Date: Wed, 18 Jun 2025 11:31:50 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: shihao zhong <zhong950419@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Fixes inconsistent behavior in vacuum when it processes multiple
 relations
Message-ID: <aFLp9sMEHFHULOFx@nathan>
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On Wed, Jun 18, 2025 at 11:15:31AM -0400, shihao zhong wrote:
> I investigated the code and found a small bug with how we're passing
> the VacuumParams pointer.
> 
> The call flow is
> ExecVacuum -> vacuum -> vacuum_rel
> 
> The initial VaccumParams pointer is set in ExecVacuum
> In vacuum_rel, this pointer might change because it needs to determine
> whether to truncate and perform index_cleanup.

Nice find!

My first reaction is to wonder whether we should 1) also make a similar
change to vacuum() for some future-proofing or 2) just teach vacuum_rel()
to make a local copy of the parameters that it can scribble on.  In the
latter case, we might want to assert that the parameters don't change after
calls to vacuum() and vacuum_rel() to prevent this problem from recurring.
That leads me to think (1) might be the better option, although I'm not too
wild about the subtlety of the fix.

-- 
nathan