Re: Tidy fill hstv array (src/backend/access/heap/pruneheap.c)

From: "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>
To: John Naylor <johncnaylorls(at)gmail(dot)com>
Cc: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Tidy fill hstv array (src/backend/access/heap/pruneheap.c)
Date: 2024-03-04 06:18:43
Message-ID: 2D923D65-5D29-475E-BF9C-990623BC4CF5@yandex-team.ru
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> On 14 Jan 2024, at 18:55, John Naylor <johncnaylorls(at)gmail(dot)com> wrote:
>
> On Sat, Jan 13, 2024 at 9:36 PM Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> wrote:
>>
>> Em ter., 9 de jan. de 2024 às 06:31, John Naylor <johncnaylorls(at)gmail(dot)com> escreveu:
>
>>> This just moves an operation from one place to the other, while
>>> obliterating the explanatory comment, so I don't see an advantage.
>>
>> Well, I think that is precisely the case for using memset.
>> The way initialization is currently done is much slower and harmful to the branch.
>> Of course, the gain should be small, but it is fully justified for switching to memset.
>
> We haven't seen any evidence or reasoning for that. Simple
> rules-of-thumb are not enough.
>

Hi Ranier,

I’ll mark CF entry [0] as “Returned with Feedback”. Feel free to reopen item in this CF or submit to the next, if you want to continue working on this.

I took a glance into the patch, and I would agree that setting field nonzero values with memset() is somewhat unusual. Please provide stronger evidence to do so.

Thanks!

Best regards, Andrey Borodin.

[0] https://commitfest.postgresql.org/47/4734/

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