Reply-To: <gnanam@zoniac.com>
From: "Gnanakumar" <gnanam@zoniac.com>
To: "'Alvaro Herrera'" <alvherre@commandprompt.com>
Cc: "'pgsql-admin'" <pgsql-admin@postgresql.org>
References: <001d01cb3913$0e5c8f60$2b15ae20$@com>
	<1281539491-sup-7017@alvh.no-ip.org>
In-Reply-To: <1281539491-sup-7017@alvh.no-ip.org>
Subject: Re: Autovacuum daemon internal handling
Date: Thu, 12 Aug 2010 10:26:34 +0530
Organization: Zoniac Software Private Limited
Message-ID: <002401cb39da$bf04aec0$3d0e0c40$@com>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Thread-Index: Acs5aFSp93FEakdZQWC4WGi9D9tAiwAb+gwQ
Content-Language: en-us

> in 8.2 "naptime" means "time to sleep after we finish a job".  So even
> if the previous task takes an hour, it will still sleep a minute =
before
> doing another round.  (Note that this setting has a different meaning =
in
> later releases).

I couldn=E2=80=99t understand the difference in meaning of =
"autovacuum_naptime" between 8.2 and later releases from the =
documentation.  May be I'm not understanding/seeing the subtle =
difference in the documentation lines mentioned.  I referred these 3 doc =
links:
http://www.postgresql.org/docs/8.2/interactive/runtime-config-autovacuum.=
html
http://www.postgresql.org/docs/8.3/interactive/runtime-config-autovacuum.=
html
http://www.postgresql.org/docs/8.4/interactive/runtime-config-autovacuum.=
html

8.2 doc says "Specifies the delay between activity rounds for the =
autovacuum daemon...."
8.3 & 8.4 doc says "Specifies the minimum delay between autovacuum runs =
on any given database....."

Can you please make me clear on this?

> If autovacuum cannot keep up with all the vacuumable tables, you're in
> trouble and should probably schedule vacuum externally.  (This also
> changed in later releases).

Can you please point me to relevant documentation links on this change?

>> 2. The columns "last_autovaccum" and 'last_autoanalyze" in
>> pg_stat_user_tables shows the start time or end time of the =
operation?

> End time.
Is there any way to find out the start time of "last_autovaccum" and/or =
'last_autoanalyze" for a given table in 8.2.3?  So that I can isolate =
the tables that are taking too long time to complete vacuum and/or =
analyze and I can perform them externally if need.