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
