Horton

Re: Track the amount of time waiting due to cost_delay

Sami Imseih <simseih@amazon.com>

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From: "Imseih (AWS), Sami" <simseih@amazon.com>
To: Robert Haas <robertmhaas@gmail.com>, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2024-06-11T18:19:23Z
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

> I'm not convinced that reporting the number of waits is useful. If we
> were going to report a possibly-inaccurate amount of actual waiting,
> then also reporting the number of waits might make it easier to figure
> out when the possibly-inaccurate number was in fact inaccurate. But I
> think it's way better to report an accurate amount of actual waiting,
> and then I'm not sure what we gain by also reporting the number of
> waits.

I think including the number of times vacuum went into sleep 
will help paint a full picture of the effect of tuning the vacuum_cost_delay 
and vacuum_cost_limit for the user, even if we are reporting accurate 
amounts of actual sleeping.

This is particularly true for autovacuum in which the cost limit is spread
across all autovacuum workers, and knowing how many times autovacuum
went to sleep will be useful along with the total time spent sleeping.

Regards,

Sami