@Override
  public int precision() {
    if (value == null) {
      return super.precision();
    }
    return BigDecimal.valueOf(value.get()).precision();
  }
A WritableConstantByteObjectInspector is a WritableByteObjectInspector
that implements ConstantObjectInspector.
serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/primitive/WritableConstantByteObjectInspector.java