title: cassandra cql delete using a less than operator on a secondary key
body: <p>I have a table similar to this </p>
  
  <pre><code>{
    CREATE TABLE timeseries (
      event_type text,
      insertion_time timestamp,
      event blob,
      PRIMARY KEY (event_type, insertion_time)
    )
  }
  </code></pre>
  
  <p>and I am trying to do </p>
  
  <pre><code>delete * from timseries where event_type='xxx' and insertion_time &lt;'12345';
  </code></pre>
  
  <p>Bad Request: Invalid operator LT for PRIMARY KEY part insertion_time. </p>
  
  <p>Does cassandra support these kind of deletes ? 
  Any help is appreciated. </p>