Date: Fri, 31 Jul 2026 15:10:29 +0200
From: Christoph Berg <myon@debian.org>
To: Tomas Vondra <tomas@vondra.me>
Cc: wenhui qiu <qiuwenhuifx@gmail.com>,
	Laurenz Albe <laurenz.albe@cybertec.at>,
	Andres Freund <andres@anarazel.de>,
	Jelte Fennema-Nio <postgres@jeltef.nl>,
	Michael Paquier <michael@paquier.xyz>,
	Japin Li <japinli@hotmail.com>, Fujii Masao <masao.fujii@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	John Naylor <johncnaylorls@gmail.com>
Subject: Re: WAL compression setting after PostgreSQL LZ4 default change
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Mail-Followup-To: Christoph Berg <myon@debian.org>,
	Tomas Vondra <tomas@vondra.me>, wenhui qiu <qiuwenhuifx@gmail.com>,
	Laurenz Albe <laurenz.albe@cybertec.at>,
	Andres Freund <andres@anarazel.de>,
	Jelte Fennema-Nio <postgres@jeltef.nl>,
	Michael Paquier <michael@paquier.xyz>,
	Japin Li <japinli@hotmail.com>, Fujii Masao <masao.fujii@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	John Naylor <johncnaylorls@gmail.com>
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Re: Tomas Vondra
> The one thing I don't quite like on the patch is that it actually
> defaults to zstd before lz4. Which seems to not quite match the intent
> to have both toast and wal default to the same thing. I don't have a
> strong preference for either algorithm, but I also don't see why to put
> zstd before lz4. I'd do it the other way around, i.e. lz4->zstd->pglz.

About the intent, I see it more as "PG19 is the version that switched
away from pglz". It could be lz4 for both, or it could be lz4 for
TOAST and zstd for WAL.

There is some value in having both the same, but I'd defer to what the
others are saying.

I don't have a preference either way. This was just the last thing
expressed here. (If we can't agree on that point, could we please
still make the change and just toss a coin about this "bit"? :D)

Christoph