Horton

Re: WAL usage calculation patch

Julien Rouhaud <rjuju123@gmail.com>

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From: Julien Rouhaud <rjuju123@gmail.com>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Justin Pryzby <pryzby@telsasoft.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>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@gmail.com>
Date: 2020-04-07T14:23:47Z
Lists: pgsql-hackers

Commits

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  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 Tue, Apr 7, 2020 at 12:00 PM Peter Eisentraut
<peter.eisentraut@2ndquadrant.com> wrote:
>
> On 2020-04-07 04:12, Amit Kapila wrote:
> > On Mon, Apr 6, 2020 at 10:01 PM Justin Pryzby <pryzby@telsasoft.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?