Hi, On Mon, Nov 09, 2026 at 10:20:06AM -0500, Tom Lane wrote: > Bertrand Drouvot <[email protected]> writes: > > Maybe we could shorten the sentence, something like: > > > " > > Users issuing ALTER SUBSCRIPTION ... SET (slot_name = ..., two_phase = > > true) must > > ensure that the replacement slot already has two_phase enabled, as the > > apply worker > > no longer enables it automatically. > > " > > Huh. That seems like a bug: you asked for two_phase = true and > didn't get it. I'm fine with an implementation restriction that > we won't change the two_phase property of an existing slot, but > shouldn't this command throw an error if what you asked for > doesn't match what the slot can do?
The current documentation [1] says: " When altering the slot_name, the failover and two_phase property values of the named slot may differ from the counterpart failover and two_phase parameters specified in the subscription. When creating the slot, ensure the slot properties failover and two_phase match their counterpart parameters of the subscription. " So the possibility of such a mismatch is documented, although I agree it is not ideal. The original doc warning was added after a discussion [2] about failover, where we chose documenting the limitation over adjusting the replacement slot at every apply worker startup. The two_phase wording was added later because the same mismatch was already possible. I don't think we considered checking the replacement slot and reporting an error on a mismatch. That would require connecting to the publisher and inspecting the replacement slot, but it would certainly make the command less surprising. So, I agree that reporting an error on a mismatch would be better. Amit, what do you think? I can have a look at preparing a patch if we want to go that way. [1]: https://www.postgresql.org/docs/devel/sql-altersubscription.html [2]: https://postgr.es/m/flat/CAA4eK1Jd9dk=5potkm9p4eyyqyzlxe-anlzhrueljzzsclz...@mail.gmail.com#aa6428a6ba8d5f3244960df5666ab590 Regards, -- Bertrand Drouvot PostgreSQL Contributors Team RDS Open Source Databases Amazon Web Services: https://aws.amazon.com
