chrome/browser/history/top_sites_database.cc - platform/external/chromium - Git at Google

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "app/sql/connection.h"
 #include "app/sql/transaction.h"
 #include "base/file_util.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
 #include "chrome/browser/diagnostics/sqlite_diagnostics.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/history/top_sites.h"
 #include "chrome/browser/history/top_sites_database.h"

 namespace history {

 static const int kVersionNumber = 1;

 TopSitesDatabase::TopSitesDatabase() : may_need_history_migration_(false) {
 }

 TopSitesDatabase::~TopSitesDatabase() {
 }

 bool TopSitesDatabase::Init(const FilePath& db_name) {
   bool file_existed = file_util::PathExists(db_name);

   if (!file_existed)
     may_need_history_migration_ = true;

   db_.reset(CreateDB(db_name));
   if (!db_.get())
     return false;

   bool does_meta_exist = sql::MetaTable::DoesTableExist(db_.get());
   if (!does_meta_exist && file_existed) {
     may_need_history_migration_ = true;

     // If the meta file doesn't exist, this version is old. We could remove all
     // the entries as they are no longer applicable, but it's safest to just
     // remove the file and start over.
     db_.reset(NULL);
     if (!file_util::Delete(db_name, false) &&
         !file_util::Delete(db_name, false)) {
       // Try to delete twice. If we can't, fail.
       LOG(ERROR) << "unable to delete old TopSites file";
       return false;
     }
     db_.reset(CreateDB(db_name));
     if (!db_.get())
       return false;
   }

   if (!meta_table_.Init(db_.get(), kVersionNumber, kVersionNumber))
     return false;

   if (!InitThumbnailTable())
     return false;

   // Version check.
   if (meta_table_.GetVersionNumber() != kVersionNumber)
     return false;

   return true;
 }

 bool TopSitesDatabase::InitThumbnailTable() {
   if (!db_->DoesTableExist("thumbnails")) {
     if (!db_->Execute("CREATE TABLE thumbnails ("
                       "url LONGVARCHAR PRIMARY KEY,"
                       "url_rank INTEGER ,"
                       "title LONGVARCHAR,"
                       "thumbnail BLOB,"
                       "redirects LONGVARCHAR,"
                       "boring_score DOUBLE DEFAULT 1.0, "
                       "good_clipping INTEGER DEFAULT 0, "
                       "at_top INTEGER DEFAULT 0, "
                       "last_updated INTEGER DEFAULT 0) ")) {
       LOG(WARNING) << db_->GetErrorMessage();
       return false;
     }
   }
   return true;
 }

 void TopSitesDatabase::GetPageThumbnails(MostVisitedURLList* urls,
                                              URLToImagesMap* thumbnails) {
   sql::Statement statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "SELECT url, url_rank, title, thumbnail, redirects, "
       "boring_score, good_clipping, at_top, last_updated "
       "FROM thumbnails ORDER BY url_rank "));

   if (!statement) {
     LOG(WARNING) << db_->GetErrorMessage();
     return;
   }

   urls->clear();
   thumbnails->clear();

   while (statement.Step()) {
     // Results are sorted by url_rank.
     MostVisitedURL url;
     GURL gurl(statement.ColumnString(0));
     url.url = gurl;
     url.title = statement.ColumnString16(2);
     std::string redirects = statement.ColumnString(4);
     SetRedirects(redirects, &url);
     urls->push_back(url);

     std::vector<unsigned char> data;
     statement.ColumnBlobAsVector(3, &data);
     Images thumbnail;
     thumbnail.thumbnail = RefCountedBytes::TakeVector(&data);
     thumbnail.thumbnail_score.boring_score = statement.ColumnDouble(5);
     thumbnail.thumbnail_score.good_clipping = statement.ColumnBool(6);
     thumbnail.thumbnail_score.at_top = statement.ColumnBool(7);
     thumbnail.thumbnail_score.time_at_snapshot =
         base::Time::FromInternalValue(statement.ColumnInt64(8));

     (*thumbnails)[gurl] = thumbnail;
   }
 }

 // static
 std::string TopSitesDatabase::GetRedirects(const MostVisitedURL& url) {
   std::vector<std::string> redirects;
   for (size_t i = 0; i < url.redirects.size(); i++)
     redirects.push_back(url.redirects[i].spec());
   return JoinString(redirects, ' ');
 }

