| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>, Ronald Cruz <cruz(at)rentec(dot)com>, pgsql-bugs(at)lists(dot)postgresql(dot)org, Peter Ford <pford(at)rentec(dot)com>, "Aaron J(dot) Garcia" <agarcia(at)rentec(dot)com> |
| Subject: | Re: Query result differences between PostgreSQL 17 vs 16 |
| Date: | 2025-02-26 07:03:30 |
| Message-ID: | CAMbWs4_SqFDZ1Mnp0Kmy-H2s7_-PdeuXva+kBG-jKSampoDHnw@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Wed, Feb 26, 2025 at 3:26 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Richard Guo <guofenglinux(at)gmail(dot)com> writes:
> > Here is the patch.
> Thanks for that. The code and comment added to
> restriction_is_always_true look good, but I can't help wondering
> whether we don't need the same in restriction_is_always_false.
> Not very sure what a query proving the need for that would
> look like, but leaving it asymmetric feels wrong.
Yeah, I think you are right. The thing here is that we don't have a
reliable way to determine if the input expression of a NullTest is
non-nullable if it's a clone clause. This applies to both
restriction_is_always_true and restriction_is_always_false. So I
think we should add the same check in restriction_is_always_false too.
I'll give it a try to find a query that shows this is necessary.
Thanks
Richard
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