exclusive locking on SELECT ?

From: James Neff <jneff(at)tethyshealth(dot)com>
To: pgsql-jdbc(at)postgresql(dot)org
Subject: exclusive locking on SELECT ?
Date: 2007-01-11 21:47:43
Message-ID: 45A6B07F.3050902@tethyshealth.com
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Greetings,

I have 3 clients trying to do a select on the same table (different
rows). pgAdmin III Server Status shows the queries and has as mode
"Exclusive Lock" for all three.

After a long while (10 minutes maybe?) things eventually get unstuck
and everything is alright.

These clients are selecting 2000 rows from the database. My suspicion
is the database servers IO is a bottleneck (running SATA drives, not
SCSI). Would fetching less number of rows at a time be better? How can
I find out what the best number of rows to fetch at a time are?

Is this a deadlock situation?

How would I go about diagnosing this situation, and how do I fix it?

I'm just using the postgresql-8.2-504.jdbc2.jar on all three clients.

I'm also researching and trying to implement the pooling suggested
before (trying DBCP first). If that will fix this problem then just
disregard this.

Thanks in advance,
James

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