public RollbackType getRollbackType() {
      return rollbackType;
    }
Value object class, that stores the rollback operation specific parameters
<ul>
  <li>Rollback type: it can be either version based or time based</li>
  <li>Rollback value: it should either a snapshot id or a timestamp in milliseconds</li>
</ul>
ql/src/java/org/apache/hadoop/hive/ql/parse/AlterTableExecuteSpec.java