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Re: Index bloat problem?

From: Mischa Sandberg <mischa(dot)sandberg(at)telus(dot)net>
To: Bill Chandler <billybobc1210(at)yahoo(dot)com>
Cc: a3a18850(at)telus(dot)net,pgsql-perform <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Index bloat problem?
Date: 2005-04-21 22:15:22
Message-ID: 1114121722.426825fa4474f@webmail.telus.net (view raw or flat)
Thread:
Lists: pgsql-performance
Quoting Bill Chandler <billybobc1210(at)yahoo(dot)com>:

> ... The normal activity is to delete 3-5% of the rows per day,
> followed by a VACUUM ANALYZE. 
...
> However, on occasion, deleting 75% of rows is a 
> legitimate action for the client to take.  

> > In case nobody else has asked: is your max_fsm_pages
> > big enough to handle all the deleted pages, 
> > across ALL tables hit by the purge?

> This parameter is most likely set incorrectly.  So
> that could be causing problems.  Could that be a
> culprit for the index bloat, though?

Look at the last few lines of vacuum verbose output.
It will say something like:

free space map: 55 relations, 88416 pages stored; 89184 total pages needed
  Allocated FSM size: 1000 relations + 1000000 pages = 5920 kB shared memory.

"1000000" here is [max_fsm_pages] from my postgresql.conf.
If the "total pages needed" is bigger than the pages 
fsm is allocated for, then you are bleeding.
-- 
"Dreams come true, not free." -- S.Sondheim, ITW


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