Re: postgres FROM clause problem (GROUP BY subquestion)

On Thu, Mar 11, 2004 at 09:43:57 +0100,
Paolo Tavalazzi <ptavalazzi(at)charta(dot)it> wrote:
> Alle 19:12, mercoledì 10 marzo 2004, hai scritto:
> > On Wed, Mar 10, 2004 at 18:33:41 +0100,
> >
> > Paolo Tavalazzi <ptavalazzi(at)charta(dot)it> wrote:
> > > I don't know what to make, help me please!
> > >
> > > Another question, in 7.4 GROUP BY clause not guarantee the ordering of
> > > result. Can I desable the new group by algorithm to maintain the
> > > coherence whit the programs that I have in production with pg_7.3
> >
> > GROUP BY never guarenteed an order. That this happened in 7.3 was an
> > implementation detail. If you want a specific order you need to use an
> > ORDER BY clause.
>
>
> Seeing that GROUP BY in 7.3 required sorting the input data to bring group members together,
> this guaranteed to me also the order of the attributes in GROUP BY clause.

This might be a language difference. You weren't guarenteed (or promised)
that the output would be sorted. It just happened that way because of how
the database implemented the group by. By reading the source code for
that version it would be possible to determine that the output would
always be sorted. However, that could change at any upgrade or if you
switched databases.