https://github.com/siennathesane/cesiumdb
Low-level LSM-tree key value store.
https://github.com/siennathesane/cesiumdb
database lsm-tree rust
Last synced: 3 months ago
JSON representation
Low-level LSM-tree key value store.
- Host: GitHub
- URL: https://github.com/siennathesane/cesiumdb
- Owner: siennathesane
- License: other
- Created: 2023-12-05T11:04:55.000Z (over 2 years ago)
- Default Branch: mainline
- Last Pushed: 2026-02-10T20:55:43.000Z (5 months ago)
- Last Synced: 2026-03-08T00:55:00.849Z (4 months ago)
- Topics: database, lsm-tree, rust
- Language: Rust
- Homepage:
- Size: 628 KB
- Stars: 2
- Watchers: 0
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: COPYING
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README
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# CesiumDB
A key-value store focused on performance.
# Work In Progress
This project is an active work-in-progress.
It will likely compile, and most tests will likely pass, but it is not feature complete yet. The current state of work
is stabilizing the embedded filesystem implementation so the front end memtables can rely on the backend embedded
filesystem. Once that work is done, then it's just implementing levels (relatively easy) and compaction (easy enough).
## Inspiration
This project was heavily inspired and influenced by (in no particular order):
* Long compile times for Facebook's `rocksdb`
* Howard Chu's `lmdb`
* CockroachDB's `pebble`
* Ben Johnson's `boltdb`
* Google's `leveldb`
* Giorgos Xanthakis et al's `parallax`
* A burning desire to have a rust-native LSM-tree that has column family/namespace support
## Interesting Features
It's :sparkles: __FAST__ :sparkles: and has a few interesting features:
* A blazingly fast hybrid logical clock (HLC) for ordering operations instead of MVCC semantics
* A high-performance, lock-free, thread-safe, portable filesystem that works with block devices
* An insanely fast bloom filter for fast lookups
### How _Fast_ is Fast?
I'm glad you asked! Here are some benchmarks:
* Internal bloom filter lookups: ~860 _picoseconds_
* Merge operator: ~115ms for a full table scan of 800,000 keys across 8 memtables
## Usage
Add this to your `Cargo.toml`:
```toml
[dependencies]
cesiumdb = "1.0"
```
And use:
```rust
use cesiumdb::CesiumDB;
// use a temp file, most useful for testing
let db = CesiumDB::default ();
// no namespace
db.put(b"key", b"value");
db.get(b"key");
// with a namespace
db.put(1, b"key", b"value");
db.get(1, b"key");
```
See the [API documentation](https://docs.rs/cesiumdb) for more information.
## Namespaces are not Column Families
CesiumDB uses a construct I call "namespacing". It's a way for data of a similar type to be grouped together, but it is
not stored separately than other namespaced data. Namespaces are ultimately glorified range markers to ensure fast data
lookups across a large set of internal data, and a bit of a way to make it easy for users to manage their data. I would
argue namespaces are closer to tables than column families.
## Hybrid Logical Clocks
CesiumDB does let you bring your own hybrid logical clock implementation for key versioning. This is useful if you have
a specific HLC implementation you want to use, or if you want to use a different clock entirely. This is done by
implementing the `HLC` trait and passing it to the `CesiumDB` constructor. However, if you can provide a more precise
clock than the provided one, please submit an issue or PR so we can all benefit from it.
## Unsafety: Or... How To Do Dangerous Things Safely
There is a non-trivial amount of `unsafe` code. Most of it is related to the internal implementation with `mmap` (which
cannot be made safe) and it's entrypoints (the handlers and such). I also make use of pointer arithmetic on
memory-mapped file locations. This is one of the areas where safety comes at the cost of performance. However, if you
can find a way to make it safe, please submit an issue or PR. I would love to see it!
There is :sparkles: __EXTENSIVE__ :sparkles: testing around the `unsafe` code, and I am confident in its correctness. My
goal is to keep this project at a high degree of code coverage with tests to help continue to ensure said confidence.
However, if you find a bug, please submit an issue or PR.
## Contributing
Contributions are welcome! Please submit a PR with your changes. If you're unsure about the changes, please submit an
issue first.
## To Do's
An alphabetical list of things I'd like to actually do for the long-term safety and stability of the project.
- [ ] Add `loom` integration tests.
- [ ] Add `miri` integration tests.
- [ ] Add more granular `madvise` commands to the filesystem to give the kernel some hints.
- [ ] Add some kind of `fsck` and block checksums since journaling is already present. There are basic unit tests for
this but no supported tool for it.
- [ ] Bloom filter size is currently hardcoded. I'd like to make it configurable.
- [ ] Determine how to expose the untrustworthiness of the bloom filter.
- [ ] Figure out how hard it would be to support `no_std` for the embedded workloads. I suspect it would be... difficult
lol
- [ ] Investigate the point at which we can no longer `mmap` a physical device. Theoretically, even without swap space,
I can `mmap` a 1TiB physical device to the filesystem implementation. But I feel like shit gets real weird. Idk, it's
a Linux-ism I want to investigate.
- [ ] Remove the question mark operator.
- [ ] Revisit the merge iterator. The benchmarks have it at ~115ms for a full scan of 8 memtables with 100,000 keys
each. I have no idea if this is a mismatch of my expectations or a gross inability of mine to optimize it further.
Every optimization I've tried is 5-20% slower (including my own cache-optimized min heap) than this.
- [ ] Write some kind of auto-configuration for the generalized configs.
## License
CesiumDB is licensed under GPL v3.0 with the Class Path Exception. This means you can safely link to CesiumDB in your
project. So it's safe for corporate consumption, just not closed-source modification :simple_smile:
If you would like a non-GPL license, please reach out :simple_smile: