Re: pg_upgrade if 'postgres' database is dropped

Robert Haas wrote:
> On Tue, Nov 1, 2011 at 2:49 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > Robert Haas wrote:
> >> >> > It turns out there was only one place that expected a 1-1 mapping of old
> >> >> > and new databases (file transfer), so I just modified that code to allow
> >> >> > skipping a database in the new cluster that didn't exist in the old
> >> >> > cluster.
> >> >>
> >> >> Urp. ?But that means that if someone has any data in that database,
> >> >> pg_upgrade will basically eat it. ?That does not seem like a step
> >> >> forward.
> >> >
> >> > Please clarify? ?We already check that all the new cluster databases are
> >> > empty, so we are effectively skipping the transfering of files into
> >> > empty new cluster databases. ?It processes all old cluster databases and
> >> > forces a new cluster match --- it is only empty new cluster database
> >> > that are being skipped.
> >>
> >> Aren't you saying that if a postgres database exists in the old
> >> database (and potentially contains data) but is missing in the new
> >> database, we'll just fail to migrate it?
> >
> > No, the reverse. ?If the 'postgres' database exists in the new cluster,
> > but not in the old, we allow it to upgrade (we skip over the 'postgres'
> > database in the new cluster use the loop in the patch).
> 
> Oh, OK.  That seems fine - in fact, that seems perfect.
> 
> > Unless I am missing something. ?Did you see something odd in the patch
> > or in my wording?
> 
> Your wording confused me, but on further review I think I'm just
> easily confused.

The concept is pretty confusing and I had to think a while before I came
up with this approach.

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

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