title: Converting dataframe columns into list of tuples
body: <p>I have:</p>
  
  <pre><code>val DF1 = sparkSession.sql("select col1,col2,col3 from table");
  val tupleList = DF1.select("col1","col2").rdd.map(r =&gt; (r(0),r(1))).collect()
  
  tupleList.foreach(x=&gt; x.productIterator.foreach(println))
  </code></pre>
  
  <p>But I do not get all the tuples in the output. Where is the issue?</p>
  
  <pre><code>col1 col2
  AA  CCC
  AA  BBB 
  DD  CCC 
  AB  BBB 
  Others  BBB 
  GG  ALL 
  EE  ALL 
  Others  ALL 
  ALL BBB 
  NU FFF 
  NU  Others 
  Others  Others 
  C   FFF 
  </code></pre>
  
  <p>The output I get is: 
      <code>CCC AA BBB AA Others AA Others DD ALL Others ALL GG ALL ALL</code></p>