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<?php
// $Id$
/**
* @file
* Database interface code for MySQL database servers.
*/
/**
* @ingroup database
* @{
*/
class DatabaseConnection_mysql extends DatabaseConnection {
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.
$this->transactionalDDLSupport = FALSE;
// Default to TCP connection on port 3306.
if (empty($connection_options['port'])) {
$connection_options['port'] = 3306;
}
$dsn = 'mysql:host=' . $connection_options['host'] . ';port=' . $connection_options['port'] . ';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.
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,
// Force column names to lower case.
PDO::ATTR_CASE => PDO::CASE_LOWER,
));
// Force MySQL to use the UTF-8 character set by default.
$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 disscussion.
$this->exec("SET sql_mode='ANSI,TRADITIONAL'");
}
public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
return $this->query($query . ' LIMIT ' . $from . ', ' . $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) {
static $shutdown_registered = FALSE;
$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 = $this->query('INSERT INTO {sequences} () VALUES ()', array(), array('return' => Database::RETURN_INSERT_ID));
}
if (!$shutdown_registered) {
register_shutdown_function(array(get_class($this), 'nextIdDelete'));
$shutdown_registered = TRUE;
}
return $new_id;
}
public static 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.
$max_id = db_query('SELECT MAX(value) FROM {sequences}')->fetchField();
// We know we are using MySQL here, so need for the slower db_delete().
db_query('DELETE FROM {sequences} WHERE value < :value', array(':value' => $max_id));
}
}
/**
* @} End of "ingroup database".
*/
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