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

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
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: 2026-06-11 07:57:32
Message-ID: 405E8B45-0D6B-48AC-97F9-38C6B08766F7@yandex-team.ru
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> On 12 May 2026, at 13:22, Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
>
> 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?

Kind reminder, let's resolve this thread. Thank you!

Best regards, Andrey Borodin.

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