On Wed, May 16, 2012 at 12:50 AM, Volker Grabsch <v...@notjusthosting.com> wrote: > I propose the following general optimization: If all window > functions are partitioned by the same first field (here: id), > then any filter on that field should be executed before > WindowAgg. So a query like this:
I think that's possible. Currently the planner doesn't think any qualification from the upper query can be pushed down to a query that has a window function. It would be possible to let it push down if the expression matches PARTITION BY expression. However, the challenge is that a query may have a number of window functions that have different PARTITION BY expressions. At the time of pushing down in the planning, it is not obvious which window function comes first. One idea is to restrict such optimization in only case of single window function, and the other is to make it generalize and cover a lot of cases. That said, our planner on window functions has a lot of improvement to be done. Every kind of optimization I see is what I raised above; they can be done easily by hacking in a small case, or they can be done by generalizing for the most of cases. My understanding is our project tends to like the latter and it takes a little time but covers more use cases. Thanks, -- Hitoshi Harada -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
