public static function clear_cache($table_name = null, $connection_name = self::DEFAULT_CONNECTION)
        {
            self::$_query_cache = [];

            if(isset(self::$_config[$connection_name]['clear_cache']) && is_callable(self::$_config[$connection_name]['clear_cache'])){
                return call_user_func_array(self::$_config[$connection_name]['clear_cache'], array($table_name, $connection_name));
            }
        }