Re: A question for Mr. Celko
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Wed, 21 Jul 2004 21:39:03 GMT
Message-Id: <pan.2004.07.21.21.39.48.461208_at_REMOVETHIS.pandora.be>
> Their selection definition hindges on the concept of "selection-comparable"
> nodes. The limitation when we are not allowed to compare arbitrary nodes in
> the tree looks rather ad-hock. What is the motivation behind it?
Date: Wed, 21 Jul 2004 21:39:03 GMT
Message-Id: <pan.2004.07.21.21.39.48.461208_at_REMOVETHIS.pandora.be>
On Wed, 21 Jul 2004 11:41:36 -0700, Mikito Harakiri wrote:
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:pan.2004.07.21.11.04.38.324586_at_REMOVETHIS.pandora.be...
>> For something a little more recent: >> >> http://citeseer.ist.psu.edu/liu94algebraic.html >>
> Their selection definition hindges on the concept of "selection-comparable"
> nodes. The limitation when we are not allowed to compare arbitrary nodes in
> the tree looks rather ad-hock. What is the motivation behind it?
As you can see in the examle in Figure 2 the let the select also make a selection in the nested records.
But frankly, I regret giving that reference. It's the only thing more or less recent, but boy is it badly written. The Colby paper is really much better. Sorry to have wasted your time with that. To make up let me give you a much better reference on opimizing selections over nested relations:
http://citeseer.ist.psu.edu/vandenbussche91evaluation.html
It takes a logical rather than an algebraic approach.
- Jan Hidders