Message-ID: <4FD6F4B3.8050509@gmail.com>
Date: Tue, 12 Jun 2012 15:50:11 +0800
From: Rural Hunter <ruralhunter@gmail.com>
User-Agent: Mozilla/5.0 (Windows NT 6.1;
	rv:13.0) Gecko/20120604 Thunderbird/13.0
MIME-Version: 1.0
To: pgsql-admin@postgresql.org
Subject: Why auto vacuum almost running all the time on one toast table?
Content-Type: text/plain; charset=GB18030; format=flowed
Content-Transfer-Encoding: 7bit

v9.1.3 on Ubuntu 10.04 server. I have one table which has frequent 
insert and weekly deletion, no update. Recently, I found the auto vacuum 
on the toast table of it almost running all the time. each run took 
around 1 hour. I don't think there are so many inerts so that it reaches 
the auto vacuum criteria(20%? changes). And there is no such frequent 
auto vacuum on the main table. The last auto vacuum of the main table is 
on 3rd Jun. what might cause this behavior?

# grep pg_toast_16922 postgresql-2012-06-12_000000.log
2012-06-12 01:22:56 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"
2012-06-12 04:27:49 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"
2012-06-12 06:58:02 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"
2012-06-12 09:27:38 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"
2012-06-12 12:17:33 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"
2012-06-12 15:05:31 CST [@] CONTEXT:  automatic vacuum of table 
"oodb.pg_toast.pg_toast_16922"