Re: [BUG] false positive in bt_index_check in case of short 4B varlena datum

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Andres Freund <andres(at)anarazel(dot)de>, Alexander Lakhin <exclusion(at)gmail(dot)com>, Michael Zhilin <m(dot)zhilin(at)postgrespro(dot)ru>, pgsql-bugs(at)postgresql(dot)org, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>
Subject: Re: [BUG] false positive in bt_index_check in case of short 4B varlena datum
Date: 2026-05-12 10:22:59
Message-ID: CAPpHfdtBHt=BBaQX73D-cVhiKn4SUWF4fMLedqF0nEZzBNqL4w@mail.gmail.com
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On Tue, May 12, 2026 at 12:17 PM Andrey Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
> > On 9 May 2026, at 04:07, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> >
> > On Mon, May 04, 2026 at 10:20:04AM +0500, Andrey Borodin wrote:
> >> However, I'd like to note that (VARSIZE_1B() < TOAST_INDEX_TARGET) is
> >> constantly true for 8Kb+ pages.
> >
> > How much slower? I cannot imagine that it matters much in this code
> > path, but you are getting me worried.
>
>
> I think there will be no performance difference.
>
> Change proposed by Alexander only prevents use of VARSIZE() against datum
> that is VARSIZE_1B. AFAICS no actual behavior would change.
>
> On some occasions we would have to normilize less tuples.

Any objections if I push and backpatch this?

------
Regards,
Alexander Korotkov
Supabase

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