Re: Fix documentation for max_wal_size and min_wal_size

On 2023/04/22 17:39, Michael Paquier wrote:
> On Tue, Apr 18, 2023 at 01:46:21AM -0700, sirisha chamarthi wrote:
>> "The default size is 80MB. However, if you have changed the WAL segment size
>> from the default of 16MB with the initdb option --wal-segsize, it will be
>> five times the segment size."
>
> Yes, I think that something close to that would be OK. Do others have
> any comments or extra ideas to offer?

If the WAL segment size is changed from the default value of 16MB during initdb,
the value of min_wal_size in postgresql.conf is set to five times the new segment
size by initdb. However, pg_settings.boot_val (the value of min_wal_size used
when the parameter is not otherwise set) is still 80MB. So if pg_settings.boot_val
should be documented as the default value, the current description seems OK.

Or we can clarify that the default value of min_wal_size is 80MB, but when initdb
is run with a non-default segment size, the value in postgresql.conf is changed
to five times the new segment size? This will help users better understand
the behavior of the setting and how it is affected by changes made during initdb.

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION