Componentize TopSites, TopSitesBackend, TopSitesDatabase

chrome/browser/history/top_sites_database.cc

Index: chrome/browser/history/top_sites_database.cc
diff --git a/chrome/browser/history/top_sites_database.cc b/chrome/browser/history/top_sites_database.cc
deleted file mode 100644
index 1fe4c25bdd1c9e4ac9353a012bbd6989a904d7d8..0000000000000000000000000000000000000000
--- a/chrome/browser/history/top_sites_database.cc
+++ /dev/null
@@ -1,736 +0,0 @@
-// Copyright (c) 2012 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 "chrome/browser/history/top_sites_database.h"
-
-#include "base/files/file_util.h"
-#include "base/memory/ref_counted.h"
-#include "base/metrics/histogram.h"
-#include "base/strings/string_split.h"
-#include "base/strings/string_util.h"
-#include "chrome/browser/history/top_sites.h"
-#include "components/history/core/browser/history_types.h"
-#include "components/history/core/common/thumbnail_score.h"
-#include "sql/connection.h"
-#include "sql/recovery.h"
-#include "sql/statement.h"
-#include "sql/transaction.h"
-#include "third_party/sqlite/sqlite3.h"
-
-// Description of database table:
-//
-// thumbnails
-//   url              URL of the sites for which we have a thumbnail.
-//   url_rank         Index of the URL in that thumbnail, 0-based. The thumbnail
-//                    with the highest rank will be the next one evicted. Forced
-//                    thumbnails have a rank of -1.
-//   title            The title to display under that thumbnail.
-//   redirects        A space separated list of URLs that are known to redirect
-//                    to this url.
-//   boring_score     How "boring" that thumbnail is. See ThumbnailScore.
-//   good_clipping    True if the thumbnail was clipped from the bottom, keeping
-//                    the entire width of the window. See ThumbnailScore.
-//   at_top           True if the thumbnail was captured at the top of the
-//                    website.
-//   last_updated     The time at which this thumbnail was last updated.
-//   load_completed   True if the thumbnail was captured after the page load was
-//                    completed.
-//   last_forced      If this is a forced thumbnail, records the last time it
-//                    was forced. If it's not a forced thumbnail, 0.
-
-namespace {
-
-// For this database, schema migrations are deprecated after two
-// years.  This means that the oldest non-deprecated version should be
-// two years old or greater (thus the migrations to get there are
-// older).  Databases containing deprecated versions will be cleared
-// at startup.  Since this database is a cache, losing old data is not
-// fatal (in fact, very old data may be expired immediately at startup
-// anyhow).
-
-// Version 3: b6d6a783/r231648 by beaudoin@chromium.org on 2013-10-29
-// Version 2: eb0b24e6/r87284 by satorux@chromium.org on 2011-05-31
-// Version 1: 809cc4d8/r64072 by sky@chromium.org on 2010-10-27 (deprecated)
-
-// NOTE(shess): When changing the version, add a new golden file for
-// the new version and a test to verify that Init() works with it.
-// NOTE(shess): RecoverDatabaseOrRaze() depends on the specific
-// version number.  The code is subtle and in development, contact me
-// if the necessary changes are not obvious.
-static const int kVersionNumber = 3;
-static const int kDeprecatedVersionNumber = 1;  // and earlier.
-
-bool InitTables(sql::Connection* db) {
-  const char kThumbnailsSql[] =
-      "CREATE TABLE IF NOT EXISTS 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,"
-      "load_completed INTEGER DEFAULT 0,"
-      "last_forced INTEGER DEFAULT 0)";
-  return db->Execute(kThumbnailsSql);
-}
-
-// Encodes redirects into a string.
-std::string GetRedirects(const history::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, ' ');
-}
-
-// Decodes redirects from a string and sets them for the url.
-void SetRedirects(const std::string& redirects, history::MostVisitedURL* url) {
-  std::vector<std::string> redirects_vector;
-  base::SplitStringAlongWhitespace(redirects, &redirects_vector);
-  for (size_t i = 0; i < redirects_vector.size(); ++i) {
-    GURL redirects_url(redirects_vector[i]);
-    if (redirects_url.is_valid())
-      url->redirects.push_back(redirects_url);
-  }
-}
-
-// Track various failure (and success) cases in recovery code.
