HIVE-20346
When we upgrade hive from a low version(1.1.0) to higher version(2.3.3), we will have to: backup the old hive metastore database Use schema tool to upgrade the hive metastore database schema. Then several days after the upgrading, new version hive have some critical problems and we want to revert to previous hive, what could we do? Since during these days the data in hive metastore has changed. So, if we directly switch to the old hive metastore, any metadata changes after the upgrading will lose. So , I think we need a rollback script, which is used to downgrade our high version metastore schema to low version schema.
