I've spent quite a bit of time reviewing the window functions patch,
and I think it is now ready to commit, other than the documentation
(which I've not looked at yet at all). Attached is my current patch
against HEAD, sans documentation. This incorporates the recently
discussed aggregate-function API changes and support for tuplestore
trimming. There's a number of things that could be improved yet:
* we really ought to have some support for non-built-in
window functions
* I think the planner could be a bit smarter about when to
sort or not
* tuplestore_advance and related code really needs to be made
more efficient; it didn't matter much before but it does now
but I think these things can be worked on after the core patch is
committed.
regards, tom lane