On Sun, 24 May 2020 at 04:14, Dmitry Dolgov <9erthalion6@gmail.com> wrote: > > > On Fri, May 22, 2020 at 08:40:17AM +1200, David Rowley wrote: > > I imagine we'll set some required UniqueKeys during > > standard_qp_callback() > > In standard_qp_callback, because pathkeys are computed at this point I > guess?
Yes. In particular, we set the pathkeys for DISTINCT clauses there.
Actually I have some issues to understand from here, then try to read index
skip scan patch to fully understand what is the requirement, but that doesn't
get it so far[1]. So what is the "UniqueKeys" in "UniqueKeys during
standard_qp_callback()" and what is the "pathkeys" in "pathkeys are computed
at this point” means? I tried to think it as root->distinct_pathkeys, however I
didn't fully understand where root->distinct_pathkeys is used for as well.