root/chrome/browser/extensions/activity_log/counting_policy.cc

DEFINITIONS

1. retention_time_
2. InitDatabase
3. ProcessAction
4. QueueAction
5. FlushDatabase
6. DoReadFilteredData
7. DoRemoveActions
8. DoRemoveURLs
9. DoRemoveExtensionData
10. DoDeleteDatabase
11. ReadFilteredData
12. RemoveActions
13. RemoveURLs
14. RemoveExtensionData
15. DeleteDatabase
16. OnDatabaseFailure
17. OnDatabaseClose
18. CleanOlderThan
19. CleanStringTables
20. Close

// Copyright 2013 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.

// A policy for storing activity log data to a database that performs
// aggregation to reduce the size of the database.  The database layout is
// nearly the same as FullStreamUIPolicy, which stores a complete log, with a
// few changes:
//   - a "count" column is added to track how many log records were merged
//     together into this row
//   - the "time" column measures the most recent time that the current row was
//     updated
// When writing a record, if a row already exists where all other columns
// (extension_id, action_type, api_name, args, urls, etc.) all match, and the
// previous time falls within today (the current time), then the count field on
// the old row is incremented.  Otherwise, a new row is written.
//
// For many text columns, repeated strings are compressed by moving string
// storage to a separate table ("string_ids") and storing only an identifier in
// the logging table.  For example, if the api_name_x column contained the
// value 4 and the string_ids table contained a row with primary key 4 and
// value 'tabs.query', then the api_name field should be taken to have the
// value 'tabs.query'.  Each column ending with "_x" is compressed in this way.
// All lookups are to the string_ids table, except for the page_url_x and
// arg_url_x columns, which are converted via the url_ids table (this
// separation of URL values is to help simplify history clearing).
//
// The activitylog_uncompressed view allows for simpler reading of the activity
// log contents with identifiers already translated to string values.

#include "chrome/browser/extensions/activity_log/counting_policy.h"

#include <map>
#include <string>
#include <vector>

#include "base/callback.h"
#include "base/files/file_path.h"
#include "base/json/json_reader.h"
#include "base/json/json_string_value_serializer.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "chrome/common/chrome_constants.h"

using content::BrowserThread;

namespace {

using extensions::Action;

// Delay between cleaning passes (to delete old action records) through the
// database.
const int kCleaningDelayInHours = 12;

// We should log the arguments to these API calls.  Be careful when
// constructing this whitelist to not keep arguments that might compromise
// privacy by logging too much data to the activity log.
//
// TODO(mvrable): The contents of this whitelist should be reviewed and
// expanded as needed.
struct ApiList {
  Action::ActionType type;
  const char* name;
};

const ApiList kAlwaysLog[] = {
    {Action::ACTION_API_CALL, "bookmarks.create"},
    {Action::ACTION_API_CALL, "bookmarks.update"},
    {Action::ACTION_API_CALL, "cookies.get"},
    {Action::ACTION_API_CALL, "cookies.getAll"},
    {Action::ACTION_API_CALL, "extension.connect"},
    {Action::ACTION_API_CALL, "extension.sendMessage"},
    {Action::ACTION_API_CALL, "fileSystem.chooseEntry"},
    {Action::ACTION_API_CALL, "socket.bind"},
    {Action::ACTION_API_CALL, "socket.connect"},
    {Action::ACTION_API_CALL, "socket.create"},
    {Action::ACTION_API_CALL, "socket.listen"},
    {Action::ACTION_API_CALL, "tabs.executeScript"},
    {Action::ACTION_API_CALL, "tabs.insertCSS"},
    {Action::ACTION_API_CALL, "types.ChromeSetting.clear"},
    {Action::ACTION_API_CALL, "types.ChromeSetting.get"},
    {Action::ACTION_API_CALL, "types.ChromeSetting.set"},
    {Action::ACTION_CONTENT_SCRIPT, ""},
    {Action::ACTION_DOM_ACCESS, "Document.createElement"},
    {Action::ACTION_DOM_ACCESS, "Document.createElementNS"},
};

