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From: Bruce Momjian <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: Laurenz Albe <[email protected]>
Cc: [email protected]
Cc: [email protected]
Subject: Re: 24.1.5.1. Multixacts And Wraparound
Date: Fri, 2 Jul 2021 18:01:14 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Thu, Jun 24, 2021 at 04:06:38PM -0400, Álvaro Herrera wrote:
> On 2021-Jun-24, Bruce Momjian wrote:
> 
> > +     As a safety device, an aggressive vacuum scan will
> > +     occur for any table whose multixact-age (see <xref
> > +     linkend="vacuum-for-multixact-wraparound"/>) is greater than <xref
> > +     linkend="guc-autovacuum-multixact-freeze-max-age"/>.  Also, if the
> > +     storage occupied by multixacts exceeds 2GB, aggressive vacuum scans
> > +     will occur more often for all tables, starting with those that have
> > +     the oldest multixact-age.  Both of these kinds of aggressive scans
> > +     will occur even if autovacuum is nominally disabled.
> 
> This looks good, thanks.
> 
> I think "the space occupied by multixacts" is a bit ambiguous -- it is
> talking about pg_multixact/members only, but you could interpret that it
> talks about both that and pg_multixact/offsets.  I'm not sure we need to
> be 100% precise about that, so perhaps what you have is sufficient.  But
> if we do want to be precise, then maybe " ... if the storage occupied by
> multixact members (<literal>pg_multixact/members/</literal>) exceeds ..."
> covers it.
> 
> (At least, that's how I remember this.  I don't think things have
> changed much since 53bb309d2d5a ...)

OK, I got "members" into the doc section and applied it to master and PG
14.

-- 
  Bruce Momjian  <[email protected]>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.

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