High priority issues with schema evolution for the ORC file format.
Schema evolution here is limited to adding new columns and a few cases of column type-widening (e.g. int to bigint).
Renaming columns, deleting column, moving columns and other schema evolution were not pursued due to lack of importance and lack of time. Also, it appears a much more sophisticated metadata would be needed to support them.
The biggest issues for users have been adding new columns for ACID table (
HIVE-11421 Support Schema evolution for ACID tables) and vectorization ( HIVE-10598 Vectorization borks when column is added to table).