Re: Index-only scan returns incorrect results when using a composite GIST index with a gist_trgm_ops column.

At Thu, 18 Jan 2018 12:57:38 +0500, Andrey Borodin <x4mmm(at)yandex-team(dot)ru> wrote in <62C2B9A0-51BC-40FF-9BCA-F203784CB9C1(at)yandex-team(dot)ru>
> Hello!
> > 18 янв. 2018 г., в 10:48, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> написал(а):
> >
> > Gist imposes the ninth strategy to perform index only scan but
> > planner is not considering that
> > ....
> > Please find the attached patch.
> I agree with you that current behavior is a bug and your patch seems correct.
> I'm a bit worried about ninth strategy words: fetch is not necessary now, if opclass lacks compress methods - index only scan is possible. See https://github.com/postgres/postgres/commit/d3a4f89d8a3e500bd7c0b7a8a8a5ce1b47859128 for details.

It is true. I don't think that fetch for trigm is feasible but it
is workable if created.

> Though there are tests in cube and seg for that, if your patch passes check-world, than this behavior is not affected.

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center