Danil Anisimow <anisimow(dot)d(at)gmail(dot)com> writes:
> In some cases, the planner underestimates FULL JOIN.
Perhaps.
> Are these simple changes enough to improve this situation?
This looks like an entirely ad-hoc change, one that could make as
many cases worse as it makes better. If you want to argue for
merging it, you at least need to provide some evidence for thinking
it's a more accurate model of what will happen. And adjust the
nearby comment to explain it.
regards, tom lane