Re: WAL usage calculation patch

On Wed, Apr 22, 2020 at 2:27 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Apr 22, 2020 at 9:25 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> >
> > On Wed, Apr 22, 2020 at 09:15:08AM +0530, Amit Kapila wrote:
> > > > > > And add the acronym to the docs:
> > > > > >
> > > > > > $ git grep 'full page' '*/explain.sgml'
> > > > > > doc/src/sgml/ref/explain.sgml:      number of records, number of full page writes and amount of WAL bytes
> > > > > >
> > > > > > "..full page writes (FPW).."
> > > > >
> > > > > Indeed!  Fixed (using lowercase to match current output).
> > > >
> > > > I searched through the documentation and AFAICS most of occurances of
> > > > "full page" are follwed by "image" and full_page_writes is used only
> > > > as the parameter name.
> > > >
> > > > I'm fine with fpw as the acronym, but "fpw means the number of full
> > > > page images" looks odd..
> > > >
> > >
> > > I don't understand this.  Where are we using such a description of fpw?
> >
> > I suggested to add " (FPW)" to the new docs for "explain(wal)"
> > But, the documentation before this commit mostly refers to "full page images".
> > So the implication is that maybe we should use that language (and FPI acronym).
> >
>
> I am not sure if it matters that much. I think we can use "full page
> writes (FPW)" in this case but we should be consistent wherever we
> refer it in the WAL usage context and I think we already are, if not
> then let's be consistent.

I agree that full page writes can be used in this case, but I'm
wondering if that can be misleading for some reader which might e.g.
confuse with the full_page_writes GUC.  And as Justin pointed out, the
documentation for now usually mentions "full page image(s)" in such
cases.