Re: pg_upgrade and logical replication

On Thu, Sep 21, 2023 at 02:35:55PM +0530, Amit Kapila wrote:
> It is because after upgrade of both publisher and subscriber, the
> subscriptions won't work. Both publisher and subscriber should work,
> otherwise, the logical replication set up won't work. I think we can
> probably do this, if we can document clearly how the user can make
> their logical replication set up work after upgrade.

Yeah, well, this comes back to my original point that the upgrade of
publisher nodes and subscriber nodes should be treated as two
different problems or we're mixing apples and oranges (and a node
could have both subscriber and publishers). While being able to
support both is a must, it is going to be a two-step process at the
end, with the subscribers done first and the publishers done after.
That's also kind of the point that Julien makes in top message of this
thread.

I agree that docs are lacking in the proposed patch in terms of
restrictions, assumptions and process flow, but taken in isolation the
problem of the publishers is not something that this patch has to take
care of. I'd certainly agree that it should mention, at least and if
merged first, to be careful if upgrading the publishers as its slots
are currently removed.
--
Michael