Horton

Re: Make COPY format extendable: Extract COPY TO format implementations

Junwang Zhao <zhjwpku@gmail.com>

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From: Junwang Zhao <zhjwpku@gmail.com>
To: Sutou Kouhei <kou@clear-code.com>
Cc: sawada.mshk@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Date: 2024-11-28T11:02:57Z
Lists: pgsql-hackers 
On Thu, Nov 28, 2024 at 2:16 PM Sutou Kouhei <kou@clear-code.com> wrote:
>
> Hi,
>
> In <CAEG8a3LUBcvjwqgt6AijJmg67YN_b_NZ4Kzoxc_dH4rpAq0pKg@mail.gmail.com>
>   "Re: Make COPY format extendable: Extract COPY TO format implementations" on Wed, 27 Nov 2024 19:49:17 +0800,
>   Junwang Zhao <zhjwpku@gmail.com> wrote:
>
> > I just gave this another round of benchmarking tests. I'd like to
> > share the number,
> > since COPY TO has some performance drawbacks, I test only COPY TO. I
> > use the run.sh Tomas provided earlier but use pgbench with a custom script, you
> > can find it here[0].
> >
> > 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
> >
> > 2 can be about -3%~+3% compared to 1, but what surprised me is that 3
> > is always better than 1 & 2.
> >
> > I reviewed the patch set of 3 and I don't see any magic.
> >
> > 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.
> >
> > [0]: https://github.com/pghacking/scripts/tree/main/extensible_copy
> > [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.

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

>
> Thanks,
> --
> kou



-- 
Regards
Junwang Zhao

Commits

  1. Refactor Copy{From|To}GetRoutine() to use pass-by-reference argument.

  2. Refactor COPY FROM to use format callback functions.

  3. Refactor COPY TO to use format callback functions.

  4. Another try to fix BF failure introduced in commit ddd5f4f54a.

  5. Revert "Refactor CopyReadAttributes{CSV,Text}() to use a callback in COPY FROM"

  6. Improve COPY TO performance when server and client encodings match

  7. Simplify signature of CopyAttributeOutCSV() in copyto.c

  8. Revert "Refactor CopyAttributeOut{CSV,Text}() to use a callback in COPY TO"

  9. Refactor CopyAttributeOut{CSV,Text}() to use a callback in COPY TO

  10. Refactor CopyReadAttributes{CSV,Text}() to use a callback in COPY FROM

  11. Add progress reporting of skipped tuples during COPY FROM.

  12. pgbench: Add \syncpipeline

  13. meson: Make gzip and tar optional

  14. Export the external file reader used in COPY FROM as APIs.