I have two PostgreSQL databases both running version 9.1.24 (no logical replication available). DB-A delivers changes to DB-B using londiste (skytools 3). I have almost zero knowledge of pgq/pgqd and londiste.
My goal is to upgrade both databases to PG 12.1 with almost zero-downtime. So, without going into details, I'm going to shutdown both databases, run pg_upgrade and start'em again.
Should it work seamlessly? Or am I missing some compatibility problem or anything like that?
I'm going to test the procedure, so I'm going to find out my answer anyway, but I'd like to get some wisdom from the almighty Internet.
Many people suggest I upgrade to PG15.
We have many databases, not only this two. Half of them are at 12.1 and the other half are at 9.1.24. Plus, we have tools that have some tweaks made to deal with version differences. So I want to upgrade everything to one version (12.1) and then plan to upgrade to the latest stable version available. This is maybe not the ideal situation but is easier and safer for us to walk this road