Re: User Interface for WAL usage data

On Fri, Apr 03, 2020 at 10:52:02AM +0530, Amit Kapila wrote:
> On Fri, Apr 3, 2020 at 10:41 AM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> >
> > > > > > > > WAL: records=2359 full page records=42 bytes=447788
> >
> > 1) records; 2) pages ("full page images"); 3) bytes
> >
> > That is exactly like sort (method/type/size) and hash (buckets/batches/size),
> > and *not* like buffers, which shows various values all in units of "pages".
> >
>
> The way you have written (2) appears to bit awkward. I would prefer
> "full page writes" or "full page images".

I didn't mean it to be the description used in the patch or anywhere else, just
the list of units.

I wonder if it should use colons instead of equals ? As in:
| WAL: Records: 2359 Full Page Images: 42 Size: 437kB

Note, that has: 1) two spaces; 2) capitalized "fields"; 3) size rather than
"bytes". That's similar to Buckets:
| Buckets: 1024 Batches: 1 Memory Usage: 44kB

I'm not sure if it should say "WAL: " or "WAL ", or perhaps "WAL: " If
there's no colon, then it looks like the first field is "WAL Records", but then
"size" isn't as tightly associated with WAL. It could say:
| WAL Records: n Full Page Images: n WAL Size: nkB

For comparison, buffers uses "equals" for the case showing multiple "fields",
which are all in units of pages:
| Buffers: shared hit=15 read=2006

Also, for now, the output can be in kB, but I think in the future we should
take a recent suggestion from Andres to make an ExplainPropertyBytes() which
handles conversion to and display of a reasonable unit.

--
Justin