title: Cassandra - iterate over all Row Keys without duplicates on random partitioner
body: <p><code>get_range_slices</code> iterates over all keys also in case of random partitioner. As I understand result of this query will not return duplicated keys, because it goes ascending over ring. Since keys are hashed, Cassandra would need additional "index" to be able to execute such query - like each key would need to keep references to next key (which is not the case).</p>
  
  <p>Could someone give me some hints on how Cassandra realizes iteration over all keys in case of random partitioner?</p>