Re: upper planner path-ification

>>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

Tom> Hm. That's a hangover from when query_planner also gave back a
Tom> Plan (singular) rather than a set of Paths. I don't see any
Tom> fundamental reason why we couldn't generalize it to be a list of
Tom> potentially useful output orderings rather than just one. But I'm
Tom> a bit concerned about the ensuing growth in planning time; is it
Tom> really all that useful?

The planning time growth is a possible concern, yes. The potential gain
is eliminating one sort step, in the case when the input has a usable
sorted path but grouping_planner happens not to ask for it (when there's
more than just a single rollup, the code currently asks for one of the
sort orders pretty much arbitrarily since it has no real way to know
otherwise). Whether that would justify it... I don't know. Maybe that's
one to save for later to see if there's any feedback from actual use.

--
Andrew (irc:RhodiumToad)