Musq

Musq is an asynchronous SQLite toolkit for Rust.

Musq bundles its own SQLite, runs each connection on a dedicated worker thread behind an async API, enables foreign key enforcement by default, and ships with sqlite-vec vector search built in.

Quickstart

//! Quickstart example from the README.

use musq::{FromRow, Musq, sql, sql_as, values};

/// User record fetched from the database.
#[derive(Debug, FromRow)]
pub struct User {
    /// User ID.
    pub id: i32,
    /// User name.
    pub name: String,
}

#[tokio::main]
async fn main() -> musq::Result<()> {
    // Create an in-memory database pool
    let pool = Musq::new().open_in_memory().await?;

    // Create a table
    sql!("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT NOT NULL);")?
        .execute(&pool)
        .await?;

    // Insert a user
    let id = 1;
    let name = "Alice";
    let user_values = values! { "id": id, "name": name }?;
    sql!("INSERT INTO users {insert:user_values}")?
        .execute(&pool)
        .await?;

    // Fetch the user and map it to our struct
    let user: User = sql_as!("SELECT id, name FROM users WHERE id = {id}")?
        .fetch_one(&pool)
        .await?;

    println!("Fetched user: {user:?}");

    Ok(())
}

Opening a database

Musq is the options builder. open() and open_in_memory() return a Pool; queries execute directly on the pool, on a Connection, a PoolConnection, or a Transaction — all interchangeably.

use musq::{JournalMode, Musq};

let pool = Musq::new()
    .max_connections(10)
    .create_if_missing(true)
    .journal_mode(JournalMode::Wal)
    .open("app.db")
    .await?;

Defaults: foreign keys on, busy timeout 5s, 10 pool connections, journal mode left unchanged (set JournalMode::Wal explicitly for WAL). Any pragma can be set with .pragma(key, value).

Queries

sql! builds a query from a format!-like string. sql_as! does the same and maps rows to a FromRow type. Interpolated values are always bound as parameters, never spliced into the SQL.

use musq::{FromRow, sql, sql_as};

#[derive(FromRow, Debug)]
struct User {
    id: i32,
    name: String,
}

let id = 1;
let name = "Bob";

sql!("INSERT INTO users (id, name) VALUES ({id}, {name})")?
    .execute(&pool)
    .await?;

let user: User = sql_as!("SELECT id, name FROM users WHERE id = {id}")?
    .fetch_one(&pool)
    .await?;

Placeholders:

let table_name = "users";
let user_ids = vec![1, 2, 3];
let columns = ["id", "name"];

let users: Vec<User> = sql_as!(
    "SELECT {idents:columns} FROM {ident:table_name} WHERE id IN ({values:user_ids})"
)?
.fetch_all(&pool)
.await?;

Run queries with .execute(), .fetch_one(), .fetch_optional(), .fetch_all(), or .fetch() (a Stream). Compose dynamic queries with Query::join, or drop down to QueryBuilder for full control.

Values

Values is an insertion-ordered column/value map consumed by the {insert:}, {set:}, {where:}, and {upsert:} placeholders. Build one with the values! macro or fluently with Values::new().val(k, v)?. Each value is encoded immediately, so construction returns Result.

use musq::{Values, sql, sql_as, values};

let user_data = values! { "id": 1, "name": "Alice", "status": "active" }?;

sql!("INSERT INTO users {insert:user_data}")?
    .execute(&pool)
    .await?;

let changes = Values::new()
    .val("name", "Alicia")?
    .val("status", "inactive")?;

sql!("UPDATE users SET {set:changes} WHERE id = 1")?
    .execute(&pool)
    .await?;

let filters = values! { "status": "inactive" }?;
let user: User = sql_as!("SELECT id, name FROM users WHERE {where:filters}")?
    .fetch_one(&pool)
    .await?;

let upsert = values! { "id": 1, "name": "Alicia", "status": "active" }?;
sql!(
    "INSERT INTO users {insert:upsert} ON CONFLICT(id) DO UPDATE SET {upsert:upsert, exclude: id}"
)?
.execute(&pool)
.await?;

Option::None encodes as SQL NULL everywhere ({where:} renders it as col IS NULL), and musq::Null is an untyped NULL literal:

async fn add_user(
    pool: &musq::Pool,
    name: &str,
    phone: Option<String>,
) -> musq::Result<()> {
    let user_data = values! {
        "name": name,
        "phone": phone,      // Option: None encodes as NULL
        "email": musq::Null, // untyped NULL literal
    }?;
    sql!("INSERT INTO users {insert:user_data}")?
        .execute(pool)
        .await?;
    Ok(())
}

DB-side computed values come from musq::expr (now_rfc3339_utc, jsonb, jsonb_text, jsonb_serde, raw):

use musq::expr;
let changes = values! {
    "updated_at": expr::now_rfc3339_utc(),
    "payload": expr::jsonb(r#"{"event":"hello"}"#),
}?;

sql!("UPDATE events SET {set:changes} WHERE id = 1")?
    .execute(&pool)
    .await?;

expr::raw(...) taints the resulting query; prefer the curated helpers.

Transactions

Pool::begin and Connection::begin return a Transaction. Calling begin on an existing transaction creates a savepoint. Dropping an uncommitted transaction rolls it back. Connection::transaction runs a closure and commits or rolls back based on its result.

let mut tx = pool.begin().await?;
sql!("INSERT INTO users (id, name) VALUES ({id}, {name})")?
    .execute(&tx)
    .await?;
tx.commit().await?;

Types

The Encode and Decode traits convert between Rust and SQLite types:

Option<T> maps None to NULL. For large strings and blobs, prefer owned or shared types (String, Vec<u8>, Arc<T>) to avoid copies; blobs can be decoded directly into Arc<Vec<u8>>. bstr::BString handles text-like BLOBs that may not be valid UTF-8.

Derived types

#[derive(musq::Codec)] implements both Encode and Decode for enums and newtype structs (Encode and Decode can also be derived individually).

Enums store as snake-cased strings ("open", "closed") by default:

#[derive(musq::Codec, Debug, PartialEq)]
enum Status {
    Open,
    Closed,
}

Or as integers with repr:

#[derive(musq::Codec, Debug, PartialEq)]
#[musq(repr = "i32")]
enum Priority {
    Low = 1,
    Medium = 2,
    High = 3,
}

Newtype structs store as their inner value:

#[derive(musq::Codec, Debug, PartialEq)]
struct UserId(i32);

#[derive(musq::Json)] stores any serde-compatible type as JSON text:

#[derive(musq::Json, serde::Serialize, serde::Deserialize, Debug, PartialEq)]
struct Metadata {
    tags: Vec<String>,
    version: i32,
}

Row mapping

#[derive(FromRow)] maps columns to fields by name. Attributes:

• #[musq(rename = "...")] — map a field to a differently named column
• #[musq(rename_all = "...")] — on the struct; case-convert all field names
• #[musq(default)] — use Default::default() when the column is absent
• #[musq(skip)] — always use Default::default()
• #[musq(try_from = "T")] — decode as T, then convert with TryFrom
• #[musq(deserialize_with = "path")] — decode with a custom fn(prefix: &str, row: &Row) -> Result<T>
• #[musq(flatten)], #[musq(flatten, prefix = "...")] — embed a nested FromRow struct, optionally prefixing its column names; an Option nested struct is None iff all of its columns are NULL

#[derive(FromRow)]
struct Address {
    street: String,
    city: String,
}

#[derive(FromRow)]
struct User {
    id: i32,
    // Reads the `street` and `city` columns.
    #[musq(flatten)]
    address: Address,
    // Reads `billing_street` and `billing_city`; None iff both are NULL.
    #[musq(flatten, prefix = "billing_")]
    billing: Option<Address>,
}

Vector search

The default vec feature registers sqlite-vec on every connection and provides the VecF32, VecInt8, and VecBit types. VecF32 binds directly to vector functions and vec0 tables; VecInt8 and VecBit must be wrapped in SQL as vec_int8(?) and vec_bit(?).

musq = { version = "0.0.4", default-features = false }  # opt out of vec

See the end-to-end example: cargo run -p musq --example vec.

SQLite runtime

Musq supports exactly the SQLite release bundled by its libsqlite3-sys dependency — currently SQLite 3.53.2 via libsqlite3-sys 0.38.1. Linking against older or system SQLite libraries is not supported; leave LIBSQLITE3_SYS_USE_PKG_CONFIG and SQLITE3_* environment variables unset.

Runtime introspection and control:

• runtime_info() — SQLite version, source ID, and compile options
• db_status(kind, reset) — per-connection status counters (page cache, lookaside, schema, statements, ...)
• wal_checkpoint(schema, mode) — run or inspect WAL checkpoints

Community

Questions, ideas, feature requests: Discord.

Just like whales once used to be land-dwelling quadrupeds, Musq started life as a focused fork of SQLx.