Date: Wed, 8 Jul 2026 00:58:59 +0200
From: Christoph Berg <myon@debian.org>
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: Michael Paquier <michael@paquier.xyz>, Japin Li <japinli@hotmail.com>,
	Fujii Masao <masao.fujii@gmail.com>,
	wenhui qiu <qiuwenhuifx@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	John Naylor <johncnaylorls@gmail.com>
Subject: Re: WAL compression setting after PostgreSQL LZ4 default change
Message-ID: <ak2Es90xR35P2jPB@msg.df7cb.de>
Mail-Followup-To: Christoph Berg <myon@debian.org>,
	Jelte Fennema-Nio <postgres@jeltef.nl>,
	Michael Paquier <michael@paquier.xyz>,
	Japin Li <japinli@hotmail.com>, Fujii Masao <masao.fujii@gmail.com>,
	wenhui qiu <qiuwenhuifx@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	John Naylor <johncnaylorls@gmail.com>
References: 
 <CAGjGUAL1b=Mwd1SCvLbo+fivEr9KDpFcu4jmqKCZXwT=6CiiGQ@mail.gmail.com>
 <akRVDdkH1ntCpTBv@paquier.xyz>
 <CAHGQGwGv8FLvOkTm3dpTsvt70puYpzKOmq3-YQSOpDCdZ8gyaQ@mail.gmail.com>
 <SY7PR01MB1092134E0AD4108661A3A65F8B6F42@SY7PR01MB10921.ausprd01.prod.outlook.com>
 <ak19GnnQE46n6myy@paquier.xyz>
 <CAGECzQQ+OWP+yafyUp_g3DDY-cKYoyATUEJRkgatLU6n70kH_A@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <CAGECzQQ+OWP+yafyUp_g3DDY-cKYoyATUEJRkgatLU6n70kH_A@mail.gmail.com>
Archived-At: 
 <https://www.postgresql.org/message-id/ak2Es90xR35P2jPB%40msg.df7cb.de>
Precedence: bulk

Re: Jelte Fennema-Nio
> A small correction though: "on" isn't the default. The default is
> "off". So this would only impact users who changed the setting in
> their cluster to "on" at some point in the past when lz4/zstd support
> did not exist yet. So we wouldn't be changing the default. We'd be
> changing the behavior for people who changed their default setting at
> some point.

If someone just wants compression and not bother with the ugly details
of compression algorithms, they might be inclined to just say "on".
By labelling one of the choices with this "easy" value, we are
effectively promoting pglz as a good choice. (I'm definitely one of
those people, if you give me too many options, I will look for some
hint what to do or walk away. Now 3 isn't "too many" but you get the
idea.)

I would like to see "on" to be moved to some better value (likely lz4,
like toast compression), and if some day, there is yet a better
choice, we should move it again.

Christoph