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From aaron morton <aa...@thelastpickle.com>
Subject Re: Composite Column Query Modeling
Date Fri, 14 Sep 2012 08:56:47 GMT
You _could_ use one wide row and do a multiget against the same row for different column slices.
Would be less efficient than a single get against the row. But you could still do big contiguous
column slices. 

You may get some benefit from the collections in CQL 3 http://www.datastax.com/dev/blog/cql3_collections

Hope that helps. 


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 14/09/2012, at 8:31 AM, Adam Holmberg <adam.holmberg.list@gmail.com> wrote:

> I'm modeling a new application and considering the use of SuperColumn vs. Composite Column
paradigms. I understand that SuperColumns are discouraged in new development, but I'm pondering
a query where it seems like SuperColumns might be better suited.
> 
> Consider a CF with SuperColumn layout as follows
> 
> t = {
>   k1: {
>     s1: { c1:v1, c2:v2 },
>     s2: { c1:v3, c2:v4 },
>     s3: { c1:v5, c2:v6}
>     ...
>   }
>   ...
> }
> 
> Which might be modeled in CQL3:
> 
> CREATE TABLE t (
>   k text,
>   s text,
>   c1 text,
>   c2 text,
>   PRIMARY KEY (k, s)
> );
> 
> I know that it is possible to do range slices with either approach. However, with SuperColumns
I can do sparse slice queries with a set (list) of column names as the SlicePredicate. I understand
that the composites API only returns contiguous slices, but I keep finding myself wanting
to do a query as follows:
> 
> SELECT * FROM t WHERE k = 'foo' AND s IN (1,3);
> 
> The question: Is there a recommended technique for emulating sparse column slices in
composites?
> 
> One suggestion I've read is to get the entire range and filter client side. This is pretty
punishing if the range is large and the second keys being queried are sparse. Additionally,
there are enough keys being queried that calling once per key is undesirable.
> 
> I also realize that I could manually composite k:s as the row key and use multiget, but
this gives away the benefit of having these records proximate when range queries are used.

> 
> Any input on modeling/query techniques would be appreciated.
> 
> Regards,
> Adam Holmberg
> 
> 
> P.S./Sidebar:
> --------------------
> What this seems like to me is a desire for 'multiget' at the second key level analogous
to multiget at the row key level. Is this something that could be implemented in the server
using SlicePredicate.column_names? Is this just an implementation gap, or is there something
technical I'm overlooking? 


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