HUDI specific validation of schema evolution should ensure that a newer schema can be used for the dataset by checking that the data written using the old schema can be read using the new schema.
Code changes:
1. Added a new config in HoodieWriteConfig to enable schema validation check (disabled by default)
2. Moved code that reads schema from base/log files into hudi-common from hudi-hive-sync
3. Added writerSchema to the extraMetadata of compaction commits in MOR table. This is same as that for commits on COW table.
Testing changes:
4. Extended TestHoodieClientBase to add insertBatch API which allows inserting a new batch of unique records into a HUDI table
5. Added a unit test to verify schema evolution for both COW and MOR tables.
6. Added unit tests for schema compatiblity checks.