// Columns in the main database table.  See the file-level comment for a
// discussion of how data is stored and the meanings of the _x columns.
const char* kTableContentFields[] = {
    "count", "extension_id_x", "time", "action_type", "api_name_x", "args_x",
    "page_url_x", "page_title_x", "arg_url_x", "other_x"};
const char* kTableFieldTypes[] = {
    "INTEGER NOT NULL DEFAULT 1", "INTEGER NOT NULL", "INTEGER", "INTEGER",
    "INTEGER", "INTEGER", "INTEGER", "INTEGER", "INTEGER",
    "INTEGER"};

// Miscellaneous SQL commands for initializing the database; these should be
// idempotent.
static const char kPolicyMiscSetup[] =
    // The activitylog_uncompressed view performs string lookups for simpler
    // access to the log data.
    "DROP VIEW IF EXISTS activitylog_uncompressed;\n"
    "CREATE VIEW activitylog_uncompressed AS\n"
    "SELECT count,\n"
    "    x1.value AS extension_id,\n"
    "    time,\n"
    "    action_type,\n"
    "    x2.value AS api_name,\n"
    "    x3.value AS args,\n"
    "    x4.value AS page_url,\n"
    "    x5.value AS page_title,\n"
    "    x6.value AS arg_url,\n"
    "    x7.value AS other,\n"
    "    activitylog_compressed.rowid AS activity_id\n"
    "FROM activitylog_compressed\n"
    "    LEFT JOIN string_ids AS x1 ON (x1.id = extension_id_x)\n"
    "    LEFT JOIN string_ids AS x2 ON (x2.id = api_name_x)\n"
    "    LEFT JOIN string_ids AS x3 ON (x3.id = args_x)\n"
    "    LEFT JOIN url_ids    AS x4 ON (x4.id = page_url_x)\n"
    "    LEFT JOIN string_ids AS x5 ON (x5.id = page_title_x)\n"
    "    LEFT JOIN url_ids    AS x6 ON (x6.id = arg_url_x)\n"
    "    LEFT JOIN string_ids AS x7 ON (x7.id = other_x);\n"
    // An index on all fields except count and time: all the fields that aren't
    // changed when incrementing a count.  This should accelerate finding the
    // rows to update (at worst several rows will need to be checked to find
    // the one in the right time range).
    "CREATE INDEX IF NOT EXISTS activitylog_compressed_index\n"
    "ON activitylog_compressed(extension_id_x, action_type, api_name_x,\n"
    "    args_x, page_url_x, page_title_x, arg_url_x, other_x)";

// SQL statements to clean old, unused entries out of the string and URL id
// tables.
static const char kStringTableCleanup[] =
    "DELETE FROM string_ids WHERE id NOT IN\n"
    "(SELECT extension_id_x FROM activitylog_compressed\n"
    "    WHERE extension_id_x IS NOT NULL\n"
    " UNION SELECT api_name_x FROM activitylog_compressed\n"
    "    WHERE api_name_x IS NOT NULL\n"
    " UNION SELECT args_x FROM activitylog_compressed\n"
    "    WHERE args_x IS NOT NULL\n"
    " UNION SELECT page_title_x FROM activitylog_compressed\n"
    "    WHERE page_title_x IS NOT NULL\n"
    " UNION SELECT other_x FROM activitylog_compressed\n"
    "    WHERE other_x IS NOT NULL)";
static const char kUrlTableCleanup[] =
    "DELETE FROM url_ids WHERE id NOT IN\n"
    "(SELECT page_url_x FROM activitylog_compressed\n"
    "    WHERE page_url_x IS NOT NULL\n"
    " UNION SELECT arg_url_x FROM activitylog_compressed\n"
    "    WHERE arg_url_x IS NOT NULL)";

