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Database performance post-VACUUM FULL

From: Karl Wright <kwright(at)metacarta(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Database performance post-VACUUM FULL
Date: 2009-09-18 12:44:05
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Lists: pgsql-performance
Hi all,

We're using Postgresql 8.3.7 on Debian.  We are seeing a very strange performance situation with our application which I am 
hoping that someone can shed light on.

Our tests find that our application runs quite well on 8.3.7 initially.  The test consists of database creation followed by 30 
cycles of creation and removal of approximately 1,000,000 rows (across all tables) per cycle.  However, when database 
maintenance takes place (which consists of a VACUUM FULL operation, and some table REINDEX operations), subsequent cycle 
performance is more than 2x worse.  What's more, after one VACUUM FULL operation has been done on the database, no subsequent 
VACUUM FULL operations *ever* seem to restore it to proper performance levels.

We used the same general maintenance procedure with 8.2 and found that it worked as expected, so we were quite surprised to 
discover this problem with 8.3.7.  Anybody know what's going on?


Karl Wright
Software Engineer

MetaCarta, Inc.
350 Massachusetts Avenue, 4th Floor, Cambridge, MA 02139 USA

(617)-301-5511 <>
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Subject: Re: Database performance post-VACUUM FULL
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Subject: Re: Different query plans for the same query

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