sync/syncable/directory_backing

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This source file includes following definitions.
BindFields
UnpackEntry
ComposeCreateTableColumnSpecs
AppendColumnList
needs_column_refresh_
needs_column_refresh_
DeleteEntries
SaveChanges
InitializeTables
RefreshColumns
LoadEntries
LoadDeleteJournals
LoadInfo
SaveEntryToDB
DropDeletedEntries
SafeDropTable
DropAllTables
ModelIdToModelTypeEnum
ModelTypeEnumToModelId
GenerateCacheGUID
MigrateToSpecifics
SetVersion
GetVersion
MigrateVersion67To68
MigrateVersion69To70
EncodeBookmarkURLAndFavicon
MigrateVersion68To69
MigrateVersion70To71
MigrateVersion71To72
MigrateVersion72To73
MigrateVersion73To74
MigrateVersion74To75
MigrateVersion75To76
MigrateVersion76To77
MigrateVersion77To78
MigrateVersion78To79
MigrateVersion79To80
MigrateVersion80To81
MigrateVersion81To82
MigrateVersion82To83
MigrateVersion83To84
MigrateVersion84To85
MigrateVersion85To86
MigrateVersion86To87
MigrateVersion87To88
CreateTables
CreateMetasTable
CreateV71ModelsTable
CreateV75ModelsTable
CreateV81ModelsTable
CreateModelsTable
CreateShareInfoTable
CreateShareInfoTableVersion71
VerifyReferenceIntegrity
PrepareSaveEntryStatement
// Copyright 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 "sync/syncable/directory_backing_store.h"

#include "build/build_config.h"

#include <limits>

#include "base/base64.h"
#include "base/debug/trace_event.h"
#include "base/logging.h"
#include "base/rand_util.h"
#include "base/strings/stringprintf.h"
#include "base/time/time.h"
#include "sql/connection.h"
#include "sql/statement.h"
#include "sql/transaction.h"
#include "sync/internal_api/public/base/node_ordinal.h"
#include "sync/protocol/bookmark_specifics.pb.h"
#include "sync/protocol/sync.pb.h"
#include "sync/syncable/syncable-inl.h"
#include "sync/syncable/syncable_columns.h"
#include "sync/syncable/syncable_util.h"
#include "sync/util/time.h"

using std::string;

namespace syncer {
namespace syncable {

// This just has to be big enough to hold an UPDATE or INSERT statement that
// modifies all the columns in the entry table.
static const string::size_type kUpdateStatementBufferSize = 2048;

// Increment this version whenever updating DB tables.
const int32 kCurrentDBVersion = 88;

// Iterate over the fields of |entry| and bind each to |statement| for
// updating.  Returns the number of args bound.
void BindFields(const EntryKernel& entry,
                sql::Statement* statement) {
  int index = 0;
  int i = 0;
  for (i = BEGIN_FIELDS; i < INT64_FIELDS_END; ++i) {
    statement->BindInt64(index++, entry.ref(static_cast<Int64Field>(i)));
  }
  for ( ; i < TIME_FIELDS_END; ++i) {
    statement->BindInt64(index++,
                         TimeToProtoTime(
                             entry.ref(static_cast<TimeField>(i))));
  }
  for ( ; i < ID_FIELDS_END; ++i) {
    statement->BindString(index++, entry.ref(static_cast<IdField>(i)).s_);
  }
  for ( ; i < BIT_FIELDS_END; ++i) {
    statement->BindInt(index++, entry.ref(static_cast<BitField>(i)));
  }
  for ( ; i < STRING_FIELDS_END; ++i) {
    statement->BindString(index++, entry.ref(static_cast<StringField>(i)));
  }
  for ( ; i < PROTO_FIELDS_END; ++i) {
    std::string temp;
    entry.ref(static_cast<ProtoField>(i)).SerializeToString(&temp);
    statement->BindBlob(index++, temp.data(), temp.length());
  }
  for ( ; i < UNIQUE_POSITION_FIELDS_END; ++i) {
    std::string temp;
    entry.ref(static_cast<UniquePositionField>(i)).SerializeToString(&temp);
    statement->BindBlob(index++, temp.data(), temp.length());
  }
}

// The caller owns the returned EntryKernel*.  Assumes the statement currently
// points to a valid row in the metas table. Returns NULL to indicate that
// it detected a corruption in the data on unpacking.
scoped_ptr<EntryKernel> UnpackEntry(sql::Statement* statement) {
  scoped_ptr<EntryKernel> kernel(new EntryKernel());
  DCHECK_EQ(statement->ColumnCount(), static_cast<int>(FIELD_COUNT));
  int i = 0;
  for (i = BEGIN_FIELDS; i < INT64_FIELDS_END; ++i) {
    kernel->put(static_cast<Int64Field>(i), statement->ColumnInt64(i));
  }
  for ( ; i < TIME_FIELDS_END; ++i) {
    kernel->put(static_cast<TimeField>(i),
                ProtoTimeToTime(statement->ColumnInt64(i)));
  }
  for ( ; i < ID_FIELDS_END; ++i) {
    kernel->mutable_ref(static_cast<IdField>(i)).s_ =
        statement->ColumnString(i);
  }
  for ( ; i < BIT_FIELDS_END; ++i) {
    kernel->put(static_cast<BitField>(i), (0 != statement->ColumnInt(i)));
  }
  for ( ; i < STRING_FIELDS_END; ++i) {
    kernel->put(static_cast<StringField>(i),
                statement->ColumnString(i));
  }
  for ( ; i < PROTO_FIELDS_END; ++i) {
    kernel->mutable_ref(static_cast<ProtoField>(i)).ParseFromArray(
        statement->ColumnBlob(i), statement->ColumnByteLength(i));
  }
  for ( ; i < UNIQUE_POSITION_FIELDS_END; ++i) {
    std::string temp;
    statement->ColumnBlobAsString(i, &temp);

    sync_pb::UniquePosition proto;
    if (!proto.ParseFromString(temp)) {
      DVLOG(1) << "Unpacked invalid position.  Assuming the DB is corrupt";
      return scoped_ptr<EntryKernel>();
    }

    kernel->mutable_ref(static_cast<UniquePositionField>(i)) =
        UniquePosition::FromProto(proto);
  }
  return kernel.Pass();
}

namespace {

string ComposeCreateTableColumnSpecs() {
  const ColumnSpec* begin = g_metas_columns;
  const ColumnSpec* end = g_metas_columns + arraysize(g_metas_columns);
  string query;
  query.reserve(kUpdateStatementBufferSize);
  char separator = '(';
  for (const ColumnSpec* column = begin; column != end; ++column) {
    query.push_back(separator);
    separator = ',';
    query.append(column->name);
    query.push_back(' ');
    query.append(column->spec);
  }
  query.push_back(')');
  return query;
}

void AppendColumnList(std::string* output) {
  const char* joiner = " ";
  // Be explicit in SELECT order to match up with UnpackEntry.
  for (int i = BEGIN_FIELDS; i < FIELD_COUNT; ++i) {
    output->append(joiner);
    output->append(ColumnName(i));
    joiner = ", ";
  }
}

}  // namespace

///////////////////////////////////////////////////////////////////////////////
// DirectoryBackingStore implementation.

