> From: Simon Riggs [mailto:si...@2ndquadrant.com] > Sent: 07 December 2012 05:44 > To: David Rowley > Cc: pgsql-hackers@postgresql.org > Subject: Re: [HACKERS] Functional dependency in GROUP BY through JOINs > > On 5 December 2012 23:37, David Rowley <dgrowle...@gmail.com> wrote: > > > Though this plan might not be quite as optimal as it could be as it > > performs the grouping after the join. > > PostgreSQL always calculates aggregation as the last step.
I didn't know that was always the case, but it makes sense I guess. This is probably a bigger project than I imagined it would be then. > > It's a well known optimisation to push-down GROUP BY clauses to the lowest > level, but we don't do that, yet. > > You're right that it can make a massive difference to many queries. > I agree. Maybe it'd be something worthwhile for the future then. Perhaps if others agree it should be something to go on the TODO list? Regards David Rowley > -- > Simon Riggs http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers