slow metadata getImportedKeys when not having database set

Actual implementation for DatabaseMetadata.getImportedKeys(String catalog, String schema, String table) is using INFORMATION_SCHEMA tables when not having database set. When database is set, implementation use SHOW CREATE TABLE, being a super fast request (more than 1000x).

Goal is to have only one implementation using SHOW CREATE TABLE, requesting that for all databases. This solution is benchmark to perform 100 times better than current one.