On 6 March 2010 09:23, Hubert Chang <huixiu@gmail.com> wrote:
Like Category, Taxonomy, or folder/file, there will be multiple level hierarchical relationship.
 How to model it in Cassandra?
Serialize all the parent id and the item id together as the key?   
How to model it when one child has many parents?

If you have parent/child data, there is a good chance that it's not big enough to need to be stored in Cassandra.

Do you have > 1 billion items? If not, then put it in a conventional RDBMS.

If you have 1 billion items, but most of them are "leaf" nodes, it might be a good idea to put only the "leaf" nodes in Cassandra, and put the parent categories in a conventional database.

Cassandra is NOT a good general purpose database, it is for very specific cases of high data volume and high write workload.