From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: Peter Geoghegan <pg@bowt.ie>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Петър Славов <pet.slavov@gmail.com>
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17485: Records missing from Primary Key index when doing REINDEX INDEX CONCURRENTLY
Date: Wed, 25 May 2022 18:43:22 +0200
Message-ID: <202205251643.2py5jjpaw7wy@alvherre.pgsql> (raw)
In-Reply-To: <CA+TgmoYP7BnHXTEoJRUnOuie2J05Qo8ti5mnE2u-1c4Hk+8zJw@mail.gmail.com>
On 2022-May-25, Robert Haas wrote:
> On Wed, May 25, 2022 at 7:45 AM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> > Another possibility (than reverting the commit altogether) might be to
> > disable HOT pruning while a process is operating on that relation with
> > PROC_IN_SAFE_IC. So CIC/RIC processes are still ignored for VACUUM,
> > while not creating corrupted indexes.
>
> I'm not sure that would be a win, because HOT pruning is great as long
> as the tuples you're pruning are old enough.
Well, the point is that VACUUM could still prune dead tuples that are
newer than the CIC in all *other* tables. VACUUM cannot run in the
table being processed by CIC/RIC (because of locks), so there's no
change; it's only HOT-pruning in the table being processed that would
change.
> Also, it seems like it would require complex new infrastructure that I
> think we should be reluctant to invent in back branches.
This is definitely true. And I think this would be expensive, because
we'd have to check in every heap_page_prune call.
> It seems to me that we should just revert.
Deciding to revert makes me sad, because this feature is extremely
valuable for users. However, I understand the danger and I don't
disagree with the rationale so I can't really object.
--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"¿Cómo puedes confiar en algo que pagas y que no ves,
y no confiar en algo que te dan y te lo muestran?" (Germán Poo)
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Cc: alvherre@alvh.no-ip.org, robertmhaas@gmail.com, andres@anarazel.de, x4mmm@yandex-team.ru, pg@bowt.ie, michael@paquier.xyz, pet.slavov@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17485: Records missing from Primary Key index when doing REINDEX INDEX CONCURRENTLY
In-Reply-To: <202205251643.2py5jjpaw7wy@alvherre.pgsql>
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