DirectoryBackingStore::DirectoryBackingStore(const string& dir_name)
  : db_(new sql::Connection()),
    dir_name_(dir_name),
    needs_column_refresh_(false) {
  db_->set_histogram_tag("SyncDirectory");
  db_->set_page_size(4096);
  db_->set_cache_size(32);
}

DirectoryBackingStore::DirectoryBackingStore(const string& dir_name,
                                             sql::Connection* db)
  : db_(db),
    dir_name_(dir_name),
    needs_column_refresh_(false) {
}

DirectoryBackingStore::~DirectoryBackingStore() {
}

bool DirectoryBackingStore::DeleteEntries(EntryTable from,
                                          const MetahandleSet& handles) {
  if (handles.empty())
    return true;

  sql::Statement statement;
  // Call GetCachedStatement() separately to get different statements for
  // different tables.
  switch (from) {
    case METAS_TABLE:
      statement.Assign(db_->GetCachedStatement(
          SQL_FROM_HERE, "DELETE FROM metas WHERE metahandle = ?"));
      break;
    case DELETE_JOURNAL_TABLE:
      statement.Assign(db_->GetCachedStatement(
          SQL_FROM_HERE, "DELETE FROM deleted_metas WHERE metahandle = ?"));
      break;
  }

  for (MetahandleSet::const_iterator i = handles.begin(); i != handles.end();
       ++i) {
    statement.BindInt64(0, *i);
    if (!statement.Run())
      return false;
    statement.Reset(true);
  }
  return true;
}

bool DirectoryBackingStore::SaveChanges(
    const Directory::SaveChangesSnapshot& snapshot) {
  DCHECK(CalledOnValidThread());
  DCHECK(db_->is_open());

  // Back out early if there is nothing to write.
  bool save_info =
    (Directory::KERNEL_SHARE_INFO_DIRTY == snapshot.kernel_info_status);
  if (snapshot.dirty_metas.empty() && snapshot.metahandles_to_purge.empty() &&
      snapshot.delete_journals.empty() &&
      snapshot.delete_journals_to_purge.empty() && !save_info) {
    return true;
  }

  sql::Transaction transaction(db_.get());
  if (!transaction.Begin())
    return false;

  PrepareSaveEntryStatement(METAS_TABLE, &save_meta_statment_);
  for (EntryKernelSet::const_iterator i = snapshot.dirty_metas.begin();
       i != snapshot.dirty_metas.end(); ++i) {
    DCHECK((*i)->is_dirty());
    if (!SaveEntryToDB(&save_meta_statment_, **i))
      return false;
  }

  if (!DeleteEntries(METAS_TABLE, snapshot.metahandles_to_purge))
    return false;

  PrepareSaveEntryStatement(DELETE_JOURNAL_TABLE,
                            &save_delete_journal_statment_);
  for (EntryKernelSet::const_iterator i = snapshot.delete_journals.begin();
       i != snapshot.delete_journals.end(); ++i) {
    if (!SaveEntryToDB(&save_delete_journal_statment_, **i))
      return false;
  }

  if (!DeleteEntries(DELETE_JOURNAL_TABLE, snapshot.delete_journals_to_purge))
    return false;

  if (save_info) {
    const Directory::PersistedKernelInfo& info = snapshot.kernel_info;
    sql::Statement s1(db_->GetCachedStatement(
            SQL_FROM_HERE,
            "UPDATE share_info "
            "SET store_birthday = ?, "
            "next_id = ?, "
            "bag_of_chips = ?"));
    s1.BindString(0, info.store_birthday);
    s1.BindInt64(1, info.next_id);
    s1.BindBlob(2, info.bag_of_chips.data(), info.bag_of_chips.size());

    if (!s1.Run())
      return false;
    DCHECK_EQ(db_->GetLastChangeCount(), 1);

    sql::Statement s2(db_->GetCachedStatement(
            SQL_FROM_HERE,
            "INSERT OR REPLACE "
            "INTO models (model_id, "
                         "progress_marker, "
                         "transaction_version, "
                         "context) "
            "VALUES (?, ?, ?, ?)"));

    ModelTypeSet protocol_types = ProtocolTypes();
    for (ModelTypeSet::Iterator iter = protocol_types.First(); iter.Good();
         iter.Inc()) {
      ModelType type = iter.Get();
      // We persist not ModelType but rather a protobuf-derived ID.
      string model_id = ModelTypeEnumToModelId(type);
      string progress_marker;
      info.download_progress[type].SerializeToString(&progress_marker);
      s2.BindBlob(0, model_id.data(), model_id.length());
      s2.BindBlob(1, progress_marker.data(), progress_marker.length());
      s2.BindInt64(2, info.transaction_version[type]);
      string context;
      info.datatype_context[type].SerializeToString(&context);
      s2.BindBlob(3, context.data(), context.length());
      if (!s2.Run())
        return false;
      DCHECK_EQ(db_->GetLastChangeCount(), 1);
      s2.Reset(true);
    }
  }

  return transaction.Commit();
}

bool DirectoryBackingStore::InitializeTables() {
  sql::Transaction transaction(db_.get());
  if (!transaction.Begin())
    return false;

  int version_on_disk = GetVersion();

  // Upgrade from version 67. Version 67 was widely distributed as the original
  // Bookmark Sync release. Version 68 removed unique naming.
  if (version_on_disk == 67) {
    if (MigrateVersion67To68())
      version_on_disk = 68;
  }
  // Version 69 introduced additional datatypes.
  if (version_on_disk == 68) {
    if (MigrateVersion68To69())
      version_on_disk = 69;
  }

  if (version_on_disk == 69) {
    if (MigrateVersion69To70())
      version_on_disk = 70;
  }

  // Version 71 changed the sync progress information to be per-datatype.
  if (version_on_disk == 70) {
    if (MigrateVersion70To71())
      version_on_disk = 71;
  }

  // Version 72 removed extended attributes, a legacy way to do extensible
  // key/value information, stored in their own table.
  if (version_on_disk == 71) {
    if (MigrateVersion71To72())
      version_on_disk = 72;
  }

  // Version 73 added a field for notification state.
  if (version_on_disk == 72) {
    if (MigrateVersion72To73())
      version_on_disk = 73;
  }

  // Version 74 added state for the autofill migration.
  if (version_on_disk == 73) {
    if (MigrateVersion73To74())
      version_on_disk = 74;
  }

  // Version 75 migrated from int64-based timestamps to per-datatype tokens.
  if (version_on_disk == 74) {
    if (MigrateVersion74To75())
      version_on_disk = 75;
  }

