entries with page numbers (keys) greater than or equal
-** to the value of the iLimit parameter passed to xTruncate(). ^If any
-** of these pages are pinned, they are implicitly unpinned, meaning that
-** they can be safely discarded.
-**
-** ^The xDestroy() method is used to delete a cache allocated by xCreate().
-** All resources associated with the specified cache should be freed. ^After
-** calling the xDestroy() method, SQLite considers the [sqlite3_pcache*]
-** handle invalid, and will not use it with any other sqlite3_pcache_methods
-** functions.
-*/
-typedef struct sqlite3_pcache_methods sqlite3_pcache_methods;
-struct sqlite3_pcache_methods {
-  void *pArg;
-  int (*xInit)(void*);
-  void (*xShutdown)(void*);
-  sqlite3_pcache *(*xCreate)(int szPage, int bPurgeable);
-  void (*xCachesize)(sqlite3_pcache*, int nCachesize);
-  int (*xPagecount)(sqlite3_pcache*);
-  void *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
-  void (*xUnpin)(sqlite3_pcache*, void*, int discard);
-  void (*xRekey)(sqlite3_pcache*, void*, unsigned oldKey, unsigned newKey);
-  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
-  void (*xDestroy)(sqlite3_pcache*);
-};
-
-/*
-** CAPI3REF: Online Backup Object
-** EXPERIMENTAL
-**
-** The sqlite3_backup object records state information about an ongoing
-** online backup operation.  ^The sqlite3_backup object is created by
-** a call to [sqlite3_backup_init()] and is destroyed by a call to
-** [sqlite3_backup_finish()].
-**
-** See Also: [Using the SQLite Online Backup API]
-*/
-typedef struct sqlite3_backup sqlite3_backup;
-
-/*
-** CAPI3REF: Online Backup API.
-** EXPERIMENTAL
-**
-** The backup API copies the content of one database into another.
-** It is useful either for creating backups of databases or
-** for copying in-memory databases to or from persistent files. 
-**
-** See Also: [Using the SQLite Online Backup API]
-**
-** ^Exclusive access is required to the destination database for the 
-** duration of the operation. ^However the source database is only
-** read-locked while it is actually being read; it is not locked
-** continuously for the entire backup operation. ^Thus, the backup may be
-** performed on a live source database without preventing other users from
-** reading or writing to the source database while the backup is underway.
-** 
-** ^(To perform a backup operation: 
-**   <ol>
-**     <li><b>sqlite3_backup_init()</b> is called once to initialize the
-**         backup, 
-**     <li><b>sqlite3_backup_step()</b> is called one or more times to transfer 
-**         the data between the two databases, and finally
-**     <li><b>sqlite3_backup_finish()</b> is called to release all resources 
-**         associated with the backup operation. 
-**   </ol>)^
-** There should be exactly one call to sqlite3_backup_finish() for each
-** successful call to sqlite3_backup_init().
-**
-** <b>sqlite3_backup_init()</b>
-**
-** ^The D and N arguments to sqlite3_backup_init(D,N,S,M) are the 
-** [database connection] associated with the destination database 
-** and the database name, respectively.
-** ^The database name is "main" for the main database, "temp" for the
-** temporary database, or the name specified after the AS keyword in
-** an [ATTACH] statement for an attached database.
-** ^The S and M arguments passed to 
-** sqlite3_backup_init(D,N,S,M) identify the [database connection]
-** and database name of the source database, respectively.
-** ^The source and destination [database connections] (parameters S and D)
-** must be different or else sqlite3_backup_init(D,N,S,M) will file with
-** an error.
-**
-** ^If an error occurs within sqlite3_backup_init(D,N,S,M), then NULL is
-** returned and an error code and error message are store3d in the
-** destination [database connection] D.
-** ^The error code and message for the failed call to sqlite3_backup_init()
-** can be retrieved using the [sqlite3_errcode()], [sqlite3_errmsg()], and/or
-** [sqlite3_errmsg16()] functions.
-** ^A successful call to sqlite3_backup_init() returns a pointer to an
-** [sqlite3_backup] object.
-** ^The [sqlite3_backup] object may be used with the sqlite3_backup_step() and
-** sqlite3_backup_finish() functions to perform the specified backup 
-** operation.
-**
-** <b>sqlite3_backup_step()</b>
-**
-** ^Function sqlite3_backup_step(B,N) will copy up to N pages between 
-** the source and destination databases specified by [sqlite3_backup] object B.
-** ^If N is negative, all remaining source pages are copied. 
-** ^If sqlite3_backup_step(B,N) successfully copies N pages and there
-** are still more pages to be copied, then the function resturns [SQLITE_OK].
-** ^If sqlite3_backup_step(B,N) successfully finishes copying all pages
-** from source to destination, then it returns [SQLITE_DONE].