 // static
 void TopSitesDatabase::SetRedirects(const std::string& redirects,
                                     MostVisitedURL* url) {
   std::vector<std::string> redirects_vector;
   base::SplitStringAlongWhitespace(redirects, &redirects_vector);
   for (size_t i = 0; i < redirects_vector.size(); ++i)
     url->redirects.push_back(GURL(redirects_vector[i]));
 }

 void TopSitesDatabase::SetPageThumbnail(const MostVisitedURL& url,
                                             int new_rank,
                                             const Images& thumbnail) {
   sql::Transaction transaction(db_.get());
   transaction.Begin();

   int rank = GetURLRank(url);
   if (rank == -1) {
     AddPageThumbnail(url, new_rank, thumbnail);
   } else {
     UpdatePageRankNoTransaction(url, new_rank);
     UpdatePageThumbnail(url, thumbnail);
   }

   transaction.Commit();
 }

 void TopSitesDatabase::UpdatePageThumbnail(
     const MostVisitedURL& url, const Images& thumbnail) {
   sql::Statement statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "UPDATE thumbnails SET "
       "title = ?, thumbnail = ?, redirects = ?, "
       "boring_score = ?, good_clipping = ?, at_top = ?, last_updated = ? "
       "WHERE url = ? "));
   if (!statement)
     return;

   statement.BindString16(0, url.title);
   if (thumbnail.thumbnail.get() && thumbnail.thumbnail->front()) {
     statement.BindBlob(1, thumbnail.thumbnail->front(),
                        static_cast<int>(thumbnail.thumbnail->size()));
   }
   statement.BindString(2, GetRedirects(url));
   const ThumbnailScore& score = thumbnail.thumbnail_score;
   statement.BindDouble(3, score.boring_score);
   statement.BindBool(4, score.good_clipping);
   statement.BindBool(5, score.at_top);
   statement.BindInt64(6, score.time_at_snapshot.ToInternalValue());
   statement.BindString(7, url.url.spec());
   if (!statement.Run())
     NOTREACHED() << db_->GetErrorMessage();
 }

 void TopSitesDatabase::AddPageThumbnail(const MostVisitedURL& url,
                                             int new_rank,
                                             const Images& thumbnail) {
   int count = GetRowCount();

   sql::Statement statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "INSERT OR REPLACE INTO thumbnails "
       "(url, url_rank, title, thumbnail, redirects, "
       "boring_score, good_clipping, at_top, last_updated) "
       "VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)"));
   if (!statement)
     return;

   statement.BindString(0, url.url.spec());
   statement.BindInt(1, count);  // Make it the last url.
   statement.BindString16(2, url.title);
   if (thumbnail.thumbnail.get() && thumbnail.thumbnail->front()) {
     statement.BindBlob(3, thumbnail.thumbnail->front(),
                        static_cast<int>(thumbnail.thumbnail->size()));
   }
   statement.BindString(4, GetRedirects(url));
   const ThumbnailScore& score = thumbnail.thumbnail_score;
   statement.BindDouble(5, score.boring_score);
   statement.BindBool(6, score.good_clipping);
   statement.BindBool(7, score.at_top);
   statement.BindInt64(8, score.time_at_snapshot.ToInternalValue());
   if (!statement.Run())
     NOTREACHED() << db_->GetErrorMessage();

   UpdatePageRankNoTransaction(url, new_rank);
 }

 void TopSitesDatabase::UpdatePageRank(const MostVisitedURL& url,
                                           int new_rank) {
   sql::Transaction transaction(db_.get());
   transaction.Begin();
   UpdatePageRankNoTransaction(url, new_rank);
   transaction.Commit();
 }

 // Caller should have a transaction open.
 void TopSitesDatabase::UpdatePageRankNoTransaction(
     const MostVisitedURL& url, int new_rank) {
   int prev_rank = GetURLRank(url);
   if (prev_rank == -1) {
     LOG(WARNING) << "Updating rank of an unknown URL: " << url.url.spec();
     return;
   }

