Horton

Re: [EXTERNAL]Re: BUG #19094: select statement on postgres 17 vs postgres 18 is returning different/duplicate results

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Lori Corbani <Lori.Corbani@jax.org>, Thomas Munro <thomas.munro@gmail.com>, "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Date: 2025-10-30T03:24:49Z
Lists: pgsql-bugs

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  1. Disable parallel plans for RIGHT_SEMI joins

On Thu, Oct 30, 2025 at 1:00 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Richard Guo <guofenglinux@gmail.com> writes:
> > After spending a bit more time experimenting, I couldn't find a better
> > query that shows a large difference between the costs of the PRSJ plan
> > and the patched version plan.  So I've updated the test case to use
> > the aforementioned one.  I also removed the reset statements and
> > switched to the begin/rollback pattern for the test case.

> v2 patch LGTM.

Thanks for the review.  I've pushed v2 and backpatched it to v18.

Thanks to Lori for the report.

- Richard