Note: The following description applies both to Postgres-XC and PostgreSQL if not described explicitly.
DISCARD releases internal resources associated with a database session. These resources are normally released at the end of the session.
DISCARD TEMP drops all temporary tables created in the current session. DISCARD PLANS releases all internally cached query plans. DISCARD ALL resets a session to its original state, discarding temporary resources and resetting session-local configuration changes.
Drops all temporary tables created in the current session.
Releases all cached query plans.
Releases all temporary resources associated with the current session and resets the session to its initial state. Currently, this has the same effect as executing the following sequence of statements:
SET SESSION AUTHORIZATION DEFAULT; RESET ALL; DEALLOCATE ALL; CLOSE ALL; UNLISTEN *; SELECT pg_advisory_unlock_all(); DISCARD PLANS; DISCARD TEMP;