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From Onur AKTAS <onur.ak...@live.com>
Subject How to perform queries on Cassandra?
Date Fri, 09 Apr 2010 21:56:10 GMT

Hi,
I want to use Cassandra for a new project, as you can guess I have a RDBMS background however
do not have any experience with NoSQL databases except key/value pair in memory data grids/caches.
(Oracle Coherence /Memcached.).
I'm trying to find out how do you perform queries with calculations on the fly without inserting
the data as calculated from the beginning.
Lets say we have latitude and longitude coordinates of all users and we have  Distance(from_lat,
from_long, to_lat, to_long) function whichgives distance between lat/longs pairs in kilometers.
Ex:user1_lat = 40 user1_long = 20user2_lat = 30 user3_long = 50
So, if we want to do same operation in regular RDBMS we can use this kind of query to get
users near to user_1's location.
* select user from users where Distance(40, 20, user.lat, user.long) = 5
How do we do this kind of operations in cassandra? 
If we insert data as calculated from the beginning, lets say we have 1 million users, then
do we need to do 1 million insert operations for just updating 1 users coordinates? (Ofcourse
no but then how?).
I believe huge complexity calculations are possible with Cassandra, but do not know about
querying out of accessing the data by it's key.
Thanks,
 		 	   		  
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