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From Eric Evans <eev...@rackspace.com>
Subject Re: Two dimensional matrices
Date Mon, 12 Apr 2010 18:00:33 GMT
On Mon, 2010-04-12 at 01:31 +0200, Philippe wrote:
> I have data that is two dimensional, time varying (think of a grid).
> At each
> cell of this grid,I store a binary array.
> My data model will be
> 
>    - single keyspace
>    - key = {Y dimension}
>    - super column family = {type of data represented in each cell}
>    - super column  = {time = week or month}
>    - column ={X dimension}
>    - value = { binary}
> 
> Will I be able to retrieve all values from a rectangle from this grid
> in a single call to cassandra for given SCF and SC ?

If I understand what you're asking, a rectangle (identified by X and Y
coordinates for a time-frame), will boil down to a single column. There
are certainly no problems with retrieving a single sub-column from a
super column.
 
> Will the result associate each value with its key and column ?

The result will be a column that contains the binary value, which you
obtained by using key, column family, and super column name. So, yes.

> Does it matter if it's a single call performance wise ? 

Yes, if for no other reason than it requires another round-trip across
the network.

-- 
Eric Evans
eevans@rackspace.com


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