Subject: Re: change default default_toast_compression to lz4?

From: Michael Paquier <[email-masked]>
Date: Fri, 27 Feb 2026 10:10:20 +0900

On Tue, Feb 24, 2026 at 10:52:39PM +0100, Peter Eisentraut wrote:
> Your patch is adding documentation for the configure option --without-lz4,
> but you are leaving the documentation for --with-lz4 in place.  You should
> delete the latter.

Ah, right.  This is what we have done for ICU in fcb21b3acdcb.  While
--with-lz4 is still allowed for backward-compatibility, we show only
--without-icu in the output of configure --help.  Reflecting the
documentation to show up the same contents as --help makes sense.

Could you update the patch, Euler?  This includes the blip in
meson.build regarding the addition of not_found_dep not really
required.
--
Michael

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From: Michael Paquier <[email-masked]>
Date: Wed, 4 Mar 2026 13:09:40 +0900

> documentation to show up the same contents as --help makes sense.

It would have been a waste to not see this change happening, so I have
looked a bit more in depth at it.  You are right that we should remove
the reference to --with-lz4, but it seems to me that this should apply
to all the references of the switch we have in the docs.  The change
in meson.build was not necessary.  Another thing not yet included was
the mandatory autoreconf.  With all that done, applied.

Now, let's see how much this breaks the buildfarm..  Because things
will break.  I'll send a poke to the buildfarm mailing list.
--
Michael

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From: Jelte Fennema-Nio <[email-masked]>
Date: Wed, 4 Mar 2026 08:15:50 +0100

On Wed, 4 Mar 2026 at 06:05, Tom Lane <[email-masked]> wrote:
>
> Michael Paquier <[email-masked]> writes:
> > Now, let's see how much this abreaks the buildfarm..  Because things
> I don't think this idea is really fully baked yet.  What happens
> if I build with liblz4, and run for a while with that so that
> there are lz4-compressed TOAST values, and then try to update
> to a build without LZ4?

That doesn't seem like a new problem to me. That's already possible
since PG14. To me it actually seems more likely to happen, because we
default to allowing builds without lz4 (which we stopped doing on
master). The fact that we haven't had (many) people complain indicates
to me that it isn't a big problem in practice.