protected static function _checkQueryCache($cache_key, $table_name = null, $connection_name = self::DEFAULT_CONNECTION)
        {
            if(isset(self::$_config[$connection_name]['check_query_cache']) && is_callable(self::$_config[$connection_name]['check_query_cache'])){
                return call_user_func_array(self::$_config[$connection_name]['check_query_cache'], array($cache_key, $table_name, $connection_name));
            } elseif (isset(self::$_query_cache[$connection_name][$cache_key])) {
                return self::$_query_cache[$connection_name][$cache_key];
            }

            return false;
        }