}  // namespace

namespace extensions {

const char* CountingPolicy::kTableName = "activitylog_compressed";
const char* CountingPolicy::kReadViewName = "activitylog_uncompressed";

CountingPolicy::CountingPolicy(Profile* profile)
    : ActivityLogDatabasePolicy(
          profile,
          base::FilePath(chrome::kExtensionActivityLogFilename)),
      string_table_("string_ids"),
      url_table_("url_ids"),
      retention_time_(base::TimeDelta::FromHours(60)) {
  for (size_t i = 0; i < arraysize(kAlwaysLog); i++) {
    api_arg_whitelist_.insert(
        std::make_pair(kAlwaysLog[i].type, kAlwaysLog[i].name));
  }
}

CountingPolicy::~CountingPolicy() {}

bool CountingPolicy::InitDatabase(sql::Connection* db) {
  if (!Util::DropObsoleteTables(db))
    return false;

  if (!string_table_.Initialize(db))
    return false;
  if (!url_table_.Initialize(db))
    return false;

  // Create the unified activity log entry table.
  if (!ActivityDatabase::InitializeTable(db,
                                         kTableName,
                                         kTableContentFields,
                                         kTableFieldTypes,
                                         arraysize(kTableContentFields)))
    return false;

  // Create a view for easily accessing the uncompressed form of the data, and
  // any necessary indexes if needed.
  return db->Execute(kPolicyMiscSetup);
}

void CountingPolicy::ProcessAction(scoped_refptr<Action> action) {
  ScheduleAndForget(this, &CountingPolicy::QueueAction, action);
}

void CountingPolicy::QueueAction(scoped_refptr<Action> action) {
  if (activity_database()->is_db_valid()) {
    action = action->Clone();
    Util::StripPrivacySensitiveFields(action);
    Util::StripArguments(api_arg_whitelist_, action);

    // If the current action falls on a different date than the ones in the
    // queue, flush the queue out now to prevent any false merging (actions
    // from different days being merged).
    base::Time new_date = action->time().LocalMidnight();
    if (new_date != queued_actions_date_)
      activity_database()->AdviseFlush(ActivityDatabase::kFlushImmediately);
    queued_actions_date_ = new_date;

    ActionQueue::iterator queued_entry = queued_actions_.find(action);
    if (queued_entry == queued_actions_.end()) {
      queued_actions_[action] = 1;
    } else {
      // Update the timestamp in the key to be the latest time seen.  Modifying
      // the time is safe since that field is not involved in key comparisons
      // in the map.
      using std::max;
      queued_entry->first->set_time(
          max(queued_entry->first->time(), action->time()));
      queued_entry->second++;
    }
    activity_database()->AdviseFlush(queued_actions_.size());
  }
}

bool CountingPolicy::FlushDatabase(sql::Connection* db) {
  // Columns that must match exactly for database rows to be coalesced.
  static const char* matched_columns[] = {
      "extension_id_x", "action_type", "api_name_x", "args_x", "page_url_x",
      "page_title_x", "arg_url_x", "other_x"};
  ActionQueue queue;
  queue.swap(queued_actions_);

  // Whether to clean old records out of the activity log database.  Do this
  // much less frequently than database flushes since it is expensive, but
  // always check on the first database flush (since there might be a large
  // amount of data to clear).
  bool clean_database = (last_database_cleaning_time_.is_null() ||
                         Now() - last_database_cleaning_time_ >
                             base::TimeDelta::FromHours(kCleaningDelayInHours));

  if (queue.empty() && !clean_database)
    return true;

