On Tue, Aug 8, 2023 at 11:14 AM Tomas Vondra <tomas.von...@enterprisedb.com> wrote: > I agree this patch shouldn't make it harder to improve these cases, but > TBH I don't quite see which part of the patch would do that? Which bit > are you objecting to? If we decide to change how match_clause_to_index() > deals with these cases, to recognize them as index quals, the patch will > be working just fine.
Well, I also recently said that I think that it's important that you figure out a way to reliably avoid visibility checks, in cases where it can be avoided entirely -- since that can lead to huge savings in heap accesses. You haven't done that yet, but you really should look into it IMV. Assuming that that happens, then it immediately gives index scans a huge advantage over bitmap index scans. At that point it seems important to describe (in high level terms) where it is that the advantage is innate, and where it's just because we haven't done the required work for bitmap index scans. I became confused on this point myself yesterday. Admittedly I should have been able to figure it out on my own -- but it is confusing. > The only thing the patch does is it looks at clauses we decided not to > treat as index quals, and do maybe still evaluate them on index. And I > don't think I want to move these goalposts much further. Avoiding the need for visibility checks completely (in at least a subset of cases) was originally your idea. I'm not going to insist on it, or anything like that. It just seems like something that'll add a great deal of value over what you have already. -- Peter Geoghegan
