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Re: Change lock requirements for adding a trigger

From: Decibel! <decibel(at)decibel(dot)org>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Change lock requirements for adding a trigger
Date: 2008-06-03 21:48:08
Message-ID: F38A0C4E-C087-4F42-B5AA-9C7A6E9026B0@decibel.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On May 30, 2008, at 9:51 AM, Simon Riggs wrote:
> 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.

Is there a good way to determine this other than depending on  
knowledge of the source code?
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828


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