title: Spark: Join dataframe column with an array
body: <p>I have two DataFrames with two columns </p>
  
  <ul>
  <li><p><code>df1</code> with schema <code>(key1:Long, Value)</code></p></li>
  <li><p><code>df2</code> with schema <code>(key2:Array[Long], Value)</code></p></li>
  </ul>
  
  <p>I need to join these DataFrames on the key columns (find matching values between <code>key1</code> and values in <code>key2</code>). But the problem is that they have not the same type. Is there a way to do this? </p>