Message-ID: <49AC4351.8050307@ca.com>
Date: Mon, 02 Mar 2009 12:36:33 -0800
From: Brian Cox <brian.cox@ca.com>
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To: "Tom Lane [tgl@sss.pgh.pa.us]" <tgl@sss.pgh.pa.us>
CC: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: "slow" queries
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Tom Lane [tgl@sss.pgh.pa.us] wrote:
> Well, that's certainly a sufficient reason, if perhaps not the only
> reason.  Dropping ts_defects_20090227 will require removal of FK triggers
> on ts_transets, and we can't do that concurrently with transactions that
> might be trying to fire those triggers.
> 
> Now admittedly, it would probably be sufficient to take ExclusiveLock
> rather than AccessExclusiveLock when removing triggers, since we do not
> have triggers ON SELECT.  Right now though, we just take
> AccessExclusiveLock for most any DDL on a table.  There was a patch
> submitted last fall to reduce DDL locking in some cases, but it hasn't
> been reworked to fix the problems that were pointed out (and I
> disremember if it addressed DROP TRIGGER in particular anyway).
> 
>                         regards, tom lane

Thanks for furthering my understanding of postgres (and probably other 
SQL servers as well). I can fix this problem easily.

Brian