Horton

Re: Track the amount of time waiting due to cost_delay

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2024-06-11T06:24:42Z
Lists: pgsql-hackers

Commits

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  1. Add delay time to VACUUM/ANALYZE (VERBOSE) and autovacuum logs.

  2. Add cost-based vacuum delay time to progress views.

  3. Add is_analyze parameter to vacuum_delay_point().

  4. Refresh cost-based delay params more frequently in autovacuum

On Mon, Jun 10, 2024 at 02:20:16PM -0500, Nathan Bossart wrote:
> On Mon, Jun 10, 2024 at 05:48:22PM +0000, Bertrand Drouvot wrote:
> > On Mon, Jun 10, 2024 at 10:36:42AM -0500, Nathan Bossart wrote:
> >> I wonder if we should also
> >> surface the effective cost limit for each autovacuum worker.
> > 
> > I'm not sure about it as I think that it could be misleading: one could query
> > pg_stat_progress_vacuum and conclude that the time_delayed he is seeing is
> > due to _this_ cost_limit. But that's not necessary true as the cost_limit could
> > have changed multiple times since the vacuum started. So, unless there is
> > frequent sampling on pg_stat_progress_vacuum, displaying the time_delayed and
> > the cost_limit could be misleadind IMHO.
> 
> Well, that's true for the delay, too, right (at least as of commit
> 7d71d3d)?

Yeah right, but the patch exposes the total amount of time the vacuum has
been delayed (not the cost_delay per say) which does not sound misleading to me.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com