From: Antonin Houska <ah@cybertec.at>
To: Andres Freund <andres@anarazel.de>
cc: Alvaro Herrera <alvherre@alvh.no-ip.org>,
    Amit Kapila <amit.kapila16@gmail.com>,
    Mihail Nikalayeu <mihailnikalayeu@gmail.com>,
    Srinath Reddy Sadipiralla <srinath2133@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]
In-reply-to: <pveffyxhnuurhb44uzqlwo3rkyzorkfh2rot7uwzlf2axhfvbp@7nrs2omysxkc>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
   message dated "Tue, 07 Apr 2026 11:48:42 -0400."
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Date: Tue, 07 Apr 2026 18:01:16 +0200
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Andres Freund <andres@anarazel.de> wrote:

> On 2026-04-07 17:38:24 +0200, Antonin Houska wrote:
> > The REPACK plugin only deforms tuples and writes them to a file, so I =
think
> > that things like this should not happen.
> =

> You don't need to do it yourself.  It just requires a shared_preload_lib=
rary
> extension to register a relcache invalidation callback that accesses sha=
red
> catalog.
> =

> It's only kind of an accident that we don't have a case today that acces=
ses
> shared catcaches during a relcache build in core (I'm not even sure ther=
e's
> nothing). You'd just need somebody to add e.g. relcache caching for
> publications for that to change. Or look up information about a reloptio=
n in
> pg_parameter_acl. Or lookup tablespace configuration.
> =

> =

> > However, I admit that an option that allows the plugin developer to de=
clare
> > "I don't need shared catalogs" may be considered deceptive.
> =

> At the very least it would need to be a runtime check rather than just a=
n
> assert. This would much more likely to be hit in production because othe=
rwise
> it's probably hard to hit the case where shared invalidations happen in =
the
> wrong moment.  And the consequences are corrupted caches, which could ca=
use
> all kinds of havoc.
> =

> =

> But I think this may need more infrastructure / deeper analysis than wha=
t we
> can do right now.

ok, thanks a lot for having looked at it.

-- =

Antonin Houska
Web: https://www.cybertec-postgresql.com