On Wed, Oct 13, 2010 at 5:54 PM, Robert Haas <robertmh...@gmail.com> wrote: > Or to put it more bluntly - what is the "problem with planner and hash > agg" that all of these functions need to solve? And why does it need > a flag in pg_proc? Why can't't we leave it to the individual > functions to perform a sort of one is needed? >
So I think that's backwards. Why is the function doing data manipulations like sorts that we usually put in the plan? Is there some some key meta information that should be flagged in pg_proc and general functionality the executor should be providing so that this general class of problems can be solved efficiently? Otherwise I fear lots of things we would expect to be efficient such as calculating the top, median, and last items in the same sort order would require three separate sorts of the same data. We have a planner capable of comparing sort orders and estimating the costs of different plans, we should be using it. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
