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

On Thu, Jun 18, 2020 at 01:42:41PM -0400, Stephen Frost wrote:
> > > > 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..
> > 
> > Do you know why we require this step?
> > 
> >     https://www.postgresql.org/docs/12/pgupgrade.html
> >     
> >     Also, change wal_level to replica in the postgresql.conf file on
> >     the new primary cluster.
> 
> Well, we'll need wal_level to be at least replica if we're going to have
> replicas streaming from the primary..

But how do they have replicas if wal_level = minimum?  Also, why not
higher replication levels?  Should we adjust that doc text?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee