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Re: Bug in ALTER SUBSCRIPTION ... SERVER / ... CONNECTION with broken old server

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Amit Kapila <amit.kapila16@gmail.com>, Chao Li <li.evan.chao@gmail.com>
Cc: Zsolt Parragi <zsolt.parragi@percona.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Ajin Cherian <itsajin@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2026-06-22T21:10:25Z
Lists: pgsql-hackers 
On Fri, 2026-06-19 at 11:40 -0700, Jeff Davis wrote:
>   * add an escape hatch for users to turn off tablesync slots so that
> DROP will always succeed

It looks like SLOT_NAME=NONE is already supposed to be this escape
hatch, even for tablesync slots. From the docs:

"To proceed in this situation, first disable the subscription by
executing ALTER SUBSCRIPTION ... DISABLE, and then disassociate it from
the replication slot by executing ALTER SUBSCRIPTION ... SET (slot_name
= NONE). After that, DROP SUBSCRIPTION will no longer attempt any
actions on a remote host."

https://www.postgresql.org/docs/devel/sql-dropsubscription.html

But DropSubscription() only does the early-return if there are no
tablesync slots. If there are tablesync slots, it still tries to
contact the publisher, even if SLOT_NAME=NONE.

>   * consider it an unimportant edge case and leave it the way it is
> (with 0001 & 0002 already done), and close the open item

I plan to close this open item, and treat the above as a pre-existing
bug, which may require a backport.

Regards,
	Jeff Davis

Commits

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

  1. Avoid errors during DROP SUBSCRIPTION when slot_name is NONE.

  2. Avoid errors during ALTER SUBSCRIPTION.

  3. Check retain_dead_tuples for ALTER SUBSCRIPTION ... SERVER.

  4. Allow multiple xacts during table sync in logical replication.