On Thu, Nov 3, 2022 at 4:26 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > * I don't believe you can prove anything from an ALL_SUBLINK SubPlan, > because it will return true if the sub-query returns zero rows, no > matter what the testexpr is. (Maybe if you could prove the sub-query > does return a row, but I doubt it's worth going there.)
Thanks for pointing this out. You're right. I didn't consider the case that the subplan produces zero rows. In this case ALL_SUBLINK will always return true, and ANY_SUBLINK will always return false. That makes ALL_SUBLINK not strict, and ANY_SUBLINK can be strict only at top level. * You need to explicitly check the subLinkType; as written this'll > consider EXPR_SUBLINK and so on. I'm not really on board with > assuming that nothing bad will happen with sublink types other than > the ones the code is expecting. > Yes, I need to check for ANY_SUBLINK and ROWCOMPARE_SUBLINK here. The testexpr is only meaningful for ALL/ANY/ROWCOMPARE, and ALL_SUBLINK has been proven not strict. * It's not apparent to me that it's okay to pass down "top_level" > rather than "false". Maybe it's all right, but it could do with > a comment. The 'top_level' param is one point that I'm not very confident about. I've added comments in the v2 patch. Thanks for reviewing this patch! Thanks Richard
v2-0001-Check-SubPlan-clause-for-nonnullable-rels-Vars.patch
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