AFAIK there is no way to get a list of the super columns, without also getting the sub columns. I do not know if there is a technical reason that would prevent this from being added. 

In general it's more efficient to make 1 request that pulls back more data, than two or more than pull back just enough data. But you also want to design to answer the queries you need to make.

Keeping an index of super column names in another CF does not sound too bad. it might pay to take another look at why you are using a super CF. It may be better to use two standard CF's if say you want to have one sort of request that gets a list of things, and another sort of request that gets the details for a number of things.

Aaron

On 16 Sep, 2010,at 07:25 PM, Saurabh Raje <saurabh@webaroo.com> wrote:

Hi,

I have a cassandra datastore as follows:
key:{
 supercol (utf8) : {
   subcol (timuuid) : data
 }
}

Now, for a particular usecase I want to do slice on 2 levels. Firstly
on supercols & then from the selected supercols results slice subcols
(mostly to restrict no of items fetched in mem). I have tried various
API's and there doesn't seem to be a way to do this. The reason being
when I slice supercols i get the subcols in the result too! Now,
ofcourse, I can add another index as follows:

key : {
   supercol (utf8) : <emptydata>
 }
}

Haven't looked at cassandra storage in too detail - but hoping there
is a better solution!

Thanks in advance