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

  // Adding an Action to the database is a two step process that depends on
  // whether the count on an existing row can be incremented or a new row needs
  // to be inserted.
  //   1. Run the query in locate_str to search for a row which matches and can
  //      have the count incremented.
  //  2a. If found, increment the count using update_str and the rowid found in
  //      step 1, or
  //  2b. If not found, insert a new row using insert_str.
  std::string locate_str =
      "SELECT rowid FROM " + std::string(kTableName) +
      " WHERE time >= ? AND time < ?";
  std::string insert_str =
      "INSERT INTO " + std::string(kTableName) + "(count, time";
  std::string update_str =
      "UPDATE " + std::string(kTableName) +
      " SET count = count + ?, time = max(?, time)"
      " WHERE rowid = ?";

  for (size_t i = 0; i < arraysize(matched_columns); i++) {
    locate_str = base::StringPrintf(
        "%s AND %s IS ?", locate_str.c_str(), matched_columns[i]);
    insert_str =
        base::StringPrintf("%s, %s", insert_str.c_str(), matched_columns[i]);
  }
  insert_str += ") VALUES (?, ?";
  for (size_t i = 0; i < arraysize(matched_columns); i++) {
    insert_str += ", ?";
  }
  locate_str += " ORDER BY time DESC LIMIT 1";
  insert_str += ")";

  for (ActionQueue::iterator i = queue.begin(); i != queue.end(); ++i) {
    const Action& action = *i->first;
    int count = i->second;

    base::Time day_start = action.time().LocalMidnight();
    base::Time next_day = Util::AddDays(day_start, 1);

    // The contents in values must match up with fields in matched_columns.  A
    // value of -1 is used to encode a null database value.
    int64 id;
    std::vector<int64> matched_values;

    if (!string_table_.StringToInt(db, action.extension_id(), &id))
      return false;
    matched_values.push_back(id);

    matched_values.push_back(static_cast<int>(action.action_type()));

    if (!string_table_.StringToInt(db, action.api_name(), &id))
      return false;
    matched_values.push_back(id);

    if (action.args()) {
      std::string args = Util::Serialize(action.args());
      // TODO(mvrable): For now, truncate long argument lists.  This is a
      // workaround for excessively-long values coming from DOM logging.  When
      // the V8ValueConverter is fixed to return more reasonable values, we can
      // drop the truncation.
      if (args.length() > 10000) {
        args = "[\"<too_large>\"]";
      }
      if (!string_table_.StringToInt(db, args, &id))
        return false;
      matched_values.push_back(id);
    } else {
      matched_values.push_back(-1);
    }

    std::string page_url_string = action.SerializePageUrl();
    if (!page_url_string.empty()) {
      if (!url_table_.StringToInt(db, page_url_string, &id))
        return false;
      matched_values.push_back(id);
    } else {
      matched_values.push_back(-1);
    }

    // TODO(mvrable): Create a title_table_?
    if (!action.page_title().empty()) {
      if (!string_table_.StringToInt(db, action.page_title(), &id))
        return false;
      matched_values.push_back(id);
    } else {
      matched_values.push_back(-1);
    }

    std::string arg_url_string = action.SerializeArgUrl();
    if (!arg_url_string.empty()) {
      if (!url_table_.StringToInt(db, arg_url_string, &id))
        return false;
      matched_values.push_back(id);
    } else {
      matched_values.push_back(-1);
    }

    if (action.other()) {
      if (!string_table_.StringToInt(db, Util::Serialize(action.other()), &id))
        return false;
      matched_values.push_back(id);
    } else {
      matched_values.push_back(-1);
    }

    // Search for a matching row for this action whose count can be
    // incremented.
    sql::Statement locate_statement(db->GetCachedStatement(
        sql::StatementID(SQL_FROM_HERE), locate_str.c_str()));
    locate_statement.BindInt64(0, day_start.ToInternalValue());
    locate_statement.BindInt64(1, next_day.ToInternalValue());
    for (size_t j = 0; j < matched_values.size(); j++) {
      // A call to BindNull when matched_values contains -1 is likely not
      // necessary as parameters default to null before they are explicitly
      // bound.  But to be completely clear, and in case a cached statement
      // ever comes with some values already bound, we bind all parameters
      // (even null ones) explicitly.
      if (matched_values[j] == -1)
        locate_statement.BindNull(j + 2);
      else
        locate_statement.BindInt64(j + 2, matched_values[j]);
    }

    if (locate_statement.Step()) {
      // A matching row was found.  Update the count and time.
      int64 rowid = locate_statement.ColumnInt64(0);
      sql::Statement update_statement(db->GetCachedStatement(
          sql::StatementID(SQL_FROM_HERE), update_str.c_str()));
      update_statement.BindInt(0, count);
      update_statement.BindInt64(1, action.time().ToInternalValue());
      update_statement.BindInt64(2, rowid);
      if (!update_statement.Run())
        return false;
    } else if (locate_statement.Succeeded()) {
      // No matching row was found, so we need to insert one.
      sql::Statement insert_statement(db->GetCachedStatement(
          sql::StatementID(SQL_FROM_HERE), insert_str.c_str()));
      insert_statement.BindInt(0, count);
      insert_statement.BindInt64(1, action.time().ToInternalValue());
      for (size_t j = 0; j < matched_values.size(); j++) {
        if (matched_values[j] == -1)
          insert_statement.BindNull(j + 2);
        else
          insert_statement.BindInt64(j + 2, matched_values[j]);
      }
      if (!insert_statement.Run())
        return false;
    } else {
      // Database error.
      return false;
    }
  }

  if (clean_database) {
    base::Time cutoff = (Now() - retention_time()).LocalMidnight();
    if (!CleanOlderThan(db, cutoff))
      return false;
    last_database_cleaning_time_ = Now();
  }

  if (!transaction.Commit())
    return false;

  return true;
}

scoped_ptr<Action::ActionVector> CountingPolicy::DoReadFilteredData(
    const std::string& extension_id,
    const Action::ActionType type,
    const std::string& api_name,
    const std::string& page_url,
    const std::string& arg_url,
    const int days_ago) {
  // Ensure data is flushed to the database first so that we query over all
  // data.
  activity_database()->AdviseFlush(ActivityDatabase::kFlushImmediately);
  scoped_ptr<Action::ActionVector> actions(new Action::ActionVector());

  sql::Connection* db = GetDatabaseConnection();
  if (!db)
    return actions.Pass();

  // Build up the query based on which parameters were specified.
  std::string where_str = "";
  std::string where_next = "";
  if (!extension_id.empty()) {
    where_str += "extension_id=?";
    where_next = " AND ";
  }
  if (!api_name.empty()) {
    where_str += where_next + "api_name=?";
    where_next = " AND ";
  }
  if (type != Action::ACTION_ANY) {
    where_str += where_next + "action_type=?";
    where_next = " AND ";
  }
  if (!page_url.empty()) {
    where_str += where_next + "page_url LIKE ?";
    where_next = " AND ";
  }
  if (!arg_url.empty()) {
    where_str += where_next + "arg_url LIKE ?";
    where_next = " AND ";
  }
  if (days_ago >= 0)
    where_str += where_next + "time BETWEEN ? AND ?";

  std::string query_str = base::StringPrintf(
      "SELECT extension_id,time, action_type, api_name, args, page_url,"
      "page_title, arg_url, other, count, activity_id FROM %s %s %s ORDER BY "
      "count DESC, time DESC LIMIT 300",
      kReadViewName,
      where_str.empty() ? "" : "WHERE",
      where_str.c_str());
  sql::Statement query(db->GetUniqueStatement(query_str.c_str()));
  int i = -1;
  if (!extension_id.empty())
    query.BindString(++i, extension_id);
  if (!api_name.empty())
    query.BindString(++i, api_name);
  if (type != Action::ACTION_ANY)
    query.BindInt(++i, static_cast<int>(type));
  if (!page_url.empty())
    query.BindString(++i, page_url + "%");
  if (!arg_url.empty())
    query.BindString(++i, arg_url + "%");
  if (days_ago >= 0) {
    int64 early_bound;
    int64 late_bound;
    Util::ComputeDatabaseTimeBounds(Now(), days_ago, &early_bound, &late_bound);
    query.BindInt64(++i, early_bound);
    query.BindInt64(++i, late_bound);
  }

