Hello, I recently encountered a case where partial indexes were surprisingly not being used. The issue is that predtest doesn't understand how boolean values and IS <boolean> expressions relate.
For example if I have: create table foo(i int, bar boolean); create index on foo(i) where bar is true; then this query: select * from foo where i = 1 and bar; doesn't use the partial index. Attached is a patch that solves that issue. It also teaches predtest about quite a few more cases involving BooleanTest expressions (e.g., how they relate to NullTest expressions). One thing I could imagine being an objection is that not all of these warrant cycles in planning. If that turns out to be the case there's not a particularly clear line in my mind about where to draw that line. As noted in a TODO in the patch itself, I think it may be worth refactoring the test_predtest module to run the "x, y" case as well as the "y, x" case with a single call so as to eliminate a lot of repetition in clause/expression test cases. If reviewers agree that's desirable, then I could do that as a precursor. Regards, James Coleman
v1-0001-Teach-predtest-about-IS-NOT-bool-proofs.patch
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