Dear Shlok,
Thanks for testing the feature!
>
> I tested a test scenario:
> I started a new publisher with 'max_replication_slots' parameter set
> to '1' and created a streaming replication with the new publisher as
> primary node.
Just to confirm what you did - you set up a physical replication and the
target of pg_upgrade was set to the primary, right?
I think we can assume that new cluster (target of pg_upgrade) is not used yet.
The documentation describes the usage [1] and it says that we must initialize
the cluster (at step 4) and then run the pg_upgrade (at step 10).
Therefore I don't think we should document anything about it.
[1]: https://www.postgresql.org/docs/devel/pgupgrade.html#:~:text=Initialize%20the%20new%20PostgreSQL%20cluster
Best Regards,
Hayato Kuroda
FUJITSU LIMITED
