Re: effective_multixact_freeze_max_age issue

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: Peter Geoghegan <pg(at)bowt(dot)ie>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "Bossart, Nathan" <bossartn(at)amazon(dot)com>, Jeremy Schneider <schneider(at)ardentperf(dot)com>
Subject: Re: effective_multixact_freeze_max_age issue
Date: 2022-08-29 22:40:13
Message-ID: 20220829224013.GA541895@nathanxps13
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On Mon, Aug 29, 2022 at 10:25:50AM -0700, Peter Geoghegan wrote:
> On Sun, Aug 28, 2022 at 4:14 PM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
>> The idea seems sound to me, and IMO your patch simplifies things nicely,
>> which might be reason enough to proceed with it.
> It is primarily a case of making things simpler. Why would it ever
> make sense to interpret age differently in the presence of a long
> running transaction, though only for the FreezeLimit/MultiXactCutoff
> cutoff calculation? And not for the closely related
> freeze_table_age/multixact_freeze_table_age calculation? It's hard to
> imagine that that was ever a deliberate choice.
> vacuum_set_xid_limits() didn't contain the logic for determining if
> its caller's VACUUM should be an aggressive VACUUM until quite
> recently. Postgres 15 commit efa4a9462a put the logic for determining
> aggressiveness right next to the logic for determining FreezeLimit,
> which made the inconsistency much more noticeable. It is easy to
> believe that this was really just an oversight, all along.


Nathan Bossart
Amazon Web Services:

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