## Main stuff - Support iterating an index backwards - Support scanning an index (instead of seeking with a condition) - Support backwards index seeks - Support backwards rowid seeks - Fix existing backwards iteration logic for table btrees - Remove ORDER BY entirely if any index satisfies the ordering - Add fuzz tests for rowid seeks, 1 and 2 column index seeks ## Bytecode examples (note the lack of order by sorting): one column index order by, forwards: ```sql limbo> explain select first_name from users order by age; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 13 0 0 Start at 13 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 274 0 0 table=age_idx, root=274 4 OpenReadAwait 0 0 0 0 5 RewindAsync 1 0 0 0 6 RewindAwait 1 12 0 0 Rewind table age_idx 7 DeferredSeek 1 0 0 0 8 Column 0 1 1 0 r[1]=users.first_name 9 ResultRow 1 1 0 0 output=r[1] 10 NextAsync 1 0 0 0 11 NextAwait 1 7 0 0 12 Halt 0 0 0 0 13 Transaction 0 0 0 0 write=false 14 Goto 0 1 0 0 ``` one column index order by, backwards: ```sql limbo> explain select first_name from users order by age desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 13 0 0 Start at 13 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 274 0 0 table=age_idx, root=274 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 DeferredSeek 1 0 0 0 8 Column 0 1 1 0 r[1]=users.first_name 9 ResultRow 1 1 0 0 output=r[1] 10 PrevAsync 1 0 0 0 11 PrevAwait 1 0 0 0 12 Halt 0 0 0 0 13 Transaction 0 0 0 0 write=false 14 Goto 0 1 0 0 ``` rowid seek, backwards: ```sql limbo> explain select * from users where id < 100 order by id desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 19 0 0 Start at 19 1 OpenReadAsync 0 2 0 0 table=users, root=2 2 OpenReadAwait 0 0 0 0 3 Integer 100 11 0 0 r[11]=100 4 SeekLT 0 18 11 0 5 RowId 0 1 0 0 r[1]=users.rowid 6 Column 0 1 2 0 r[2]=users.first_name 7 Column 0 2 3 0 r[3]=users.last_name 8 Column 0 3 4 0 r[4]=users.email 9 Column 0 4 5 0 r[5]=users.phone_number 10 Column 0 5 6 0 r[6]=users.address 11 Column 0 6 7 0 r[7]=users.city 12 Column 0 7 8 0 r[8]=users.state 13 Column 0 8 9 0 r[9]=users.zipcode 14 Column 0 9 10 0 r[10]=users.age 15 ResultRow 1 10 0 0 output=r[1..10] 16 PrevAsync 0 0 0 0 17 PrevAwait 0 0 0 0 18 Halt 0 0 0 0 19 Transaction 0 0 0 0 write=false 20 Goto 0 1 0 0 ``` two column order by, setup: ```sql cargo run dualpk.db Limbo v0.0.18-pre.3 Enter ".help" for usage hints. limbo> .schema CREATE TABLE a(b,c,d,e, primary key (d,c)); ``` two column order by, forwards: ```sql limbo> explain select * from a order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 RewindAsync 1 0 0 0 6 RewindAwait 1 15 0 0 Rewind table sqlite_autoindex_a_1 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 NextAsync 1 0 0 0 14 NextAwait 1 7 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, forwards with index seek: ```sql limbo> explain select * from a where d > 100 order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Integer 100 5 0 0 r[5]=100 6 SeekGT 1 15 5 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 NextAsync 1 0 0 0 14 NextAwait 1 7 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, forwards with index scan and termination condition: ```sql limbo> explain select * from a where d < 100 order by d,c; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 18 0 0 Start at 18 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Null 0 5 0 0 r[5]=NULL 6 SeekGT 1 17 5 0 7 Integer 100 6 0 0 r[6]=100 8 IdxGE 1 17 6 0 9 DeferredSeek 1 0 0 0 10 Column 0 0 1 0 r[1]=a.b 11 Column 0 1 2 0 r[2]=a.c 12 Column 0 2 3 0 r[3]=a.d 13 Column 0 3 4 0 r[4]=a.e 14 ResultRow 1 4 0 0 output=r[1..4] 15 NextAsync 1 0 0 0 16 NextAwait 1 7 0 0 17 Halt 0 0 0 0 18 Transaction 0 0 0 0 write=false 19 Goto 0 1 0 0 ``` two column order by, backwards: ```sql limbo> explain select * from a order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 PrevAsync 1 0 0 0 14 PrevAwait 1 0 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, backwards with index seek: ```sql limbo> explain select * from a where d < 100 order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 16 0 0 Start at 16 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 Integer 100 5 0 0 r[5]=100 6 SeekLT 1 15 5 0 7 DeferredSeek 1 0 0 0 8 Column 0 0 1 0 r[1]=a.b 9 Column 0 1 2 0 r[2]=a.c 10 Column 0 2 3 0 r[3]=a.d 11 Column 0 3 4 0 r[4]=a.e 12 ResultRow 1 4 0 0 output=r[1..4] 13 PrevAsync 1 0 0 0 14 PrevAwait 1 0 0 0 15 Halt 0 0 0 0 16 Transaction 0 0 0 0 write=false 17 Goto 0 1 0 0 ``` two column order by, backwards with index scan and termination condition: ```sql limbo> explain select * from a where d > 100 order by d desc,c desc; addr opcode p1 p2 p3 p4 p5 comment ---- ----------------- ---- ---- ---- ------------- -- ------- 0 Init 0 18 0 0 Start at 18 1 OpenReadAsync 0 2 0 0 table=a, root=2 2 OpenReadAwait 0 0 0 0 3 OpenReadAsync 1 3 0 0 table=sqlite_autoindex_a_1, root=3 4 OpenReadAwait 0 0 0 0 5 LastAsync 1 0 0 0 6 LastAwait 1 0 0 0 7 Integer 100 6 0 0 r[6]=100 8 IdxLE 1 17 6 0 9 DeferredSeek 1 0 0 0 10 Column 0 0 1 0 r[1]=a.b 11 Column 0 1 2 0 r[2]=a.c 12 Column 0 2 3 0 r[3]=a.d 13 Column 0 3 4 0 r[4]=a.e 14 ResultRow 1 4 0 0 output=r[1..4] 15 PrevAsync 1 0 0 0 16 PrevAwait 1 0 0 0 17 Halt 0 0 0 0 18 Transaction 0 0 0 0 write=false 19 Goto 0 1 0 0 ``` Reviewed-by: Preston Thorpe (@PThorpe92) Closes #1209
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
✨ 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!
