root/sql/meta_table.cc

DEFINITIONS

1. RecordDeprecationEvent
2. DoesTableExist
3. RazeIfDeprecated
4. Init
5. Reset
6. SetVersionNumber
7. GetVersionNumber
8. SetCompatibleVersionNumber
9. GetCompatibleVersionNumber
10. SetValue
11. SetValue
12. SetValue
13. GetValue
14. GetValue
15. GetValue
16. DeleteKey
17. PrepareSetStatement
18. PrepareGetStatement

// 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 "sql/meta_table.h"

#include "base/logging.h"
#include "base/metrics/histogram.h"
#include "base/strings/string_util.h"
#include "sql/connection.h"
#include "sql/statement.h"
#include "sql/transaction.h"

namespace {

// Key used in our meta table for version numbers.
const char kVersionKey[] = "version";
const char kCompatibleVersionKey[] = "last_compatible_version";

// Used to track success/failure of deprecation checks.
enum DeprecationEventType {
  // Database has info, but no meta table.  This is probably bad.
  DEPRECATION_DATABASE_NOT_EMPTY = 0,

  // No meta, unable to query sqlite_master.  This is probably bad.
  DEPRECATION_DATABASE_UNKNOWN,

  // Failure querying meta table, corruption or similar problem likely.
  DEPRECATION_FAILED_VERSION,

  // Version key not found in meta table.  Some sort of update error likely.
  DEPRECATION_NO_VERSION,

  // Version was out-dated, database successfully razed.  Should only
  // happen once per long-idle user, low volume expected.
  DEPRECATION_RAZED,

  // Version was out-dated, database raze failed.  This user's
  // database will be stuck.
  DEPRECATION_RAZE_FAILED,

  // Always keep this at the end.
  DEPRECATION_EVENT_MAX,
};

void RecordDeprecationEvent(DeprecationEventType deprecation_event) {
  UMA_HISTOGRAM_ENUMERATION("Sqlite.DeprecationVersionResult",
                            deprecation_event, DEPRECATION_EVENT_MAX);
}

}  // namespace

namespace sql {

MetaTable::MetaTable() : db_(NULL) {
}

MetaTable::~MetaTable() {
}

// static
bool MetaTable::DoesTableExist(sql::Connection* db) {
  DCHECK(db);
  return db->DoesTableExist("meta");
}

// static
void MetaTable::RazeIfDeprecated(Connection* db, int deprecated_version) {
  DCHECK_GT(deprecated_version, 0);
  DCHECK_EQ(0, db->transaction_nesting());

  if (!DoesTableExist(db)) {
    sql::Statement s(db->GetUniqueStatement(
        "SELECT COUNT(*) FROM sqlite_master"));
    if (s.Step()) {
      if (s.ColumnInt(0) != 0) {
        RecordDeprecationEvent(DEPRECATION_DATABASE_NOT_EMPTY);
      }
      // NOTE(shess): Empty database at first run is expected, so
      // don't histogram that case.
    } else {
      RecordDeprecationEvent(DEPRECATION_DATABASE_UNKNOWN);
    }
    return;
  }

  // TODO(shess): Share sql with PrepareGetStatement().
  sql::Statement s(db->GetUniqueStatement(
                       "SELECT value FROM meta WHERE key=?"));
  s.BindCString(0, kVersionKey);
  if (!s.Step()) {
    if (!s.Succeeded()) {
      RecordDeprecationEvent(DEPRECATION_FAILED_VERSION);
    } else {
      RecordDeprecationEvent(DEPRECATION_NO_VERSION);
    }
    return;
  }

  int version = s.ColumnInt(0);
  s.Clear();  // Clear potential automatic transaction for Raze().
  if (version <= deprecated_version) {
    if (db->Raze()) {
      RecordDeprecationEvent(DEPRECATION_RAZED);
    } else {
      RecordDeprecationEvent(DEPRECATION_RAZE_FAILED);
    }
    return;
  }

