title: How aggregate by value in apache spark
body: <p>i have sucess read cassandra from spark, using this syntax :</p>
  
  <pre><code>val rddSelect = sc.cassandraTable("keyspace", "nametable").select("column1", "column2").take(100)
  </code></pre>
  
  <p>i need to do aggregate group by column1 and column2 in spark</p>
  
  <p>i have tried groupbykey and another transformations, but it's error :</p>
  
  <pre><code>value reduceByKey is not a member of Array[com.datastax.spark.connector.CassandraRow]
  </code></pre>
  
  <p>maybe anyone can give me a clue, thx</p>
  
  <p>NB : i use scala</p>