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In-Reply-To: <2f48399f-2959-4483-938f-64edb863ca76@postgrespro.ru>
From: Alexander Korotkov <aekorotkov@gmail.com>
Date: Mon, 2 Jun 2025 19:25:28 +0300
Message-ID: 
 <CAPpHfdtQd29O15Cmp1qeqTCerQF0Y+BGh63qtX3RkA7k=0TZ1Q@mail.gmail.com>
Subject: Re: Vacuum statistics
To: Alena Rybakina <a.rybakina@postgrespro.ru>
Cc: Amit Kapila <amit.kapila16@gmail.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>,
	Jim Nasby <jnasby@upgrade.com>,
 Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
	Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>,
 Kirill Reshke <reshkekirill@gmail.com>,
	Andrei Zubkov <zubkov@moonset.ru>, Masahiko Sawada <sawada.mshk@gmail.com>,
	Melanie Plageman <melanieplageman@gmail.com>,
 jian he <jian.universality@gmail.com>,
	a.lepikhov@postgrespro.ru, Sami Imseih <samimseih@gmail.com>,
	vignesh C <vignesh21@gmail.com>
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On Tue, May 13, 2025 at 12:49=E2=80=AFPM Alena Rybakina
<a.rybakina@postgrespro.ru> wrote:
> On 12.05.2025 08:30, Amit Kapila wrote:
> > On Fri, May 9, 2025 at 5:34=E2=80=AFPM Alena Rybakina <a.rybakina@postg=
respro.ru> wrote:
> >> I did a rebase and finished the part with storing statistics separatel=
y from the relation statistics - now it is possible to disable the collecti=
on of statistics for relationsh using gucs and
> >> this allows us to solve the problem with the memory consumed.
> >>
> > I think this patch is trying to collect data similar to what we do for
> > pg_stat_statements for SQL statements. So, can't we follow a similar
> > idea such that these additional statistics will be collected once some
> > external module like pg_stat_statements is enabled? That module should
> > be responsible for accumulating and resetting the data, so we won't
> > have this memory consumption issue.
> The idea is good, it will require one hook for the pgstat_report_vacuum
> function, the extvac_stats_start and extvac_stats_end functions can be
> run if the extension is loaded, so as not to add more hooks.

+1
Nice idea of a hook.  Given the volume of the patch, it might be a
good idea to keep this as an extension.

> But I see a problem here with tracking deleted objects for which
> statistics are no longer needed. There are two solutions to this and I
> don't like both of them, to be honest.
> The first way is to add a background process that will go through the
> table with saved statistics and check whether the relation or the
> database are relevant now or not and if not, then
> delete the vacuum statistics information for it. This may be
> resource-intensive. The second way is to add hooks for deleting the
> database and relationships (functions dropdb, index_drop,
> heap_drop_with_catalog).

Can we workaround this with object_access_hook?

------
Regards,
Alexander Korotkov
Supabase