@Override
      public Object setValue(Object field, HiveDecimalWritable value) {
        if (null == field) {
          field = initValue(null);
        }
        return ((SettableHiveDecimalObjectInspector) this.objectInspector).set(field, value);
      }
Compiles the appropriate vector expression writers based on a struct object
inspector.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorExpressionWriterFactory.java