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From: Aleksander Alekseev <aleksander@timescale.com>
Date: Tue, 5 Nov 2024 17:53:07 +0300
Message-ID: <CAJ7c6TOoJ_zBHOymO9iCzXx=PsEpx=ijXpfLEF0uC1_CcCDhtA@mail.gmail.com>
Subject: Re: COPY performance on Windows
To: "Ryohei Takahashi (Fujitsu)" <r.takahashi_2@fujitsu.com>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
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Hi Ryohei,

Thanks for the patch. Here are my two cents.

> I noticed that the COPY performance on PG 17.0 Windows is worse than PG 16.4.
>
>  [...]
>
> By applying the attached patch to PG 17.0, the copy result is 401.5s.

So we are trading a potential 3.8% speedup in certain environments for
the increased code complexity due to a couple of added #ifdef's here.

If we really want to do this, firstly the patch should have detailed
comments in front of #ifdefs so that in 10+ years from now someone who
didn't read this thread would know what they are for.

Secondly, more detailed research should be made on how this patch
affects the performance on Windows depending on the software version
and particular choice of hardware. Perhaps what you found is not the
only and/or the most important bottleneck. Your patch may (or may not)
cause performance degradation in other setups.

Last but not least one should double check that this will not cause
performance degradation on *nix systems.

To be honest, personally I wouldn't bother because of 3.8% speedup at
best (for 10+% - maybe). This being said perhaps you and other people
on the mailing list (reviewers, committers) feel otherwise.

-- 
Best regards,
Aleksander Alekseev