Horton

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

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Claudio Freire <klaussfreire@gmail.com>
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: 2018-02-08T02:29:34Z
Lists: pgsql-hackers 
Claudio Freire wrote:
> 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" ?

I was thinking in first doing 
  SELECT array_agg(DISTINCT virtualtransaction) vxids
    FROM pg_locks \gset

and then in a DO block loop until

   SELECT DISTINCT virtualtransaction
     FROM pg_locks
INTERSECT
   SELECT (unnest(:'vxids'::text[]));

returns empty; something along those lines.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Prefetch blocks during lazy vacuum's truncation scan

  2. Explain unaccounted for space in pgstattuple.