-** ^If an error occurs while running sqlite3_backup_step(B,N),
-** then an [error code] is returned. ^As well as [SQLITE_OK] and
-** [SQLITE_DONE], a call to sqlite3_backup_step() may return [SQLITE_READONLY],
-** [SQLITE_NOMEM], [SQLITE_BUSY], [SQLITE_LOCKED], or an
-** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX] extended error code.
-**
-** ^The sqlite3_backup_step() might return [SQLITE_READONLY] if the destination
-** database was opened read-only or if
-** the destination is an in-memory database with a different page size
-** from the source database.
-**
-** ^If sqlite3_backup_step() cannot obtain a required file-system lock, then
-** the [sqlite3_busy_handler | busy-handler function]
-** is invoked (if one is specified). ^If the 
-** busy-handler returns non-zero before the lock is available, then 
-** [SQLITE_BUSY] is returned to the caller. ^In this case the call to
-** sqlite3_backup_step() can be retried later. ^If the source
-** [database connection]
-** is being used to write to the source database when sqlite3_backup_step()
-** is called, then [SQLITE_LOCKED] is returned immediately. ^Again, in this
-** case the call to sqlite3_backup_step() can be retried later on. ^(If
-** [SQLITE_IOERR_ACCESS | SQLITE_IOERR_XXX], [SQLITE_NOMEM], or
-** [SQLITE_READONLY] is returned, then 
-** there is no point in retrying the call to sqlite3_backup_step(). These 
-** errors are considered fatal.)^  The application must accept 
-** that the backup operation has failed and pass the backup operation handle 
-** to the sqlite3_backup_finish() to release associated resources.
-**
-** ^The first call to sqlite3_backup_step() obtains an exclusive lock
-** on the destination file. ^The exclusive lock is not released until either 
-** sqlite3_backup_finish() is called or the backup operation is complete 
-** and sqlite3_backup_step() returns [SQLITE_DONE].  ^Every call to
-** sqlite3_backup_step() obtains a [shared lock] on the source database that
-** lasts for the duration of the sqlite3_backup_step() call.
-** ^Because the source database is not locked between calls to
-** sqlite3_backup_step(), the source database may be modified mid-way
-** through the backup process.  ^If the source database is modified by an
-** external process or via a database connection other than the one being
-** used by the backup operation, then the backup will be automatically
-** restarted by the next call to sqlite3_backup_step(). ^If the source 
-** database is modified by the using the same database connection as is used
-** by the backup operation, then the backup database is automatically
-** updated at the same time.
-**
-** <b>sqlite3_backup_finish()</b>
-**
-** When sqlite3_backup_step() has returned [SQLITE_DONE], or when the 
-** application wishes to abandon the backup operation, the application
-** should destroy the [sqlite3_backup] by passing it to sqlite3_backup_finish().
-** ^The sqlite3_backup_finish() interfaces releases all
-** resources associated with the [sqlite3_backup] object. 
-** ^If sqlite3_backup_step() has not yet returned [SQLITE_DONE], then any
-** active write-transaction on the destination database is rolled back.
-** The [sqlite3_backup] object is invalid
-** and may not be used following a call to sqlite3_backup_finish().
-**
-** ^The value returned by sqlite3_backup_finish is [SQLITE_OK] if no
-** sqlite3_backup_step() errors occurred, regardless or whether or not
-** sqlite3_backup_step() completed.
-** ^If an out-of-memory condition or IO error occurred during any prior
-** sqlite3_backup_step() call on the same [sqlite3_backup] object, then
-** sqlite3_backup_finish() returns the corresponding [error code].
-**
-** ^A return of [SQLITE_BUSY] or [SQLITE_LOCKED] from sqlite3_backup_step()
-** is not a permanent error and does not affect the return value of
-** sqlite3_backup_finish().
-**
-** <b>sqlite3_backup_remaining(), sqlite3_backup_pagecount()</b>
-**
-** ^Each call to sqlite3_backup_step() sets two values inside
-** the [sqlite3_backup] object: the number of pages still to be backed
-** up and the total number of pages in the source databae file.
-** The sqlite3_backup_remaining() and sqlite3_backup_pagecount() interfaces
-** retrieve these two values, respectively.
-**
-** ^The values returned by these functions are only updated by
-** sqlite3_backup_step(). ^If the source database is modified during a backup
-** operation, then the values are not updated to account for any extra
-** pages that need to be updated or the size of the source database file
-** changing.
-**
-** <b>Concurrent Usage of Database Handles</b>
-**
-** ^The source [database connection] may be used by the application for other
-** purposes while a backup operation is underway or being initialized.
-** ^If SQLite is compiled and configured to support threadsafe database
-** connections, then the source database connection may be used concurrently
-** from within other threads.
