public VectorExpressionWriter init(ObjectInspector objectInspector) throws HiveException {
      this.objectInspector = objectInspector;
      return this;
    }
The object inspector associated with this expression. This is created from the expression
NodeDesc (compile metadata) not from the VectorColumn info and thus preserves the type info
lost by the vectorization process.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorExpressionWriterFactory.java