Feedback-ID: ia2694551:Fastmail
Date: Fri, 27 Mar 2026 00:14:50 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Antonin Houska <ah@cybertec.at>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
	Mihail Nikalayeu <mihailnikalayeu@gmail.com>,
 Matthias van de Meent <boekewurm+postgres@gmail.com>,
	Pg Hackers <pgsql-hackers@lists.postgresql.org>,
 Robert Treat <rob@xzilla.net>
Subject: Re: Adding REPACK [concurrently]
Message-ID: <202603262307.gfa5jbpesfro@alvherre.pgsql>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <23138.1774518710@localhost>
Archived-At: 
 <https://www.postgresql.org/message-id/202603262307.gfa5jbpesfro%40alvherre.pgsql>
Precedence: bulk

On 2026-Mar-26, Antonin Houska wrote:

> I haven't thought of it because I'm not familiar with the deadlock detector,
> but what you do seems consistent with the way blocking by autovacuum is
> handled.
> 
> The only problem I noticed is that PROC_IN_CONCURRENT_REPACK is not cleared at
> the end of transaction. Perhaps it should be added to PROC_VACUUM_STATE_MASK
> (name of which is already misleading due to the presence of PROC_IN_SAFE_IC,
> but that's another problem).

Yeah, good observation -- we should absolutely clear it at transaction
end, and adding it to PROC_VACUUM_STATE_MASK seems the cleanest way to
make that happen.  However, we should also clear it as soon as we've
acquired the AccessExclusiveLock on all rels.  At that point we no
longer need it, and it makes more sense to have other transactions
resume the normal waiting behavior instead of having them fail right
away.

> Maybe just add a new permutation to repack.spec? I don't remembery if I
> created repack_toast.spec as a separate file just for better readability or if
> there was some other issue, but the deadlock test might fit into repack.spec.

Yeah, that was my first impulse too, but it's not clear to me that
things are better one way or the other.  I haven't decided yet.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"[PostgreSQL] is a great group; in my opinion it is THE best open source
development communities in existence anywhere."                (Lamar Owen)