   // Shift the ranks.
   if (prev_rank > new_rank) {
     // Shift up
     sql::Statement shift_statement(db_->GetCachedStatement(
         SQL_FROM_HERE,
         "UPDATE thumbnails "
         "SET url_rank = url_rank + 1 "
         "WHERE url_rank >= ? AND url_rank < ?"));
     shift_statement.BindInt(0, new_rank);
     shift_statement.BindInt(1, prev_rank);
     if (shift_statement)
       shift_statement.Run();
   } else if (prev_rank < new_rank) {
     // Shift down
     sql::Statement shift_statement(db_->GetCachedStatement(
         SQL_FROM_HERE,
         "UPDATE thumbnails "
         "SET url_rank = url_rank - 1 "
         "WHERE url_rank > ? AND url_rank <= ?"));
     shift_statement.BindInt(0, prev_rank);
     shift_statement.BindInt(1, new_rank);
     if (shift_statement)
       shift_statement.Run();
   }

   // Set the url's rank.
   sql::Statement set_statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "UPDATE thumbnails "
       "SET url_rank = ? "
       "WHERE url == ?"));
   set_statement.BindInt(0, new_rank);
   set_statement.BindString(1, url.url.spec());
   if (set_statement)
     set_statement.Run();
 }

 bool TopSitesDatabase::GetPageThumbnail(const GURL& url,
                                             Images* thumbnail) {
   sql::Statement statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "SELECT thumbnail, boring_score, good_clipping, at_top, last_updated "
       "FROM thumbnails WHERE url=?"));

   if (!statement) {
     LOG(WARNING) << db_->GetErrorMessage();
     return false;
   }

   statement.BindString(0, url.spec());
   if (!statement.Step())
     return false;

   std::vector<unsigned char> data;
   statement.ColumnBlobAsVector(0, &data);
   thumbnail->thumbnail = RefCountedBytes::TakeVector(&data);
   thumbnail->thumbnail_score.boring_score = statement.ColumnDouble(1);
   thumbnail->thumbnail_score.good_clipping = statement.ColumnBool(2);
   thumbnail->thumbnail_score.at_top = statement.ColumnBool(3);
   thumbnail->thumbnail_score.time_at_snapshot =
       base::Time::FromInternalValue(statement.ColumnInt64(4));
   return true;
 }

 int TopSitesDatabase::GetRowCount() {
   int result = 0;
   sql::Statement select_statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "SELECT COUNT (url) FROM thumbnails"));
   if (!select_statement) {
     LOG(WARNING) << db_->GetErrorMessage();
     return result;
   }

   if (select_statement.Step())
     result = select_statement.ColumnInt(0);

   return result;
 }

 int TopSitesDatabase::GetURLRank(const MostVisitedURL& url) {
   int result = -1;
   sql::Statement select_statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "SELECT url_rank "
       "FROM thumbnails WHERE url=?"));
   if (!select_statement) {
     LOG(WARNING) << db_->GetErrorMessage();
     return result;
   }

   select_statement.BindString(0, url.url.spec());
   if (select_statement.Step())
     result = select_statement.ColumnInt(0);

   return result;
 }

 // Remove the record for this URL. Returns true iff removed successfully.
 bool TopSitesDatabase::RemoveURL(const MostVisitedURL& url) {
   int old_rank = GetURLRank(url);
   if (old_rank < 0)
     return false;

   sql::Transaction transaction(db_.get());
   transaction.Begin();
   // Decrement all following ranks.
   sql::Statement shift_statement(db_->GetCachedStatement(
       SQL_FROM_HERE,
       "UPDATE thumbnails "
       "SET url_rank = url_rank - 1 "
       "WHERE url_rank > ?"));
   if (!shift_statement)
     return false;
   shift_statement.BindInt(0, old_rank);
   shift_statement.Run();

   sql::Statement delete_statement(
       db_->GetCachedStatement(SQL_FROM_HERE,
                               "DELETE FROM thumbnails WHERE url = ?"));
   if (!delete_statement)
     return false;
   delete_statement.BindString(0, url.url.spec());
   delete_statement.Run();

   return transaction.Commit();
 }

 sql::Connection* TopSitesDatabase::CreateDB(const FilePath& db_name) {
   scoped_ptr<sql::Connection> db(new sql::Connection());
   // Settings copied from ThumbnailDatabase.
   db->set_error_delegate(GetErrorHandlerForThumbnailDb());
   db->set_page_size(4096);
   db->set_cache_size(32);

   if (!db->Open(db_name)) {
     LOG(ERROR) << db->GetErrorMessage();
     return NULL;
   }

   return db.release();
 }

 }  // namespace history
	// Copyright (c) 2009 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "app/sql/connection.h"
	#include "app/sql/transaction.h"
	#include "base/file_util.h"
	#include "base/string_split.h"
	#include "base/string_util.h"
	#include "chrome/browser/diagnostics/sqlite_diagnostics.h"
	#include "chrome/browser/history/history_types.h"
	#include "chrome/browser/history/top_sites.h"
	#include "chrome/browser/history/top_sites_database.h"

	namespace history {

	static const int kVersionNumber = 1;

