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Date: Mon, 21 Jun 2021 22:50:23 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: eric.mutta@gmail.com, pgsql-docs@lists.postgresql.org
Subject: Re: 24.1.5.1. Multixacts And Wraparound
Message-ID: <20210622025023.GH22121@momjian.us>
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On Fri, Jun 18, 2021 at 08:51:00AM +0200, Laurenz Albe wrote:
> On Thu, 2021-06-17 at 18:31 +0000, PG Doc comments form wrote:
> > In section "24.1.5.1. Multixacts And Wraparound" of
> > https://www.postgresql.org/docs/current/routine-vacuuming.html we find the
> > following sentence towards the end of the section:
> > 
> > "...If the amount of used member storage space exceeds the amount 50% of the
> > addressable storage space."
> > 
> > I am having trouble parsing "...exceeds the amount 50% of the
> > addressable..." part.
> > 
> > It seems like the sentence is trying to say "...space exceeds 50% of the
> > addressable storage space" or maybe even "...space exceeds the amount of the
> > addressable storage space". Which is which?
> 
> +1
> 
> I think that the second "the amount" in the sentence should be removed.

I think it is worse than that.  Here is the full paragraph:

     As a safety device, an aggressive vacuum scan will occur for any table
     whose multixact-age is greater than
     <xref linkend="guc-autovacuum-multixact-freeze-max-age"/>.  Aggressive
     vacuum scans will also occur progressively for all tables, starting with
     those that have the oldest multixact-age, if the amount of used member
     storage space exceeds the amount 50% of the addressable storage space.
     Both of these kinds of aggressive scans will occur even if autovacuum is
     nominally disabled.

What does "the amount of used member storage space exceeds 50% of the
addressable storage space" mean?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

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