Horton

Re: WAL usage calculation patch

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: amit.kapila16@gmail.com
Cc: dilipbalaut@gmail.com, rjuju123@gmail.com, kuntalghosh.2007@gmail.com, masao.fujii@oss.nttdata.com, kirill.bychik@gmail.com, pgsql-hackers@postgresql.org, thomas.munro@gmail.com
Date: 2020-04-03T01:45:35Z
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.

Hello.

The v13 patch seems failing to apply on the master.

At Fri, 3 Apr 2020 06:37:21 +0530, Amit Kapila <amit.kapila16@gmail.com> wrote in 
> On Thu, Apr 2, 2020 at 8:06 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> > On Thu, Apr 2, 2020 at 6:41 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > 4.
> > > /* # of WAL full page image generated */
> > > Can we change it to "/* # of WAL full page image records generated */"?
> >
> > IMHO, "# of WAL full-page image records" seems like the number of wal
> > record which contains the full-page image.
> >
> 
> I think this resembles what you have written here.
> 
> >  But, actually, this is the
> > total number of the full-page images, not the number of records that
> > have a full-page image.
> >
> 
> We count this when forming WAL records.  As per my understanding, all
> three counters are about WAL records.  This counter tells how many
> records have full page images and one of the purposes of having this
> counter is to check what percentage of records contain full page
> image.

Aside from which is desirable or useful, acutually XLogRecordAssemble
in v13-0001 counts the number of attached images then XLogInsertRecord
sums up the number of images in pgWalUsage.wal_num_fpw.

FWIW, it seems to me that the main concern here is the source of WAL
size. If it is the case I think that the number of full page image is
more useful.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center