From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roel Janssen <roel@gnu.org>
Subject: Re: postgres 9.6.2 update breakage
Date: Mon, 15 May 2017 08:48:47 +0200
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To: Jan Nieuwenhuizen <janneke@gnu.org>
Cc: guix-devel@gnu.org, Pg Hackers <pgsql-hackers@postgresql.org>


Jan Nieuwenhuizen writes:

> Roel Janssen writes:
>
>> So, it would be something like:
>> postgres pg_upgrade \
>> ...
>
> It's great to have a recipe `that works', so thanks!
>
> However, whether or not we automate this, I cannot help to wonder if
> we should support downgrading -- at least to the previous version
> in this case?
>
> If I'm not mistaken, everything else in GuixSD will run if I select a
> previous system generation in Grub...except for this?
>
> Is involving postgres developers an option, I'm sure a least one of
> the postgresql hackers[cc] are already looking at Guix[SD]?
>
> Greetings,
> janneke

Ah yes, I see the point.  The problem here is that when new features are
added to PostgreSQL, and you rely upon them in your database schemas,
downgrading will most likely cause loss of information.

Maybe we need a wrapper script that also makes a dump of all of the
data?  Now that could become a security hole.

Or the wrapper script warns about this situation, and recommends making
a (extra) back-up of the database before upgrading.

Or.. the upgrade is something a user should do explicitly, basically
giving up on the "just works" concept.  Guix already provides a nice way
to get the previous version of the exact binaries used before the
upgrade.

Kind regards,
Roel Janssen