	TopSitesDatabase::TopSitesDatabase() : may_need_history_migration_(false) {
	}

	TopSitesDatabase::~TopSitesDatabase() {
	}

	bool TopSitesDatabase::Init(const FilePath& db_name) {
	bool file_existed = file_util::PathExists(db_name);

	if (!file_existed)
	may_need_history_migration_ = true;

	db_.reset(CreateDB(db_name));
	if (!db_.get())
	return false;

	bool does_meta_exist = sql::MetaTable::DoesTableExist(db_.get());
	if (!does_meta_exist && file_existed) {
	may_need_history_migration_ = true;

	// If the meta file doesn't exist, this version is old. We could remove all
	// the entries as they are no longer applicable, but it's safest to just
	// remove the file and start over.
	db_.reset(NULL);
	if (!file_util::Delete(db_name, false) &&
	!file_util::Delete(db_name, false)) {
	// Try to delete twice. If we can't, fail.
	LOG(ERROR) << "unable to delete old TopSites file";
	return false;
	}
	db_.reset(CreateDB(db_name));
	if (!db_.get())
	return false;
	}

	if (!meta_table_.Init(db_.get(), kVersionNumber, kVersionNumber))
	return false;

	if (!InitThumbnailTable())
	return false;

	// Version check.
	if (meta_table_.GetVersionNumber() != kVersionNumber)
	return false;

	return true;
	}

	bool TopSitesDatabase::InitThumbnailTable() {
	if (!db_->DoesTableExist("thumbnails")) {
	if (!db_->Execute("CREATE TABLE thumbnails ("
	"url LONGVARCHAR PRIMARY KEY,"
	"url_rank INTEGER ,"
	"title LONGVARCHAR,"
	"thumbnail BLOB,"
	"redirects LONGVARCHAR,"
	"boring_score DOUBLE DEFAULT 1.0, "
	"good_clipping INTEGER DEFAULT 0, "
	"at_top INTEGER DEFAULT 0, "
	"last_updated INTEGER DEFAULT 0) ")) {
	LOG(WARNING) << db_->GetErrorMessage();
	return false;
	}
	}
	return true;
	}

	void TopSitesDatabase::GetPageThumbnails(MostVisitedURLList* urls,
	URLToImagesMap* thumbnails) {
	sql::Statement statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"SELECT url, url_rank, title, thumbnail, redirects, "
	"boring_score, good_clipping, at_top, last_updated "
	"FROM thumbnails ORDER BY url_rank "));

	if (!statement) {
	LOG(WARNING) << db_->GetErrorMessage();
	return;
	}

	urls->clear();
	thumbnails->clear();

	while (statement.Step()) {
	// Results are sorted by url_rank.
	MostVisitedURL url;
	GURL gurl(statement.ColumnString(0));
	url.url = gurl;
	url.title = statement.ColumnString16(2);
	std::string redirects = statement.ColumnString(4);
	SetRedirects(redirects, &url);
	urls->push_back(url);

	std::vector<unsigned char> data;
	statement.ColumnBlobAsVector(3, &data);
	Images thumbnail;
	thumbnail.thumbnail = RefCountedBytes::TakeVector(&data);
	thumbnail.thumbnail_score.boring_score = statement.ColumnDouble(5);
	thumbnail.thumbnail_score.good_clipping = statement.ColumnBool(6);
	thumbnail.thumbnail_score.at_top = statement.ColumnBool(7);
	thumbnail.thumbnail_score.time_at_snapshot =
	base::Time::FromInternalValue(statement.ColumnInt64(8));

	(*thumbnails)[gurl] = thumbnail;
	}
	}

	// static
	std::string TopSitesDatabase::GetRedirects(const MostVisitedURL& url) {
	std::vector<std::string> redirects;
	for (size_t i = 0; i < url.redirects.size(); i++)
	redirects.push_back(url.redirects[i].spec());
	return JoinString(redirects, ' ');
	}

