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From: shveta malik <shveta.malik@gmail.com>
Date: Mon, 6 Jul 2026 10:42:24 +0530
Message-ID: 
 <CAJpy0uDaboZmDV3DPKNo4bxfgsS1Bps96OmsypmDC1189YZhuw@mail.gmail.com>
Subject: Re: [PATCH] Preserve replication origin OIDs in pg_upgrade
To: Ajin Cherian <itsajin@gmail.com>
Cc: Zsolt Parragi <zsolt.parragi@percona.com>,
 pgsql-hackers@lists.postgresql.org,
	shveta malik <shveta.malik@gmail.com>
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On Wed, Jul 1, 2026 at 8:20=E2=80=AFAM Ajin Cherian <itsajin@gmail.com> wro=
te:
>
> All the above changes are updated in patch v10.
>

Thanks for the patch. I have not reviewed completely yet, but please
find comments so far:


1)
+ * In binary-upgrade mode, skip origin creation here. This is required to
+ * preserve the roident from the old cluster for this subscription's origi=
n.

Shall we slightly tweak it to:
/*
 * In binary-upgrade mode, skip origin creation here. It will be
 * created separately so that the origin ID (roident) from the
 * old cluster can be preserved for this subscription.
 */

dumpReplicationOrigins:
2)
+ appendPQExpBufferStr(buf,
+ "SELECT o.*, os.remote_lsn "

It will be better to be more specific here to make it more future proof:
SELECT o.roident, o.roname, os.remote_lsn

3)
+ if (PQntuples(res) > 0)
+ fprintf(OPF, "--\n-- Replication Origins \n--\n\n");
+
+ for (int i =3D 0; i < PQntuples(res); i++)

Instead of fetching it in loop, we can fetch it once and use it:
ntups =3D PQntuples(res)

4)
+ appendPQExpBufferStr(buf, "\n-- For binary upgrade, must preserve
replication origin roident and remote_lsn\n");

Seeing the pattern of other such comments in file, we can change
'origin' to be more specific 'pg_replication_origin'

5)
get_replication_origin_info:
+ res =3D executeQueryOrDie(conn, "SELECT count(*) AS norigins "
+    "FROM pg_catalog.pg_replication_origin");

I don't see alias 'norigins' being sued anywhere. We can get rid of it
if not needed.

6)
get_subscription_info: I think a bug is introduced with the new change.

Earlier query was below which will always return a row even if there
is no subscription entry:

postgres=3D# SELECT count(*) AS nsub,
       'f' AS retain_dead_tuples
FROM pg_catalog.pg_subscription;
 nsub | retain_dead_tuples
------+--------------------
    0 | f

Now, this will not even return a result if there are no subscription entrie=
s:

postgres=3D# SELECT 'f' AS retain_dead_tuples
FROM pg_catalog.pg_subscription;
 retain_dead_tuples
--------------------
(0 rows)

So this line of code will access a non existing result:

  i_retain_dead_tuples =3D PQfnumber(res, "retain_dead_tuples");


Should we simply do:
res =3D executeQueryOrDie(conn,
"SELECT false AS retain_dead_tuples");
(false/'f' anything is fine)

instead of:
res =3D executeQueryOrDie(conn,
"SELECT 'f' AS retain_dead_tuples "
"FROM pg_catalog.pg_subscription");

thanks
Shveta