Re: apply_scanjoin_target_to_paths and partitionwise join

1. I think the order by pk frac limit plans had just to similar
performance behaviour for me to bother.
But afaics the main point of your proposal is not related to frac plans
at all.

2. We can't expect the optimizers to simply yield better results by
being given more options to be wrong. (Let me give a simple example:

This patch makes our lack of cross table cross column statistics worse.
We give it more opportunity to pick something horrible.

3. I dislike, that this patch makes much harder to debug, why no
partitionwise join is chosen.