  // Version 76 removed all (5) autofill migration related columns.
  if (version_on_disk == 75) {
    if (MigrateVersion75To76())
      version_on_disk = 76;
  }

  // Version 77 standardized all time fields to ms since the Unix
  // epoch.
  if (version_on_disk == 76) {
    if (MigrateVersion76To77())
      version_on_disk = 77;
  }

  // Version 78 added the column base_server_specifics to the metas table.
  if (version_on_disk == 77) {
    if (MigrateVersion77To78())
      version_on_disk = 78;
  }

  // Version 79 migration is a one-time fix for some users in a bad state.
  if (version_on_disk == 78) {
    if (MigrateVersion78To79())
      version_on_disk = 79;
  }

  // Version 80 migration is adding the bag_of_chips column.
  if (version_on_disk == 79) {
    if (MigrateVersion79To80())
      version_on_disk = 80;
  }

  // Version 81 replaces the int64 server_position_in_parent_field
  // with a blob server_ordinal_in_parent field.
  if (version_on_disk == 80) {
    if (MigrateVersion80To81())
      version_on_disk = 81;
  }

  // Version 82 migration added transaction_version column per data type.
  if (version_on_disk == 81) {
    if (MigrateVersion81To82())
      version_on_disk = 82;
  }

  // Version 83 migration added transaction_version column per sync entry.
  if (version_on_disk == 82) {
    if (MigrateVersion82To83())
      version_on_disk = 83;
  }

  // Version 84 migration added deleted_metas table.
  if (version_on_disk == 83) {
    if (MigrateVersion83To84())
      version_on_disk = 84;
  }

  // Version 85 migration removes the initial_sync_ended bits.
  if (version_on_disk == 84) {
    if (MigrateVersion84To85())
      version_on_disk = 85;
  }

  // Version 86 migration converts bookmarks to the unique positioning system.
  // It also introduces a new field to store a unique ID for each bookmark.
  if (version_on_disk == 85) {
    if (MigrateVersion85To86())
      version_on_disk = 86;
  }

  // Version 87 migration adds a collection of attachment ids per sync entry.
  if (version_on_disk == 86) {
    if (MigrateVersion86To87())
      version_on_disk = 87;
  }

  // Version 88 migration adds datatype contexts to the models table.
  if (version_on_disk == 87) {
    if (MigrateVersion87To88())
      version_on_disk = 88;
  }

  // If one of the migrations requested it, drop columns that aren't current.
  // It's only safe to do this after migrating all the way to the current
  // version.
  if (version_on_disk == kCurrentDBVersion && needs_column_refresh_) {
    if (!RefreshColumns())
      version_on_disk = 0;
  }

  // A final, alternative catch-all migration to simply re-sync everything.
  if (version_on_disk != kCurrentDBVersion) {
    if (version_on_disk > kCurrentDBVersion)
      return false;

    // Fallback (re-sync everything) migration path.
    DVLOG(1) << "Old/null sync database, version " << version_on_disk;
    // Delete the existing database (if any), and create a fresh one.
    DropAllTables();
    if (!CreateTables())
      return false;
  }

  sql::Statement s(db_->GetUniqueStatement(
          "SELECT db_create_version, db_create_time FROM share_info"));
  if (!s.Step())
    return false;
  string db_create_version = s.ColumnString(0);
  int db_create_time = s.ColumnInt(1);
  DVLOG(1) << "DB created at " << db_create_time << " by version " <<
      db_create_version;

  return transaction.Commit();
}

// This function drops unused columns by creating a new table that contains only
// the currently used columns then copying all rows from the old tables into
// this new one.  The tables are then rearranged so the new replaces the old.
bool DirectoryBackingStore::RefreshColumns() {
  DCHECK(needs_column_refresh_);

  // Create a new table named temp_metas.
  SafeDropTable("temp_metas");
  if (!CreateMetasTable(true))
    return false;

  // Populate temp_metas from metas.
  //
  // At this point, the metas table may contain columns belonging to obsolete
  // schema versions.  This statement explicitly lists only the columns that
  // belong to the current schema version, so the obsolete columns will be
  // effectively dropped once we rename temp_metas over top of metas.
  std::string query = "INSERT INTO temp_metas (";
  AppendColumnList(&query);
  query.append(") SELECT ");
  AppendColumnList(&query);
  query.append(" FROM metas");
  if (!db_->Execute(query.c_str()))
    return false;

  // Drop metas.
  SafeDropTable("metas");

  // Rename temp_metas -> metas.
  if (!db_->Execute("ALTER TABLE temp_metas RENAME TO metas"))
    return false;

  // Repeat the process for share_info.
  SafeDropTable("temp_share_info");
  if (!CreateShareInfoTable(true))
    return false;

  // TODO(rlarocque, 124140): Remove notification_state.
  if (!db_->Execute(
          "INSERT INTO temp_share_info (id, name, store_birthday, "
          "db_create_version, db_create_time, next_id, cache_guid,"
          "notification_state, bag_of_chips) "
          "SELECT id, name, store_birthday, db_create_version, "
          "db_create_time, next_id, cache_guid, notification_state, "
          "bag_of_chips "
          "FROM share_info"))
    return false;

  SafeDropTable("share_info");
  if (!db_->Execute("ALTER TABLE temp_share_info RENAME TO share_info"))
    return false;

  needs_column_refresh_ = false;
  return true;
}

bool DirectoryBackingStore::LoadEntries(
    Directory::MetahandlesMap* handles_map) {
  string select;
  select.reserve(kUpdateStatementBufferSize);
  select.append("SELECT ");
  AppendColumnList(&select);
  select.append(" FROM metas");

  sql::Statement s(db_->GetUniqueStatement(select.c_str()));

  while (s.Step()) {
    scoped_ptr<EntryKernel> kernel = UnpackEntry(&s);
    // A null kernel is evidence of external data corruption.
    if (!kernel)
      return false;

    int64 handle = kernel->ref(META_HANDLE);
    (*handles_map)[handle] = kernel.release();
  }
  return s.Succeeded();
}

bool DirectoryBackingStore::LoadDeleteJournals(
    JournalIndex* delete_journals) {
  string select;
  select.reserve(kUpdateStatementBufferSize);
  select.append("SELECT ");
  AppendColumnList(&select);
  select.append(" FROM deleted_metas");

  sql::Statement s(db_->GetUniqueStatement(select.c_str()));

  while (s.Step()) {
    scoped_ptr<EntryKernel> kernel = UnpackEntry(&s);
    // A null kernel is evidence of external data corruption.
    if (!kernel)
      return false;
    delete_journals->insert(kernel.release());
  }
  return s.Succeeded();
}

bool DirectoryBackingStore::LoadInfo(Directory::KernelLoadInfo* info) {
  {
    sql::Statement s(
        db_->GetUniqueStatement(
            "SELECT store_birthday, next_id, cache_guid, bag_of_chips "
            "FROM share_info"));
    if (!s.Step())
      return false;

    info->kernel_info.store_birthday = s.ColumnString(0);
    info->kernel_info.next_id = s.ColumnInt64(1);
    info->cache_guid = s.ColumnString(2);
    s.ColumnBlobAsString(3, &(info->kernel_info.bag_of_chips));

