title: SQL Alchemy with oracle: converting column overflows integer datatype
body: <p>I extract data from an Oracle database with python 2.7 64 Bit . There is a field of the numeric type with 35 digits: 1200000000000000000000000000005151</p>
  
  <p>If I want to read this field with SQL Alchemy, I get the following error:</p>
  
  <pre><code>File "D:\Produkte\CoCo\Sourcen\ConsultingConnector\src\ais.py", line 253, in tabledata2table
      for row in tabledata.yield_per(buffersize).enable_eagerloads(False):
    File "C:\Python27\lib\site-packages\sqlalchemy\orm\loading.py", line 98, in instances
      util.raise_from_cause(err)
    File "C:\Python27\lib\site-packages\sqlalchemy\util\compat.py", line 203, in raise_from_cause
      reraise(type(exception), exception, tb=exc_tb, cause=cause)
    File "C:\Python27\lib\site-packages\sqlalchemy\orm\loading.py", line 71, in instances
      fetch = cursor.fetchmany(query._yield_per)
    File "C:\Python27\lib\site-packages\sqlalchemy\engine\result.py", line 1166, in fetchmany
      self.cursor, self.context)
    File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1413, in _handle_dbapi_exception
      exc_info
    File "C:\Python27\lib\site-packages\sqlalchemy\util\compat.py", line 203, in raise_from_cause
      reraise(type(exception), exception, tb=exc_tb, cause=cause)
    File "C:\Python27\lib\site-packages\sqlalchemy\engine\result.py", line 1159, in fetchmany
      l = self.process_rows(self._fetchmany_impl(size))
    File "C:\Python27\lib\site-packages\sqlalchemy\engine\result.py", line 1076, in _fetchmany_impl
      return self.cursor.fetchmany(size)
  sqlalchemy.exc.DatabaseError: (cx_Oracle.DatabaseError) ORA-01455: converting column overflows integer datatype (Background on this error at: http://sqlalche.me/e/4xp6)
  </code></pre>
  
  <p>It seems that SQL Alchemy is trying to cast in int, even though it's a long.
  Do you have any idea how I can solve the problem or something like a workaround?</p>
  
  <p>Thanks in advance,
  Jassin</p>