darion-yaphet opened a new pull request, #55696:
URL: https://github.com/apache/spark/pull/55696
### What changes were proposed in this pull request?
This PR refactors RocksDBPersistenceEngine to improve performance and
operational flexibility by:
1. Introducing dedicated Column Families (app_, worker_, driver_) for
different metadata types.
2. Optimizing the read operation from O(N_total) to O(N_type) by using
type-specific Column Family iterators.
3. Replacing expensive string-based prefix matching (new
String(iter.key()).startsWith(...)) with a zero-allocation byte-level
comparison helper.
4. Implementing an automatic data migration path to move existing records
from the default Column Family to their respective new Column Families upon
startup.
5. Ensuring proper resource management by overriding close() to release
RocksDB handles and the database instance.
### Why are the changes needed?
Previously, all metadata was stored in the default Column Family. This
caused several issues:
- Scan efficiency: Even when reading a specific type of data (e.g.,
Applications), the iterator had to be filtered via prefix checks across the
entire keyspace.
- Performance overhead: Every iteration involved creating a new String
object from the byte array key for prefix verification, leading to significant
GC pressure in metadata-heavy clusters.
- Operational limits: Lack of granular configuration for different data
types (e.g., Memtable size, compression strategy).
### Does this PR introduce _any_ user-facing change?
No. The migration logic ensures that existing persisted state is
transparently moved to the new structure without data loss.
### How was this patch tested?
- Verified with existing Standalone Master recovery tests.
- Manual verification of data migration from legacy single-CF RocksDB
instances.
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