These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.
- HBASE-26274 | Major | Create an option to reintroduce BlockCache to mapreduce job
Introduce `hfile.onheap.block.cache.fixed.size` and default to disable. When using ClientSideRegionScanner, it will be enabled with a fixed size for caching INDEX/LEAF_INDEX block when a client, e.g. snapshot scanner, scans the entire HFile and does not need to seek/reseek to index block multiple times.