Re: BUG #16497: old and new pg_controldata WAL segment sizes are invalid or do not match

Greetings,

* Bruce Momjian (bruce(at)momjian(dot)us) wrote:
> On Thu, Jun 18, 2020 at 11:41:53AM -0400, Stephen Frost wrote:
> > Sure, most options to initdb need to be the same between the old cluster
> > and the new cluster, but this specific option doesn't have to be, since
> > we require that it's a cleanly shut down cluster, so why are we
> > complaining about it if it's different..?
>
> Did you not read my previous email that we might have added this so we
> can upgrade replicas?

I don't see how this option is related to dealing with replicas..?

> I am sure I can dig out the commit that added
> this and find the original cause, but running pg_upgrade on replicas is
> enough of a reason to me.

pg_upgrade can't be run on replicas, so I don't understand what you're
referring to here.. The 'upgrading replicas' process that involves
rsync also requires everything to have been shut down cleanly.

> Yeah, we could add a flag to pg_upgrade to
> allow this if you are not upgrading replicas, but why bother? It might
> even work if you create the new replicas with the same WAL segment size,
> but why add complexity for pg_upgrade, which is already complex enough.

Users already have to deal with various options that need to be
configured to match up between the primary and replicas, so this really
seems like it's entirely independent of pg_upgrade and isn't something
pg_upgrade needs to be worrying about..

Thanks,

Stephen