I use PostgreSQL to Hive Metastore. And I saw the following message at PostgreSQL log.
< 2015-06-26 10:58:15.488 JST >ERROR: syntax error at or near "@@" at character 5
< 2015-06-26 10:58:15.488 JST >STATEMENT: SET @@session.sql_mode=ANSI_QUOTES
< 2015-06-26 10:58:15.489 JST >ERROR: relation "v$instance" does not exist at character 21
< 2015-06-26 10:58:15.489 JST >STATEMENT: SELECT version FROM v$instance
< 2015-06-26 10:58:15.490 JST >ERROR: column "version" does not exist at character 10
< 2015-06-26 10:58:15.490 JST >STATEMENT: SELECT @@version
When Hive CLI and Beeline embedded mode are carried out, this message is output to PostgreSQL log.
These queries are called from MetaStoreDirectSql#determineDbType. And if we use MetaStoreDirectSql#getProductName, we need not to call these queries.