    // Verify there was only one row returned.
    DCHECK(!s.Step());
    DCHECK(s.Succeeded());
  }

  {
    sql::Statement s(
        db_->GetUniqueStatement(
            "SELECT model_id, progress_marker, "
            "transaction_version, context FROM models"));

    while (s.Step()) {
      ModelType type = ModelIdToModelTypeEnum(s.ColumnBlob(0),
                                              s.ColumnByteLength(0));
      if (type != UNSPECIFIED && type != TOP_LEVEL_FOLDER) {
        info->kernel_info.download_progress[type].ParseFromArray(
            s.ColumnBlob(1), s.ColumnByteLength(1));
        info->kernel_info.transaction_version[type] = s.ColumnInt64(2);
        info->kernel_info.datatype_context[type].ParseFromArray(
            s.ColumnBlob(3), s.ColumnByteLength(3));
      }
    }
    if (!s.Succeeded())
      return false;
  }
  {
    sql::Statement s(
        db_->GetUniqueStatement(
            "SELECT MAX(metahandle) FROM metas"));
    if (!s.Step())
      return false;

    info->max_metahandle = s.ColumnInt64(0);

    // Verify only one row was returned.
    DCHECK(!s.Step());
    DCHECK(s.Succeeded());
  }
  return true;
}

/* static */
bool DirectoryBackingStore::SaveEntryToDB(sql::Statement* save_statement,
                                          const EntryKernel& entry) {
  save_statement->Reset(true);
  BindFields(entry, save_statement);
  return save_statement->Run();
}

bool DirectoryBackingStore::DropDeletedEntries() {
  if (!db_->Execute("DELETE FROM metas "
                    "WHERE is_del > 0 "
                    "AND is_unsynced < 1 "
                    "AND is_unapplied_update < 1")) {
    return false;
  }
  if (!db_->Execute("DELETE FROM metas "
                    "WHERE is_del > 0 "
                    "AND id LIKE 'c%'")) {
    return false;
  }
  return true;
}

bool DirectoryBackingStore::SafeDropTable(const char* table_name) {
  string query = "DROP TABLE IF EXISTS ";
  query.append(table_name);
  return db_->Execute(query.c_str());
}

void DirectoryBackingStore::DropAllTables() {
  SafeDropTable("metas");
  SafeDropTable("temp_metas");
  SafeDropTable("share_info");
  SafeDropTable("temp_share_info");
  SafeDropTable("share_version");
  SafeDropTable("extended_attributes");
  SafeDropTable("models");
  SafeDropTable("temp_models");
  needs_column_refresh_ = false;
}

// static
ModelType DirectoryBackingStore::ModelIdToModelTypeEnum(
    const void* data, int size) {
  sync_pb::EntitySpecifics specifics;
  if (!specifics.ParseFromArray(data, size))
    return UNSPECIFIED;
  return GetModelTypeFromSpecifics(specifics);
}

// static
string DirectoryBackingStore::ModelTypeEnumToModelId(ModelType model_type) {
  sync_pb::EntitySpecifics specifics;
  AddDefaultFieldValue(model_type, &specifics);
  return specifics.SerializeAsString();
}

// static
std::string DirectoryBackingStore::GenerateCacheGUID() {
  // Generate a GUID with 128 bits of randomness.
  const int kGuidBytes = 128 / 8;
  std::string guid;
  base::Base64Encode(base::RandBytesAsString(kGuidBytes), &guid);
  return guid;
}

bool DirectoryBackingStore::MigrateToSpecifics(
    const char* old_columns,
    const char* specifics_column,
    void (*handler_function)(sql::Statement* old_value_query,
                             int old_value_column,
                             sync_pb::EntitySpecifics* mutable_new_value)) {
  std::string query_sql = base::StringPrintf(
      "SELECT metahandle, %s, %s FROM metas", specifics_column, old_columns);
  std::string update_sql = base::StringPrintf(
      "UPDATE metas SET %s = ? WHERE metahandle = ?", specifics_column);

  sql::Statement query(db_->GetUniqueStatement(query_sql.c_str()));
  sql::Statement update(db_->GetUniqueStatement(update_sql.c_str()));

  while (query.Step()) {
    int64 metahandle = query.ColumnInt64(0);
    std::string new_value_bytes;
    query.ColumnBlobAsString(1, &new_value_bytes);
    sync_pb::EntitySpecifics new_value;
    new_value.ParseFromString(new_value_bytes);
    handler_function(&query, 2, &new_value);
    new_value.SerializeToString(&new_value_bytes);

    update.BindBlob(0, new_value_bytes.data(), new_value_bytes.length());
    update.BindInt64(1, metahandle);
    if (!update.Run())
      return false;
    update.Reset(true);
  }
  return query.Succeeded();
}

bool DirectoryBackingStore::SetVersion(int version) {
  sql::Statement s(db_->GetCachedStatement(
          SQL_FROM_HERE, "UPDATE share_version SET data = ?"));
  s.BindInt(0, version);

  return s.Run();
}

int DirectoryBackingStore::GetVersion() {
  if (!db_->DoesTableExist("share_version"))
    return 0;

  sql::Statement statement(db_->GetUniqueStatement(
          "SELECT data FROM share_version"));
  if (statement.Step()) {
    return statement.ColumnInt(0);
  } else {
    return 0;
  }
}

bool DirectoryBackingStore::MigrateVersion67To68() {
  // This change simply removed three columns:
  //   string NAME
  //   string UNSANITIZED_NAME
  //   string SERVER_NAME
  // No data migration is necessary, but we should do a column refresh.
  SetVersion(68);
  needs_column_refresh_ = true;
  return true;
}

bool DirectoryBackingStore::MigrateVersion69To70() {
  // Added "unique_client_tag", renamed "singleton_tag" to unique_server_tag
  SetVersion(70);
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN unique_server_tag varchar"))
    return false;
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN unique_client_tag varchar"))
    return false;
  needs_column_refresh_ = true;

  if (!db_->Execute(
          "UPDATE metas SET unique_server_tag = singleton_tag"))
    return false;

  return true;
}

namespace {

// Callback passed to MigrateToSpecifics for the v68->v69 migration.  See
// MigrateVersion68To69().
void EncodeBookmarkURLAndFavicon(sql::Statement* old_value_query,
                                 int old_value_column,
                                 sync_pb::EntitySpecifics* mutable_new_value) {
  // Extract data from the column trio we expect.
  bool old_is_bookmark_object = old_value_query->ColumnBool(old_value_column);
  std::string old_url = old_value_query->ColumnString(old_value_column + 1);
  std::string old_favicon;
  old_value_query->ColumnBlobAsString(old_value_column + 2, &old_favicon);
  bool old_is_dir = old_value_query->ColumnBool(old_value_column + 3);

  if (old_is_bookmark_object) {
    sync_pb::BookmarkSpecifics* bookmark_data =
        mutable_new_value->mutable_bookmark();
    if (!old_is_dir) {
      bookmark_data->set_url(old_url);
      bookmark_data->set_favicon(old_favicon);
    }
  }
}

