So in the grouping sets patch post, I said:
>> There is one current weakness which I don't see a good solution for:
>> the planner code still has to pick a single value for group_pathkeys
>> before planning the input path. This means that we sometimes can't
>> choose a minimal set of sorts, because we may have chosen a sort
>> order for a grouping set that should have been hashed,
Of course there is one good solution, which is to have query_planner
take a set of acceptable output sort orders rather than just a single
one.
How wild an idea is this? I guess a possible hazard is an increase in
the number of possible mergejoin paths to consider. What other possible
issues are there?
--
Andrew (irc:RhodiumToad)