Re: pg_migrator to /contrib in a later 9.0 beta

Robert Haas wrote:
> > My guess is that when that happens we would just document/enforce it
> > in
> > pg_migrator, but I don't see why we would arbitrarily restrict
> > pg_migrator at this time.
> 
> Yeah. It's not uncommon to want to upgrade by more than one release at
> a time, and I haven't heard any reason why we should arbitrarily
> refuse to support that. Of course we may need to do that eventually
> for some specific reason, but it seems like we should only consider
> imposing such a restriction in the face of a tangible need.

Yea, we will need it one day, and if pg_migrator was more tied to system
table changes and such, it would be smart to do it now, but if you look
at the C code you will see that most of the effort is related to
compatibility with the _target_ major version, not the _source_ major
version, and by definition, the source major version never changes as we
release new major versions.  (Remember, pg_dump already does the heavy
lifting of moving our database schema to the new major version.)

A lot of understanding pg_migrator is understanding the source/target
matrix of compatibility --- something we as a community have not thought
about very much at this level.

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