| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Tomas Vondra <tomas(at)vondra(dot)me> |
| Cc: | wenhui qiu <qiuwenhuifx(at)gmail(dot)com>, Christoph Berg <myon(at)debian(dot)org>, Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>, Japin Li <japinli(at)hotmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, John Naylor <johncnaylorls(at)gmail(dot)com> |
| Subject: | Re: WAL compression setting after PostgreSQL LZ4 default change |
| Date: | 2026-07-16 22:00:10 |
| Message-ID: | allUaU_1C1-sSwh8@paquier.xyz |
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| Lists: | pgsql-hackers |
On Thu, Jul 16, 2026 at 05:00:58PM +0200, Tomas Vondra wrote:
> My opinion is "on" should be a generic "pick compression" option, giving
> the database the mandate to pick an algorithm. A user who wants a
> particular algorithm can specify that.
>
> The only reason why "on" means "pglz" is that initially that was the
> only supported algorithm (until PG 15). But if we supported multiple
> algorithms from the beginning, would we do it that way? I don't think
> so. We'd either not have "on" at all, or it'd pick the best algorithm.
I have worked on both things. I cannot go back in time, but I suspect
that I would have picked up pglz as default for "on" out of safety as
a start point.
A few releases later, where I know that many deployments are using
either lz4 or zstd and nobody has complained back, I see a much better
argument in changing the behavior of "on" to mean "zstd" -> "lz4" ->
"pglz" in order of priority, based on how efficient these algorithms
are known to be.
--
Michael
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