From: Antonin Houska <ah@cybertec.at>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
    Amit Kapila <amit.kapila16@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]
In-reply-to: <202604031712.bqmynktpnakw@alvherre.pgsql>
References: <202604031712.bqmynktpnakw@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@alvh.no-ip.org>
   message dated "Fri, 03 Apr 2026 19:24:30 +0200."
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Date: Sat, 04 Apr 2026 10:50:14 +0200
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Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> On 2026-Apr-03, Antonin Houska wrote:
> =

> > diff --git a/src/backend/commands/repack_worker.c b/src/backend/comman=
ds/repack_worker.c
> > index 00b21ede481..c25dbeadff3 100644
> > --- a/src/backend/commands/repack_worker.c
> > +++ b/src/backend/commands/repack_worker.c
> =

> > @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid)
> >  =

> >  	EnsureLogicalDecodingEnabled();
> >  =

> > +	/*
> > +	 * By declaring that our output plugin does not need shared catalogs=
, we
> > +	 * avoid waiting for completion of transactions running in other dat=
abases
> > +	 * than the one we're connected to.
> > +	 */
> > +	accessSharedCatalogsInDecoding =3D false;
> > +
> >  	/*
> >  	 * Neither prepare_write nor do_write callback nor update_progress i=
s
> >  	 * useful for us.
> =

> I find this reliance on a global variable for this a bit icky.  Would it
> work to instead change the CreateInitDecodingContext() signature, so
> that instead of "bool need_full_snapshot" it has a three-valued boolean
> to distinguish the two cases from the original plus this new one?  I
> think the value could be stored in LogicalDecodingContext, from where
> standby_decode() could obtain it.

I agree that the global variable is not handy, but instead of modifying
CreateInitDecodingContext(), how about adding a boolean returning callback=
 to
OutputPluginCallbacks? The point is that whether shared catalogs are neede=
d
during the decoding or not is actually property of the plugin.

-- =

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