title: How to get all columns after groupby on Dataset<Row> in spark sql 2.1.0
body: <p>First, I am very new to SPARK</p>
  
  <p>I have millions of records in my Dataset and i wanted to groupby with name column and finding names which having maximum age. I am getting correct results but I need all columns in my resultset.</p>
  
  <pre><code>Dataset&lt;Row&gt; resultset = studentDataSet.select("*").groupBy("name").max("age");
  resultset.show(1000,false);
  </code></pre>
  
  <p>I am getting only name and max(age) in my resultset dataset.</p>