Horton

Re: WAL usage calculation patch

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: 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: 2020-04-06T09:04:36Z
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 Mon, Apr 6, 2020 at 1:53 PM Julien Rouhaud <rjuju123@gmail.com> wrote:
>
> On Mon, Apr 06, 2020 at 08:55:01AM +0530, Amit Kapila wrote:
> >
> > Here, we are not displaying Buffers related data, so why do we think
> > it is important to display WAL data?  I see some point in displaying
> > Buffers and WAL data in a vacuum (verbose), but I feel it is better to
> > make a case for both the statistics together rather than just
> > displaying one and leaving other.  I think the other change related to
> > autovacuum stats seems okay to me.
>
> One thing is that the amount of WAL, and more precisely FPW, is quite
> unpredictable wrt. vacuum and even more anti-wraparound vacuum, so this is IMHO
> a very useful metric.
>

I agree but we already have a way via pg_stat_statements to find it if
the metric is so useful.

>  That being said I totally agree with you that both
> should be displayed.  Should I send a patch to also expose it?
>

I think this should be a separate proposal.  Let's not add things
unless they are really essential.  We can separately discuss of
enhancing vacuum verbose for Buffer and WAL usage stats and see if
others also find that information useful.  I think you can send a
patch by removing the code I mentioned above if you agree.  Thanks for
working on this.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com