Re: Doc about how to set max_wal_senders when setting minimal wal_level

On Fri, 04 Mar 2022 at 14:05, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> At Fri, 04 Mar 2022 12:18:29 +0800, Japin Li <japinli(at)hotmail(dot)com> wrote in
>>
>> On Thu, 03 Mar 2022 at 12:10, Japin Li <japinli(at)hotmail(dot)com> wrote:
>>
>> Attach v3 patch to fix missing close varname tag.
>
> + A precondition for using minimal WAL is to disable WAL archiving and
> + streaming replication by setting <xref linkend="guc-max-wal-senders"/>
> + to <literal>0</literal>, and <varname>archive_mode</varname>
> + to <literal>off</literal>.
>
> It is a bit odd that the features to stop and the corresponding GUCs
> are written irrespectively. It would be better they're in the same
> order.
>

Thanks for your review. Modified.

> + servers. If setting <varname>max_wal_senders</varname> to
> + <literal>0</literal> consider also reducing the amount of WAL produced
> + by changing <varname>wal_level</varname> to <literal>minimal</literal>.
>
> Those who anively follow this suggestion may bump into failure when
> arhive_mode is on. Thus archive_mode is also worth referred to. But,
> anyway, IMHO, it is mere a performance tips that is not necessarily
> required in this section, or even in this documentaiotn. Addtion to
> that, if we write this for max_wal_senders, archive_mode will deserve
> the similar tips but I think it is too verbose. In short, I think I
> would not add that description at all.
>

It already has a tip about wal_level for archive_mode [1], IIUC.

archive_mode cannot be enabled when wal_level is set to minimal.

[1] https://www.postgresql.org/docs/devel/runtime-config-wal.html#GUC-ARCHIVE-MODE

--
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.