Horton

Re: track_planning causing performance regression

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: "Tharakan, Robins" <tharar@amazon.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-06-29T23:00:19Z
Lists: pgsql-hackers 
Hi,

On 2020-06-29 09:05:18 +0200, Julien Rouhaud wrote:
> I can't reproduce this on my laptop, but I can certainly believe that
> running the same 3 queries using more connections than available cores
> will lead to extra overhead.

> I disagree with the conclusion though.  It seems to me that if you
> really have this workload that consists in these few queries and want
> to get better performance, you'll anyway use a connection pooler
> and/or use prepared statements, which will make this overhead
> disappear entirely, and will also yield an even bigger performance
> improvement.

It's an extremely common to have have times where there's more active
queries than CPUs. And a pooler won't avoid that fully, at least not
without drastically reducing overall throughput.

Greetings,

Andres Freund

Commits

  1. doc: Fix description about pg_stat_statements.track_planning.

  2. doc: Add note about possible performance overhead by enabling track_planning.

  3. Change default of pg_stat_statements.track_planning to off.