	// static
	void TopSitesDatabase::SetRedirects(const std::string& redirects,
	MostVisitedURL* url) {
	std::vector<std::string> redirects_vector;
	base::SplitStringAlongWhitespace(redirects, &redirects_vector);
	for (size_t i = 0; i < redirects_vector.size(); ++i)
	url->redirects.push_back(GURL(redirects_vector[i]));
	}

	void TopSitesDatabase::SetPageThumbnail(const MostVisitedURL& url,
	int new_rank,
	const Images& thumbnail) {
	sql::Transaction transaction(db_.get());
	transaction.Begin();

	int rank = GetURLRank(url);
	if (rank == -1) {
	AddPageThumbnail(url, new_rank, thumbnail);
	} else {
	UpdatePageRankNoTransaction(url, new_rank);
	UpdatePageThumbnail(url, thumbnail);
	}

	transaction.Commit();
	}

	void TopSitesDatabase::UpdatePageThumbnail(
	const MostVisitedURL& url, const Images& thumbnail) {
	sql::Statement statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"UPDATE thumbnails SET "
	"title = ?, thumbnail = ?, redirects = ?, "
	"boring_score = ?, good_clipping = ?, at_top = ?, last_updated = ? "
	"WHERE url = ? "));
	if (!statement)
	return;

	statement.BindString16(0, url.title);
	if (thumbnail.thumbnail.get() && thumbnail.thumbnail->front()) {
	statement.BindBlob(1, thumbnail.thumbnail->front(),
	static_cast<int>(thumbnail.thumbnail->size()));
	}
	statement.BindString(2, GetRedirects(url));
	const ThumbnailScore& score = thumbnail.thumbnail_score;
	statement.BindDouble(3, score.boring_score);
	statement.BindBool(4, score.good_clipping);
	statement.BindBool(5, score.at_top);
	statement.BindInt64(6, score.time_at_snapshot.ToInternalValue());
	statement.BindString(7, url.url.spec());
	if (!statement.Run())
	NOTREACHED() << db_->GetErrorMessage();
	}

	void TopSitesDatabase::AddPageThumbnail(const MostVisitedURL& url,
	int new_rank,
	const Images& thumbnail) {
	int count = GetRowCount();

	sql::Statement statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"INSERT OR REPLACE INTO thumbnails "
	"(url, url_rank, title, thumbnail, redirects, "
	"boring_score, good_clipping, at_top, last_updated) "
	"VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)"));
	if (!statement)
	return;

	statement.BindString(0, url.url.spec());
	statement.BindInt(1, count); // Make it the last url.
	statement.BindString16(2, url.title);
	if (thumbnail.thumbnail.get() && thumbnail.thumbnail->front()) {
	statement.BindBlob(3, thumbnail.thumbnail->front(),
	static_cast<int>(thumbnail.thumbnail->size()));
	}
	statement.BindString(4, GetRedirects(url));
	const ThumbnailScore& score = thumbnail.thumbnail_score;
	statement.BindDouble(5, score.boring_score);
	statement.BindBool(6, score.good_clipping);
	statement.BindBool(7, score.at_top);
	statement.BindInt64(8, score.time_at_snapshot.ToInternalValue());
	if (!statement.Run())
	NOTREACHED() << db_->GetErrorMessage();

	UpdatePageRankNoTransaction(url, new_rank);
	}

	void TopSitesDatabase::UpdatePageRank(const MostVisitedURL& url,
	int new_rank) {
	sql::Transaction transaction(db_.get());
	transaction.Begin();
	UpdatePageRankNoTransaction(url, new_rank);
	transaction.Commit();
	}

	// Caller should have a transaction open.
	void TopSitesDatabase::UpdatePageRankNoTransaction(
	const MostVisitedURL& url, int new_rank) {
	int prev_rank = GetURLRank(url);
	if (prev_rank == -1) {
	LOG(WARNING) << "Updating rank of an unknown URL: " << url.url.spec();
	return;
	}

