Re: Short-circuit sort_inner_and_outer if there are no mergejoin clauses

Quickly looking at the function, the patch would make it more apparent that the function is a noop when mergeclause_list is empty.

I haven't looked closely to see if creating unique path nonetheless is useful somewhere else.

It seems that one of the side effects of create_unique_path is that it
caches the generated unique path so that we can avoid creating it
repeatedly for the same rel.  But this does not seem to justify calling

Please add to the next commitfest.

If the patch shows some measurable performance improvement, it would become more attractive.

I doubt that there is measurable performance improvement.  But I found
that throughout the run of the regression tests, sort_inner_and_outer is
called a total of 44,424 times.  Among these calls, there are 11,064
instances where mergeclause_list is found to be empty.  This accounts
for ~1/4.  I think maybe this suggests that it's worth the shortcut as
the patch does.

Thanks