}  // namespace

bool DirectoryBackingStore::MigrateVersion68To69() {
  // In Version 68, there were columns on table 'metas':
  //   string BOOKMARK_URL
  //   string SERVER_BOOKMARK_URL
  //   blob BOOKMARK_FAVICON
  //   blob SERVER_BOOKMARK_FAVICON
  // In version 69, these columns went away in favor of storing
  // a serialized EntrySpecifics protobuf in the columns:
  //   protobuf blob SPECIFICS
  //   protobuf blob SERVER_SPECIFICS
  // For bookmarks, EntrySpecifics is extended as per
  // bookmark_specifics.proto. This migration converts bookmarks from the
  // former scheme to the latter scheme.

  // First, add the two new columns to the schema.
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN specifics blob"))
    return false;
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN server_specifics blob"))
    return false;

  // Next, fold data from the old columns into the new protobuf columns.
  if (!MigrateToSpecifics(("is_bookmark_object, bookmark_url, "
                           "bookmark_favicon, is_dir"),
                          "specifics",
                          &EncodeBookmarkURLAndFavicon)) {
    return false;
  }
  if (!MigrateToSpecifics(("server_is_bookmark_object, "
                           "server_bookmark_url, "
                           "server_bookmark_favicon, "
                           "server_is_dir"),
                          "server_specifics",
                          &EncodeBookmarkURLAndFavicon)) {
    return false;
  }

  // Lastly, fix up the "Google Chrome" folder, which is of the TOP_LEVEL_FOLDER
  // ModelType: it shouldn't have BookmarkSpecifics.
  if (!db_->Execute(
          "UPDATE metas SET specifics = NULL, server_specifics = NULL WHERE "
          "singleton_tag IN ('google_chrome')"))
    return false;

  SetVersion(69);
  needs_column_refresh_ = true;  // Trigger deletion of old columns.
  return true;
}

// Version 71, the columns 'initial_sync_ended' and 'last_sync_timestamp'
// were removed from the share_info table.  They were replaced by
// the 'models' table, which has these values on a per-datatype basis.
bool DirectoryBackingStore::MigrateVersion70To71() {
  if (!CreateV71ModelsTable())
    return false;

  // Move data from the old share_info columns to the new models table.
  {
    sql::Statement fetch(db_->GetUniqueStatement(
            "SELECT last_sync_timestamp, initial_sync_ended FROM share_info"));
    if (!fetch.Step())
      return false;

    int64 last_sync_timestamp = fetch.ColumnInt64(0);
    bool initial_sync_ended = fetch.ColumnBool(1);

    // Verify there were no additional rows returned.
    DCHECK(!fetch.Step());
    DCHECK(fetch.Succeeded());

    sql::Statement update(db_->GetUniqueStatement(
            "INSERT INTO models (model_id, "
            "last_download_timestamp, initial_sync_ended) VALUES (?, ?, ?)"));
    string bookmark_model_id = ModelTypeEnumToModelId(BOOKMARKS);
    update.BindBlob(0, bookmark_model_id.data(), bookmark_model_id.size());
    update.BindInt64(1, last_sync_timestamp);
    update.BindBool(2, initial_sync_ended);

    if (!update.Run())
      return false;
  }

  // Drop the columns from the old share_info table via a temp table.
  const bool kCreateAsTempShareInfo = true;

  if (!CreateShareInfoTableVersion71(kCreateAsTempShareInfo))
    return false;
  if (!db_->Execute(
          "INSERT INTO temp_share_info (id, name, store_birthday, "
          "db_create_version, db_create_time, next_id, cache_guid) "
          "SELECT id, name, store_birthday, db_create_version, "
          "db_create_time, next_id, cache_guid FROM share_info"))
    return false;
  SafeDropTable("share_info");
  if (!db_->Execute(
          "ALTER TABLE temp_share_info RENAME TO share_info"))
    return false;
  SetVersion(71);
  return true;
}

bool DirectoryBackingStore::MigrateVersion71To72() {
  // Version 72 removed a table 'extended_attributes', whose
  // contents didn't matter.
  SafeDropTable("extended_attributes");
  SetVersion(72);
  return true;
}

bool DirectoryBackingStore::MigrateVersion72To73() {
  // Version 73 added one column to the table 'share_info': notification_state
  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN notification_state BLOB"))
    return false;
  SetVersion(73);
  return true;
}

bool DirectoryBackingStore::MigrateVersion73To74() {
  // Version 74 added the following columns to the table 'share_info':
  //   autofill_migration_state
  //   bookmarks_added_during_autofill_migration
  //   autofill_migration_time
  //   autofill_entries_added_during_migration
  //   autofill_profiles_added_during_migration

  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN "
          "autofill_migration_state INT default 0"))
    return false;

  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN "
          "bookmarks_added_during_autofill_migration "
          "INT default 0"))
    return false;

  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN autofill_migration_time "
          "INT default 0"))
    return false;

  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN "
          "autofill_entries_added_during_migration "
          "INT default 0"))
    return false;

  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN "
          "autofill_profiles_added_during_migration "
          "INT default 0"))
    return false;

  SetVersion(74);
  return true;
}

bool DirectoryBackingStore::MigrateVersion74To75() {
  // In version 74, there was a table 'models':
  //     blob model_id (entity specifics, primary key)
  //     int last_download_timestamp
  //     boolean initial_sync_ended
  // In version 75, we deprecated the integer-valued last_download_timestamp,
  // using insted a protobuf-valued progress_marker field:
  //     blob progress_marker
  // The progress_marker values are initialized from the value of
  // last_download_timestamp, thereby preserving the download state.