	// Shift the ranks.
	if (prev_rank > new_rank) {
	// Shift up
	sql::Statement shift_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"UPDATE thumbnails "
	"SET url_rank = url_rank + 1 "
	"WHERE url_rank >= ? AND url_rank < ?"));
	shift_statement.BindInt(0, new_rank);
	shift_statement.BindInt(1, prev_rank);
	if (shift_statement)
	shift_statement.Run();
	} else if (prev_rank < new_rank) {
	// Shift down
	sql::Statement shift_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"UPDATE thumbnails "
	"SET url_rank = url_rank - 1 "
	"WHERE url_rank > ? AND url_rank <= ?"));
	shift_statement.BindInt(0, prev_rank);
	shift_statement.BindInt(1, new_rank);
	if (shift_statement)
	shift_statement.Run();
	}

	// Set the url's rank.
	sql::Statement set_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"UPDATE thumbnails "
	"SET url_rank = ? "
	"WHERE url == ?"));
	set_statement.BindInt(0, new_rank);
	set_statement.BindString(1, url.url.spec());
	if (set_statement)
	set_statement.Run();
	}

	bool TopSitesDatabase::GetPageThumbnail(const GURL& url,
	Images* thumbnail) {
	sql::Statement statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"SELECT thumbnail, boring_score, good_clipping, at_top, last_updated "
	"FROM thumbnails WHERE url=?"));

	if (!statement) {
	LOG(WARNING) << db_->GetErrorMessage();
	return false;
	}

	statement.BindString(0, url.spec());
	if (!statement.Step())
	return false;

	std::vector<unsigned char> data;
	statement.ColumnBlobAsVector(0, &data);
	thumbnail->thumbnail = RefCountedBytes::TakeVector(&data);
	thumbnail->thumbnail_score.boring_score = statement.ColumnDouble(1);
	thumbnail->thumbnail_score.good_clipping = statement.ColumnBool(2);
	thumbnail->thumbnail_score.at_top = statement.ColumnBool(3);
	thumbnail->thumbnail_score.time_at_snapshot =
	base::Time::FromInternalValue(statement.ColumnInt64(4));
	return true;
	}

	int TopSitesDatabase::GetRowCount() {
	int result = 0;
	sql::Statement select_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"SELECT COUNT (url) FROM thumbnails"));
	if (!select_statement) {
	LOG(WARNING) << db_->GetErrorMessage();
	return result;
	}

	if (select_statement.Step())
	result = select_statement.ColumnInt(0);

	return result;
	}

	int TopSitesDatabase::GetURLRank(const MostVisitedURL& url) {
	int result = -1;
	sql::Statement select_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"SELECT url_rank "
	"FROM thumbnails WHERE url=?"));
	if (!select_statement) {
	LOG(WARNING) << db_->GetErrorMessage();
	return result;
	}

	select_statement.BindString(0, url.url.spec());
	if (select_statement.Step())
	result = select_statement.ColumnInt(0);

	return result;
	}

	// Remove the record for this URL. Returns true iff removed successfully.
	bool TopSitesDatabase::RemoveURL(const MostVisitedURL& url) {
	int old_rank = GetURLRank(url);
	if (old_rank < 0)
	return false;

	sql::Transaction transaction(db_.get());
	transaction.Begin();
	// Decrement all following ranks.
	sql::Statement shift_statement(db_->GetCachedStatement(
	SQL_FROM_HERE,
	"UPDATE thumbnails "
	"SET url_rank = url_rank - 1 "
	"WHERE url_rank > ?"));
	if (!shift_statement)
	return false;
	shift_statement.BindInt(0, old_rank);
	shift_statement.Run();

	sql::Statement delete_statement(
	db_->GetCachedStatement(SQL_FROM_HERE,
	"DELETE FROM thumbnails WHERE url = ?"));
	if (!delete_statement)
	return false;
	delete_statement.BindString(0, url.url.spec());
	delete_statement.Run();

	return transaction.Commit();
	}

	sql::Connection* TopSitesDatabase::CreateDB(const FilePath& db_name) {
	scoped_ptr<sql::Connection> db(new sql::Connection());
	// Settings copied from ThumbnailDatabase.
	db->set_error_delegate(GetErrorHandlerForThumbnailDb());
	db->set_page_size(4096);
	db->set_cache_size(32);

	if (!db->Open(db_name)) {
	LOG(ERROR) << db->GetErrorMessage();
	return NULL;
	}

	return db.release();
	}

	} // namespace history