Re: WAL compression setting after PostgreSQL LZ4 default change

On Fri, Jul 03, 2026 at 04:38:06PM +0800, Japin Li wrote:
> On Fri, 03 Jul 2026 at 11:58, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>> On Wed, Jul 1, 2026 at 8:45 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>>>
>>> On Tue, Jun 30, 2026 at 06:25:09PM +0800, wenhui qiu wrote:
>>> > The recent PostgreSQL commit changes the default TOAST compression to lz4
>>> > when LZ4 support is available, based on the rationale that LZ4 is generally
>>> > more efficient than pglz in terms of CPU usage and compression
>>> > ratio. Given that, should we also consider changing the default
>>> > compression method used by wal_compression = on from pglz to lz4?
>>>
>>> "on" is just a backward-compatible value, so we could let it as-is.
>>
>> Yes, so +1 to leaving "on" as it is. Making its meaning depend on
>> the build options seems very confusing. Users who want lz4 or zstd
>> can simply specify those methods explicitly instead of using "on".
>
> Understood. I'll withdraw this from the CommitFest.

I disagree. The whole argument is that most users don't bother
changing the defaults. Here, a change between lz4/zstd and pglz is
like day and night; folks are going to see improvements all the time
if we switch to a better default when we can, in terms of CPU, memory
and IO.
--
Michael