Re: Update table performance

From: Piotr Kołaczkowski <P(dot)Kolaczkowski(at)elka(dot)pw(dot)edu(dot)pl>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Update table performance
Date: 2007-08-07 13:44:17
Message-ID: 200708071544.17399.P.Kolaczkowski@elka.pw.edu.pl
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Hi,

update valley set test='this is a test'

Such query updates ALL of your records in the table.
5 million records * 47 fields - that can be several gigabytes of data.
The system has to scan that gigabytes to change every record. This is a huge
task. Try vacuuming and see if it helps. It can help a lot, if you perform
such 'whole table updates' often.

Best regards,
Piotr Kolaczkowski

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