On Fri, Jan 10, 2014 at 10:01 PM, Greg Stark <stark@mit.edu> wrote:
>> So you schedule a class that clashes with 3 other classes, and you
>> want to update all 3 rows/classes with details from your one row
>> proposed for insertion?
>
>
> Well, perhaps you want to mark the events as conflicting with your new event?
But short of a sophisticated persistent value locking implementation
(which I'm pretty skeptical of the feasibility of), more conflicting
events could be added at any moment. I doubt that you're appreciably
any better off than if you were to simply check with a select query,
even though that approach is obviously broken. In general, making row
locking work for exclusion constraints, so you can treat them in a way
that allows you to merge on arbitrary operators seems to me like a tar
pit.
--
Peter Geoghegan