MIME-Version: 1.0
References: 
 <CABeG9LsZ2ozUMcqtqWu_-GiFKB17ih3p8wBHXcpfnHqhCnsc7A@mail.gmail.com>
 <1c6fa18692a77ff6098dedc0c150df24ffe9db89.camel@cybertec.at>
 <f311f6eda1bd8a6c319a969881b0c15e6fbbfaa8.camel@cybertec.at>
 <CAApHDvrSDxi2jvStdi4vnrD3JjMffSkEZhK8C3-NsLV+CFhL8A@mail.gmail.com>
 <db6f5ddc36bf358affaa83a57487ab6ce77d5bcc.camel@cybertec.at>
 <CAApHDvqu_6JetmiPUuM-_f=r7GHXiaxLXJu8JFe-vjMPHW73eg@mail.gmail.com>
 <CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com>
In-Reply-To: 
 <CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com>
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Mon, 19 Jul 2021 17:27:10 +0900
Message-ID: 
 <CAD21AoCSDmnejmpOnqDWq0NpC5PqEqNnoi8kVoqxFYGSJmKkFQ@mail.gmail.com>
Subject: Re: Update maintenance_work_mem/autovacuum_work_mem to reflect the
 1GB limitation with VACUUM
To: David Rowley <dgrowleyml@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>,
 =?UTF-8?B?TWFydMOtbiBNYXJxdcOpcw==?= <martin.marques@gmail.com>,
	PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Content-Type: text/plain; charset="UTF-8"
Archived-At: 
 <https://www.postgresql.org/message-id/CAD21AoCSDmnejmpOnqDWq0NpC5PqEqNnoi8kVoqxFYGSJmKkFQ%40mail.gmail.com>
Precedence: bulk

On Wed, Jul 7, 2021 at 8:44 PM David Rowley <dgrowleyml@gmail.com> wrote:
>
> On Sun, 4 Jul 2021 at 22:38, David Rowley <dgrowleyml@gmail.com> 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/