Re: Todo: Teach planner to evaluate multiple windows in the optimal order

David Rowley <dgrowleyml@gmail.com> writes:
> Ideally, our sort costing would just be better, but I think that
> raises the bar a little too high to start thinking of making
> improvements to that for this patch.

It's trickier than it looks, cf f4c7c410e.  But if you just want
to add a small correction based on number of columns being sorted
by, that seems within reach.  See the comment for cost_sort though.
Also, I suppose for incremental sorts we'd want to consider only
the number of newly-sorted columns, but I'm not sure if that info
is readily at hand either.

            regards, tom lane