-**
-** However, the application must guarantee that the destination 
-** [database connection] is not passed to any other API (by any thread) after 
-** sqlite3_backup_init() is called and before the corresponding call to
-** sqlite3_backup_finish().  SQLite does not currently check to see
-** if the application incorrectly accesses the destination [database connection]
-** and so no error code is reported, but the operations may malfunction
-** nevertheless.  Use of the destination database connection while a
-** backup is in progress might also also cause a mutex deadlock.
-**
-** If running in [shared cache mode], the application must
-** guarantee that the shared cache used by the destination database
-** is not accessed while the backup is running. In practice this means
-** that the application must guarantee that the disk file being 
-** backed up to is not accessed by any connection within the process,
-** not just the specific connection that was passed to sqlite3_backup_init().
-**
-** The [sqlite3_backup] object itself is partially threadsafe. Multiple 
-** threads may safely make multiple concurrent calls to sqlite3_backup_step().
-** However, the sqlite3_backup_remaining() and sqlite3_backup_pagecount()
-** APIs are not strictly speaking threadsafe. If they are invoked at the
-** same time as another thread is invoking sqlite3_backup_step() it is
-** possible that they return invalid values.
-*/
-SQLITE_API sqlite3_backup *sqlite3_backup_init(
-  sqlite3 *pDest,                        /* Destination database handle */
-  const char *zDestName,                 /* Destination database name */
-  sqlite3 *pSource,                      /* Source database handle */
-  const char *zSourceName                /* Source database name */
-);
-SQLITE_API int sqlite3_backup_step(sqlite3_backup *p, int nPage);
-SQLITE_API int sqlite3_backup_finish(sqlite3_backup *p);
-SQLITE_API int sqlite3_backup_remaining(sqlite3_backup *p);
-SQLITE_API int sqlite3_backup_pagecount(sqlite3_backup *p);
-
-/*
-** CAPI3REF: Unlock Notification
-** EXPERIMENTAL
-**
-** ^When running in shared-cache mode, a database operation may fail with
-** an [SQLITE_LOCKED] error if the required locks on the shared-cache or
-** individual tables within the shared-cache cannot be obtained. See
-** [SQLite Shared-Cache Mode] for a description of shared-cache locking. 
-** ^This API may be used to register a callback that SQLite will invoke 
-** when the connection currently holding the required lock relinquishes it.
-** ^This API is only available if the library was compiled with the
-** [SQLITE_ENABLE_UNLOCK_NOTIFY] C-preprocessor symbol defined.
-**
-** See Also: [Using the SQLite Unlock Notification Feature].
-**
-** ^Shared-cache locks are released when a database connection concludes
-** its current transaction, either by committing it or rolling it back. 
-**
-** ^When a connection (known as the blocked connection) fails to obtain a
-** shared-cache lock and SQLITE_LOCKED is returned to the caller, the
-** identity of the database connection (the blocking connection) that
-** has locked the required resource is stored internally. ^After an 
-** application receives an SQLITE_LOCKED error, it may call the
-** sqlite3_unlock_notify() method with the blocked connection handle as 
-** the first argument to register for a callback that will be invoked
-** when the blocking connections current transaction is concluded. ^The
-** callback is invoked from within the [sqlite3_step] or [sqlite3_close]
-** call that concludes the blocking connections transaction.
-**
-** ^(If sqlite3_unlock_notify() is called in a multi-threaded application,
-** there is a chance that the blocking connection will have already
-** concluded its transaction by the time sqlite3_unlock_notify() is invoked.
-** If this happens, then the specified callback is invoked immediately,
-** from within the call to sqlite3_unlock_notify().)^
-**
-** ^If the blocked connection is attempting to obtain a write-lock on a
-** shared-cache table, and more than one other connection currently holds
-** a read-lock on the same table, then SQLite arbitrarily selects one of 
-** the other connections to use as the blocking connection.
-**
-** ^(There may be at most one unlock-notify callback registered by a 
-** blocked connection. If sqlite3_unlock_notify() is called when the
-** blocked connection already has a registered unlock-notify callback,
-** then the new callback replaces the old.)^ ^If sqlite3_unlock_notify() is
-** called with a NULL pointer as its second argument, then any existing
-** unlock-notify callback is cancelled. ^The blocked connections 
-** unlock-notify callback may also be canceled by closing the blocked
-** connection using [sqlite3_close()].
-**
-** The unlock-notify callback is not reentrant. If an application invokes
-** any sqlite3_xxx API functions from within an unlock-notify callback, a
-** crash or deadlock may be the result.
-**
-** ^Unless deadlock is detected (see below), sqlite3_unlock_notify() always
-** returns SQLITE_OK.
-**
-** <b>Callback Invocation Details</b>
-**
-** When an unlock-notify callback is registered, the application provides a 
-** single void* pointer that is passed to the callback when it is invoked.
