public ObjectInspector getObjectInspector() {
    return oi;
  }
An AvroObjectInspectorGenerator takes an Avro schema and creates the three
data structures Hive needs to work with Avro-encoded data:
  * A list of the schema field names
  * A list of those fields equivalent types in Hive
  * An ObjectInspector capable of working with an instance of that datum.
serde/src/java/org/apache/hadoop/hive/serde2/avro/AvroObjectInspectorGenerator.java