Mine

CREATE OR REPLACE FUNCTION my_function(int4)  RETURNS SETOF int8 AS$BODY$SELECTCASE WHEN (some_condition)     THEN (         SELECT ... -- some arbitrary select statement (returning row(s) of int8 values)     )     ELSE (         SELECT ... -- some arbitrary select statement (returning row(s) of int8 values)     )END$BODY$LANGUAGE 'sql' VOLATILE;