From: Antonin Houska <ah@cybertec.at>
To: Robert Treat <rob@xzilla.net>
cc: jian he <jian.universality@gmail.com>,
    Alvaro Herrera <alvherre@alvh.no-ip.org>,
    Pg Hackers <pgsql-hackers@lists.postgresql.org>,
    Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Subject: Re: Adding REPACK [concurrently]
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Comments: In-reply-to Robert Treat <rob@xzilla.net>
   message dated "Wed, 05 Nov 2025 00:10:47 -0500."
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Date: Wed, 05 Nov 2025 08:12:19 +0100
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Robert Treat <rob@xzilla.net> wrote:

> On Tue, Nov 4, 2025 at 9:48=E2=80=AFPM jian he <jian.universality@gmail.c=
om> wrote:

> > what the expectation of
> > pg_repackdb --index=3Dindex_name, the doc is not very helpful.
> >
> > pg_repackdb --analyze --index=3Dzz --verbose
> > pg_repackdb: repacking database "src3"
> > pg_repackdb: error: processing of database "src3" failed: ERROR:  "zz"
> > is not an index for table "tenk1"
> >
> > select pg_get_indexdef ('zz'::regclass);
> >                   pg_get_indexdef
> > ---------------------------------------------------
> >  CREATE INDEX zz ON public.tenk2 USING btree (two)
> >
>=20
> Hmm... yes, this is a bit confusing. I didn't verify it in the code,
> but from memory I think the --index option is meant to be used only in
> conjunction with --table, in which case it would repack the table
> using the specified index. I could be overlooking something though.

The corresponding code is:

+	/*
+	 * In REPACK mode, if the 'using_index' option was given but no index
+	 * name, filter only tables that have an index with indisclustered set.
+	 * (If an index name is given, we trust the user to pass a reasonable list
+	 * of tables.)
+	 *
+	 * XXX it may be worth printing an error if an index name is given with no
+	 * list of tables.
+	 */
+	if (vacopts->mode =3D=3D MODE_REPACK &&
+		vacopts->using_index && !vacopts->indexname)
+	{
+		appendPQExpBufferStr(&catalog_query,
+							 " AND EXISTS (SELECT 1 FROM pg_catalog.pg_index\n"
+							 "    WHERE indrelid =3D c.oid AND indisclustered)\n");
+	}

I'm not sure if it's worth allowing the --index option to have an
argument. Since the user can specify multiple tables, he should also be able
to specify multiple indexes. And then the question would be: what should
happen if the user forgot to specify (or just mistyped) the index name for a
table which does not yet have the clustering index set? Skip that table (and
print out a warning)? Or consider it an error?

--=20
Antonin Houska
Web: https://www.cybertec-postgresql.com