RocksDB 4.6.0 发布了，RocksDB 是一个来自 facebook 的可嵌入式的支持持久化的 key-value 存储系统，也可作为 C/S 模式下的存储数据库，但主要目的还是嵌入式。RocksDB 基于 LevelDB 构建。关于 RocksDB 的性能说明。
改进日志：
Change default of BlockBasedTableOptions.format_version to 2. It means default DB created by 4.6 or up cannot be opened by RocksDB version 3.9 or earlier.
Added strict_capacity_limit option to NewLRUCache. If the flag is set to true, insert to cache will fail if no enough capacity can be free. Signiture of Cache::Insert() is updated accordingly.
Tickers [NUMBER_DB_NEXT, NUMBER_DB_PREV, NUMBER_DB_NEXT_FOUND, NUMBER_DB_PREV_FOUND, ITER_BYTES_READ] are not updated immediately. The are updated when the Iterator is deleted.
Add monotonically increasing counter (DB property "rocksdb.current-super-version-number") that increments upon any change to the LSM tree. ### New Features
Add CompactionPri::kMinOverlappingRatio, a compaction picking mode friendly to write amplification.
Deprecate Iterator::IsKeyPinned() and replace it with Iterator::GetProperty() with prop_name="rocksdb.iterator.is.key.pinned"
更多请看：https://github.com/facebook/rocksdb/blob/master/HISTORY.md