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From aaron morton <aa...@thelastpickle.com>
Subject Re: find smallest counter
Date Mon, 22 Oct 2012 07:29:34 GMT
> So the groups are a super column with CategoryId as key, GroupId as superColumnName and
then columns for the group members.
If this is a new project please consider not using Super Columns. They have some limitations
http://wiki.apache.org/cassandra/CassandraLimitations and are often slower than a model that
only uses Standard CF's 

> But I can't figure out how to grab just the smallest group.
You cannot do that in a single statement / request. Cassandra does not support ordering by
column value (outside of secondary indexes) nor does it support aggregate operations. 

You will need to iterate the columns and find the smallest value. 

Cheers

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

On 22/10/2012, at 2:28 PM, Paul Loy <keteracel@gmail.com> wrote:

> I have a set of categories. In these categories I want to add groups of users. If a user
does not specify the group they want to join in a category, I want to add them to the least
subscribed group.
> 
> So the groups are a super column with CategoryId as key, GroupId as superColumnName and
then columns for the group members.
> 
> Then I was planning on having some counters so I could keep track of the group sizes.
I figured I'd have a counter column for the groups. The key being the CategoryId, then counter
columns named by the GroupId. But I can't figure out how to grab just the smallest group.
> 
> Many thanks in advance,
> 
> Paul.
> 
> -- 
> ---------------------------------------------
> Paul Loy
> paul@keteracel.com
> http://uk.linkedin.com/in/paulloy


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