title: Apache Spark 2.0 - date_add function
body: <p>I have a simple schema with a date and an int. I want to use date_add to add the int to the date.</p>
  
  <pre><code>scala&gt; val ds1 = spark.read.option("inferSchema",true).csv("samp.csv")
  
  ds1.printSchema();
  
  root
   |-- _c0: timestamp (nullable = true)
   |-- _c1: integer (nullable = true)
  </code></pre>
  
  <p>I cannot get the first param to date_add work...please help!</p>
  
  <pre><code>scala&gt; val ds2 = ds1.map ( x =&gt; date_add(x.getAs[timestamp]("_c0"),  x.getAs[Int]("_c1")))
  &lt;console&gt;:28: error: not found: type timestamp
  
  scala&gt; val ds2 = ds1.map ( x =&gt; date_add(x.getAs[Column]("_c0"), x.getAs[Int] ("_c1")))
  &lt;console&gt;:28: error: not found: type Column
  </code></pre>