Feedback-ID: i0fe9450f:Fastmail
Date: Wed, 8 Jul 2026 07:26:34 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Japin Li <japinli@hotmail.com>
Cc: Fujii Masao <masao.fujii@gmail.com>, wenhui qiu <qiuwenhuifx@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	John Naylor <johncnaylorls@gmail.com>,
	Christoph Berg <myon@debian.org>
Subject: Re: WAL compression setting after PostgreSQL LZ4 default change
Message-ID: <ak19GnnQE46n6myy@paquier.xyz>
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On Fri, Jul 03, 2026 at 04:38:06PM +0800, Japin Li wrote:
> On Fri, 03 Jul 2026 at 11:58, Fujii Masao <masao.fujii@gmail.com> wrote:
>> On Wed, Jul 1, 2026 at 8:45=E2=80=AFAM Michael Paquier <michael@paquier.=
xyz> wrote:
>>>
>>> On Tue, Jun 30, 2026 at 06:25:09PM +0800, wenhui qiu wrote:
>>> > The recent PostgreSQL commit changes the default TOAST compression to=
 lz4
>>> > when LZ4 support is available, based on the rationale that LZ4 is gen=
erally
>>> > more efficient than pglz in terms of CPU usage and compression
>>> > ratio.  Given that, should we also consider changing the default
>>> > compression method used by wal_compression =3D on from pglz to lz4?
>>>
>>> "on" is just a backward-compatible value, so we could let it as-is.
>>
>> Yes, so +1 to leaving "on" as it is. Making its meaning depend on
>> the build options seems very confusing. Users who want lz4 or zstd
>> can simply specify those methods explicitly instead of using "on".
>=20
> Understood.  I'll withdraw this from the CommitFest.

I disagree.  The whole argument is that most users don't bother
changing the defaults.  Here, a change between lz4/zstd and pglz is
like day and night; folks are going to see improvements all the time
if we switch to a better default when we can, in terms of CPU, memory
and IO.
--
Michael

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