Jussi Saurio 0b627ed331 Merge 'btree/balance: support case where immediate parent page of unbalanced child page also overflows' from Jussi Saurio
Closes #2241
## What
When an index interior cell is deleted, it steals the leaf cell with the
largest key in its left subtree, deletes the old interior cell and then
replaces it with the stolen cell. This ensures the binary-search-tree
aspect of the btree remains correct. However, this can cause a situation
where both are true:
1. The leaf page is now UNDERFULL and must be rebalanced
2. The leaf's IMMEDIATE parent page is now OVERFULL and must be
rebalanced
## Why is this a problem
We simply didn't support the case where:
- Leaf page P is unbalanced and rebalancing starts on it
- Its immediate parent is ALSO unbalanced and _overflows_.
We had an assertion against this happening (see #2241)
## The fix
Allow exactly 1 overflow cell in the parent under very particular
conditions:
1. The parent page must be an index interior page
2. The parent must be positioned exactly at the divider cell whose left
child page underflows
This is the _only_ case where the immediate parent of a page about to
undergo rebalancing can have overflow cells.
## Implementation details
The parent overflow cell is folded into `cell_array` fairly early on and
`parent.overflow_cells` is cleared. However we need to be careful with
`cell_idx` for dividers other than the overflow cell because they get
shifted left on the page in `drop_cell()`. I've added a long comment
about this.
## Testing
Adds fuzz test that does inserts and deletes on an index btree and
asserts that all the expected keys are found at the end in the right
order. This test runs into this case quite frequently so I was able to
verify it.

Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>

Closes #2243
2025-07-24 18:48:36 +03:00
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Turso Database

Turso Database

Turso Database is an in-process SQL database, compatible with SQLite.

PyPI PyPI PyPI

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Chat with other users of Turso (and Turso Cloud) on Discord


Features

Turso Database is a work-in-progress, in-process OLTP database engine library written in Rust that has:

  • SQLite compatibility for SQL dialect, file formats, and the C API [see document for details]
  • Change data capture (CDC) for real-time tracking of database changes.
  • Language support for
  • Asynchronous I/O support on Linux with io_uring
  • OS support for Linux, macOS, and Windows

Roadmap

The following features are on our current roadmap:

  • BEGIN CONCURRENT for improved write throughput using multi-version concurrency control (MVCC).
  • Better schema management, including extended ALTER support, faster schema changes, and strict column types by default.
  • Incremental computation using DBSP to implement query subscriptions, incremental view maintenance, and triggers.
  • Vector indexing for fast approximate vector search, similar to libSQL vector search.

Getting Started

Please see the Turso Database Manual for more information.

💻 Command Line
You can install the latest `turso` release with:
curl --proto '=https' --tlsv1.2 -LsSf \
  https://github.com/tursodatabase/turso/releases/latest/download/turso_cli-installer.sh | sh

Then launch the shell to execute SQL statements:

Turso
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database
turso> CREATE TABLE users (id INT, username TEXT);
turso> INSERT INTO users VALUES (1, 'alice');
turso> INSERT INTO users VALUES (2, 'bob');
turso> SELECT * FROM users;
1|alice
2|bob

You can also build and run the latest development version with:

cargo run

MCP Server Mode

The Turso CLI includes a built-in Model Context Protocol (MCP) server that allows AI assistants to interact with your databases. Start the MCP server with:

tursodb your_database.db --mcp

The MCP server provides seven tools for database interaction:

Available Tools

  1. list_tables - List all tables in the database
  2. describe_table - Describe the structure of a specific table
  3. execute_query - Execute read-only SELECT queries
  4. insert_data - Insert new data into tables
  5. update_data - Update existing data in tables
  6. delete_data - Delete data from tables
  7. schema_change - Execute schema modification statements (CREATE TABLE, ALTER TABLE, DROP TABLE)

Example Usage

The MCP server runs as a single process that handles multiple JSON-RPC requests over stdin/stdout. Here's how to interact with it:

Example with In-Memory Database

cat << 'EOF' | tursodb --mcp
{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {"protocolVersion": "2024-11-05", "capabilities": {}, "clientInfo": {"name": "client", "version": "1.0"}}}
{"jsonrpc": "2.0", "id": 2, "method": "tools/call", "params": {"name": "schema_change", "arguments": {"query": "CREATE TABLE users (id INTEGER, name TEXT, email TEXT)"}}}
{"jsonrpc": "2.0", "id": 3, "method": "tools/call", "params": {"name": "list_tables", "arguments": {}}}
{"jsonrpc": "2.0", "id": 4, "method": "tools/call", "params": {"name": "insert_data", "arguments": {"query": "INSERT INTO users VALUES (1, 'Alice', 'alice@example.com')"}}}
{"jsonrpc": "2.0", "id": 5, "method": "tools/call", "params": {"name": "execute_query", "arguments": {"query": "SELECT * FROM users"}}}
EOF

Example with Existing Database

# Working with an existing database file
cat << 'EOF' | tursodb mydb.db --mcp
{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {"protocolVersion": "2024-11-05", "capabilities": {}, "clientInfo": {"name": "client", "version": "1.0"}}}
{"jsonrpc": "2.0", "id": 2, "method": "tools/call", "params": {"name": "list_tables", "arguments": {}}}
EOF
🦀 Rust
cargo add turso

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 @tursodatabase/turso

Example usage:

import { Database } from '@tursodatabase/turso';

const db = new Database('sqlite.db');
const stmt = db.prepare('SELECT * FROM users');
const users = stmt.all();
console.log(users);
🐍 Python
pip install pyturso

Example usage:

import turso

con = turso.connect("sqlite.db")
cur = con.cursor()
res = cur.execute("SELECT * FROM users")
print(res.fetchone())
🦫 Go
  1. Clone the repository
  2. Build the library and set your LD_LIBRARY_PATH to include turso's target directory
cargo build --package limbo-go
export LD_LIBRARY_PATH=/path/to/limbo/target/debug:$LD_LIBRARY_PATH
  1. Use the driver
go get github.com/tursodatabase/turso
go install github.com/tursodatabase/turso

Example usage:

import (
    "database/sql"
    _ "github.com/tursodatabase/turso"
)

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 Turso Database into JDBC. For detailed instructions on how to use Turso Database with java, please refer to the README.md under bindings/java.

Contributing

We'd love to have you contribute to Turso Database! Please check out the contribution guide to get started.

Found a data corruption bug? Get up to $1,000.00

SQLite is loved because it is the most reliable database in the world. The next evolution of SQLite has to match or surpass this level of reliability. Turso is built with Deterministic Simulation Testing from the ground up, and is also tested by Antithesis.

Even during Alpha, if you find a bug that leads to a data corruption and demonstrate how our simulator failed to catch it, you can get up to $1,000.00. As the project matures we will increase the size of the prize, and the scope of the bugs.

More details here.

You can see an example of an awarded case on #2049.

Turso core staff are not eligible.

FAQ

Is Turso Database ready for production use?

Turso Database is currently under heavy development and is not ready for production use.

How is Turso Database different from Turso's libSQL?

Turso Database is a project to build the next 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, Turso Database is not - although it is evolving rapidly. 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 Turso Database by you, shall be licensed as MIT, without any additional terms or conditions.

Partners

Thanks to all the partners of Turso!

Contributors

Thanks to all the contributors to Turso Database!

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