Re: pg_migrator issue with contrib

Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Tom Lane wrote:
> >> There is a different problem though: sometimes the recommended fix for
> >> contrib-module incompatibilities is to load the new contrib module into
> >> the target database before trying to load your old dump file.  (We told
> >> people to do that for 8.2->8.3 tsearch2, for example.)  In the
> >> pg_migrator context there is no way to insert the new contrib module
> >> first, and also no way to ignore the duplicate-object errors that you
> >> typically get while loading the old dump.
> 
> > Ah, OK, interesting.  We could have pg_migrator detect this issue and
> > fail right away with a message indicating pg_migrator cannot be used
> > unless those objects are dumped manually and the /contrib removed.
> 
> How would it detect it?  I think the only thing you could do is
> hard-wire tests for specific objects, which is klugy and doesn't
> extend to third-party modules that you don't know about.

Yep, that is the only way.  The good news is that we are not modifying
any data so it is just a detection issue, i.e. it would not destabilize
pg_migrator's operation.

> In most cases where there are major incompatibilities, attempting to
> load the old dump file would fail anyway, so I don't think pg_migrator
> really needs any hard-wired test.  It's the minor changes that are
> risky.  I think ultimately the burden for those has to be on the module
> author: he has to either avoid cross-version incompatibilities or make
> sure they will fail safely.

Yep.

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