On Wed, 9 Apr 2025 at 18:48, Richard Guo <guofengli...@gmail.com> wrote: > > On Thu, Mar 20, 2025 at 3:02 PM David Rowley <dgrowle...@gmail.com> wrote: > > For making this work, I think the attached should be about the guts of > > the code changes. I didn't look at the comments. Right now I can't > > think of any reason why this can't be done, but some experimentation > > might reveal some reason that it can't. > > I conducted some experiments, and I'm afraid it's not safe to consider > Memoize for semi or anti joins, unless the inner side is provably > unique. As an example, please consider:
Thanks for checking that. I was just looking at the spot you'd need to adjust to prove the inner_unique for anti joins and found I'd written: /* * XXX it may be worth proving this to allow a Memoize to be * considered for Nested Loop Semi/Anti Joins. */ Looks like I must have known that at one point in time... > Perhaps we could spend some planner cycles proving inner_unique for > anti joins, so that Memoize nodes can be considered for them? Worth a try. It should be pretty easy to enable, as far as I can see. It might just be a case of shuffling the cases around in the switch statement in add_paths_to_joinrel(). David
