Re: pgsql: Improve nbtree skip scan primitive scan scheduling.

On Sat, Apr 26, 2025 at 8:53 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:

> On Sat, Apr 26, 2025 at 10:39 PM Mark Dilger
> <mark(dot)dilger(at)enterprisedb(dot)com> wrote:
> > Peter, Matthias, thanks kindly for the good work on skipscans!
>
> Thanks!
>
> > I found a test case which fails after commit
> 21a152b37f36c9563d1b0b058fe1436baf578b4c. Please find a reproducible test
> case, attached.
>
> The bug isn't actually in commit
> 21a152b37f36c9563d1b0b058fe1436baf578b4c -- it's just an accident that
> the mechanism added by that commit happens to make your test case
> fail. The underlying issue was introduced in commit 8a510275, "Further
> optimize nbtree search scan key comparisons".
>
> This looks to have been a silly oversight in our handling of NULL
> tuple datums within _bt_check_compare. Attached provisional fix makes
> your test case pass.
>
> --
> Peter Geoghegan
>

I can confirm that your patch fixes the problem, having spent some four
hours trying to find other test cases which still fail, finding none.

Thank you for the quick reply, and again for the work on btree.

--
—
Mark Dilger
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