On 04/06/18 09:37, Pavel Stehule wrote: > > > 2018-06-04 9:24 GMT+02:00 Heikki Linnakangas <hlinn...@iki.fi > <mailto:hlinn...@iki.fi>>: > > On 04/06/18 09:12, Pavel Stehule wrote: > > It requires introduction of new "safe" functions (& operators). > Immutable > functions are not enough safe. > > CREATE OR REPLACE FUNCTION public.fx() > RETURNS integer > LANGUAGE plpgsql > IMMUTABLE > AS $function$ > BEGIN > RETURN (SELECT count(*) FROM pg_class); > END; > $function$ > > postgres=# SELECT fx(); > ┌─────┐ > │ fx │ > ╞═════╡ > │ 343 │ > └─────┘ > (1 row) > > > That function is incorrectly marked as IMMUTABLE. In that situation, > it's enough that we throw a sane error like "ERROR: no snapshot > available". > > Yes, it is incorrect mark. Unfortunately - this is often workaround for > wrong estimations - so I afraid, in this case, your proposed fix breaks > lot of applications.
I would say such applications are already broken. -- Vik Fearing +33 6 46 75 15 36 http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support
