Date: Fri, 29 Nov 2024 10:07:13 +0900 (JST)
Message-Id: <20241129.100713.891341792145967125.kou@clear-code.com>
To: zhjwpku@gmail.com
Cc: sawada.mshk@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Subject: Re: Make COPY format extendable: Extract COPY TO format
 implementations
From: Sutou Kouhei <kou@clear-code.com>
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Hi,

In <CAEG8a3+BmNeEOLmApOCyktYbiZW=s95dvpod_FxJS+3ieVZQ7w@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Thu, 28 Nov 2024 19:02:57 +0800,
  Junwang Zhao <zhjwpku@gmail.com> wrote:

>> > I tested 3 branches:
>> >
>> > 1. the master branch
>> > 2. all v26 patch sets applied
>> > 3. Emitting JSON to file using COPY TO v13 patch set[1], this add some
>> > if branch in CopyOneRowTo, so I was expecting this slower than master
>> >
>> > You can see the detailed results here[2], I can not upload files so I
>> > just shared the google doc link, ping me if you can not open the link.
>> >
>> > [1]: https://www.postgresql.org/message-id/CACJufxH8J0uD-inukxAmd3TVwt-b-y7d7hLGSBdEdLXFGJLyDA%40mail.gmail.com
>> > [2]: https://docs.google.com/spreadsheets/d/1wJPXZF4LHe34X9IU1pLG7rI9sCkSy2dEkdj7w7avTqM/edit?usp=sharing
>>
>> Thanks for sharing your numbers.
>>
>> 1. and 2. shows that there is at least no significant
>> performance regression.
> 
> Agreed.

Can we focus on only 1. and 2. in this thread?

>> I see the patch set of 3. and I think that the result
>> (there is no performance difference between 1. and 3.) isn't
>> strange. The patch set adds some if branches but they aren't
>> used with "text" format at least in per row process.
> 
> It is not used in "text" format, but it adds some assembly code
> to the CopyOneRowTo function, so this will have some impact
> on the cpu i cache I guess.
> 
> There is difference between 1 and 3, 3 is always better than 1
> upto 4% improvement

Can we discuss 1. and 3. in the [1] thread?

(Anyway, we may want to confirm whether these numbers are
reproducible or not as the first step.)

>                      I forgot to mention that the comparisons
> are in *sheet2*.

Thanks. I missed it.


Thanks,
-- 
kou