RE: pg_upgrade and logical replication

Dear Michael,

> > 1. Your approach must be back-patched to older versions which support logical
> >    replication feature, but the oldest one (PG10) has already been
> unsupported.
> >    We should not modify such a branch.
>
> This suggestion would be only for HEAD as it changes the behavior of -b.
>
> > 2. Also, "max_logical_replication_workers = 0" approach would be consistent
> >    with what we are doing now and for upgrade of publisher patch.
> >    Please see the previous discussion [1].
>
> Yeah, you're right.  Consistency would be good across the board, and
> we'd need to take care of the old clusters as well, so the GUC
> enforcement would be needed as well.  It does not strike me that this
> extra IsBinaryUpgrade would hurt anyway?  Forcing the hand of the
> backend has the merit of allowing the removal of the tweak with
> max_logical_replication_workers at some point in the future.

Hmm, our initial motivation is to suppress registering the launcher, and adding
a GUC setting is sufficient for it. Indeed, registering a launcher may be harmful,
but it seems not the goal of this thread (changing -b workflow in HEAD is not
sufficient alone for the issue). I'm not sure it should be included in patch sets
here.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED