Horton

Re: WAL usage calculation patch

Julien Rouhaud <rjuju123@gmail.com>

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From: Julien Rouhaud <rjuju123@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Dilip Kumar <dilipbalaut@gmail.com>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Fujii Masao <masao.fujii@oss.nttdata.com>, Kirill Bychik <kirill.bychik@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@gmail.com>
Date: 2020-04-23T05:31:47Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Change the display of WAL usage statistics in Explain.

  2. Cosmetic fixups for WAL usage work.

  3. Allow parallel create index to accumulate buffer usage stats.

  4. Allow autovacuum to log WAL usage statistics.

  5. Add the option to report WAL usage in EXPLAIN and auto_explain.

  6. Allow pg_stat_statements to track WAL usage statistics.

  7. Add infrastructure to track WAL usage.

  8. Include information on buffer usage during planning phase, in EXPLAIN output, take two.

  9. Include information on buffer usage during planning phase, in EXPLAIN output.

  10. Allow parallel vacuum to accumulate buffer usage.

  11. Allow pg_stat_statements to track planning statistics.

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.