Re: BUG #17495: Regression in 15beta1 when filtering subquery including row_number window function

On Wed, May 25, 2022 at 10:17 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> On Wed, 25 May 2022 at 12:51, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> >
> > On Tue, May 24, 2022 at 04:17:35PM +0000, PG Bug reporting form wrote:
> > > From testing with 15beta1, I think there is a regression in filtering a
> > > subquery using the result of the row_number window function. Here is
> the
> > > code:
> > >
> > > This was discovered by the tests for Sequel, a Ruby database access
> > > library.
> >
> > Inconsistency reproduced here, thanks for the detailed report and the
> > test case! I have added an open item:
> > https://wiki.postgresql.org/wiki/PostgreSQL_15_Open_Items
>
> Thanks for adding. I've put myself as the owner of this and will look
> at it soon.
>

This should be introduced in by 9d9c02cc. The rel of the subquery loses
its baserestrictinfo, which is (x_sequel_row_number_x <= 2), when
generating SubqueryScan access paths for it. As a result, the
WindowFunc target entry is removed as an unused targetlist item.

Thanks
Richard