Re: Wrong results from self-join elimination with different restriction operators

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> 于2026年10月15日周四 04:56写道：
>
> If we're going to refuse that, I wonder if we couldn't simplify
> match_unique_clauses a great deal: just insist that the two OpExpr
> clauses be equal(), after the ChangeVarNodes substitution on the outer
> clause. Your proposal already breaks commuted-clause cases, which
> seem like the only justification for all the futzing around with left
> and right operands. I doubt that detecting that is of any real-world
> value anyway.
>

Attached is v2, following your suggestion to compare the complete
clauses with equal() after the ChangeVarNodes substitution. I also
removed the test added in v1.

I ran the regression tests and found no plan differences. This
suggests the existing tests don't cover cases where matching commuted
restrictions enables self-join elimination.

--
Thanks,
Tender Wang