From: Fd Habash <fmhabash@gmail.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: RE: What is pg_stat_user_tables Showing NULL for last_autoanalyze &last_autovacuum
Date: Thu, 28 Feb 2019 08:34:54 -0500
Message-ID: <5c77e37c.1c69fb81.ec2b6.6cef@mx.google.com> (raw)
In-Reply-To: <20190227161556.GD28750@telsasoft.com>
References: <5c76a2f0.1c69fb81.a4b54.6182@mx.google.com>
<20190227161556.GD28750@telsasoft.com>
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
----------------
Thank you
From: Justin Pryzby
Sent: Wednesday, February 27, 2019 11:15 AM
To: Fd Habash
Cc: pgsql-performance@postgresql.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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: fmhabash@gmail.com, pryzby@telsasoft.com
Subject: RE: What is pg_stat_user_tables Showing NULL for last_autoanalyze &last_autovacuum
In-Reply-To: <5c77e37c.1c69fb81.ec2b6.6cef@mx.google.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox