We often run into some issues like HIVE-6131which is due to inconsistent column descriptors between table and partitions after alter table.
HIVE-8441/ HIVE-7971 provided the flexibility to alter table at partition level. But most cases we have need change the table and partitions at same time. In addition, "alter table" is usually required prior to "alter table partition .." since querying table partition data is also through table. Instead of do that in two steps, here we provide a convenient ddl like "alter table ... cascade" to cascade table changes to partitions as well. The changes are only limited and applicable to add/replace columns and change column name, datatype, position and comment.