# Re: Character string relation and functional dependencies

From: Tegiri Nenashi <TegiriNenashi_at_gmail.com>

Date: Tue, 11 Dec 2007 12:47:52 -0800 (PST)

Message-ID: <38860a21-e69a-46a4-a798-cc16dde1c4a7_at_e10g2000prf.googlegroups.com>

Date: Tue, 11 Dec 2007 12:47:52 -0800 (PST)

Message-ID: <38860a21-e69a-46a4-a798-cc16dde1c4a7_at_e10g2000prf.googlegroups.com>

On Dec 11, 12:37 pm, Tegiri Nenashi <TegiriNena..._at_gmail.com> wrote:

> Well, in traditional databases index structures are auxiliary.

*> Likewise, I would like to keep functions hidden. After all there is
**> one relation
**>
**> x + y = z
**>
**> but there are three functions that can index it.
*

Let me elaborate a little more. Suppose we are asked to evaluate the query

- Evaluate x=1
- Evaluate z=4
- Build a Cartesian product result
- Join with the relation x + y = z using the index (x,z)->z-x