From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200510301410.j9UEAnj02881@candle.pha.pa.us>
Subject: Re: Effects of cascading references in foreign keys
In-Reply-To: <F7B49CB0-86E6-4744-9D37-3C1EAEDBA15E@sitening.com>
To: "Thomas F. O'Connell" <tfo@sitening.com>
Date: Sun, 30 Oct 2005 09:10:49 -0500 (EST)
Cc: PgSQL Performance <pgsql-performance@postgresql.org>
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Thomas F. O'Connell wrote:
> > In 8.1 there is a check to see if the foreign key value has changed  
> > and if
> > not a trigger isn't queued. In the currently released versions any  
> > update
> > will fire triggers.
> > The check in comment for trigger.c didn't say if this optimization  
> > applied
> > to both referencing and referenced keys or just one of those.
> > If you need to know more you can look at the code at:
> > http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/
> > for trigger.c.
> 
> It seems like this warrants an item somewhere in the release notes,  
> and I'm not currently seeing it (or a related item) anywhere. Perhaps  
> E.1.3.1 (Performance Improvements)? For some of the more extreme  
> UPDATE scenarios I've seen, this could be a big win.

Hard to say, perhaps:

	Prevent referential integrity triggers from firing if referenced
	columns are not changed by an UPDATE

	Previously, triggers would fire but do nothing.

However, the description seems more complex than it is worth.

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