"Rhys Stewart" <rhys.stewart@xxxxxxxxx> writes: > had a similar problem a while back. so i made and abs_time function: > > CREATE OR REPLACE FUNCTION abs_time(interval) > RETURNS interval AS > $BODY$ > BEGIN > if > $1 < '00:00:00'::interval > then > return ($1 * -1)::interval; > else > return $1; > END IF; > END; > $BODY$ > LANGUAGE 'plpgsql' VOLATILE; I believe that you can declare this IMMUTABLE. For a given interval it will always return the same value, so you can benefit from some optimization. http://www.postgresql.org/docs/8.2/interactive/xfunc-volatility.html An IMMUTABLE function cannot modify the database and is guaranteed to return the same results given the same arguments forever. This category allows the optimizer to pre-evaluate the function when a query calls it with constant arguments. For example, a query like SELECT ... WHERE x = 2 + 2 can be simplified on sight to SELECT ... WHERE x = 4, because the function underlying the integer addition operator is marked IMMUTABLE. -- Jorge Godoy <jgodoy@xxxxxxxxx>
