Re: 24.1.5.1. Multixacts And Wraparound

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?

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EDB https://enterprisedb.com

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