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

On Mon, Jul 18, 2022 at 6:27 PM Japin Li <japinli(at)hotmail(dot)com> wrote:

>
> On Tue, 19 Jul 2022 at 03:58, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > On Fri, Jul 15, 2022 at 09:29:20PM +0800, Japin Li wrote:
> >>
> >> On Fri, 15 Jul 2022 at 08:49, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >> > On Tue, Jul 5, 2022 at 08:02:33PM -0400, Tom Lane wrote:
> >> >> "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."
> >> >
> >> > I have created the attached patch to try to improve this text.
> >>
> >> IMO we can add the following sentence for wal_level description, since
> >> if wal_level = minimal and max_wal_senders > 0, we cannot start the
> database.
> >>
> >> To set wal_level to minimal, you must also set max_wal_senders to 0,
> >> which has the effect of disabling both WAL archiving and streaming
> >> replication.
> >
> > Okay, text added in the attached patch.
>
> Thanks for updating the patch! LGTM.
>
>
+0.90

Consider changing:

"makes any base backups taken before this unusable"

to:

"makes existing base backups unusable"

As I try to justify this, though, it isn't quite true, maybe:

"makes point-in-time recovery, using existing base backups, unable to
replay future WAL."

David J.