Re: WAL usage calculation patch

On Tue, Apr 7, 2020 at 12:00 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
>
> 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.

The parsability problem Justin was mentioning is only due to "full
page writes", so we could use "full_page_writes" or "fpw" instead and
remove the extra spaces. There would be a small discrepancy with the
verbose autovacuum log, but there are others differences already.

I'd slightly in favor of "fpw" to be more concise. Would that be ok?