  // NOTE(shess): Successfully getting a version which is not
  // deprecated is expected, so don't histogram that case.
}

bool MetaTable::Init(Connection* db, int version, int compatible_version) {
  DCHECK(!db_ && db);
  db_ = db;

  // If values stored are null or missing entirely, 0 will be reported.
  // Require new clients to start with a greater initial version.
  DCHECK_GT(version, 0);
  DCHECK_GT(compatible_version, 0);

  // Make sure the table is created an populated atomically.
  sql::Transaction transaction(db_);
  if (!transaction.Begin())
    return false;

  if (!DoesTableExist(db)) {
    if (!db_->Execute("CREATE TABLE meta"
        "(key LONGVARCHAR NOT NULL UNIQUE PRIMARY KEY, value LONGVARCHAR)"))
      return false;

    // Note: there is no index over the meta table. We currently only have a
    // couple of keys, so it doesn't matter. If we start storing more stuff in
    // there, we should create an index.
    SetVersionNumber(version);
    SetCompatibleVersionNumber(compatible_version);
  } else {
    db_->AddTaggedHistogram("Sqlite.Version", GetVersionNumber());
  }
  return transaction.Commit();
}

void MetaTable::Reset() {
  db_ = NULL;
}

void MetaTable::SetVersionNumber(int version) {
  DCHECK_GT(version, 0);
  SetValue(kVersionKey, version);
}

int MetaTable::GetVersionNumber() {
  int version = 0;
  return GetValue(kVersionKey, &version) ? version : 0;
}

void MetaTable::SetCompatibleVersionNumber(int version) {
  DCHECK_GT(version, 0);
  SetValue(kCompatibleVersionKey, version);
}

int MetaTable::GetCompatibleVersionNumber() {
  int version = 0;
  return GetValue(kCompatibleVersionKey, &version) ? version : 0;
}

bool MetaTable::SetValue(const char* key, const std::string& value) {
  Statement s;
  PrepareSetStatement(&s, key);
  s.BindString(1, value);
  return s.Run();
}

bool MetaTable::SetValue(const char* key, int value) {
  Statement s;
  PrepareSetStatement(&s, key);
  s.BindInt(1, value);
  return s.Run();
}

bool MetaTable::SetValue(const char* key, int64 value) {
  Statement s;
  PrepareSetStatement(&s, key);
  s.BindInt64(1, value);
  return s.Run();
}

bool MetaTable::GetValue(const char* key, std::string* value) {
  Statement s;
  if (!PrepareGetStatement(&s, key))
    return false;

  *value = s.ColumnString(0);
  return true;
}

bool MetaTable::GetValue(const char* key, int* value) {
  Statement s;
  if (!PrepareGetStatement(&s, key))
    return false;

  *value = s.ColumnInt(0);
  return true;
}

bool MetaTable::GetValue(const char* key, int64* value) {
  Statement s;
  if (!PrepareGetStatement(&s, key))
    return false;

  *value = s.ColumnInt64(0);
  return true;
}

bool MetaTable::DeleteKey(const char* key) {
  DCHECK(db_);
  Statement s(db_->GetUniqueStatement("DELETE FROM meta WHERE key=?"));
  s.BindCString(0, key);
  return s.Run();
}

void MetaTable::PrepareSetStatement(Statement* statement, const char* key) {
  DCHECK(db_ && statement);
  statement->Assign(db_->GetCachedStatement(SQL_FROM_HERE,
      "INSERT OR REPLACE INTO meta (key,value) VALUES (?,?)"));
  statement->BindCString(0, key);
}

bool MetaTable::PrepareGetStatement(Statement* statement, const char* key) {
  DCHECK(db_ && statement);
  statement->Assign(db_->GetCachedStatement(SQL_FROM_HERE,
      "SELECT value FROM meta WHERE key=?"));
  statement->BindCString(0, key);
  return statement->Step();
}

}  // namespace sql