Re: WAL usage calculation patch

On Tue, Apr 7, 2020 at 3:30 PM Peter Eisentraut
<peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>
> On 2020-04-07 04:12, Amit Kapila wrote:
> > On Mon, Apr 6, 2020 at 10:01 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> >>
> >> On Mon, Apr 06, 2020 at 05:01:30PM +0200, Peter Eisentraut wrote:
> >>> I noticed in some of the screenshots that were tweeted that for example in
> >>>
> >>> WAL: records=1 bytes=56
> >>>
> >>> there are two spaces between pieces of data. This doesn't match the rest of
> >>> the EXPLAIN output. Can that be adjusted?
> >>
> >> We talked about that here:
> >> https://www.postgresql.org/message-id/20200402054120.GC14618%40telsasoft.com
> >>
> >
> > Yeah. Just to brief here, the main reason was that one of the fields
> > (full page writes) already had a single space and then we had prior
> > cases as mentioned in Justin's email [1] where we use two spaces which
> > lead us to decide using two spaces in this case.
>
> We also have existing cases for the other way:
>
> actual time=0.050..0.052
> Buffers: shared hit=3 dirtied=1
>

Buffers case is not the same because 'shared' is used for 'hit',
'read', 'dirtied', etc. However, I think it is arguable.

> The cases mentioned by Justin are not formatted in a key=value format,
> so it's not quite the same, but it also raises the question why they are
> not.
>
> Let's figure out a way to consolidate this without making up a third format.
>

Sure, I think my intention is to keep the format of WAL stats as close
to Buffers stats as possible because both depict I/O and users would
probably be interested to check/read both together. There is a point
to keep things in a format so that it is easier for someone to parse
but I guess as these as fixed 'words', it shouldn't be difficult
either way and we should give more weightage to consistency. Any
suggestions?

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com