-//
-// TODO(shess): The recovery code is complete, but by nature runs in challenging
-// circumstances, so initially the default error response is to leave the
-// existing database in place.  This histogram is intended to expose the
-// failures seen in the fleet.  Frequent failure cases can be explored more
-// deeply to see if the complexity to fix them is warranted.  Infrequent failure
-// cases can be resolved by marking the database unrecoverable (which will
-// delete the data).
-//
-// Based on the thumbnail_database.cc recovery code, FAILED_SCOPER should
-// dominate, followed distantly by FAILED_META, with few or no other failures.
-enum RecoveryEventType {
-  // Database successfully recovered.
-  RECOVERY_EVENT_RECOVERED = 0,
-
-  // Database successfully deprecated.
-  RECOVERY_EVENT_DEPRECATED,
-
-  // Sqlite.RecoveryEvent can usually be used to get more detail about the
-  // specific failure (see sql/recovery.cc).
-  RECOVERY_EVENT_FAILED_SCOPER,
-  RECOVERY_EVENT_FAILED_META_VERSION,
-  RECOVERY_EVENT_FAILED_META_WRONG_VERSION,
-  RECOVERY_EVENT_FAILED_META_INIT,
-  RECOVERY_EVENT_FAILED_SCHEMA_INIT,
-  RECOVERY_EVENT_FAILED_AUTORECOVER_THUMBNAILS,
-  RECOVERY_EVENT_FAILED_COMMIT,
-
-  // Track invariants resolved by FixThumbnailsTable().
-  RECOVERY_EVENT_INVARIANT_RANK,
-  RECOVERY_EVENT_INVARIANT_REDIRECT,
-  RECOVERY_EVENT_INVARIANT_CONTIGUOUS,
-
-  // Always keep this at the end.
-  RECOVERY_EVENT_MAX,
-};
-
-void RecordRecoveryEvent(RecoveryEventType recovery_event) {
-  UMA_HISTOGRAM_ENUMERATION("History.TopSitesRecovery",
-                            recovery_event, RECOVERY_EVENT_MAX);
-}
-
-// Most corruption comes down to atomic updates between pages being broken
-// somehow.  This can result in either missing data, or overlapping data,
-// depending on the operation broken.  This table has large rows, which will use
-// overflow pages, so it is possible (though unlikely) that a chain could fit
-// together and yield a row with errors.
-void FixThumbnailsTable(sql::Connection* db) {
-  // Enforce invariant separating forced and non-forced thumbnails.
-  const char kFixRankSql[] =
-      "DELETE FROM thumbnails "
-      "WHERE (url_rank = -1 AND last_forced = 0) "
-      "OR (url_rank <> -1 AND last_forced <> 0)";
-  ignore_result(db->Execute(kFixRankSql));
-  if (db->GetLastChangeCount() > 0)
-    RecordRecoveryEvent(RECOVERY_EVENT_INVARIANT_RANK);
-
-  // Enforce invariant that url is in its own redirects.
-  const char kFixRedirectsSql[] =
-      "DELETE FROM thumbnails "
-      "WHERE url <> substr(redirects, -length(url), length(url))";
-  ignore_result(db->Execute(kFixRedirectsSql));
-  if (db->GetLastChangeCount() > 0)
-    RecordRecoveryEvent(RECOVERY_EVENT_INVARIANT_REDIRECT);
-
-  // Enforce invariant that url_rank>=0 forms a contiguous series.
-  // TODO(shess): I have not found an UPDATE+SUBSELECT method of managing this.
-  // It can be done with a temporary table and a subselect, but doing it
-  // manually is easier to follow.  Another option would be to somehow integrate
-  // the renumbering into the table recovery code.
-  const char kByRankSql[] =
-      "SELECT url_rank, rowid FROM thumbnails WHERE url_rank <> -1 "
-      "ORDER BY url_rank";
-  sql::Statement select_statement(db->GetUniqueStatement(kByRankSql));
-
-  const char kAdjustRankSql[] =
-      "UPDATE thumbnails SET url_rank = ? WHERE rowid = ?";
-  sql::Statement update_statement(db->GetUniqueStatement(kAdjustRankSql));
-
-  // Update any rows where |next_rank| doesn't match |url_rank|.
-  int next_rank = 0;
-  bool adjusted = false;
-  while (select_statement.Step()) {
-    const int url_rank = select_statement.ColumnInt(0);
-    if (url_rank != next_rank) {
-      adjusted = true;
-      update_statement.Reset(true);
-      update_statement.BindInt(0, next_rank);
-      update_statement.BindInt64(1, select_statement.ColumnInt64(1));
-      update_statement.Run();
-    }
-    ++next_rank;
-  }
-  if (adjusted)
-    RecordRecoveryEvent(RECOVERY_EVENT_INVARIANT_CONTIGUOUS);
-}
-
-// Recover the database to the extent possible, razing it if recovery is not
-// possible.
