Re: pg_upgrade and logical replication

On Mon, Sep 25, 2023 at 05:35:18AM +0000, Hayato Kuroda (Fujitsu) wrote:
> Personally, I prefer to change max_logical_replication_workers. Mainly there are
> two reasons:
> 
> 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.
--
Michael