Re: PostgreSQL - 'SKYLINE OF' clause added!

FWIW, this sounds like a subset of the Query By Example stuff that
someone is working on. I don't have a URL handy since I'm on a plane,
but I think google can find it.

On Mar 3, 2007, at 8:12 AM, ranbeer makin wrote:

>
> Here is a description of what the SKYLINE operator is:
> ---
> Suppose you wish to purchase books and you are looking for books
> with high rating and low price. However, both the criteria of
> selecting books are complementary since books of higher rating are
> generally more expensive. For finding such books, you'll query the
> database system of the book store which will return a set of
> interesting books. The word 'interesting' implies all the books
> which are as good or better in both the dimensions (rating and
> price) and better in at least one dimension. This set of
> interesting points forms the Skyline.
> Skyline operator finds points which are not dominated by other data
> points. A point dominates another point if it is as good or better
> in all dimensions and better in at least one dimension.
>
> For specifying the Skyline queries, we extend SQL SELECT statement
> by an optional SKYLINE OF clause as given below:
>
> SELECT ... FROM ... WHERE...
>
> GROUP BY ... HAVING...
>
> SKYLINE OF [DISTINCT] d1 [MIN | MAX | DIFF], .., dm [MIN | MAX |
> DIFF]
>
> ORDER BY...
>
>
> Where, d1, d2 ,…, dm denote the dimensions of the Skyline, and MIN,
> MAX, DIFF specify whether the value in that dimension should be
> minimized, maximized, or simply be different. When DIFF is
> specified, two tuples are compared only if the value of the
> attribute on which DIFF is applied is different.
>
> When DISTINCT clause is specified and if there are two or more
> tuples with the same values of skyline attributes, then only one of
> them is retained in the skyline set. Otherwise, all of them are
> retained.
>
> Let's consider the above example of purchasing books with high
> rating and low price.
>
>
> Book Name
>
> Rating (out of 5)
>
> Price (Rs)
>
> Prodigal Daughter
>
> 3
>
> 250
>
> The city of Joy
>
> 5
>
> 400
>
> Vanishing Acts
>
> 2
>
> 250
>
> The Notebook
>
> 4
>
> 300
>
> Fountain Head
>
> 5
>
> 350
>
> Dear John
>
> 5
>
> 500
>
> Table1. Sample of book database
>
>
> Now, in order to get books with high rating and low price, you
> simply can issue the following query:
>
> SELECT *
>
> FROM Books
>
> SKYLINE OF rating MAX, price MIN;
>
>
> The Skyline set returned will be:
>
>
> Book Name
>
> Rating (out of 5)
>
> Price (Rs)
>
> Prodigal Daughter
>
> 3
>
> 250
>
> The Notebook
>
> 4
>
> 300
>
> Fountain Head
>
> 5
>
> 350
>
> Table2. Skyline set
>
>
> From this set, you can now make your choice of books, by weighing
> your personal preferences for price and rating of the books.
>
> For more information, you can refer to:
> S. Borzsonyi, D. Kossmann, and K. Stocker. The skyline operator. In
> ICDE, pages 421.430, 2001
>
> ---
>
> Thanks.
>
>
>
> On 3/3/07, Martijn van Oosterhout <kleptog(at)svana(dot)org> wrote: On
> Sat, Mar 03, 2007 at 07:02:41PM +0530, ranbeer makin wrote:
> > We at International Institute of Information Technology (IIIT)
> Hyderabad,
> > India, have extended the Postgres database
> > system with the skyline operation. For this work, we were guided
> by our
> > Prof. Kamalakar Karlapalem
> > (http://www.iiit.ac.in/~kamal/).
>
> <snip>
>
> > Can this piece of work contribute to PostgreSQL? If yes, then
> we'll send out
> > a detailed report of this project including changes
> > made, issues involved/need to be solved, limitations, future
> work, and the
> > source code etc.
>
> Well, that kind of depends. I have no idea what "Skyline" means so
> telling us what it is would be a good start
>
> Have a nice day,
> --
> Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/
> kleptog/
> > From each according to his ability. To each according to his
> ability to litigate.
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.1 (GNU/Linux)
>
> iD8DBQFF6XrkIB7bNG8LQkwRAqw8AJ0UKAy41OMxdgLUdY1G+e7R6/jGPwCZAQY4
> 9uCKFUW65UBIx7fpogR75Yo=
> =6Yc0
> -----END PGP SIGNATURE-----
>
>

--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)