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

Dear Jonathan,

Thank you for reading the thread!

> 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.

The main reason was that there were no major complaints till now. This decision
followed the related discussion, for upgrading the subscriber [1]. As mentioned
there, current style might have more flexibility. Of course we could change that
if there are more opinions around here.
(I believe that this feature is useful for everyone, but changing the default may
affect others...)

As for the implementation, I did not check so deeply but there is no challenge.
We cannot change the style pg_dump option due to the pg_resetwal ordering issue[2],
but it option is not visible from users. I will check deeper when we want to do...

How do you think?

[1]: https://www.postgresql.org/message-id/CAA4eK1KD-hZ3syruxJA6fK-JtSBzL6etkwToPuTmVkrCvT6ASw%40mail.gmail.com
[2]: https://www.postgresql.org/message-id/TYAPR01MB58668C61A3C6EE82AE436C07F539A%40TYAPR01MB5866.jpnprd01.prod.outlook.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED