Re: Adding REPACK [concurrently]

From: Mihail Nikalayeu <mihailnikalayeu(at)gmail(dot)com>
To: Antonin Houska <ah(at)cybertec(dot)at>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Treat <rob(at)xzilla(dot)net>
Subject: Re: Adding REPACK [concurrently]
Date: 2026-04-09 09:11:16
Message-ID: CADzfLwX78LmnZ6ZE3oSwuyw98WqY8g2HLHrSRRUBcgVQhMW=2Q@mail.gmail.com
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Hi!

On Thu, Apr 9, 2026 at 10:43 AM Antonin Houska <ah(at)cybertec(dot)at> wrote:
> This approach LGTM when it comes to concurrent DDLs. However, consider REPACK
> holding ShareUpdateExclusiveLock (SUEL) and VACUUM (w/o VACOPT_SKIP_LOCKED)
> waiting for the same lock. Once REPACK releases its SUEL, VACUUM gets it and
> processes the table, then REPACK finally gets AccessExclusiveLock (AEL) and
> finishes too.

> One more thing we may prevent from sneaking into that hole is a
> VACUUM. It will not break anything, but will be huge waste of time and
> resources.

I thought about that too, I think we may just add some kind of
CheckTableNotInUse in VACUUM after getting the SUEL.

Mikhail.

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