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Re: very long updates very small tables

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: <pgsql-performance(at)postgresql(dot)org>, "Lars Feistner" <feistner(at)uni-heidelberg(dot)de>
Subject: Re: very long updates very small tables
Date: 2011-03-29 19:28:14
Message-ID: 4D91EC7E020000250003BEEC@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-performance
Lars Feistner <feistner(at)uni-heidelberg(dot)de> wrote:
 
> The log tells me that certain update statements take sometimes
> about 3-10 minutes. But we are talking about updates on tables
> with 1000 to 10000 rows and updates that are supposed to update 1
> row.
 
The top possibilities that come to my mind are:
 
(1)  The tables are horribly bloated.  If autovacuum is off or not
aggressive enough, things can degenerate to this level.
 
(2)  Memory is over-committed and your machine is thrashing.
 
(3)  There are explicit LOCK commands in the software which is
contributing to the blocking.
 
(4)  There is some external delay within the transaction, such as
waiting for user input while the transaction is open.
 
Maybe there's a combination of the above at play.  Can you rule any
of these out?
 
-Kevin

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