-** However, the signature of the callback function allows SQLite to pass
-** it an array of void* context pointers. The first argument passed to
-** an unlock-notify callback is a pointer to an array of void* pointers,
-** and the second is the number of entries in the array.
-**
-** When a blocking connections transaction is concluded, there may be
-** more than one blocked connection that has registered for an unlock-notify
-** callback. ^If two or more such blocked connections have specified the
-** same callback function, then instead of invoking the callback function
-** multiple times, it is invoked once with the set of void* context pointers
-** specified by the blocked connections bundled together into an array.
-** This gives the application an opportunity to prioritize any actions 
-** related to the set of unblocked database connections.
-**
-** <b>Deadlock Detection</b>
-**
-** Assuming that after registering for an unlock-notify callback a 
-** database waits for the callback to be issued before taking any further
-** action (a reasonable assumption), then using this API may cause the
-** application to deadlock. For example, if connection X is waiting for
-** connection Y's transaction to be concluded, and similarly connection
-** Y is waiting on connection X's transaction, then neither connection
-** will proceed and the system may remain deadlocked indefinitely.
-**
-** To avoid this scenario, the sqlite3_unlock_notify() performs deadlock
-** detection. ^If a given call to sqlite3_unlock_notify() would put the
-** system in a deadlocked state, then SQLITE_LOCKED is returned and no
-** unlock-notify callback is registered. The system is said to be in
-** a deadlocked state if connection A has registered for an unlock-notify
-** callback on the conclusion of connection B's transaction, and connection
-** B has itself registered for an unlock-notify callback when connection
-** A's transaction is concluded. ^Indirect deadlock is also detected, so
-** the system is also considered to be deadlocked if connection B has
-** registered for an unlock-notify callback on the conclusion of connection
-** C's transaction, where connection C is waiting on connection A. ^Any
-** number of levels of indirection are allowed.
-**
-** <b>The "DROP TABLE" Exception</b>
-**
-** When a call to [sqlite3_step()] returns SQLITE_LOCKED, it is almost 
-** always appropriate to call sqlite3_unlock_notify(). There is however,
-** one exception. When executing a "DROP TABLE" or "DROP INDEX" statement,
-** SQLite checks if there are any currently executing SELECT statements
-** that belong to the same connection. If there are, SQLITE_LOCKED is
-** returned. In this case there is no "blocking connection", so invoking
-** sqlite3_unlock_notify() results in the unlock-notify callback being
-** invoked immediately. If the application then re-attempts the "DROP TABLE"
-** or "DROP INDEX" query, an infinite loop might be the result.
-**
-** One way around this problem is to check the extended error code returned
-** by an sqlite3_step() call. ^(If there is a blocking connection, then the
-** extended error code is set to SQLITE_LOCKED_SHAREDCACHE. Otherwise, in
-** the special "DROP TABLE/INDEX" case, the extended error code is just 
-** SQLITE_LOCKED.)^
-*/
-SQLITE_API int sqlite3_unlock_notify(
-  sqlite3 *pBlocked,                          /* Waiting connection */
-  void (*xNotify)(void **apArg, int nArg),    /* Callback function to invoke */
-  void *pNotifyArg                            /* Argument to pass to xNotify */
-);
-
-
-/*
-** CAPI3REF: String Comparison
-** EXPERIMENTAL
-**
-** ^The [sqlite3_strnicmp()] API allows applications and extensions to
-** compare the contents of two buffers containing UTF-8 strings in a
-** case-indendent fashion, using the same definition of case independence 
-** that SQLite uses internally when comparing identifiers.
-*/
-SQLITE_API int sqlite3_strnicmp(const char *, const char *, int);
-
-/*
-** CAPI3REF: Error Logging Interface
-** EXPERIMENTAL
-**
-** ^The [sqlite3_log()] interface writes a message into the error log
-** established by the [SQLITE_CONFIG_ERRORLOG] option to [sqlite3_config()].
-**
-** The sqlite3_log() interface is intended for use by extensions such as
-** virtual tables, collating functions, and SQL functions.  While there is
-** nothing to prevent an application from calling sqlite3_log(), doing so
-** is considered bad form.
-**
-** To avoid deadlocks and other threading problems, the sqlite3_log() routine
-** will not use dynamically allocated memory.  The log message is stored in
-** a fixed-length buffer on the stack.  If the log message is longer than
-** a few hundred characters, it will be truncated to the length of the
-** buffer.
-*/
-SQLITE_API void sqlite3_log(int iErrCode, const char *zFormat, ...);
-
-/*
-** Undo the hack that converts floating point types to integer for
-** builds on processors without floating point support.
-*/
-#ifdef SQLITE_OMIT_FLOATING_POINT
-# undef double
-#endif
-
-#ifdef __cplusplus
-}  /* End of the 'extern "C"' block */
-#endif
-#endif
-