Re: mxid_score can become Infinity in pg_stat_autovacuum_scores

From: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
To: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Cc: Sami Imseih <samimseih(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: mxid_score can become Infinity in pg_stat_autovacuum_scores
Date: 2026-06-17 18:37:12
Message-ID: CALj2ACUdSyn9JXqNdJLQRA8=vDR3on+fuSrq0oXRab0MjH6t-A@mail.gmail.com
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Hi,

On Wed, Jun 17, 2026 at 9:18 AM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
>
> On Tue, Jun 16, 2026 at 11:21:57AM -0500, Sami Imseih wrote:
> > I think this particular scenario is very clear to explain just like how
> > we explain the failsafe scenario. Also, the suggested docs in the view
> > link to the already existing detailed explanation of this behavior.
> >
> > More generally, I think anytime there is a drastic change in a score,
> > like jumping from a gradually ramping value around 1.x to suddenly
> > hundreds of millions, that's something worth calling out in the docs.
> > Users monitoring pg_stat_autovacuum_scores will notice that jump and want
> > to understand why it happened.
>
> Okay. I fiddled with the patch a bit and came up with the attached. WDYT?

+ of multixact member entries created exceeds approximately 2 billion

Although 2 billion is an internal threshold that may change to a
configurable parameter in the future depending on the workload and
disk space (per commit bd8d9c9bdf), I'm fine keeping it as is.

Attached v2 patch LGTM.

--
Bharath Rupireddy
Amazon Web Services: https://aws.amazon.com

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