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From: Masahiko Sawada <[email protected]>
To: David Rowley <[email protected]>
Cc: Laurenz Albe <[email protected]>
Cc: Martín Marqués <[email protected]>
Cc: PostgreSQL Developers <[email protected]>
Subject: Re: Update maintenance_work_mem/autovacuum_work_mem to reflect the 1GB limitation with VACUUM
Date: Mon, 19 Jul 2021 17:27:10 +0900
Message-ID: <CAD21AoCSDmnejmpOnqDWq0NpC5PqEqNnoi8kVoqxFYGSJmKkFQ@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com>
References: <CABeG9LsZ2ozUMcqtqWu_-GiFKB17ih3p8wBHXcpfnHqhCnsc7A@mail.gmail.com>
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On Wed, Jul 7, 2021 at 8:44 PM David Rowley <[email protected]> wrote:
>
> On Sun, 4 Jul 2021 at 22:38, David Rowley <[email protected]> wrote:
> > I could do with a 2nd opinion about if we should just adjust the
> > maximum value for the autovacuum_work_mem GUC to 1GB in master.
> >
> > I'm also not sure if since we'd not backpatch the GUC max value
> > adjustment if we need to document the upper limit in the manual.
>
> I was just looking at this again and I see that GIN indexes are able
> to use more than 1GB of memory during VACUUM.

I think you meant that autovacuums can use more than 1GB of memory
during cleaning up a gin pending list (in ginInsertCleanup()). The
description updated by that commit is not true as of now as you
pointed out but IIUC it uses maintenance_work_mem *in addition to* the
same amount memory used by lazy vacuum. This memory usage seems rather
weird to me. Is it worh considering having gin pending list cleanup
use work_mem instead of maintenance_work_mem also in autovacuum cases
like btree indexes do? If we do that, the description will become
true, although we might need to update work_mem section somewhat.

Regards,

--
Masahiko Sawada
EDB:  https://www.enterprisedb.com/





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