| From: | Hannu Krosing <hannuk(at)google(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(at)vondra(dot)me> |
| Cc: | Andreas Karlsson <andreas(at)proxel(dot)se>, Christoph Berg <myon(at)debian(dot)org>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, 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: | 2026-08-04 11:15:30 |
| Message-ID: | CAMT0RQQaj6wjpGwjYkFYL+iAHxhcNAZGstvGXqkocUwRPE-HCA@mail.gmail.com |
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On Tue, Aug 4, 2026 at 12:01 PM Tomas Vondra <tomas(at)vondra(dot)me> wrote:
>
> On 8/4/26 09:03, Hannu Krosing wrote:
> > On Mon, Aug 3, 2026 at 10:36 PM Tomas Vondra <tomas(at)vondra(dot)me> wrote:
...
> > It's a bit more complicated than that - we use zstd level 1 while the
> > default for the zstd command-line utility is level 3
> >
> > We should keep this in mind when running any manual compression tests.
> >
>
> Are you sure? Because I see xloginsert.c does this:
>
> len = ZSTD_compress(dest, COMPRESS_BUFSIZE, source, orig_len,
> ZSTD_CLEVEL_DEFAULT);
>
> and ZSTD_CLEVEL_DEFAULT (=3) is the constant from zstd library. So at
> least for WAL we should be using the "normal" compression level.
Yes, you are right.
I was confused by development-time list discussions which mostly
talked about using level=1, even though the default was 3 (or even 6)
---
Hannu
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