public function getDbConnection()
 {
     if ($this->shardUserId) {
         self::$db = DbManager::getUserShard($this->shardUserId, $this->dbComponentId);
     } elseif ($this->dbComponentId) {
         self::$db = DbManager::getDb($this->dbComponentId);
     }
     return parent::getDbConnection();
 }
 public static function model($className = __CLASS__)
 {
     return parent::model($className);
 }