Horton

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

Sutou Kouhei <kou@clear-code.com>

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From: Sutou Kouhei <kou@clear-code.com>
To: andrew@dunslane.net
Cc: michael@paquier.xyz, sawada.mshk@gmail.com, zhjwpku@gmail.com, nathandbossart@gmail.com, pgsql-hackers@postgresql.org
Date: 2024-01-24T14:17:26Z
Lists: pgsql-hackers 
Hi,

In <10025bac-158c-ffe7-fbec-32b42629121f@dunslane.net>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Wed, 24 Jan 2024 07:15:55 -0500,
  Andrew Dunstan <andrew@dunslane.net> wrote:

> 
> On 2024-01-24 We 03:11, Michael Paquier wrote:
>> On Wed, Jan 24, 2024 at 02:49:36PM +0900, Sutou Kouhei wrote:
>>> For COPY TO:
>>>
>>> 0001: This adds CopyToRoutine and use it for text/csv/binary
>>> formats. No implementation change. This just move codes.
>> 10M without this change:
>>
>>      format,elapsed time (ms)
>>      text,1090.763
>>      csv,1136.103
>>      binary,1137.141
>>
>> 10M with this change:
>>
>>      format,elapsed time (ms)
>>      text,1082.654
>>      csv,1196.991
>>      binary,1069.697
>>
>> These numbers point out that binary is faster by 6%, csv is slower by
>> 5%, while text stays around what looks like noise range.  That's not
>> negligible.  Are these numbers reproducible?  If they are, that could
>> be a problem for anybody doing bulk-loading of large data sets.  I am
>> not sure to understand where the improvement for binary comes from by
>> reading the patch, but perhaps perf would tell more for each format?
>> The loss with csv could be blamed on the extra manipulations of the
>> function pointers, likely.
> 
> 
> I don't think that's at all acceptable.
> 
> We've spent quite a lot of blood sweat and tears over the years to make COPY
> fast, and we should not sacrifice any of that lightly.

These numbers aren't reproducible. Because these benchmarks
executed on my normal machine not a machine only for
benchmarking. The machine runs another processes such as
editor and Web browser.

For example, here are some results with master
(94edfe250c6a200d2067b0debfe00b4122e9b11e):

Format,N records,Elapsed time (ms)
csv,10000000,1073.715
csv,10000000,1022.830
csv,10000000,1073.584
csv,10000000,1090.651
csv,10000000,1052.259

Here are some results with master + the 0001 patch:

Format,N records,Elapsed time (ms)
csv,10000000,1025.356
csv,10000000,1067.202
csv,10000000,1014.563
csv,10000000,1032.088
csv,10000000,1058.110


I uploaded my benchmark script so that you can run the same
benchmark on your machine:

https://gist.github.com/kou/be02e02e5072c91969469dbf137b5de5

Could anyone try the benchmark with master and master+0001?


Thanks,
-- 
kou

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.