| From: | Amit Langote <amitlangote09(at)gmail(dot)com> |
|---|---|
| To: | Emre Hasegeli <emre(at)hasegeli(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, keisuke kuroda <keisuke(dot)kuroda(dot)3862(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: In PG12, query with float calculations is slower than PG11 |
| Date: | 2020-02-10 07:33:13 |
| Message-ID: | CA+HiwqFhXZU6-G+7YJuNk+NPOns=o=pOKvA-rZzGEsW_NEJPOQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Feb 7, 2020 at 11:43 PM Emre Hasegeli <emre(at)hasegeli(dot)com> wrote:
> > > The patch looks unduly invasive to me, but I think that it might be
> > > right that we should go back to a macro-based implementation, because
> > > otherwise we don't have a good way to be certain that the function
> > > parameter won't get evaluated first.
> >
> > I'd first like to see some actual evidence of this being a problem,
> > rather than just the order of the checks.
>
> There seem to be enough evidence of this being the problem. We are
> better off going back to the macro-based implementation. I polished
> Keisuke Kuroda's patch commenting about the performance issue, removed
> the check_float*_val() functions completely, and added unlikely() as
> Tom Lane suggested. It is attached. I confirmed with different
> compilers that the macro, and unlikely() makes this noticeably faster.
Thanks for updating the patch.
Should we update the same macro in contrib/btree_gist/btree_utils_num.h too?
Regards,
Amit
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