DISCARD

The DISCARD statement releases state the current session has built up, so a connection can be handed to the next client as if it were new. Connection poolers run DISCARD ALL between clients.

Targets

Statement	Effect
DISCARD ALL	Everything below, plus DEALLOCATE ALL and RESET ALL: every prepared statement of the session is dropped, and every setting the session changed returns to its default, the session authorization and the role included.
DISCARD TEMP	Drops the temporary tables, views, sequences, functions and types of the session. DISCARD TEMPORARY is the same statement.
DISCARD SEQUENCES	Forgets the session's sequence state: currval fails for every sequence until the next nextval on it.
DISCARD PLANS	Accepted and has no effect: prepared statements stay prepared.

DISCARD ALL cannot run inside a transaction block. A DISCARD TEMP inside a transaction is undone by ROLLBACK.

Examples

Drop the temporary objects of the session:

SQL

CREATE TEMP TABLE scratch (id INTEGER);
DISCARD TEMP;
SELECT * FROM scratch;

error (?i).*scratch.*

Reset the session: the setting returns to its default and the prepared statement is gone:

SQL

SET statement_timeout = '5s';
PREPARE recent AS SELECT 1;
DISCARD ALL;
SHOW statement_timeout;
EXECUTE recent;

 statement_timeout
-------------------
                 0

db error: ERROR: prepared statement "recent" does not exist

DISCARD ALL is rejected inside a transaction block:

SQL

BEGIN;
DISCARD ALL;
ROLLBACK;

db error: ERROR: DISCARD ALL cannot run inside a transaction block