Date: Wed, 27 Feb 2019 10:15:56 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Fd Habash <fmhabash@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: What is pg_stat_user_tables Showing NULL for last_autoanalyze &
 last_autovacuum
Message-ID: <20190227161556.GD28750@telsasoft.com>
References: <5c76a2f0.1c69fb81.a4b54.6182@mx.google.com>
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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