On 5 December 2012 23:37, David Rowley <dgrowleyml(at)gmail(dot)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