Horton

Re: Two issues with version checks in CREATE SUBSCRIPTION

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Fujii Masao <masao.fujii@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-12-23T04:51:16Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix CREATE SUBSCRIPTION failure when the publisher runs on pre-PG19.

  2. Fix version check for retain_dead_tuples subscription option.

On Mon, Dec 22, 2025 at 10:57 PM Fujii Masao <masao.fujii@gmail.com> wrote:
>
> While looking at subscription-related code, I noticed two issues related to
> version checks.
>
>         if (walrcv_server_version(wrconn) < 19000)
>             ereport(ERROR,
>                 errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
>                 errmsg("cannot enable retain_dead_tuples if the
> publisher is running a version earlier than PostgreSQL 19"));
>
> First, in subscriptioncmds.c this check rejects enabling retain_dead_tuples
> when the publisher is running an older version. However, the comparison uses
> 19000 as v19 value. Since server versions are encoded as 190000 for v19,
> this appears to be a typo and allows the option to be enabled unexpectedly
> on pre-v19 publishers. The attached 0001 patch fixes this by correcting
> the version constant.
>
> Second, CREATE SUBSCRIPTION with copy_data=true and origin='none' currently
> fails when the publisher is running a version earlier than v19, although
> this combination should be supported. The failure occurs because the command
> issues a query calling pg_get_publication_sequences on the publisher,
> which does not exist before v19. The attached 0002 patch fixes this
> by skipping that query when the publisher runs an older version.
>

The changes look good to me though I haven't tested the patches. So,
please feel free to push after the relevant test. Thanks for catching
and fixing these issues.

-- 
With Regards,
Amit Kapila.