title: Why is Scala Join Timing Out?
body: <p>I am trying to join a table to itself. I am getting rows of a table, then, on a second request, getting rows again (so they may or may not be the same rows) and limiting each of them to 10 rows each. I can show each of the result sets, but when I join them, Scala just hangs and then times out. What could be the issue?</p>
  
  <pre><code>override def joinMe(): Unit = {
  val conf: Config = ConfigFactory.load()
  
  val options = SparkOptions.createOptions(conf.getString("dashDb.driver"),
    conf.getString("dashDb.url"),
    conf.getString("dashDb.username"),
    conf.getString("dashDb.password"),
    "1000",
    conf.getString("dashDb.dbTable")
  )
  val sourceDF = JdbcRepository.read(options).limit(10)
  
  sourceDF.show()
  
  val targetDF = sourceDF
  
  targetDF.show()
  
  sourceDF.join(
    targetDF,
    sourceDF("EMPLOYEE_CNUM_ID") === targetDF("EMPLOYEE_CNUM_ID")
  ).show(10)
  }
  </code></pre>
  
  <p>but I receive this error:</p>
  
  <pre><code>Exception in thread "main" java.util.concurrent.TimeoutException: Futures timed out after [300 seconds]
  </code></pre>
  
  <p><strong>Thanks for your time!</strong></p>