README.md

A K.I.S.S. implementation of log-structured merge trees (LSM-trees/LSMTs) in Rust.

About

This is the most feature-rich LSM-tree implementation in Rust! It features:

• Thread-safe BTreeMap-like API
• Mostly safe & 100% stable Rust
• Block-based tables with compression support & prefix truncation
  • Optional block hash indexes in data blocks for faster point lookups [3]
  • Per-level filter/index block pinning configuration
• Range & prefix searching with forward and reverse iteration
• Block caching to keep hot data in memory
• File descriptor caching with upper bound to reduce fopen syscalls
• AMQ filters (currently Bloom filters) to improve point lookup performance
• Multi-versioning of KVs, enabling snapshot reads
• Optionally partitioned block index & filters for better cache efficiency [1]
• Leveled and FIFO compaction
• Optional key-value separation for large value workloads [2], with automatic garbage collection
• Single deletion tombstones ("weak" deletion)
• Optional compaction filters to run custom logic during compactions

Keys are limited to 65536 bytes, values are limited to $2^{32}$ bytes. As is normal with any kind of storage engine, larger keys and values have a bigger performance impact.

Sponsors

Feature flags

lz4

Allows using LZ4 compression, powered by lz4_flex.

Disabled by default.

bytes_1

Uses bytes 1.x as the underlying Slice type.

Disabled by default.

Run unit benchmarks

cargo bench --features lz4

License

All source code is licensed under MIT OR Apache-2.0.

All contributions are to be licensed as MIT OR Apache-2.0.

Footnotes

[1] https://rocksdb.org/blog/2017/05/12/partitioned-index-filter.html

[2] https://github.com/facebook/rocksdb/wiki/BlobDB

[3] https://rocksdb.org/blog/2018/08/23/data-block-hash-index.html