On Wed, Jul 18, 2012 at 09:36:51AM -0400, Robert Haas wrote:
> On Tue, Jul 17, 2012 at 6:02 PM, Bruce Momjian <br...@momjian.us> wrote:
> > However, I have two ideas.  First, I don't know _why_ the
> > primary/standby would be any different after pg_upgrade, so I added the
> > documentation mention because I couldn't _guarantee_ they were the same.
> > Actually, if people can test this, we might be able to say this is safe.
> >
> > Second, the user files (large) are certainly identical, it is only the
> > system tables (small) that _might_ be different, so rsync'ing just those
> > would add the guarantee, but I know of no easy way to rsync just the
> > system tables.
> I'm scratching my head in confusion here.  After pg_upgrade, the
> master is a completely new cluster.  The system catalog contents are
> completely different, and so are things like the database system
> identifier and the WAL position - yeah, the latter is approximately
> the same, but almost doesn't count except in horseshoes.  Obviously
> any attempt to replay WAL from the new cluster on the old cluster is
> doomed to failure, at least unless we do a bunch more engineering here
> that hasn't really been thought about yet.

No, the point is they run pg_upgrade on the stopped primary and stopped
standbys.  Are those the same?  I am not really sure.

  Bruce Momjian  <br...@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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