  // Execute the query and get results.
  while (query.is_valid() && query.Step()) {
    scoped_refptr<Action> action =
        new Action(query.ColumnString(0),
                   base::Time::FromInternalValue(query.ColumnInt64(1)),
                   static_cast<Action::ActionType>(query.ColumnInt(2)),
                   query.ColumnString(3), query.ColumnInt64(10));

    if (query.ColumnType(4) != sql::COLUMN_TYPE_NULL) {
      scoped_ptr<base::Value> parsed_value(
          base::JSONReader::Read(query.ColumnString(4)));
      if (parsed_value && parsed_value->IsType(base::Value::TYPE_LIST)) {
        action->set_args(make_scoped_ptr(
            static_cast<base::ListValue*>(parsed_value.release())));
      }
    }

    action->ParsePageUrl(query.ColumnString(5));
    action->set_page_title(query.ColumnString(6));
    action->ParseArgUrl(query.ColumnString(7));

    if (query.ColumnType(8) != sql::COLUMN_TYPE_NULL) {
      scoped_ptr<base::Value> parsed_value(
          base::JSONReader::Read(query.ColumnString(8)));
      if (parsed_value && parsed_value->IsType(base::Value::TYPE_DICTIONARY)) {
        action->set_other(make_scoped_ptr(
            static_cast<base::DictionaryValue*>(parsed_value.release())));
      }
    }
    action->set_count(query.ColumnInt(9));
    actions->push_back(action);
  }

  return actions.Pass();
}

void CountingPolicy::DoRemoveActions(const std::vector<int64>& action_ids) {
  if (action_ids.empty())
    return;

  sql::Connection* db = GetDatabaseConnection();
  if (!db) {
    LOG(ERROR) << "Unable to connect to database";
    return;
  }

  // Flush data first so the activity removal affects queued-up data as well.
  activity_database()->AdviseFlush(ActivityDatabase::kFlushImmediately);

  sql::Transaction transaction(db);
  if (!transaction.Begin())
    return;

  std::string statement_str =
      base::StringPrintf("DELETE FROM %s WHERE rowid = ?", kTableName);
  sql::Statement statement(db->GetCachedStatement(
      sql::StatementID(SQL_FROM_HERE), statement_str.c_str()));
  for (size_t i = 0; i < action_ids.size(); i++) {
    statement.Reset(true);
    statement.BindInt64(0, action_ids[i]);
    if (!statement.Run()) {
      LOG(ERROR) << "Removing activities from database failed: "
                 << statement.GetSQLStatement();
      break;
    }
  }

  CleanStringTables(db);

  if (!transaction.Commit()) {
    LOG(ERROR) << "Removing activities from database failed";
  }
}

void CountingPolicy::DoRemoveURLs(const std::vector<GURL>& restrict_urls) {
  sql::Connection* db = GetDatabaseConnection();
  if (!db) {
    LOG(ERROR) << "Unable to connect to database";
    return;
  }

  // Flush data first so the URL clearing affects queued-up data as well.
  activity_database()->AdviseFlush(ActivityDatabase::kFlushImmediately);

  // If no restrictions then then all URLs need to be removed.
  if (restrict_urls.empty()) {
    std::string sql_str = base::StringPrintf(
      "UPDATE %s SET page_url_x=NULL,page_title_x=NULL,arg_url_x=NULL",
      kTableName);

    sql::Statement statement;
    statement.Assign(db->GetCachedStatement(
        sql::StatementID(SQL_FROM_HERE), sql_str.c_str()));

    if (!statement.Run()) {
      LOG(ERROR) << "Removing all URLs from database failed: "
                 << statement.GetSQLStatement();
      return;
    }
  }

