DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com;
	h=Message-ID:Received:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding;
	b=irjqBVGdvGK2goCH5TaDvTfu9RQE044l14zjIPuiPfBWbuK/D46CkE1nWZd6UCfI/4s1B3AWEa9Ta9zVvSyEIS7u/bvSt9cO2pIfeRSgh3jdeNGmcgTjj9PybHrn0K+5dvGneAOxREN+5XcN5CxglWhRbzyg5wj5rL9+MmdZH3E=
	;
Message-ID: <20060308230419.53923.qmail@web54308.mail.yahoo.com>
Date: Wed, 8 Mar 2006 15:04:18 -0800 (PST)
From: chester c young <chestercyoung@yahoo.com>
Subject: Re: Is there any way to stop triggers from cycling?
To: josh@agliodbs.com, pgsql-sql@postgresql.org
In-Reply-To: <200603081358.25185.josh@agliodbs.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit

trying to do this exlusively in triggers is a forray into folly.

take advantage of "instead of" or "do also" rules to create a compound
statement before your triggers do their work.  (in terms of maintenance
and sanity, it's best if a trigger touches only its own record.)

as a handsweep example:

create view tree_v as select * from tree;
grant select, insert, update on tree_v to public;

create or replace rule 'tree_update' as
  on update
  to tree_v
do instead(
  --
  update tree set seq = seq+1
  where old.pnt=new.pnt and old.seq<new.seq-1
  and   pnt = old.pnt and seq between old.seq and new.neq;
  --
  update tree set set = new.seq
  where old.pnt=new.pnt and old.seq != new.seq
  and   pnt = old.pnt and seq = new.seq;
);

note two conditions on the where clause: first is rule when to do it,
and second is what record to do it on.

you might not need the intermediate view, but I always use a view
between my app and the table - for reasons like this and many, many
others.


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com