Horton

Re: [HACKERS] Vacuum: allow usage of more than 1GB of work mem

Claudio Freire <klaussfreire@gmail.com>

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From: Claudio Freire <klaussfreire@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, Thomas Munro <thomas.munro@enterprisedb.com>, Stephen Frost <sfrost@snowman.net>, Michael Paquier <michael.paquier@gmail.com>, Daniel Gustafsson <daniel@yesql.se>, Andres Freund <andres@anarazel.de>, Masahiko Sawada <sawada.mshk@gmail.com>, Anastasia Lubennikova <a.lubennikova@postgrespro.ru>, Anastasia Lubennikova <lubennikovaav@gmail.com>, PostgreSQL-Dev <pgsql-hackers@postgresql.org>
Date: 2018-02-08T00:21:29Z
Lists: pgsql-hackers

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On Wed, Feb 7, 2018 at 8:52 PM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>> Waiting as you say would be akin to what the patch does by putting
>> vacuum on its own parallel group.
>
> I don't think it's the same.  We don't need to wait until all the
> concurrent tests are done -- we only need to wait until the transactions
> that were current when the delete finished are done, which is very
> different since each test runs tons of small transactions rather than
> one single big transaction.

Um... maybe "lock pg_class" ?

That should conflict with basically any other running transaction and
have pretty much that effect.

Attached is a version of patch 1 with that approach.

Commits

  1. Prefetch blocks during lazy vacuum's truncation scan

  2. Explain unaccounted for space in pgstattuple.