title: Drop spark dataframe from cache
body: <p>I am using Spark 1.3.0 with python api. While transforming huge dataframes, I cache many DFs for faster execution;</p>
  
  <pre><code>df1.cache()
  df2.cache()
  </code></pre>
  
  <p>Once use of certain dataframe is over and is no longer needed how can I drop DF from memory (or un-cache it??)? </p>
  
  <p>For example, <code>df1</code> is used through out the code while <code>df2</code> is utilized for few transformations and after that, it is never needed.  I want to forcefully drop <code>df2</code> to release more memory space.  </p>