David Rowley <dgrowle...@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