Re: MERGE vs REPLACE

On Tue, Nov 22, 2005 at 11:57:48AM +0100, Martijn van Oosterhout wrote:
<excellent research snipped>

> Rather than trying to make MERGE do something it wasn't designed for,
> we should probably be spending our efforts on triggers for error
> conditions. Maybe something like:
> 
> CREATE TRIGGER foo AFTER ERROR ON bar EXECUTE baz();
> 
> Where baz would be passed NEW and OLD just like a normal trigger and if
> the trigger return NULL, the update is ignored. In the meantime the
> function can divert the insert to another table if it likes. This seems
> like a much more workable and useful addition.

I agree that we shouldn't try and distort MERGE into something fancy.
The AFTER ERROR trigger is a very interesting idea, since it could
handle many different cases. But I'm worried that people might not want
that behavior on by default for everything done against some table. I
think it'd be better to have some way to specify in a command that
you want to use some kind of error-handling trigger. Though presumably
the underlying framework would be same, so it shouldn't be hard to
support both.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461