Horton

Re: [HACKERS] Custom compression methods

x4mmm@yandex-team.ru

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From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alexander Korotkov <a.korotkov@postgrespro.ru>, David Steele <david@pgmasters.net>, Ildus Kurbangaliev <i.kurbangaliev@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2020-12-29T17:48:49Z
Lists: pgsql-hackers

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> 28 дек. 2020 г., в 11:14, Andrey Borodin <x4mmm@yandex-team.ru> написал(а):
> 
>> Thanks for the patch.  Maybe we can allow setting custom compression
>> methods for wal compression as well.
> 
> No, unfortunately, we can't use truly custom methods. Custom compression handlers are WAL-logged. So we can use only static set of hardcoded compression methods.

So, I've made some very basic benchmarks on my machine [0].
With pglz after checkpoint I observe 1146 and 1225 tps.
With lz4 I observe 1485 and 1524 tps.
Without wal_compression I see 1529 tps.

These observations can be explained with plain statement: pglz is bottleneck on my machine, lz4 is not.
While this effect can be reached with other means [1] I believe having lz4 for WAL FPIs would be much more CPU efficient.

FPA lz4 for WAL FPI patch v17. Changes: fixed some frontend issues, added some comments.

Best regards, Andrey Borodin.

[0] https://yadi.sk/d/6y5YiROXQRkoEw
[1] https://www.postgresql.org/message-id/flat/25991595-1848-4178-AA57-872B10309DA2%40yandex-team.ru#e7bb0e048358bcff281011dcf115ad42

Commits

  1. docs: Update TOAST storage docs for configurable compression.

  2. Further tweaking of pg_dump's handling of default_toast_compression.

  3. Fix interaction of TOAST compression with expression indexes.

  4. Tidy up more loose ends related to configurable TOAST compression.

  5. Short-circuit slice requests that are for more than the object's size.

  6. Mostly-cosmetic adjustments of TOAST-related macros.

  7. Remove useless configure probe for <lz4/lz4.h>.

  8. Error on invalid TOAST compression in CREATE or ALTER TABLE.

  9. docs: Fix omissions related to configurable TOAST compression.

  10. More code cleanup for configurable TOAST compression.

  11. Bring configure support for LZ4 up to snuff.

  12. Make compression.sql regression test independent of default.

  13. Use valid compression method in brin_form_tuple

  14. Fix up pg_dump's handling of per-attribute compression options.

  15. Allow configurable LZ4 TOAST compression.

  16. Fix inconsistencies in the code

  17. Mostly-cosmetic improvements in memory chunk header alignment coding.

  18. Allow numeric to use a more compact, 2-byte header in many cases.