Re: pg_stat_bgwriter.buffers_backend is pretty meaningless (and more?)

At Tue, 12 Jul 2022 19:18:22 -0700, Andres Freund <andres(at)anarazel(dot)de> wrote in
> Hi,
>
> On 2022-07-13 11:00:07 +0900, Kyotaro Horiguchi wrote:
> > I imagined to use B_INVALID as a kind of "default" partition, which
> > accepts all unknown backend types.
>
> There shouldn't be any unknown backend types. Something has gone wrong if we
> get far without a backend type set.
>
>
> > We can just ignore that values but then we lose the clue for malfunction of
> > stats machinery. I thought that that backend-type as the sentinel for
> > malfunctions. Thus we can emit logs instead.
> >
> > I feel that the stats machinery shouldn't stop the server as possible,
> > or I think it is overreaction to abort for invalid values that can be
> > easily coped with.
>
> I strongly disagree. That just ends up with hard to find bugs.

I was not sure about the policy on that since, as Melanie (and I)
mentioned, GetBackendTypeDesc() is gracefully treating invalid values.

Since both of you are agreeing on this point, I'm fine with
Assert()ing assuming that GetBackendTypeDesc() (or other places
backend-type is handled) is modified to behave the same way.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center