Hi Nikhil,
From the pgupgrade docs:
> 9. Prepare for standby server upgrades
>
> If you are upgrading standby servers using methods outlined in section
> Step 11, verify that the old standby servers are caught up by running
> pg_controldata against the old primary and standby clusters. Verify
> that the “Latest checkpoint location” values match in all clusters.
> (There will be a mismatch if old standby servers were shut down before
> the old primary or if the old standby servers are still running.)
> Also, make sure wal_level is not set to minimal in the postgresql.conf
> file on the new primary cluster.
(source: https://www.postgresql.org/docs/devel/pgupgrade.html)
I'm a new contributor so please forgive me if I'm on the wrong track,
but if you follow this step, won't you also be ensuring that replication
slots do not need to be migrated, since you've just ensured that standby
clusters are in sync with the primary cluster? Please let me know if I'm
missing anything!
Thank You,
Jack DeVries