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

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)

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