  // If URLs are specified then restrict to only those URLs.
  for (size_t i = 0; i < restrict_urls.size(); ++i) {
    int64 url_id;
    if (!restrict_urls[i].is_valid() ||
        !url_table_.StringToInt(db, restrict_urls[i].spec(), &url_id)) {
      continue;
    }

    // Remove any that match the page_url.
    std::string sql_str = base::StringPrintf(
      "UPDATE %s SET page_url_x=NULL,page_title_x=NULL WHERE page_url_x IS ?",
      kTableName);

    sql::Statement statement;
    statement.Assign(db->GetCachedStatement(
        sql::StatementID(SQL_FROM_HERE), sql_str.c_str()));
    statement.BindInt64(0, url_id);

    if (!statement.Run()) {
      LOG(ERROR) << "Removing page URL from database failed: "
                 << statement.GetSQLStatement();
      return;
    }

    // Remove any that match the arg_url.
    sql_str = base::StringPrintf(
      "UPDATE %s SET arg_url_x=NULL WHERE arg_url_x IS ?", kTableName);

    statement.Assign(db->GetCachedStatement(
        sql::StatementID(SQL_FROM_HERE), sql_str.c_str()));
    statement.BindInt64(0, url_id);

    if (!statement.Run()) {
      LOG(ERROR) << "Removing arg URL from database failed: "
                 << statement.GetSQLStatement();
      return;
    }
  }

  // Clean up unused strings from the strings and urls table to really delete
  // the urls and page titles. Should be called even if an error occured when
  // removing a URL as there may some things to clean up.
  CleanStringTables(db);
}

void CountingPolicy::DoRemoveExtensionData(const std::string& extension_id) {
  if (extension_id.empty())
    return;

  sql::Connection* db = GetDatabaseConnection();
  if (!db) {
    LOG(ERROR) << "Unable to connect to database";
    return;
  }

  // Make sure any queued in memory are sent to the database before cleaning.
  activity_database()->AdviseFlush(ActivityDatabase::kFlushImmediately);

  std::string sql_str = base::StringPrintf(
      "DELETE FROM %s WHERE extension_id_x=?", kTableName);
  sql::Statement statement(
      db->GetCachedStatement(sql::StatementID(SQL_FROM_HERE), sql_str.c_str()));
  int64 id;
  if (string_table_.StringToInt(db, extension_id, &id)) {
    statement.BindInt64(0, id);
  } else {
    // If the string isn't listed, that means we never recorded anything about
    // the extension so there's no deletion to do.
    statement.Clear();
    return;
  }
  if (!statement.Run()) {
    LOG(ERROR) << "Removing URLs for extension "
               << extension_id << "from database failed: "
               << statement.GetSQLStatement();
  }
  CleanStringTables(db);
}

void CountingPolicy::DoDeleteDatabase() {
  sql::Connection* db = GetDatabaseConnection();
  if (!db) {
    LOG(ERROR) << "Unable to connect to database";
    return;
  }

  queued_actions_.clear();

