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

Sorry for the late reply.

On Wed, 06 Jul 2022 at 08:02, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Japin Li <japinli(at)hotmail(dot)com> writes:
>> [ v4-wal-level-documentation.patch ]
>
> Hm, I don't care for the wording here:
>
> + A precondition for using minimal WAL is to disable WAL archiving and
> + streaming replication by setting <varname>archive_mode</varname> to
> + <literal>off</literal>, and <xref linkend="guc-max-wal-senders"/> to
> + <literal>0</literal>.
>
> "Precondition" is an overly fancy word that makes things less clear
> not more so. Does it mean that setting wal_level = minimal will fail
> if you don't do these other things, or does it just mean that you
> won't be getting the absolute minimum WAL volume? If the former,
> I think it'd be better to say something like "To set wal_level to minimal,
> you must also set [these variables], which has the effect of disabling
> both WAL archiving and streaming replication."

Yeah, it's the former case.

>
> + 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>.
>
> I don't think this is great advice. It will encourage people to use
> wal_level = minimal even if they have other requirements that weigh
> against it. If they feel that their system is producing too much
> WAL, I doubt they'll have a hard time finding the wal_level knob.
>

Agreed. It isn't good advice. We can remove the suggestion.

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