From: Cédric Villemain <cedric.villemain.debian@gmail.com>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Kevin Grittner <kevin.grittner@wicourts.gov>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Florian Helmberger <fh@25th-floor.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum
Date: Wed, 25 May 2011 21:14:06 +0200
Message-ID: <BANLkTinKDYoBo8ZpreagS3E5wkfL5zYNcg@mail.gmail.com> (raw)
In-Reply-To: <1306344946-sup-417@alvh.no-ip.org>
References: <4DD28F73.6010108@25th-floor.com>
<25017.1306291669@sss.pgh.pa.us>
<4DDCA801.70805@25th-floor.com>
<19738.1306338472@sss.pgh.pa.us>
<1306339028-sup-6948@alvh.no-ip.org>
<22173.1306340636@sss.pgh.pa.us>
<4DDCE9F4020000250003DC48@gw.wicourts.gov>
<1306342228-sup-2964@alvh.no-ip.org>
<BANLkTimyfvQXsLswzBCV5PFi+NN_TeDZ+g@mail.gmail.com>
<1306344946-sup-417@alvh.no-ip.org>
2011/5/25 Alvaro Herrera <alvherre@commandprompt.com>:
> Excerpts from Cédric Villemain's message of mié may 25 13:24:01 -0400 2011:
>
>> > Well, we only actually need to store one number, because you can figure
>> > out a much more precise number-of-pages figure with pg_relation_size()
>> > divided by configured page size.
>
>> I may miss something but we need relation size in costsize.c even if
>> we have a reldensity (or we need a reltuples). Else what values should
>> be used to estimate the relation size ? (pg_relation_size() goes down
>> to kernel/fs to ask the stat.st_size, is it really what we want?)
>
> Actually yes, the planner does go to kernel to determine the current
> relation size, and then multiplies by density as computed from catalog
> data to figure out current reasonably accurate number of tuples.
Okay! I just read that part. Interesting.
(If I dive correctly, we search our last segment and then use a
fileseek to the end of this segment to get our information)
make more sense, suddendly :)
>
> --
> Álvaro Herrera <alvherre@commandprompt.com>
> The PostgreSQL Company - Command Prompt, Inc.
> PostgreSQL Replication, Consulting, Custom Development, 24x7 support
>
--
Cédric Villemain 2ndQuadrant
http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support
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-admin@postgresql.org
Cc: cedric.villemain.debian@gmail.com, alvherre@commandprompt.com, kevin.grittner@wicourts.gov, tgl@sss.pgh.pa.us, fh@25th-floor.com, pgsql-hackers@postgresql.org
Subject: Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum
In-Reply-To: <BANLkTinKDYoBo8ZpreagS3E5wkfL5zYNcg@mail.gmail.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