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<?php

/**

 * @file

 * Database interface code for MySQL database servers.

 */

/**

 * @addtogroup database

 * @{

 */

class DatabaseConnection_mysql extends DatabaseConnection {

  /**

   * Flag to indicate if the cleanup function in __destruct() should run.

   *

   * @var boolean

   */

  protected $needsCleanup = 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']);

    }

    // Character set is added to dsn to ensure PDO uses the proper character

    // set when escaping. This has security implications. See

    // https://www.drupal.org/node/1201452 for further discussion.

    $dsn .= ';charset=utf8';

    $dsn .= ';dbname=' . $connection_options['database'];

    // Allow PDO options to be overridden.

    $connection_options += array(

      'pdo' => array(),

    );

    $connection_options['pdo'] += array(

      // So we don't have to mess around with cursors and unbuffered queries by default.

      PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => TRUE,

      // Because MySQL's prepared statements skip the query cache, because it's dumb.

      PDO::ATTR_EMULATE_PREPARES => TRUE,

    );

    parent::__construct($dsn, $connection_options['username'], $connection_options['password'], $connection_options['pdo']);

    // 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');

    }

    // Set MySQL init_commands if not already defined.  Default Drupal's MySQL

    // 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. Also, as MySQL 5.5

    // changed the meaning of TRADITIONAL we need to spell out the modes one by

    // one.

    $connection_options += array(

      'init_commands' => array(),

    );

    $connection_options['init_commands'] += array(

      'sql_mode' => "SET sql_mode = 'ANSI,STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER'",

    );

    // Set connection options.

    $this->exec(implode('; ', $connection_options['init_commands']));

  }

  public function __destruct() {

    if ($this->needsCleanup) {

      $this->nextIdDelete();

    }

  }

  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('CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY ' . $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));

    }

    $this->needsCleanup = 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) {

    }

  }

  /**

   * Overridden to work around issues to MySQL not supporting transactional DDL.

   */

  protected function popCommittableTransactions() {

    // Commit all the committable layers.

    foreach (array_reverse($this->transactionLayers) as $name => $active) {

      // Stop once we found an active transaction.

      if ($active) {

        break;

      }

      // If there are no more layers left then we should commit.

      unset($this->transactionLayers[$name]);

      if (empty($this->transactionLayers)) {

        if (!PDO::commit()) {

          throw new DatabaseTransactionCommitFailedException();

        }

      }

      else {

        // Attempt to release this savepoint in the standard way.

        try {

          $this->query('RELEASE SAVEPOINT ' . $name);

        }

        catch (PDOException $e) {

          // However, in MySQL (InnoDB), savepoints are automatically committed

          // when tables are altered or created (DDL transactions are not

          // supported). This can cause exceptions due to trying to release

          // savepoints which no longer exist.

          //

          // To avoid exceptions when no actual error has occurred, we silently

          // succeed for MySQL error code 1305 ("SAVEPOINT does not exist").

          if ($e->errorInfo[1] == '1305') {

            // If one SAVEPOINT was released automatically, then all were.

            // Therefore, clean the transaction stack.

            $this->transactionLayers = array();

            // We also have to explain to PDO that the transaction stack has

            // been cleaned-up.

            PDO::commit();

          }

          else {

            throw $e;

          }

        }

      }

    }

  }

}

/**

 * @} End of "addtogroup database".

 */