Re: Functional dependency in GROUP BY through JOINs

On 5 December 2012 23:37, David Rowley <dgrowleyml@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.

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.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services