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Re: ALTER TABLE ADD COLUMN Hangs - Mailing list pgsql-admin

From Ross J. Reedstrom
Subject Re: ALTER TABLE ADD COLUMN Hangs
Date
Msg-id 20100422034317.GA3902@rice.edu
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In response to ALTER TABLE ADD COLUMN Hangs  (Samuel Stearns <SStearns@internode.com.au>)
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On Thu, Apr 22, 2010 at 11:47:34AM +0930, Samuel Stearns wrote:
> Howdy,
>
> I'm running in an 8.3.3 environment.  What could cause, or how can I diagnose, why an 'ALTER TABLE <name> ADD COLUMN'
statementruns for hours eventually locking users out and requiring to be killed in the end? 
>

ALTER TABLE commands require an exclusive lock on the table. I'm
guessing you've got a long-running transaction ahead of the ALTER TABLE.
take a look at pg_stat_activity, in particular 'waiting' and pg_locks.

Ross
--
Ross Reedstrom, Ph.D.                                 reedstrm@rice.edu
Systems Engineer & Admin, Research Scientist        phone: 713-348-6166
The Connexions Project      http://cnx.org            fax: 713-348-3665
Rice University MS-375, Houston, TX 77005
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