  // Move aside the old table and create a new empty one at the current schema.
  if (!db_->Execute("ALTER TABLE models RENAME TO temp_models"))
    return false;
  if (!CreateV75ModelsTable())
    return false;

  sql::Statement query(db_->GetUniqueStatement(
          "SELECT model_id, last_download_timestamp, initial_sync_ended "
          "FROM temp_models"));

  sql::Statement update(db_->GetUniqueStatement(
          "INSERT INTO models (model_id, "
          "progress_marker, initial_sync_ended) VALUES (?, ?, ?)"));

  while (query.Step()) {
    ModelType type = ModelIdToModelTypeEnum(query.ColumnBlob(0),
                                            query.ColumnByteLength(0));
    if (type != UNSPECIFIED) {
      // Set the |timestamp_token_for_migration| on a new
      // DataTypeProgressMarker, using the old value of last_download_timestamp.
      // The server will turn this into a real token on our behalf the next
      // time we check for updates.
      sync_pb::DataTypeProgressMarker progress_marker;
      progress_marker.set_data_type_id(
          GetSpecificsFieldNumberFromModelType(type));
      progress_marker.set_timestamp_token_for_migration(query.ColumnInt64(1));
      std::string progress_blob;
      progress_marker.SerializeToString(&progress_blob);

      update.BindBlob(0, query.ColumnBlob(0), query.ColumnByteLength(0));
      update.BindBlob(1, progress_blob.data(), progress_blob.length());
      update.BindBool(2, query.ColumnBool(2));
      if (!update.Run())
        return false;
      update.Reset(true);
    }
  }
  if (!query.Succeeded())
    return false;

  // Drop the old table.
  SafeDropTable("temp_models");

  SetVersion(75);
  return true;
}

bool DirectoryBackingStore::MigrateVersion75To76() {
  // This change removed five columns:
  //   autofill_migration_state
  //   bookmarks_added_during_autofill_migration
  //   autofill_migration_time
  //   autofill_entries_added_during_migration
  //   autofill_profiles_added_during_migration
  // No data migration is necessary, but we should do a column refresh.
  SetVersion(76);
  needs_column_refresh_ = true;
  return true;
}

bool DirectoryBackingStore::MigrateVersion76To77() {
  // This change changes the format of stored timestamps to ms since
  // the Unix epoch.
#if defined(OS_WIN)
// On Windows, we used to store timestamps in FILETIME format (100s of
// ns since Jan 1, 1601).  Magic numbers taken from
// http://stackoverflow.com/questions/5398557/
//     java-library-for-dealing-with-win32-filetime
// .
#define TO_UNIX_TIME_MS(x) #x " = " #x " / 10000 - 11644473600000"
#else
// On other platforms, we used to store timestamps in time_t format (s
// since the Unix epoch).
#define TO_UNIX_TIME_MS(x) #x " = " #x " * 1000"
#endif
  sql::Statement update_timestamps(db_->GetUniqueStatement(
          "UPDATE metas SET "
          TO_UNIX_TIME_MS(mtime) ", "
          TO_UNIX_TIME_MS(server_mtime) ", "
          TO_UNIX_TIME_MS(ctime) ", "
          TO_UNIX_TIME_MS(server_ctime)));
#undef TO_UNIX_TIME_MS
  if (!update_timestamps.Run())
    return false;
  SetVersion(77);
  return true;
}

bool DirectoryBackingStore::MigrateVersion77To78() {
  // Version 78 added one column to table 'metas': base_server_specifics.
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN base_server_specifics BLOB")) {
    return false;
  }
  SetVersion(78);
  return true;
}

bool DirectoryBackingStore::MigrateVersion78To79() {
  // Some users are stuck with a DB that causes them to reuse existing IDs.  We
  // perform this one-time fixup on all users to help the few that are stuck.
  // See crbug.com/142987 for details.
  if (!db_->Execute(
          "UPDATE share_info SET next_id = next_id - 65536")) {
    return false;
  }
  SetVersion(79);
  return true;
}

bool DirectoryBackingStore::MigrateVersion79To80() {
  if (!db_->Execute(
          "ALTER TABLE share_info ADD COLUMN bag_of_chips BLOB"))
    return false;
  sql::Statement update(db_->GetUniqueStatement(
          "UPDATE share_info SET bag_of_chips = ?"));
  // An empty message is serialized to an empty string.
  update.BindBlob(0, NULL, 0);
  if (!update.Run())
    return false;
  SetVersion(80);
  return true;
}

bool DirectoryBackingStore::MigrateVersion80To81() {
  if(!db_->Execute(
         "ALTER TABLE metas ADD COLUMN server_ordinal_in_parent BLOB"))
    return false;

  sql::Statement get_positions(db_->GetUniqueStatement(
      "SELECT metahandle, server_position_in_parent FROM metas"));

  sql::Statement put_ordinals(db_->GetUniqueStatement(
      "UPDATE metas SET server_ordinal_in_parent = ?"
      "WHERE metahandle = ?"));

  while(get_positions.Step()) {
    int64 metahandle = get_positions.ColumnInt64(0);
    int64 position = get_positions.ColumnInt64(1);

    const std::string& ordinal = Int64ToNodeOrdinal(position).ToInternalValue();
    put_ordinals.BindBlob(0, ordinal.data(), ordinal.length());
    put_ordinals.BindInt64(1, metahandle);

    if(!put_ordinals.Run())
      return false;
    put_ordinals.Reset(true);
  }

  SetVersion(81);
  needs_column_refresh_ = true;
  return true;
}

bool DirectoryBackingStore::MigrateVersion81To82() {
  if (!db_->Execute(
      "ALTER TABLE models ADD COLUMN transaction_version BIGINT default 0"))
    return false;
  sql::Statement update(db_->GetUniqueStatement(
      "UPDATE models SET transaction_version = 0"));
  if (!update.Run())
    return false;
  SetVersion(82);
  return true;
}

bool DirectoryBackingStore::MigrateVersion82To83() {
  // Version 83 added transaction_version on sync node.
  if (!db_->Execute(
      "ALTER TABLE metas ADD COLUMN transaction_version BIGINT default 0"))
    return false;
  sql::Statement update(db_->GetUniqueStatement(
      "UPDATE metas SET transaction_version = 0"));
  if (!update.Run())
    return false;
  SetVersion(83);
  return true;
}

bool DirectoryBackingStore::MigrateVersion83To84() {
  // Version 84 added deleted_metas table to store deleted metas until we know
  // for sure that the deletions are persisted in native models.
  string query = "CREATE TABLE deleted_metas ";
  query.append(ComposeCreateTableColumnSpecs());
  if (!db_->Execute(query.c_str()))
    return false;
  SetVersion(84);
  return true;
}

bool DirectoryBackingStore::MigrateVersion84To85() {
  // Version 85 removes the initial_sync_ended flag.
  if (!db_->Execute("ALTER TABLE models RENAME TO temp_models"))
    return false;
  if (!CreateV81ModelsTable())
    return false;
  if (!db_->Execute("INSERT INTO models SELECT "
                    "model_id, progress_marker, transaction_version "
                    "FROM temp_models")) {
    return false;
  }
  SafeDropTable("temp_models");

