Re: pg_upgrade libraries check

On Fri, May 25, 2012 at 11:08:10PM -0400, Bruce Momjian wrote:
> On Fri, May 25, 2012 at 10:20:29AM -0400, Andrew Dunstan wrote:
> > pg_upgrade is a little over-keen about checking for shared libraries
> > that back functions. In particular, it checks for libraries that
> > support functions created in pg_catalog, even if pg_dump doesn't
> > export the function.
> >
> > The attached patch mimics the filter that pg_dump uses for functions
> > so that only the relevant libraries are checked.
> >
> > This would remove the need for a particularly ugly hack in making
> > the 9.1 backport of JSON binary upgradeable.
>
> Andrew is right that pg_upgrade is overly restrictive in checking _any_
> shared object file referenced in pg_proc.  I never expected that
> pg_catalog would have such references, but in Andrew's case it does, and
> pg_dump doesn't dump them, so I guess pg_upgrade shouldn't check them
> either.
>
> In some sense this is a hack for the JSON type, but it also gives users
> a way to create shared object references in old clusters that are _not_
> checked by pg_upgrade, and not migrated to the new server, so I suppose
> it is fine.

OK, now I know it is _not_ fine.  :-(

I just realized the problem as part of debugging the report of a problem
with plpython_call_handler():

    http://archives.postgresql.org/pgsql-hackers/2012-03/msg01101.php
    http://archives.postgresql.org/pgsql-bugs/2012-05/msg00205.php

The problem is that functions defined in the "pg_catalog" schema, while
no explicitly dumped by pg_dump, are implicitly dumped by things like
CREATE LANGUAGE plperl.

I have added a pg_upgrade C comment documenting this issue in case we
revisit it later.

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

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