Message-ID: <46D83427.60001@livedatagroup.com>
Date: Fri, 31 Aug 2007 11:30:47 -0400
From: Pallav Kalva <pkalva@livedatagroup.com>
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To: pgsql-performance@postgresql.org
Subject: 8.2 Autovacuum BUG ? 
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Hi,


    We turned on autovacuums on 8.2 and we have a database which is read 
only , it is basically a USPS database used only for address lookups 
(only SELECTS, no updates/deletes/inserts).

    This database has about 10gig data and yesterday autovacuum started 
on this database and all of a sudden I see lot of archive logs generated 
during this time, I guess it might have generated close to 3-4gig data 
during this period.

    It was doing only vacuum not vacuum analyze. 

    My question is why does it have to generate so many archive logs on 
static tables ?

   I am thinking these archive logs are mostly empty , the reason I am 
saying that because I noticed that when I restore the db using PITR 
backups for my reporting db these same logs are recovered in seconds 
compared to the logs generated while vacuums are not running.

   Is this a BUG ? or am I missing something here ?


Vacuum Settings
---------------------
vacuum_cost_delay = 30
vacuum_cost_limit = 150
checkpoint_segments = 64
checkpoint_timeout = 5min           
checkpoint_warning = 30s
autovacuum = on
autovacuum_naptime = 120min
autovacuum_vacuum_threshold = 500
autovacuum_analyze_threshold = 250
autovacuum_vacuum_scale_factor = 0.001
autovacuum_analyze_scale_factor = 0.001
autovacuum_freeze_max_age = 200000000
autovacuum_vacuum_cost_delay = -1
autovacuum_vacuum_cost_limit = -1


Thanks!
Pallav.