-void RecoverDatabaseOrRaze(sql::Connection* db, const base::FilePath& db_path) {
-  // NOTE(shess): If the version changes, review this code.
-  DCHECK_EQ(3, kVersionNumber);
-
-  // It is almost certain that some operation against |db| will fail, prevent
-  // reentry.
-  db->reset_error_callback();
-
-  // For generating histogram stats.
-  size_t thumbnails_recovered = 0;
-  int64 original_size = 0;
-  base::GetFileSize(db_path, &original_size);
-
-  scoped_ptr<sql::Recovery> recovery = sql::Recovery::Begin(db, db_path);
-  if (!recovery) {
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_SCOPER);
-    return;
-  }
-
-  // Setup the meta recovery table and fetch the version number from the corrupt
-  // database.
-  int version = 0;
-  if (!recovery->SetupMeta() || !recovery->GetMetaVersionNumber(&version)) {
-    // TODO(shess): Prior histograms indicate all failures are in creating the
-    // recover virtual table for corrupt.meta.  The table may not exist, or the
-    // database may be too far gone.  Either way, unclear how to resolve.
-    sql::Recovery::Rollback(recovery.Pass());
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_META_VERSION);
-    return;
-  }
-
-  // This code runs in a context which may be able to read version information
-  // that the regular deprecation path cannot.  The effect of this code will be
-  // to raze the database.
-  if (version <= kDeprecatedVersionNumber) {
-    sql::Recovery::Unrecoverable(recovery.Pass());
-    RecordRecoveryEvent(RECOVERY_EVENT_DEPRECATED);
-    return;
-  }
-
-  // TODO(shess): Earlier versions have been deprecated, later versions should
-  // be impossible.  Unrecoverable() seems like a feasible response if this is
-  // infrequent enough.
-  if (version != 2 && version != 3) {
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_META_WRONG_VERSION);
-    sql::Recovery::Rollback(recovery.Pass());
-    return;
-  }
-
-  // Both v2 and v3 recover to current schema version.
-  sql::MetaTable recover_meta_table;
-  if (!recover_meta_table.Init(recovery->db(), kVersionNumber,
-                               kVersionNumber)) {
-    sql::Recovery::Rollback(recovery.Pass());
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_META_INIT);
-    return;
-  }
-
-  // Create a fresh version of the schema.  The recovery code uses
-  // conflict-resolution to handle duplicates, so any indices are necessary.
-  if (!InitTables(recovery->db())) {
-    // TODO(shess): Unable to create the new schema in the new database.  The
-    // new database should be a temporary file, so being unable to work with it
-    // is pretty unclear.
-    //
-    // What are the potential responses, even?  The recovery database could be
-    // opened as in-memory.  If the temp database had a filesystem problem and
-    // the temp filesystem differs from the main database, then that could fix
-    // it.
-    sql::Recovery::Rollback(recovery.Pass());
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_SCHEMA_INIT);
-    return;
-  }
-
-  // The |1| is because v2 [thumbnails] has one less column than v3 did.  In the
-  // v2 case the column will get default values.
-  if (!recovery->AutoRecoverTable("thumbnails", 1, &thumbnails_recovered)) {
-    sql::Recovery::Rollback(recovery.Pass());
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_AUTORECOVER_THUMBNAILS);
-    return;
-  }
-
-  // TODO(shess): Inline this?
-  FixThumbnailsTable(recovery->db());
-
-  if (!sql::Recovery::Recovered(recovery.Pass())) {
-    // TODO(shess): Very unclear what this failure would actually mean, and what
-    // should be done.  Add histograms to Recovered() implementation to get some
-    // insight.
-    RecordRecoveryEvent(RECOVERY_EVENT_FAILED_COMMIT);
-    return;
-  }
-
-  // Track the size of the recovered database relative to the size of the input
-  // database.  The size should almost always be smaller, unless the input
-  // database was empty to start with.  If the percentage results are very low,
-  // something is awry.
