> On Sat, Oct 4, 2008 at 8:49 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > >> "Gurjeet Singh" <singh.gurjeet@gmail.com> writes: >> > Shouldn't PG make all efforts to not execute something when the result is >> > already known? >> >> Not if said effort would cost more than is saved, which would be by far >> the most likely result if we tried to cache all function results. >> > > Sorry Tom, I confused STABLE with IMMUTABLE; my bad.
No, this is equally untrue for immutable.
Yup... I realized that after a bit of more testing after the mail... Immutable functions are single-call-per-command only of you are passing constants-only as parameters; if we have an expression involving columns, then they will be called for every row.
