Re: Removing unneeded self joins

From: Tender Wang <tndrwang(at)gmail(dot)com>
To: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Cc: Daniel Gustafsson <daniel(at)yesql(dot)se>, Andrei Lepikhov <lepihov(at)gmail(dot)com>, Richard Guo <guofenglinux(at)gmail(dot)com>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, Alena Rybakina <a(dot)rybakina(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alexander Lakhin <exclusion(at)gmail(dot)com>, "Gregory Stark (as CFM)" <stark(dot)cfm(at)gmail(dot)com>, Michał Kłeczek <michal(at)kleczek(dot)org>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>
Subject: Re: Removing unneeded self joins
Date: 2025-04-06 13:09:22
Message-ID: CAHewXNkfZinf5=Buvb8_ysKqxLbncfeQ2N4WF3TxjewyjCsEHQ@mail.gmail.com
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Alexander Korotkov <aekorotkov(at)gmail(dot)com> 于2025年4月6日周日 19:50写道：

> On Sun, Apr 6, 2025 at 2:42 PM Tender Wang <tndrwang(at)gmail(dot)com> wrote:
> > Daniel Gustafsson <daniel(at)yesql(dot)se> 于2025年4月6日周日 19:23写道：
> >>
> >> > On 6 Apr 2025, at 06:02, Tender Wang <tndrwang(at)gmail(dot)com> wrote:
> >>
> >> > I find that the postgresql.conf.sample file doesn't contain
> enable_self_join_elimination guc.
> >> > If this is necessary, please see the attached patch.
> >>
> >> The GUC is marked as not supposed by the in the sample file, either it
> really
> >> shouldn't or that needs to be removed from the GUC declaration.
> >
> >
> > Sorry, I didn't see the GUC_NOT_IN_SAMPLE flag. Thanks for the reminder.
> > Please ignore the noise.
>
> Also, sorry for thoughtless commit of that.
> Nevertheless, should we consider revisiting this flag? I see the only
> other GUC simultaneously QUERY_TUNING_METHOD and GUC_NOT_IN_SAMPLE is
> optimize_bounded_sort, which is not exposed in a standard build.
>

Agree.
Putting enable_self_join_elimination into sample file seems a good choice.

--
Thanks, Tender Wang

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