* @since 2.0 */ class DbDependency extends Dependency { /** * @var string the ID of the [[Connection|DB connection]] application component. Defaults to 'db'. */ public $connectionID = 'db'; /** * @var Query the SQL query whose result is used to determine if the dependency has been changed. * Only the first row of the query result will be used. */ public $query; /** * @var Connection the DB connection instance */ private $_db; /** * Constructor. * @param Query $query the SQL query whose result is used to determine if the dependency has been changed. */ public function __construct($query = null) { $this->query = $query; } /** * PHP sleep magic method. * This method ensures that the database instance is set null because it contains resource handles. * @return array */ public function __sleep() { $this->_db = null; return array_keys((array)$this); } /** * Generates the data needed to determine if dependency has been changed. * This method returns the value of the global state. * @return mixed the data needed to determine if dependency has been changed. */ protected function generateDependencyData() { $db = $this->getDbConnection(); $command = $this->query->createCommand($db); if ($db->queryCachingDuration >= 0) { // temporarily disable and re-enable query caching $duration = $db->queryCachingDuration; $db->queryCachingDuration = -1; $result = $command->queryRow(); $db->queryCachingDuration = $duration; } else { $result = $command->queryRow(); } return $result; } /** * Returns the DB connection instance used for caching purpose. * @return Connection the DB connection instance * @throws Exception if [[connectionID]] does not point to a valid application component. */ public function getDbConnection() { if ($this->_db === null) { $db = \Yii::$application->getComponent($this->connectionID); if ($db instanceof Connection) { $this->_db = $db; } else { throw new Exception("DbDependency.connectionID must refer to the ID of a DB connection application component."); } } return $this->_db; } /** * Sets the DB connection used by the cache component. * @param Connection $value the DB connection instance */ public function setDbConnection($value) { $this->_db = $value; } }