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Drupal example source code file (database.inc)

This example Drupal source code file (database.inc) is included in the DevDaily.com "Drupal Source Code Warehouse" project. The intent of this project is to help you "Learn Drupal by Example".

PHP - Drupal tags/keywords

args, array, dsn, from, function, if, new_id, options, php, public, query, return, sequences, value

The database.inc Drupal example source code

// $Id: database.inc,v 1.34 2010/10/03 01:29:41 dries Exp $

 * @file
 * Database interface code for MySQL database servers.

 * @ingroup database
 * @{

class DatabaseConnection_mysql extends DatabaseConnection {

   * Flag to indicate if we have registered the nextID cleanup function.
   * @var boolean
  protected $shutdownRegistered = FALSE;

  public function __construct(array $connection_options = array()) {
    // This driver defaults to transaction support, except if explicitly passed FALSE.
    $this->transactionSupport = !isset($connection_options['transactions']) || ($connection_options['transactions'] !== FALSE);

    // MySQL never supports transactional DDL.
    $this->transactionalDDLSupport = FALSE;

    $this->connectionOptions = $connection_options;

    // The DSN should use either a socket or a host/port.
    if (isset($connection_options['unix_socket'])) {
      $dsn = 'mysql:unix_socket=' . $connection_options['unix_socket'];
    else {
      // Default to TCP connection on port 3306.
      $dsn = 'mysql:host=' . $connection_options['host'] . ';port=' . (empty($connection_options['port']) ? 3306 : $connection_options['port']);
    $dsn .= ';dbname=' . $connection_options['database'];
    parent::__construct($dsn, $connection_options['username'], $connection_options['password'], array(
      // So we don't have to mess around with cursors and unbuffered queries by default.
      // Because MySQL's prepared statements skip the query cache, because it's dumb.
      // Force column names to lower case.

    // Force MySQL to use the UTF-8 character set. Also set the collation, if a
    // certain one has been set; otherwise, MySQL defaults to 'utf8_general_ci'
    // for UTF-8.
    if (!empty($connection_options['collation'])) {
      $this->exec('SET NAMES utf8 COLLATE ' . $connection_options['collation']);
    else {
      $this->exec('SET NAMES utf8');

    // Force MySQL's behavior to conform more closely to SQL standards.
    // This allows Drupal to run almost seamlessly on many different
    // kinds of database systems. These settings force MySQL to behave
    // the same as postgresql, or sqlite in regards to syntax interpretation
    // and invalid data handling. See http://drupal.org/node/344575 for further discussion.
    $this->exec("SET sql_mode='ANSI,TRADITIONAL'");

  public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
    return $this->query($query . ' LIMIT ' . (int) $from . ', ' . (int) $count, $args, $options);

  public function queryTemporary($query, array $args = array(), array $options = array()) {
    $tablename = $this->generateTemporaryTableName();
    $this->query(preg_replace('/^SELECT/i', 'CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY SELECT', $query), $args, $options);
    return $tablename;

  public function driver() {
    return 'mysql';

  public function databaseType() {
    return 'mysql';

  public function mapConditionOperator($operator) {
    // We don't want to override any of the defaults.
    return NULL;

  public function nextId($existing_id = 0) {
    $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
    // This should only happen after an import or similar event.
    if ($existing_id >= $new_id) {
      // If we INSERT a value manually into the sequences table, on the next
      // INSERT, MySQL will generate a larger value. However, there is no way
      // of knowing whether this value already exists in the table. MySQL
      // provides an INSERT IGNORE which would work, but that can mask problems
      // other than duplicate keys. Instead, we use INSERT ... ON DUPLICATE KEY
      // UPDATE in such a way that the UPDATE does not do anything. This way,
      // duplicate keys do not generate errors but everything else does.
      $this->query('INSERT INTO {sequences} (value) VALUES (:value) ON DUPLICATE KEY UPDATE value = value', array(':value' => $existing_id));
      $new_id = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
    if (!$this->shutdownRegistered) {
      // Use register_shutdown_function() here to keep the database system
      // independent of Drupal.
      register_shutdown_function(array($this, 'nextIdDelete'));
      $shutdownRegistered = TRUE;
    return $new_id;

  public function nextIdDelete() {
    // While we want to clean up the table to keep it up from occupying too
    // much storage and memory, we must keep the highest value in the table
    // because InnoDB  uses an in-memory auto-increment counter as long as the
    // server runs. When the server is stopped and restarted, InnoDB
    // reinitializes the counter for each table for the first INSERT to the
    // table based solely on values from the table so deleting all values would
    // be a problem in this case. Also, TRUNCATE resets the auto increment
    // counter.
    try {
      $max_id = $this->query('SELECT MAX(value) FROM {sequences}')->fetchField();
      // We know we are using MySQL here, no need for the slower db_delete().
      $this->query('DELETE FROM {sequences} WHERE value < :value', array(':value' => $max_id));
    // During testing, this function is called from shutdown with the
    // simpletest prefix stored in $this->connection, and those tables are gone
    // by the time shutdown is called so we need to ignore the database
    // errors. There is no problem with completely ignoring errors here: if
    // these queries fail, the sequence will work just fine, just use a bit
    // more database storage and memory.
    catch (PDOException $e) {

 * @} End of "ingroup database".

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