| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, hu_yajun(at)qq(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #18442: Unnecessary Sort operator in indexScan Plan |
| Date: | 2024-04-22 06:16:08 |
| Message-ID: | CAMbWs4-jV8sr7pR3wzhe0YngYjuqbxXkbfbRqTnaZ1iikcPgCQ@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Mon, Apr 22, 2024 at 9:53 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> Presumably, if a=b is strict then effectively nothing could match as
> the strict qual ensures NULLs never match and the IS NULL only allows
> NULLs.
Yeah, in this case the two restrictions are self-inconsistent and that
makes the relation dummy and need not be scanned. I think the planner
would figure that out in relation_excluded_by_constraints when the GUC
constraint_exclusion is on, but in a different way than ECs.
Thanks
Richard
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