  SetVersion(85);
  return true;
}

bool DirectoryBackingStore::MigrateVersion85To86() {
  // Version 86 removes both server ordinals and local NEXT_ID, PREV_ID and
  // SERVER_{POSITION,ORDINAL}_IN_PARENT and replaces them with UNIQUE_POSITION
  // and SERVER_UNIQUE_POSITION.
  if (!db_->Execute("ALTER TABLE metas ADD COLUMN "
                    "server_unique_position BLOB")) {
    return false;
  }
  if (!db_->Execute("ALTER TABLE metas ADD COLUMN "
                    "unique_position BLOB")) {
    return false;
  }
  if (!db_->Execute("ALTER TABLE metas ADD COLUMN "
                    "unique_bookmark_tag VARCHAR")) {
    return false;
  }

  // Fetch the cache_guid from the DB, because we don't otherwise have access to
  // it from here.
  sql::Statement get_cache_guid(db_->GetUniqueStatement(
      "SELECT cache_guid FROM share_info"));
  if (!get_cache_guid.Step()) {
    return false;
  }
  std::string cache_guid = get_cache_guid.ColumnString(0);
  DCHECK(!get_cache_guid.Step());
  DCHECK(get_cache_guid.Succeeded());

  sql::Statement get(db_->GetUniqueStatement(
      "SELECT "
      "  metahandle, "
      "  id, "
      "  specifics, "
      "  is_dir, "
      "  unique_server_tag, "
      "  server_ordinal_in_parent "
      "FROM metas"));

  // Note that we set both the local and server position based on the server
  // position.  We wll lose any unsynced local position changes.  Unfortunately,
  // there's nothing we can do to avoid that.  The NEXT_ID / PREV_ID values
  // can't be translated into a UNIQUE_POSTION in a reliable way.
  sql::Statement put(db_->GetCachedStatement(
      SQL_FROM_HERE,
      "UPDATE metas SET"
      "  server_unique_position = ?,"
      "  unique_position = ?,"
      "  unique_bookmark_tag = ?"
      "WHERE metahandle = ?"));

  while (get.Step()) {
    int64 metahandle = get.ColumnInt64(0);

    std::string id_string;
    get.ColumnBlobAsString(1, &id_string);

    sync_pb::EntitySpecifics specifics;
    specifics.ParseFromArray(
        get.ColumnBlob(2), get.ColumnByteLength(2));

    bool is_dir = get.ColumnBool(3);

    std::string server_unique_tag = get.ColumnString(4);

    std::string ordinal_string;
    get.ColumnBlobAsString(5, &ordinal_string);
    NodeOrdinal ordinal(ordinal_string);


    std::string unique_bookmark_tag;

    // We only maintain positions for bookmarks that are not server-defined
    // top-level folders.
    UniquePosition position;
    if (GetModelTypeFromSpecifics(specifics) == BOOKMARKS
        && !(is_dir && !server_unique_tag.empty())) {
      if (id_string.at(0) == 'c') {
        // We found an uncommitted item.  This is rare, but fortunate.  This
        // means we can set the bookmark tag according to the originator client
        // item ID and originator cache guid, because (unlike the other case) we
        // know that this client is the originator.
        unique_bookmark_tag = syncable::GenerateSyncableBookmarkHash(
            cache_guid,
            id_string.substr(1));
      } else {
        // If we've already committed the item, then we don't know who the
        // originator was.  We do not have access to the originator client item
        // ID and originator cache guid at this point.
        //
        // We will base our hash entirely on the server ID instead.  This is
        // incorrect, but at least all clients that undergo this migration step
        // will be incorrect in the same way.
        //
        // To get everyone back into a synced state, we will update the bookmark
        // tag according to the originator_cache_guid and originator_item_id
        // when we see updates for this item.  That should ensure that commonly
        // modified items will end up with the proper tag values eventually.
        unique_bookmark_tag = syncable::GenerateSyncableBookmarkHash(
            std::string(), // cache_guid left intentionally blank.
            id_string.substr(1));
      }

      int64 int_position = NodeOrdinalToInt64(ordinal);
      position = UniquePosition::FromInt64(int_position, unique_bookmark_tag);
    } else {
      // Leave bookmark_tag and position at their default (invalid) values.
    }

    std::string position_blob;
    position.SerializeToString(&position_blob);
    put.BindBlob(0, position_blob.data(), position_blob.length());
    put.BindBlob(1, position_blob.data(), position_blob.length());
    put.BindBlob(2, unique_bookmark_tag.data(), unique_bookmark_tag.length());
    put.BindInt64(3, metahandle);

    if (!put.Run())
      return false;
    put.Reset(true);
  }

  SetVersion(86);
  needs_column_refresh_ = true;
  return true;
}

bool DirectoryBackingStore::MigrateVersion86To87() {
  // Version 87 adds AttachmentMetadata proto.
  if (!db_->Execute(
          "ALTER TABLE metas ADD COLUMN "
          "attachment_metadata BLOB")) {
    return false;
  }
  SetVersion(87);
  needs_column_refresh_ = true;
  return true;
}

bool DirectoryBackingStore::MigrateVersion87To88() {
  // Version 88 adds the datatype context to the models table.
  if (!db_->Execute("ALTER TABLE models ADD COLUMN context blob"))
    return false;

  SetVersion(88);
  return true;
}

bool DirectoryBackingStore::CreateTables() {
  DVLOG(1) << "First run, creating tables";
  // Create two little tables share_version and share_info
  if (!db_->Execute(
          "CREATE TABLE share_version ("
          "id VARCHAR(128) primary key, data INT)")) {
    return false;
  }

  {
    sql::Statement s(db_->GetUniqueStatement(
            "INSERT INTO share_version VALUES(?, ?)"));
    s.BindString(0, dir_name_);
    s.BindInt(1, kCurrentDBVersion);

    if (!s.Run())
      return false;
  }

  const bool kCreateAsTempShareInfo = false;
  if (!CreateShareInfoTable(kCreateAsTempShareInfo)) {
    return false;
  }

  {
    sql::Statement s(db_->GetUniqueStatement(
            "INSERT INTO share_info VALUES"
            "(?, "  // id
            "?, "   // name
            "?, "   // store_birthday
            "?, "   // db_create_version
            "?, "   // db_create_time
            "-2, "  // next_id
            "?, "   // cache_guid
            // TODO(rlarocque, 124140): Remove notification_state field.
            "?, "   // notification_state
            "?);"));  // bag_of_chips
    s.BindString(0, dir_name_);                   // id
    s.BindString(1, dir_name_);                   // name
    s.BindString(2, std::string());               // store_birthday
    // TODO(akalin): Remove this unused db_create_version field. (Or
    // actually use it for something.) http://crbug.com/118356
    s.BindString(3, "Unknown");                   // db_create_version
    s.BindInt(4, static_cast<int32>(time(0)));    // db_create_time
    s.BindString(5, GenerateCacheGUID());         // cache_guid
    // TODO(rlarocque, 124140): Remove this unused notification-state field.
    s.BindBlob(6, NULL, 0);                       // notification_state
    s.BindBlob(7, NULL, 0);                       // bag_of_chips
    if (!s.Run())
      return false;
  }

  if (!CreateModelsTable())
    return false;

