title: data load time when using spark with oracle
body: <p>I am trying to load data from oracle to spark in juypter notebook.But each time I try to pot graph the time taken is huge. How do I make it faster?</p>
  
  <pre><code>query = "(select * from db.schema where lqtime between trunc(sysdate)-30 and trunc(sysdate) )"
  %time df = sqlContext.read.format('jdbc').options(url="jdbc:oracle:thin:useradmin/pass12@//localhost:1521/aldb",dbtable=query,driver="oracle.jdbc.OracleDriver").load()
  </code></pre>
  
  <p>Now I group by node:</p>
  
  <pre><code>%time fo_node = df.select('NODE').groupBy('NODE').count().sort('count',ascending=False)
  %time fo_node.show(10)
  </code></pre>
  
  <p>The load time is 4m or more each time I run this.</p>