  // Not wrapped in a transaction because a late failure shouldn't undo a
  // previous deletion.
  std::string sql_str = base::StringPrintf("DELETE FROM %s", kTableName);
  sql::Statement statement(db->GetCachedStatement(
      sql::StatementID(SQL_FROM_HERE),
      sql_str.c_str()));
  if (!statement.Run()) {
    LOG(ERROR) << "Deleting the database failed: "
               << statement.GetSQLStatement();
    return;
  }
  statement.Clear();
  string_table_.ClearCache();
  statement.Assign(db->GetCachedStatement(sql::StatementID(SQL_FROM_HERE),
                                          "DELETE FROM string_ids"));
  if (!statement.Run()) {
    LOG(ERROR) << "Deleting the database failed: "
               << statement.GetSQLStatement();
    return;
  }
  statement.Clear();
  url_table_.ClearCache();
  statement.Assign(db->GetCachedStatement(sql::StatementID(SQL_FROM_HERE),
                                          "DELETE FROM url_ids"));
  if (!statement.Run()) {
    LOG(ERROR) << "Deleting the database failed: "
               << statement.GetSQLStatement();
    return;
  }
  statement.Clear();
  statement.Assign(db->GetCachedStatement(sql::StatementID(SQL_FROM_HERE),
                                          "VACUUM"));
  if (!statement.Run()) {
    LOG(ERROR) << "Vacuuming the database failed: "
               << statement.GetSQLStatement();
  }
}

void CountingPolicy::ReadFilteredData(
    const std::string& extension_id,
    const Action::ActionType type,
    const std::string& api_name,
    const std::string& page_url,
    const std::string& arg_url,
    const int days_ago,
    const base::Callback
        <void(scoped_ptr<Action::ActionVector>)>& callback) {
  BrowserThread::PostTaskAndReplyWithResult(
      BrowserThread::DB,
      FROM_HERE,
      base::Bind(&CountingPolicy::DoReadFilteredData,
                 base::Unretained(this),
                 extension_id,
                 type,
                 api_name,
                 page_url,
                 arg_url,
                 days_ago),
      callback);
}

void CountingPolicy::RemoveActions(const std::vector<int64>& action_ids) {
  ScheduleAndForget(this, &CountingPolicy::DoRemoveActions, action_ids);
}

void CountingPolicy::RemoveURLs(const std::vector<GURL>& restrict_urls) {
  ScheduleAndForget(this, &CountingPolicy::DoRemoveURLs, restrict_urls);
}

void CountingPolicy::RemoveExtensionData(const std::string& extension_id) {
  ScheduleAndForget(this, &CountingPolicy::DoRemoveExtensionData, extension_id);
}

void CountingPolicy::DeleteDatabase() {
  ScheduleAndForget(this, &CountingPolicy::DoDeleteDatabase);
}

void CountingPolicy::OnDatabaseFailure() {
  queued_actions_.clear();
}

void CountingPolicy::OnDatabaseClose() {
  delete this;
}

// Cleans old records from the activity log database.
bool CountingPolicy::CleanOlderThan(sql::Connection* db,
                                    const base::Time& cutoff) {
  std::string clean_statement =
      "DELETE FROM " + std::string(kTableName) + " WHERE time < ?";
  sql::Statement cleaner(db->GetCachedStatement(sql::StatementID(SQL_FROM_HERE),
                                                clean_statement.c_str()));
  cleaner.BindInt64(0, cutoff.ToInternalValue());
  if (!cleaner.Run())
    return false;
  return CleanStringTables(db);
}

// Cleans unused interned strings from the database.  This should be run after
// deleting rows from the main log table to clean out stale values.
bool CountingPolicy::CleanStringTables(sql::Connection* db) {
  sql::Statement cleaner1(db->GetCachedStatement(
      sql::StatementID(SQL_FROM_HERE), kStringTableCleanup));
  if (!cleaner1.Run())
    return false;
  if (db->GetLastChangeCount() > 0)
    string_table_.ClearCache();

  sql::Statement cleaner2(db->GetCachedStatement(
      sql::StatementID(SQL_FROM_HERE), kUrlTableCleanup));
  if (!cleaner2.Run())
    return false;
  if (db->GetLastChangeCount() > 0)
    url_table_.ClearCache();

  return true;
}

void CountingPolicy::Close() {
  // The policy object should have never been created if there's no DB thread.
  DCHECK(BrowserThread::IsMessageLoopValid(BrowserThread::DB));
  ScheduleAndForget(activity_database(), &ActivityDatabase::Close);
}

}  // namespace extensions