11. The server of claim 10 , wherein the query performance engine determining unit checks whether a query performance engine is predetermined by a user based on the received criterion.
16. The server of claim 11 , wherein the query performance engine determining unit determines a characteristic of the query when a query performance engine is not predetermined to select one of the plurality of query performance engines based on a value calculated by assigning a prescribed weight to a load on each of the plurality of query performance engines.