  // Create the big metas table.
  if (!CreateMetasTable(false))
    return false;

  {
    // Insert the entry for the root into the metas table.
    const int64 now = TimeToProtoTime(base::Time::Now());
    sql::Statement s(db_->GetUniqueStatement(
            "INSERT INTO metas "
            "( id, metahandle, is_dir, ctime, mtime ) "
            "VALUES ( \"r\", 1, 1, ?, ? )"));
    s.BindInt64(0, now);
    s.BindInt64(1, now);

    if (!s.Run())
      return false;
  }

  return true;
}

bool DirectoryBackingStore::CreateMetasTable(bool is_temporary) {
  string query = "CREATE TABLE ";
  query.append(is_temporary ? "temp_metas" : "metas");
  query.append(ComposeCreateTableColumnSpecs());
  if (!db_->Execute(query.c_str()))
    return false;

  // Create a deleted_metas table to save copies of deleted metas until the
  // deletions are persisted. For simplicity, don't try to migrate existing
  // data because it's rarely used.
  SafeDropTable("deleted_metas");
  query = "CREATE TABLE deleted_metas ";
  query.append(ComposeCreateTableColumnSpecs());
  return db_->Execute(query.c_str());
}

bool DirectoryBackingStore::CreateV71ModelsTable() {
  // This is an old schema for the Models table, used from versions 71 to 74.
  return db_->Execute(
      "CREATE TABLE models ("
      "model_id BLOB primary key, "
      "last_download_timestamp INT, "
      // Gets set if the syncer ever gets updates from the
      // server and the server returns 0.  Lets us detect the
      // end of the initial sync.
      "initial_sync_ended BOOLEAN default 0)");
}

bool DirectoryBackingStore::CreateV75ModelsTable() {
  // This is an old schema for the Models table, used from versions 75 to 80.
  return db_->Execute(
      "CREATE TABLE models ("
      "model_id BLOB primary key, "
      "progress_marker BLOB, "
      // Gets set if the syncer ever gets updates from the
      // server and the server returns 0.  Lets us detect the
      // end of the initial sync.
      "initial_sync_ended BOOLEAN default 0)");
}

bool DirectoryBackingStore::CreateV81ModelsTable() {
  // This is an old schema for the Models table, used from versions 81 to 87.
  return db_->Execute(
      "CREATE TABLE models ("
      "model_id BLOB primary key, "
      "progress_marker BLOB, "
      // Gets set if the syncer ever gets updates from the
      // server and the server returns 0.  Lets us detect the
      // end of the initial sync.
      "transaction_version BIGINT default 0)");
}

bool DirectoryBackingStore::CreateModelsTable() {
  // This is the current schema for the Models table, from version 88
  // onward.  If you change the schema, you'll probably want to double-check
  // the use of this function in the v84-v85 migration.
  return db_->Execute(
      "CREATE TABLE models ("
      "model_id BLOB primary key, "
      "progress_marker BLOB, "
      // Gets set if the syncer ever gets updates from the
      // server and the server returns 0.  Lets us detect the
      // end of the initial sync.
      "transaction_version BIGINT default 0,"
      "context BLOB)");
}

bool DirectoryBackingStore::CreateShareInfoTable(bool is_temporary) {
  const char* name = is_temporary ? "temp_share_info" : "share_info";
  string query = "CREATE TABLE ";
  query.append(name);
  // This is the current schema for the ShareInfo table, from version 76
  // onward.
  query.append(" ("
      "id TEXT primary key, "
      "name TEXT, "
      "store_birthday TEXT, "
      "db_create_version TEXT, "
      "db_create_time INT, "
      "next_id INT default -2, "
      "cache_guid TEXT, "
      // TODO(rlarocque, 124140): Remove notification_state field.
      "notification_state BLOB, "
      "bag_of_chips BLOB"
      ")");
  return db_->Execute(query.c_str());
}

bool DirectoryBackingStore::CreateShareInfoTableVersion71(
    bool is_temporary) {
  const char* name = is_temporary ? "temp_share_info" : "share_info";
  string query = "CREATE TABLE ";
  query.append(name);
  // This is the schema for the ShareInfo table used from versions 71 to 72.
  query.append(" ("
      "id TEXT primary key, "
      "name TEXT, "
      "store_birthday TEXT, "
      "db_create_version TEXT, "
      "db_create_time INT, "
      "next_id INT default -2, "
      "cache_guid TEXT )");
  return db_->Execute(query.c_str());
}

// This function checks to see if the given list of Metahandles has any nodes
// whose PARENT_ID values refer to ID values that do not actually exist.
// Returns true on success.
bool DirectoryBackingStore::VerifyReferenceIntegrity(
    const Directory::MetahandlesMap* handles_map) {
  TRACE_EVENT0("sync", "SyncDatabaseIntegrityCheck");
  using namespace syncable;
  typedef base::hash_set<std::string> IdsSet;

  IdsSet ids_set;
  bool is_ok = true;

  for (Directory::MetahandlesMap::const_iterator it = handles_map->begin();
       it != handles_map->end(); ++it) {
    EntryKernel* entry = it->second;
    bool is_duplicate_id = !(ids_set.insert(entry->ref(ID).value()).second);
    is_ok = is_ok && !is_duplicate_id;
  }

  IdsSet::iterator end = ids_set.end();
  for (Directory::MetahandlesMap::const_iterator it = handles_map->begin();
       it != handles_map->end(); ++it) {
    EntryKernel* entry = it->second;
    bool parent_exists = (ids_set.find(entry->ref(PARENT_ID).value()) != end);
    if (!parent_exists) {
      return false;
    }
  }
  return is_ok;
}

void DirectoryBackingStore::PrepareSaveEntryStatement(
    EntryTable table, sql::Statement* save_statement) {
  if (save_statement->is_valid())
    return;

  string query;
  query.reserve(kUpdateStatementBufferSize);
  switch (table) {
    case METAS_TABLE:
      query.append("INSERT OR REPLACE INTO metas ");
      break;
    case DELETE_JOURNAL_TABLE:
      query.append("INSERT OR REPLACE INTO deleted_metas ");
      break;
  }

  string values;
  values.reserve(kUpdateStatementBufferSize);
  values.append(" VALUES ");
  const char* separator = "( ";
  int i = 0;
  for (i = BEGIN_FIELDS; i < FIELD_COUNT; ++i) {
    query.append(separator);
    values.append(separator);
    separator = ", ";
    query.append(ColumnName(i));
    values.append("?");
  }
  query.append(" ) ");
  values.append(" )");
  query.append(values);
  save_statement->Assign(db_->GetUniqueStatement(
      base::StringPrintf(query.c_str(), "metas").c_str()));
}

}  // namespace syncable
}  // namespace syncer
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root/sync/syncable/directory_backing_store.cc

DEFINITIONS
