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MapDB 0.9.1 发布了，MapDB 提供了并发的 TreeMap 和 HashMap ，使用基于磁盘的存储。快速、可伸缩性以及易用。
0.9.1 版本修复了首个 0.9.0 版本中一些非常紧急的 bug，包括：
- Issue #119 - BTreeMap (TreeMap) may not release all locks and consequently crash. This is unconfirmed and hard to replicate concurrent bug. I temporarily added assertion which slows down BTreeMap updates, but helps to diagnose this problem
- Issue #118 - StoreWAL fails to create log for unknown reasons and crashes. Not reproduced yet, need to investigate.
- FIX #111 - Compaction fails with large data sets
- FIX - BTreeKeySerializer.ZERO_OR_POSITIVE_INT was broken
- FIX #89 - StoreAppend reopen failed
- FIX #112 - Compaction fails with WAL enabled
- FIX #114 - RandomAccessFile fails with WAL
- FIX #113 - MemoryMappedFile was not unlocked on Windows after DB close
- FIX - rewrite AsynwWriteEngine, fix many concurrent bugs
- FIX - Files were not synced on DB.close(). Possible data loss.
- FIX - free space reuse did not worked in StoreDirect and StoreWAL. Storage file grown infinitely with each update.
- FIX #116 - HTreeMap.isEmpty returned wrong result.
- FIX #121 - WAL could get corrupted in some cases.
- ADD - basic benchmark
- ADD - error message if file rename fails after compaction finishes
- ADD - #119 BTreeMap locking could not be fixed, I added assertion to help diagnose issue. Small performance drop on BTreeMap updates.
- ADD - performance improvement if Snapshot engine is not used.