Closes #747 - Creates an automatic ephemeral (in-memory) index on the right-side table of a join if otherwise a nested table scan would be selected. - This behavior is not hardcoded; instead this PR introduces a (quite dumb) cost estimator that naturally deincentivizes building ephemeral indexes where they don't make sense (e.g. the outermost table). I will probably build this estimator to be smarter in the future when working on join reordering optimizations ### Example bytecode plans and runtimes (note that this is debug mode) Example query with no persistent indexes to choose from. Without ephemeral index it's a nested scan: ```sql limbo> explain select * from t1 natural join t2; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 13 0 0 Start at 13 1 OpenRead 0 2 0 0 table=t1, root=2 2 OpenRead 1 3 0 0 table=t2, root=3 3 Rewind 0 12 0 0 Rewind t1 4 Rewind 1 11 0 0 Rewind t2 5 Column 0 0 2 0 r[2]=t1.a 6 Column 1 0 3 0 r[3]=t2.a 7 Ne 2 3 10 0 if r[2]!=r[3] goto 10 8 Column 0 0 1 0 r[1]=t1.a 9 ResultRow 1 1 0 0 output=r[1] 10 Next 1 5 0 0 11 Next 0 4 0 0 12 Halt 0 0 0 0 13 Transaction 0 0 0 0 write=false 14 Goto 0 1 0 0 limbo> .timer on limbo> select * from t1 natural join t2; ┌───┐ │ a │ ├───┤ └───┘ Command stats: ---------------------------- total: 953 ms (this includes parsing/coloring of cli app) ``` Same query with autoindexing enabled: ```sql limbo> explain select * from t1 natural join t2; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 22 0 0 Start at 22 1 OpenRead 0 2 0 0 table=t1, root=2 2 OpenRead 1 3 0 0 table=t2, root=3 3 Rewind 0 21 0 0 Rewind t1 4 Once 12 0 0 0 goto 12 # execute block 5-11 only once, on subsequent iters jump straight to 12 5 OpenAutoindex 3 0 0 0 cursor=3 6 Rewind 1 12 0 0 Rewind t2 # open source table for ephemeral index 7 Column 1 0 2 0 r[2]=t2.a 8 RowId 1 3 0 0 r[3]=t2.rowid 9 MakeRecord 2 2 4 0 r[4]=mkrec(r[2..3]) 10 IdxInsert 3 4 2 0 key=r[4] # insert stuff to ephemeral index 11 Next 1 7 0 0 12 Column 0 0 5 0 r[5]=t1.a 13 IsNull 5 20 0 0 if (r[5]==NULL) goto 20 14 SeekGE 3 20 5 0 key=[5..5] # perform seek on ephemeral index 15 IdxGT 3 20 5 0 key=[5..5] 16 DeferredSeek 3 1 0 0 17 Column 0 0 1 0 r[1]=t1.a 18 ResultRow 1 1 0 0 output=r[1] 19 Next 2 15 0 0 20 Next 0 4 0 0 21 Halt 0 0 0 0 22 Transaction 0 0 0 0 write=false 23 Goto 0 1 0 0 limbo> .timer on limbo> select * from t1 natural join t2; ┌───┐ │ a │ ├───┤ └───┘ Command stats: ---------------------------- total: 220 ms (this includes parsing/coloring of cli app) ``` Closes #1356
Project Limbo
Limbo is a project to build the modern evolution of SQLite.
Features and Roadmap
Limbo is a work-in-progress, in-process OLTP database engine library written in Rust 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, Go, Python, and Java
- OS support for Linux, macOS, and Windows
In the future, we will be also working on:
- Integrated vector search for embeddings and vector similarity.
BEGIN CONCURRENTfor improved write throughput.- Improved schema management including better
ALTERsupport and strict column types by default.
Getting Started
💻 Command Line
You can install the latest `limbo` release with:
curl --proto '=https' --tlsv1.2 -LsSf \
https://github.com/tursodatabase/limbo/releases/latest/download/limbo_cli-installer.sh | sh
Then launch the shell to execute SQL statements:
Limbo
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database
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
You can also build and run the latest development version with:
cargo run
🦀 Rust
cargo add limbo
Example usage:
let db = Builder::new_local("sqlite.db").build().await?;
let conn = db.connect()?;
let res = conn.query("SELECT * FROM users", ()).await?;
✨ JavaScript
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
pip install pylimbo
Example usage:
import limbo
con = limbo.connect("sqlite.db")
cur = con.cursor()
res = cur.execute("SELECT * FROM users")
print(res.fetchone())
🐹 Go
- Clone the repository
- Build the library and set your LD_LIBRARY_PATH to include limbo's target directory
cargo build --package limbo-go
export LD_LIBRARY_PATH=/path/to/limbo/target/debug:$LD_LIBRARY_PATH
- Use the driver
go get github.com/tursodatabase/limbo
go install github.com/tursodatabase/limbo
Example usage:
import (
"database/sql"
_"github.com/tursodatabase/limbo"
)
conn, _ = sql.Open("sqlite3", "sqlite.db")
defer conn.Close()
stmt, _ := conn.Prepare("select * from users")
defer stmt.Close()
rows, _ = stmt.Query()
for rows.Next() {
var id int
var username string
_ := rows.Scan(&id, &username)
fmt.Printf("User: ID: %d, Username: %s\n", id, username)
}
☕️ Java
We integrated Limbo into JDBC. For detailed instructions on how to use Limbo with java, please refer to the README.md under bindings/java.
Contributing
We'd love to have you contribute to Limbo! Please check out the contribution guide to get started.
FAQ
How is Limbo different from Turso's libSQL?
Limbo is a project to build the modern evolution of SQLite in Rust, with a strong open contribution focus and features like native async support, vector search, and more. The libSQL project is also an attempt to evolve SQLite in a similar direction, but through a fork rather than a rewrite.
Rewriting SQLite in Rust started as an unassuming experiment, and due to its incredible success, replaces libSQL as our intended direction. At this point, libSQL is production ready, Limbo is not - although it is evolving rapidly. As the project starts to near production readiness, we plan to rename it to just "Turso". More details here.
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]
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.
Contributors
Thanks to all the contributors to Limbo!
