Re: WAL usage calculation patch

On Mon, Apr 06, 2020 at 02:34:36PM +0530, Amit Kapila wrote:
> On Mon, Apr 6, 2020 at 1:53 PM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
> >
> > On Mon, Apr 06, 2020 at 08:55:01AM +0530, Amit Kapila wrote:
> > >
> > > Here, we are not displaying Buffers related data, so why do we think
> > > it is important to display WAL data? I see some point in displaying
> > > Buffers and WAL data in a vacuum (verbose), but I feel it is better to
> > > make a case for both the statistics together rather than just
> > > displaying one and leaving other. I think the other change related to
> > > autovacuum stats seems okay to me.
> >
> > One thing is that the amount of WAL, and more precisely FPW, is quite
> > unpredictable wrt. vacuum and even more anti-wraparound vacuum, so this is IMHO
> > a very useful metric.
> >
>
> I agree but we already have a way via pg_stat_statements to find it if
> the metric is so useful.
>

Agreed.

>
> > That being said I totally agree with you that both
> > should be displayed. Should I send a patch to also expose it?
> >
>
> I think this should be a separate proposal. Let's not add things
> unless they are really essential. We can separately discuss of
> enhancing vacuum verbose for Buffer and WAL usage stats and see if
> others also find that information useful. I think you can send a
> patch by removing the code I mentioned above if you agree. Thanks for
> working on this.

Thanks! v15 attached.