RE: What is pg_stat_user_tables Showing NULL for last_autoanalyze &last_autovacuum

Thank you …

Are the calculations for triggering autovacuum dependent upon statistics generated by auto-anaylyze. In other words, if autoanalyze does not run at all, will autovac be able to run its math for threshold (updates & deletes) & scale factor (table rows) to do its thing?

My understanding from the documentation is that it does not need autoanalyze stats.

Thanks

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Thank you

From: Justin Pryzby
Sent: Wednesday, February 27, 2019 11:15 AM
To: Fd Habash
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: What is pg_stat_user_tables Showing NULL for last_autoanalyze &last_autovacuum

On Wed, Feb 27, 2019 at 09:47:13AM -0500, Fd Habash wrote:
> I have been able to locate four google search results with the same inquiry. What’ve been able to understand is …
>
> 1. If auto-vaccum is working as expected, stats collector does not nullify these values as part of a startup sequence or regular Maitenance. If a relation gets auto[vacuumed|analyzed], the timestamps should remain.
> 2. A database engine crash or restart with ‘immediate’ option will cause the timestamps to nullify.
> 3. Table never qualified for vacuuming based on auto-vacuum settings.

Can you give an example ?

If it's an empty inheritence parent (relkind=r), then it won't trigger
autovacuum/analyze thresholds (but you should analyze it manually).

Note that relkind=p "partitioned" tables don't have entries at all.
https://www.postgresql.org/message-id/flat/20180503141430.GA28019%40telsasoft.com

If it's never DELETEd from, then it won't trigger autovacuum (but may trigger
autoanalyze).

Justin