-  int64 final_size = 0;
-  if (original_size > 0 &&
-      base::GetFileSize(db_path, &final_size) &&
-      final_size > 0) {
-    UMA_HISTOGRAM_PERCENTAGE("History.TopSitesRecoveredPercentage",
-                             final_size * 100 / original_size);
-  }
-
-  // Using 10,000 because these cases mostly care about "none recovered" and
-  // "lots recovered".  More than 10,000 rows recovered probably means there's
-  // something wrong with the profile.
-  UMA_HISTOGRAM_COUNTS_10000("History.TopSitesRecoveredRowsThumbnails",
-                             thumbnails_recovered);
-
-  RecordRecoveryEvent(RECOVERY_EVENT_RECOVERED);
-}
-
-void DatabaseErrorCallback(sql::Connection* db,
-                           const base::FilePath& db_path,
-                           int extended_error,
-                           sql::Statement* stmt) {
-  // TODO(shess): Assert that this is running on a safe thread.  AFAICT, should
-  // be the history thread, but at this level I can't see how to reach that.
-
-  // Attempt to recover corrupt databases.
-  int error = (extended_error & 0xFF);
-  if (error == SQLITE_CORRUPT ||
-      error == SQLITE_CANTOPEN ||
-      error == SQLITE_NOTADB) {
-    RecoverDatabaseOrRaze(db, db_path);
-  }
-
-  // TODO(shess): This database's error histograms look like:
-  // 84% SQLITE_CORRUPT, SQLITE_CANTOPEN, SQLITE_NOTADB
-  //  7% SQLITE_ERROR
-  //  6% SQLITE_IOERR variants
-  //  2% SQLITE_READONLY
-  // .4% SQLITE_FULL
-  // nominal SQLITE_TOBIG, SQLITE_AUTH, and SQLITE_BUSY.  In the case of
-  // thumbnail_database.cc, as soon as the recovery code landed, SQLITE_IOERR
-  // shot to leadership.  If the I/O error is system-level, there is probably no
-  // hope, but if it is restricted to something about the database file, it is
-  // possible that the recovery code could be brought to bear.  In fact, it is
-  // possible that running recovery would be a reasonable default when errors
-  // are seen.
-
-  // The default handling is to assert on debug and to ignore on release.
-  if (!sql::Connection::ShouldIgnoreSqliteError(extended_error))
-    DLOG(FATAL) << db->GetErrorMessage();
-}
-
-}  // namespace
-
-namespace history {
-
-// static
-const int TopSitesDatabase::kRankOfForcedURL = -1;
-
-// static
-const int TopSitesDatabase::kRankOfNonExistingURL = -2;
-
-TopSitesDatabase::TopSitesDatabase() {
-}
-
-TopSitesDatabase::~TopSitesDatabase() {
-}
-
-bool TopSitesDatabase::Init(const base::FilePath& db_name) {
-  // Retry failed InitImpl() in case the recovery system fixed things.
-  // TODO(shess): Instrument to figure out if there are any persistent failure
-  // cases which do not resolve themselves.
-  const size_t kAttempts = 2;
-
-  for (size_t i = 0; i < kAttempts; ++i) {
-    if (InitImpl(db_name))
-      return true;
-
-    meta_table_.Reset();
-    db_.reset();
-  }
-  return false;
-}
-
-bool TopSitesDatabase::InitImpl(const base::FilePath& db_name) {
-  const bool file_existed = base::PathExists(db_name);
-
-  db_.reset(CreateDB(db_name));
-  if (!db_)
-    return false;
-
-  // An older version had data with no meta table.  Deprecate by razing.
-  // TODO(shess): Just have RazeIfDeprecated() handle this case.
-  const bool does_meta_exist = sql::MetaTable::DoesTableExist(db_.get());
-  if (!does_meta_exist && file_existed) {
-    if (!db_->Raze())
-      return false;
-  }
-
-  // Clear databases which are too old to process.
-  DCHECK_LT(kDeprecatedVersionNumber, kVersionNumber);
-  sql::MetaTable::RazeIfDeprecated(db_.get(), kDeprecatedVersionNumber);
-
-  // Scope initialization in a transaction so we can't be partially
-  // initialized.
-  sql::Transaction transaction(db_.get());
-  // TODO(shess): Failure to open transaction is bad, address it.
-  if (!transaction.Begin())
-    return false;
-
-  if (!meta_table_.Init(db_.get(), kVersionNumber, kVersionNumber))
-    return false;
-
-  if (!InitTables(db_.get()))
-    return false;
-
-  if (meta_table_.GetVersionNumber() == 2) {
-    if (!UpgradeToVersion3()) {
-      LOG(WARNING) << "Unable to upgrade top sites database to version 3.";
-      return false;
-    }
-  }
-
-  // Version check.
