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Message-ID: <4AB9676A.6070301@obviously.com>
Date: Tue, 22 Sep 2009 17:10:18 -0700
From: Bryce Nesbitt <bryce2@obviously.com>
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To: pgsql-sql@postgresql.org
Subject: Re: AccessExclusiveLock on CREATE TABLE REFERENCES deadlocks
	(formatted better)
References: <4AB90198.2010109@obviously.com> <13526.1253640939@sss.pgh.pa.us>
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Tom Lane wrote:
<blockquote cite="mid:13526.1253640939@sss.pgh.pa.us" type="cite">
  <pre wrap="">Bryce Nesbitt <a class="moz-txt-link-rfc2396E" href="mailto:bryce2@obviously.com">&lt;bryce2@obviously.com&gt;</a> writes:
  </pre>
  <blockquote type="cite">
    <pre wrap="">1) Why the AccessExclusiveLock on create table?
    </pre>
  </blockquote>
  <pre wrap=""><!---->
It has to install a trigger on the referenced table.  There has been
some discussion that maybe CREATE TRIGGER could take just ExclusiveLock
and not AccessExclusiveLock, but it hasn't been done yet; and I'm not
sure how much that would help you anyway.  It would only help if the
referenced table (contexts) is essentially read-only to the rest of
your workload, else it'll block anyhow.</pre>
</blockquote>
Thanks for the great info.<br>
<br>
In our case all the long running access is read-only.&nbsp; We have a poorly
designed table that several postgres consultants have burned out on
trying to fix.<br>
<br>
Most notably there are also zillions of short read-only references that
presently block while the create table attempts to gain the
AccessExclusiveLock. <br>
<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; -Bryce<br>
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