From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Peter Eisentraut <peter@eisentraut.org>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: change default default_toast_compression to lz4?
In-reply-to: <ic2tfxsj73zdmhs3ogigph3k6no6rym3hiu2xcdjyb5zagkix3@64nnst4scso3>
References: <435df33a-129e-4f0c-a803-f3935c5a5ecb@eisentraut.org>
 <ic2tfxsj73zdmhs3ogigph3k6no6rym3hiu2xcdjyb5zagkix3@64nnst4scso3>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Fri, 21 Nov 2025 11:10:14 -0500"
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Date: Fri, 21 Nov 2025 11:16:21 -0500
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Andres Freund <andres@anarazel.de> writes:
> On 2025-11-21 12:11:38 +0100, Peter Eisentraut wrote:
>> I suppose one issue is that lz4 support is not compiled-in by default, =
but
>> in practice most users will have it.  The default could be lz4 if lz4
>> support is built, otherwise pglz.  This would be similar to other param=
eters
>> where the default is the best one depending on the build configuration.

> I think we should mark lz4 as a default-required dependency if we change=
 the
> default. That way one needs to explicitly opt into a build that won't be
> compatible with existing data directories created (due to pre-existing l=
z4 .

Agreed --- we should make it act like icu or readline, you have to
opt out.  (I'm not voting one way or the other on changing the
default, but if we do we should do it that way.)

			regards, tom lane