This really depends on the operations you want to optimize for.  What's important to you?  Aggregate queries?  Finding children/siblings/ancestors?  Reorganizing the tree/hierarchy?

For Cassandra, you really need to spend time thinking about how you'll be accessing things and design for that.

If it's a 2-3 level hierarchy, then straight forward approaches like what Jeff suggested seem logical.

Otherwise, I'd say if you've got an arbitrary-level hierarchy, then you'll have to think about how to efficiently adapt one of the usual suspects for this stuff (adjacency lists, nested sets, materialized paths, etc.).  I, for one, would be interested in knowing if anyone else's experienced with this kind of stuff in Cassandra.

http://stackoverflow.com/questions/192220/what-is-the-most-efficient-elegant-way-to-parse-a-flat-table-into-a-tree/192462#192462 

and the like might be good places to start.

On Sat, Mar 6, 2010 at 2:13 AM, Jeff Zhang <zjffdu@gmail.com> wrote:
use the parent as column family and the child as the column under the column family if this is two-level.
And you can use the super-column if there are more than two-levels



 

On Sat, Mar 6, 2010 at 1:31 AM, HubertChang <huixiu@gmail.com> wrote:

For examples, like tags, many parents to many children.
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Jeff Zhang



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