Re: [PoC] pg_upgrade: allow to upgrade publisher node

On Wed, Aug 2, 2023 at 7:46 AM Jonathan S. Katz <jkatz(at)postgresql(dot)org> wrote:
>
> Can I take this a step further on the user interface and ask why the
> flag would be "--include-logical-replication-slots" vs. being enabled by
> default?
>
> Are there reasons why we wouldn't enable this feature by default on
> pg_upgrade, and instead (if need be) have a flag that would be
> "--exclude-logical-replication-slots"? Right now, not having the ability
> to run pg_upgrade with logical replication slots enabled on the
> publisher is a a very big pain point for users, so I would strongly
> recommend against adding friction unless there is a very large challenge
> with such an implementation.
>

Thanks for acknowledging the need/importance of this feature. I also
don't see a need to have such a flag for pg_upgrade. The only reason
why one might want to exclude slots is that they are not up to date
w.r.t WAL being consumed. For example, one has not consumed all the
WAL from manually created slots or say some subscription has been
disabled before shutdown. I guess in those cases we should give an
error to the user and ask to remove such slots before the upgrade
because anyway, those won't be usable after the upgrade.

Having said that, I think we need a flag for pg_dump to dump the slots.

--
With Regards,
Amit Kapila.