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From Peter Chang <pete...@gmail.com>
Subject Re: How to perform queries on Cassandra?
Date Sat, 10 Apr 2010 16:12:49 GMT
I'm going to eventually want to do something similar so I took particular
note of a thread that came up earlier in this forum. I haven't fully
investigated it but I think it's a great start for what you need to do.

http://www.mail-archive.com/user@cassandra.apache.org/msg00201.html

<http://www.mail-archive.com/user@cassandra.apache.org/msg00201.html>In
particular, it talks about representing coordinates as hashes. I believe
that points that are close to each other have similar hash stems (eg.
"abcdefg" is with x distance of "abcdeff").

I haven't looked it in detail.

Peter

2010/4/9 Onur AKTAS <onur.aktas@live.com>

>  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 which
> gives distance between lat/longs pairs in kilometers.
>
> Ex:
> user1_lat = 40 user1_long = 20
> user2_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, u ser.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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>

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