title: Python pandas read_sql returns generator object
body: <p>I am pulling data from Oracle db using pyodbc and pandas read_sql.</p>
  
  <p>I see no errors when I enter this line</p>
  
  <pre><code>df = pd.read_sql(sql_str,cnxn,chunksize=10)
  </code></pre>
  
  <p>But when I try to see </p>
  
  <pre><code>df
  </code></pre>
  
  <p>I get this error</p>
  
  <pre><code>&lt;generator object _query_iterator at 0x092D40F8&gt;
  </code></pre>
  
  <p>My search as to what this error means or what could be causing it yielded no satisfactory answers. </p>
  
  <p>The reason for using chunksize is that I have a Oracle db table with 60 million rows, and plan to download in bits and then put them together, just like here: 
  <a href="https://stackoverflow.com/questions/18107953/how-to-create-a-large-pandas-dataframe-from-an-sql-query-without-running-out-of">How to create a large pandas dataframe from an sql query without running out of memory?</a></p>