@Override
  public ObjectInspector getWritableObjectInspector() {
    if (writableObjectInspector == null) {
      writableObjectInspector = TypeInfoUtils.getStandardWritableObjectInspectorFromTypeInfo(typeInfo);
    }
    return writableObjectInspector;
  }
This class uses a writableObjectInspector rather than a TypeInfo to store
the canonical type information for this NodeDesc.
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeGenericFuncDesc.java