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List:       postgresql-general
Subject:    Re: [HACKERS] Change lock requirements for adding a trigger
From:       Simon Riggs <simon () 2ndquadrant ! com>
Date:       2008-05-30 14:51:34
Message-ID: 1212159094.4120.114.camel () ebony ! site
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On Thu, 2008-05-29 at 19:18 -0500, Decibel! wrote:

> Is there a reason that we can't add a trigger to a table while a  
> select is running? This is a serious pain when trying to setup  
> londiste or slony.

This is constrained by locking.

There are a subset of DDL commands that might be able to be performed
with just an ExclusiveLock or ShareLock rather than an
AccessExclusiveLock. Nobody has studied which sub-statements this might
apply to, but its do-able since CREATE INDEX already does this.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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