-  if (meta_table_.GetVersionNumber() != kVersionNumber)
-    return false;
-
-  // Initialization is complete.
-  if (!transaction.Commit())
-    return false;
-
-  return true;
-}
-
-bool TopSitesDatabase::UpgradeToVersion3() {
-  // Add 'last_forced' column.
-  if (!db_->Execute(
-          "ALTER TABLE thumbnails ADD last_forced INTEGER DEFAULT 0")) {
-    NOTREACHED();
-    return false;
-  }
-  meta_table_.SetVersionNumber(3);
-  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, load_completed, "
-      "last_forced FROM thumbnails ORDER BY url_rank, last_forced"));
-
-  if (!statement.is_valid()) {
-    LOG(WARNING) << db_->GetErrorMessage();
-    return;
-  }
-
-  urls->clear();
-  thumbnails->clear();
-
-  while (statement.Step()) {
-    // Results are sorted by url_rank. For forced thumbnails with url_rank = -1,
-    // thumbnails are sorted by last_forced.
-    MostVisitedURL url;
-    GURL gurl(statement.ColumnString(0));
-    url.url = gurl;
-    url.title = statement.ColumnString16(2);
-    url.last_forced_time =
-        base::Time::FromInternalValue(statement.ColumnInt64(10));
-    std::string redirects = statement.ColumnString(4);
-    SetRedirects(redirects, &url);
-    urls->push_back(url);
-
-    std::vector<unsigned char> data;
-    statement.ColumnBlobAsVector(3, &data);
-    Images thumbnail;
-    if (!data.empty())
-      thumbnail.thumbnail = base::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));
-    thumbnail.thumbnail_score.load_completed = statement.ColumnBool(9);
-    (*thumbnails)[gurl] = thumbnail;
-  }
-}
-
-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 == kRankOfNonExistingURL) {
-    AddPageThumbnail(url, new_rank, thumbnail);
-  } else {
-    UpdatePageRankNoTransaction(url, new_rank);
-    UpdatePageThumbnail(url, thumbnail);
-  }
-
-  transaction.Commit();
-}
-
-bool 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 = ?, "
-      "load_completed = ?, last_forced = ?"
-      "WHERE url = ? "));
-  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.BindBool(7, score.load_completed);
-  statement.BindInt64(8, url.last_forced_time.ToInternalValue());
-  statement.BindString(9, url.url.spec());
-
-  return statement.Run();
-}
-
-void TopSitesDatabase::AddPageThumbnail(const MostVisitedURL& url,
-                                        int new_rank,
-                                        const Images& thumbnail) {
-  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, load_completed, "
-      "last_forced) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"));
-  statement.BindString(0, url.url.spec());
-  statement.BindInt(1, kRankOfForcedURL);  // Fist make it a forced thumbnail.
-  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());
-  statement.BindBool(9, score.load_completed);
-  int64 last_forced = url.last_forced_time.ToInternalValue();
-  DCHECK((last_forced == 0) == (new_rank != kRankOfForcedURL))
-      << "Thumbnail without a forced time stamp has a forced rank, or the "
-      << "opposite.";
-  statement.BindInt64(10, last_forced);
-  if (!statement.Run())
-    return;
-
-  // Update rank if this is not a forced thumbnail.
-  if (new_rank != kRankOfForcedURL)
-    UpdatePageRankNoTransaction(url, new_rank);
-}
-
-void TopSitesDatabase::UpdatePageRank(const MostVisitedURL& url,
-                                      int new_rank) {
-  DCHECK((url.last_forced_time.ToInternalValue() == 0) ==
-         (new_rank != kRankOfForcedURL))
-      << "Thumbnail without a forced time stamp has a forced rank, or the "
-      << "opposite.";
-  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) {
-  DCHECK_GT(db_->transaction_nesting(), 0);
-  DCHECK((url.last_forced_time.is_null()) == (new_rank != kRankOfForcedURL))
-      << "Thumbnail without a forced time stamp has a forced rank, or the "
-      << "opposite.";
-
-  int prev_rank = GetURLRank(url);
-  if (prev_rank == kRankOfNonExistingURL) {
-    LOG(WARNING) << "Updating rank of an unknown URL: " << url.url.spec();
-    return;
-  }
-
-  // Shift the ranks.
