From: David Gould <daveg@sonic.net>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Alina Alexeeva <alexeeva@adobe.com>
Cc: Ullas Lakkur Raghavendra <lakkurra@adobe.com>
Subject: Re: [patch] BUG #15005: ANALYZE can make pg_class.reltuples inaccurate.
Date: Sun, 4 Mar 2018 19:19:18 -0800
Message-ID: <20180304191918.39e95382@engels> (raw)
In-Reply-To: <CAMkU=1yQz4OEmoWSnY_wE03KdpoQ4zpzmjpyPDUQwz+tbsU21g@mail.gmail.com>
References: <20180117164916.3fdcf2e9@engels>
<CAMkU=1yQz4OEmoWSnY_wE03KdpoQ4zpzmjpyPDUQwz+tbsU21g@mail.gmail.com>
On Sun, 4 Mar 2018 07:49:46 -0800
Jeff Janes <jeff.janes@gmail.com> wrote:
> I don't see how it could have caused the problem in the first place. In
> your demonstration case, you had to turn off autovac in order to get it to
> happen, and then when autovac is turned back on, it is all primed for an
> autovac to launch, go through, touch almost all of the pages, and fix it
> for you. How did your original table get into a state where this wouldn't
> happen?
One more way for this to happen, vacuum was including the dead tuples in the
estimate in addition to the live tuples. This is a separate bug that tends
to aggravate the one I'm trying to fix. See the thread re BUG #15005 at:
https://www.postgresql.org/message-id/16db4468-edfa-830a-f921-39a50498e77e%402ndquadrant.com> It seems to me that VACUUM and ANALYZE somewhat disagree on what exactly
> reltuples means. VACUUM seems to be thinking that
>
> reltuples = live + dead
>
> while ANALYZE apparently believes that
>
> reltuples = live
There is a patch for this one from Tomas Vondra/Tom Lane that I hope it will
land in the next set of releases.
-dg
--
David Gould daveg@sonic.net
If simplicity worked, the world would be overrun with insects.
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-hackers@postgresql.org
Cc: daveg@sonic.net, jeff.janes@gmail.com, pgsql-hackers@lists.postgresql.org, alexeeva@adobe.com, lakkurra@adobe.com
Subject: Re: [patch] BUG #15005: ANALYZE can make pg_class.reltuples inaccurate.
In-Reply-To: <20180304191918.39e95382@engels>
* 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