private static VectorExpressionWriter genVectorExpressionWritableByte(
      SettableByteObjectInspector fieldObjInspector) throws HiveException {
    return new VectorExpressionWriterLong() {
      private Object obj;

      public VectorExpressionWriter init(SettableByteObjectInspector objInspector)
          throws HiveException {
        super.init(objInspector);
        this.obj = initValue(null);
        return this;
      }

      @Override
      public Object writeValue(long value) throws HiveException {
        ((SettableByteObjectInspector) this.objectInspector).set(this.obj, (byte) value);
        return this.obj;
      }

      @Override
      public Object setValue(Object field, long value) throws HiveException {
        if (null == field) {
          field = initValue(null);
        }
        ((SettableByteObjectInspector) this.objectInspector).set(field, (byte) value);
        return field;
      }

      @Override
      public Object initValue(Object ignored) {
        return ((SettableByteObjectInspector) this.objectInspector)
            .create((byte) 0);
      }
    }.init(fieldObjInspector);
  }
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