af039ffa6e
#708 This PR adds basic support for the following API for defining Aggregates, and changes the existing API for scalars. ```rust register_extension! { scalars: { Double }, aggregates: { MedianState }, } #[derive(ScalarDerive)] struct Double; impl Scalar for Double { fn name(&self) -> &'static str { "double" } fn call(&self, args: &[Value]) -> Value { if let Some(arg) = args.first() { match arg.value_type() { ValueType::Float => { let val = arg.to_float().unwrap(); Value::from_float(val * 2.0) } ValueType::Integer => { let val = arg.to_integer().unwrap(); Value::from_integer(val * 2) } _ => { println!("arg: {:?}", arg); Value::null() } } } else { Value::null() } } } #[derive(AggregateDerive)] struct MedianState; impl AggFunc for MedianState { type State = Vec<f64>; fn name(&self) -> &'static str { "median" } fn args(&self) -> i32 { 1 } fn step(state: &mut Self::State, args: &[Value]) { if let Some(val) = args.first().and_then(Value::to_float) { state.push(val); } } fn finalize(state: Self::State) -> Value { if state.is_empty() { return Value::null(); } let mut sorted = state; sorted.sort_by(|a, b| a.partial_cmp(b).unwrap()); let len = sorted.len(); if len % 2 == 1 { Value::from_float(sorted[len / 2]) } else { let mid1 = sorted[len / 2 - 1]; let mid2 = sorted[len / 2]; Value::from_float((mid1 + mid2) / 2.0) } } } ``` I know it's a bit more verbose than the previous version, but I think in the long run this will be more robust, and it matches the aggregate API of implementing a trait on a struct that you derive the relevant trait on. Also this allows for better registration of functions, I think passing in the struct identifiers just feels much better than the `"func_name" => function_ptr` Closes #721
Limbo
Limbo is a work-in-progress, in-process OLTP database management system, compatible with SQLite.
Features
Limbo is an in-process OLTP database engine library that has:
- Asynchronous I/O support on Linux with
io_uring - SQLite compatibility [doc] for SQL dialect, file formats, and the C API
- Language bindings for JavaScript/WebAssembly, Rust, Python, and Java
- OS support for Linux, macOS, and Windows
Getting Started
CLI
Install limbo with:
curl --proto '=https' --tlsv1.2 -LsSf \
https://github.com/tursodatabase/limbo/releases/latest/download/limbo-installer.sh | sh
Then use the SQL shell to create and query a database:
$ limbo database.db
Limbo v0.0.6
Enter ".help" for usage hints.
limbo> CREATE TABLE users (id INT PRIMARY KEY, username TEXT);
limbo> INSERT INTO users VALUES (1, 'alice');
limbo> INSERT INTO users VALUES (2, 'bob');
limbo> SELECT * FROM users;
1|alice
2|bob
JavaScript (wip)
Installation:
npm i limbo-wasm
Example usage:
import { Database } from 'limbo-wasm';
const db = new Database('sqlite.db');
const stmt = db.prepare('SELECT * FROM users');
const users = stmt.all();
console.log(users);
Python (wip)
pip install pylimbo
Example usage:
import limbo
con = limbo.connect("sqlite.db")
cur = con.cursor()
res = cur.execute("SELECT * FROM users")
print(res.fetchone())
Developing
Build and run limbo cli:
cargo run --package limbo --bin limbo database.db
Run tests:
cargo test
Test coverage report:
cargo tarpaulin -o html
Note
Generation of coverage report requires tarpaulin binary to be installed. You can install it with
cargo install cargo-tarpaulin
Tip
If coverage fails with "Test failed during run" error and all of the tests passed it might be the result of tarpaulin bug. You can temporarily set dynamic libraries linking manually as a workaround, e.g. for linux
LD_LIBRARY_PATH="$(rustc --print=target-libdir)" cargo tarpaulin -o html.
Run benchmarks:
cargo bench
Run benchmarks and generate flamegraphs:
echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
cargo bench --bench benchmark -- --profile-time=5
FAQ
How is Limbo different from libSQL?
Limbo is a research project to build a SQLite compatible in-process database in Rust with native async support. The libSQL project, on the other hand, is an open source, open contribution fork of SQLite, with focus on production features such as replication, backups, encryption, and so on. There is no hard dependency between the two projects. Of course, if Limbo becomes widely successful, we might consider merging with libSQL, but that is something that will be decided in the future.
Publications
- Pekka Enberg, Sasu Tarkoma, Jon Crowcroft Ashwin Rao (2024). Serverless Runtime / Database Co-Design With Asynchronous I/O. In EdgeSys ‘24. [PDF]
- Pekka Enberg, Sasu Tarkoma, and Ashwin Rao (2023). Towards Database and Serverless Runtime Co-Design. In CoNEXT-SW ’23. [PDF] [Slides]
Contributing
We'd love to have you contribute to Limbo! Check out the contribution guide to get started.
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Limbo by you, shall be licensed as MIT, without any additional terms or conditions.