-  if (prev_rank > new_rank) {
-    if (new_rank == kRankOfForcedURL) {
-      // From non-forced to forced, shift down.
-      // Example: 2 -> -1
-      // -1, -1, -1, 0, 1, [2 -> -1], [3 -> 2], [4 -> 3]
-      sql::Statement shift_statement(db_->GetCachedStatement(
-          SQL_FROM_HERE,
-          "UPDATE thumbnails "
-          "SET url_rank = url_rank - 1 "
-          "WHERE url_rank > ?"));
-      shift_statement.BindInt(0, prev_rank);
-      shift_statement.Run();
-    } else {
-      // From non-forced to non-forced, shift up.
-      // Example: 3 -> 1
-      // -1, -1, -1, 0, [1 -> 2], [2 -> 3], [3 -> 1], 4
-      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);
-      shift_statement.Run();
-    }
-  } else if (prev_rank < new_rank) {
-    if (prev_rank == kRankOfForcedURL) {
-      // From non-forced to forced, shift up.
-      // Example: -1 -> 2
-      // -1, [-1 -> 2], -1, 0, 1, [2 -> 3], [3 -> 4], [4 -> 5]
-      sql::Statement shift_statement(db_->GetCachedStatement(
-          SQL_FROM_HERE,
-          "UPDATE thumbnails "
-          "SET url_rank = url_rank + 1 "
-          "WHERE url_rank >= ?"));
-      shift_statement.BindInt(0, new_rank);
-      shift_statement.Run();
-    } else {
-      // From non-forced to non-forced, shift down.
-      // Example: 1 -> 3.
-      // -1, -1, -1, 0, [1 -> 3], [2 -> 1], [3 -> 2], 4
-      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);
-      shift_statement.Run();
-    }
-  }
-
-  // Set the url's rank and last_forced, since the latter changes when a URL
-  // goes from forced to non-forced and vice-versa.
-  sql::Statement set_statement(db_->GetCachedStatement(
-      SQL_FROM_HERE,
-      "UPDATE thumbnails "
-      "SET url_rank = ?, last_forced = ? "
-      "WHERE url == ?"));
-  set_statement.BindInt(0, new_rank);
-  set_statement.BindInt64(1, url.last_forced_time.ToInternalValue());
-  set_statement.BindString(2, url.url.spec());
-  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=?"));
-  statement.BindString(0, url.spec());
-  if (!statement.Step())
-    return false;
-
-  std::vector<unsigned char> data;
-  statement.ColumnBlobAsVector(0, &data);
-  thumbnail->thumbnail = base::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::GetURLRank(const MostVisitedURL& url) {
-  sql::Statement select_statement(db_->GetCachedStatement(
-      SQL_FROM_HERE,
-      "SELECT url_rank "
-      "FROM thumbnails WHERE url=?"));
-  select_statement.BindString(0, url.url.spec());
-  if (select_statement.Step())
-    return select_statement.ColumnInt(0);
-
-  return kRankOfNonExistingURL;
-}
-
-// 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 == kRankOfNonExistingURL)
-    return false;
-
-  sql::Transaction transaction(db_.get());
-  transaction.Begin();
-  if (old_rank != kRankOfForcedURL) {
-    // Decrement all following ranks.
-    sql::Statement shift_statement(db_->GetCachedStatement(
-        SQL_FROM_HERE,
-        "UPDATE thumbnails "
-        "SET url_rank = url_rank - 1 "
-        "WHERE url_rank > ?"));
-    shift_statement.BindInt(0, old_rank);
-
-    if (!shift_statement.Run())
-      return false;
-  }
-
-  sql::Statement delete_statement(
-      db_->GetCachedStatement(SQL_FROM_HERE,
-                              "DELETE FROM thumbnails WHERE url = ?"));
-  delete_statement.BindString(0, url.url.spec());
-
-  if (!delete_statement.Run())
-    return false;
-
-  return transaction.Commit();
-}
-
-sql::Connection* TopSitesDatabase::CreateDB(const base::FilePath& db_name) {
-  scoped_ptr<sql::Connection> db(new sql::Connection());
-  // Settings copied from ThumbnailDatabase.
-  db->set_histogram_tag("TopSites");
-  db->set_error_callback(base::Bind(&DatabaseErrorCallback,
-                                    db.get(), db_name));
-  db->set_page_size(4096);
-  db->set_cache_size(32);
-
-  if (!db->Open(db_name))
-    return NULL;
-  return db.release();
-}
-
-}  // namespace history