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From: Andrew Dunstan <andrew@dunslane.net>
To: AI Rumman <rummandba@gmail.com>
Cc: depesz@depesz.com
Cc: pgsql-performance@postgresql.org
Subject: Re: add column with default value is very slow
Date: Tue, 11 Sep 2012 10:07:04 -0400
Message-ID: <504F4588.7030900@dunslane.net> (raw)
In-Reply-To: <CAGoODpeorc_7U57NYKsf68Gd3wi9VM+=2kJDZ=89Tk=J=XE=pg@mail.gmail.com>
References: <CAGoODpdBTkhXDuOQDLxuEJYrWfsZZCi_tkjgzDyzPRGDHeQ9ag@mail.gmail.com>
	<20120911134425.GA27828@depesz.com>
	<CAGoODpeorc_7U57NYKsf68Gd3wi9VM+=2kJDZ=89Tk=J=XE=pg@mail.gmail.com>


On 09/11/2012 09:55 AM, AI Rumman wrote:
> I added the excel file for locks data.
> I was surprised to see that while I was updating a single column value 
> for all records in a tables, all indexes are locked by the server.


Any ALTER TABLE command locks the whole table in ACCESS EXCLUSIVE mode, 
indexes included. See the description of ACCESS EXCLUSIVE lock at 
<http://www.postgresql.org/docs/current/static/explicit-locking.html;

cheers

andrew

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