title: Pyspark error while querying cassandra to convert into dataframes
body: <p>I am getting the following error while executing the command:</p>
  
  <pre><code>user = sc.cassandraTable("DB NAME", "TABLE NAME").toDF()
  
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/local/src/spark/spark-1.4.1/python/pyspark/sql/context.py", line 60, in toDF
      return sqlContext.createDataFrame(self, schema, sampleRatio)
    File "/usr/local/src/spark/spark-1.4.1/python/pyspark/sql/context.py", line 333, in createDataFrame
      schema = self._inferSchema(rdd, samplingRatio)
    File "/usr/local/src/spark/spark-1.4.1/python/pyspark/sql/context.py", line 220, in _inferSchema
      raise ValueError("Some of types cannot be determined by the "
  ValueError: Some of types cannot be determined by the first 100 rows, please try again with sampling
  </code></pre>