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Re: What is syslog:duration reporting ... ?

From: Aldor <an(at)mediaroot(dot)de>
To: Michael Fuhr <mike(at)fuhr(dot)org>
Cc: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>,pgsql-admin(at)postgresql(dot)org
Subject: Re: What is syslog:duration reporting ... ?
Date: 2005-08-25 23:50:29
Message-ID: 430E5945.4000408@mediaroot.de (view raw or flat)
Thread:
Lists: pgsql-admin
Aug 25 14:53:32 forgehouse-s1 postgres[23721]: [2-1] LOG:  duration: 
567.559 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='7537b74eab488de54d6e0167d1919207';
Aug 25 14:53:32 forgehouse-s1 postgres[23722]: [2-1] LOG:  duration: 
565.966 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='d84613009a95296fb511c2cb051ad618';
Aug 25 14:53:33 forgehouse-s1 postgres[23723]: [2-1] LOG:  duration: 
1192.789 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='d84613009a95296fb511c2cb051ad618';
Aug 25 14:53:53 forgehouse-s1 postgres[23727]: [2-1] LOG:  duration: 
12159.162 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='d84613009a95296fb511c2cb051ad618';
Aug 25 14:53:54 forgehouse-s1 postgres[23728]: [2-1] LOG:  duration: 
3283.185 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='7537b74eab488de54d6e0167d1919207';
Aug 25 14:53:57 forgehouse-s1 postgres[23729]: [2-1] LOG:  duration: 
2116.516 ms  statement: UPDATE session SET hit_time=now() WHERE 
md5='7537b74eab488de54d6e0167d1919207';

Take a look to the timestamps... they are not really close to each other...

Michael Fuhr wrote:
> On Thu, Aug 25, 2005 at 01:55:08PM -0600, Michael Fuhr wrote:
> 
>>Are the updates happening inside a transaction?  Is it possible
>>that they're being blocked by other transactions that update the
>>same record around the same time and don't commit immediately?
>>I can duplicate the results you're seeing by doing that.
> 
> 
> As for why you don't see long durations with EXPLAIN ANALYZE, here's
> a possible explanation: "ordinary" updates of the same record might
> happen close together because that's how the application works, but
> by the time you run EXPLAIN ANALYZE no other transactions are updating
> that record so the update executes immediately.
> 

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