Edmund Horner <ejrh00@gmail.com> writes:
> For the forward scan, I seem to recall, from your merge join example,
> that it's useful to set the pathkeys even when there are no
> query_pathkeys. We just have to unconditionally set them so that the
> larger plan can make use of them.
No. Look at indxpath.c: it does not worry about pathkeys unless
has_useful_pathkeys is true, and it definitely does not generate
pathkeys that don't get past truncate_useless_pathkeys. Those
functions are responsible for worrying about whether mergejoin
can use the pathkeys. It's not tidpath.c's job to outthink them.
regards, tom lane