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From: Donkers@fel.tno.nl (DONKERS H.C. 436/3H01/2-5)
To: postgres@postgres.Berkeley.EDU
Subject: newbie question about types
Date: 13 Jun 95 10:29:27 EDT
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Resent-Date: Tue, 13 Jun 95 01:41:01 -0700
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Hello,

I'm currnetle doing a graduate project at TNO-FEL in the Netherlands.
Thereby I'm using Postgres, whith which I haven't got any thorough 
experience.

My data in the database consists of 2D polygons. These polygons are
of a self-made type POLYGON2 (I got this from somebody who worked
with Postgres, but he's not working here anymore.).
These polygons all lie in the same 2 dimensional plane.

The program I'm making (for visualisation of the data) is supposed
to handle very large databases (probably up to some Gigabytes), so
it's not very wise to import my data all at once. 

What I want to do is as follows:
The user walks around in the database and with him moves a 'window' 
on the database. So I want to query the database as follows:

RETRIEVE (plg.all)
WHERE overlap(plg.poly, window)

Here window is a constant of type box, polygon or something else if 
that achieves better performance.

My questions now are about the function overlap.
Can you write this youselve?
Is it hard?
Does it take a lot of time?
Could I better convert my data to the type polygon, which comes 
standard with postgres?
Does such a function exist allready for that type?

If you have any questions please ask them, because I really need 
these answers quick.
Any help would be greatly appreciated.

Greetings,
Kurt.

***
In /dev/null no one can hear you scream
***

H.C. (Kurt) Donkers
TNO Physics & Electronical Lab.
P.O. Box 96864
2509 JG The Hague
The Netherlands
Tel: +31 70 3264221
Fax: +31 70 3280961
E-mail: donkers@fel.tno.nl

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