Re: WAL compression setting after PostgreSQL LZ4 default change

From: Tomas Vondra <tomas(at)vondra(dot)me>
To: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Cc: Ken Marshall <ktm(at)rice(dot)edu>, Hannu Krosing <hannuk(at)google(dot)com>, Andreas Karlsson <andreas(at)proxel(dot)se>, Christoph Berg <myon(at)debian(dot)org>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, Andres Freund <andres(at)anarazel(dot)de>, Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>, Michael Paquier <michael(at)paquier(dot)xyz>, Japin Li <japinli(at)hotmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, John Naylor <johncnaylorls(at)gmail(dot)com>
Subject: Re: WAL compression setting after PostgreSQL LZ4 default change
Date: 2026-08-07 10:22:36
Message-ID: 438ce1b2-54d5-4730-99aa-47b9b8f97a19@vondra.me
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On 8/7/26 10:34, Andrey Borodin wrote:
> Tomas, thanks for benchmarks! I agree that x2 WAL reduction actually makes Zstd
> a good default when wal_compression = on.
>
>> On 7 Aug 2026, at 13:23, Tomas Vondra <tomas(at)vondra(dot)me> wrote:
>>
>> 8.25% postgres libzstd.so.1.5.7 [.] ZSTD_createDCtx_internal
>
> (sorry for offtopic)
>
> That's an interesting profile.
> Along with published patch to retain compression context we can also
> retain decompression context. But that's for PG20 anyway.
>

Right, there may be a way to make the zstd decompression cheaper. But
it's too late for PG19.

regards

--
Tomas Vondra

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