Rust

The crate compiles the bundled amalgamation itself (via build.rs and the cc crate), so there are no system dependencies:

cargo add sqlite-predict
cargo add rusqlite --features bundled

Register it as an auto-extension once at startup; every connection you open afterward has the functions:

fn main() -> rusqlite::Result<()> {
    // Registers sqlite-predict process-wide. Call once, before opening
    // connections. `register` is unsafe: it registers a C entry point globally.
    unsafe { sqlite_predict::register().expect("register sqlite-predict") };

    let db = rusqlite::Connection::open_in_memory()?;
    let version: String = db.query_row("select predict_version()", [], |r| r.get(0))?;
    println!("{version}");

    db.execute_batch(
        "create table readings(ts text, value real);
         insert into readings
           select printf('2024-01-01T%02d:00:00', n), 50 + n
           from (with recursive c(n) as (select 0 union all select n+1 from c where n < 23)
                 select n from c);",
    )?;

    // forecast() is an aggregate like sum(): plain SQL supplies the rows
    // (WHERE, joins, bound params compose, GROUP BY splits the series),
    // and each group returns one JSON document
    let doc: String = db.query_row(
        "select forecast(ts, value, 6) from readings", [], |r| r.get(0))?;
    println!("{doc}");
    Ok(())
}

Because register() uses sqlite3_auto_extension, every connection any rusqlite-based stack opens afterward has the functions, Diesel and sqlx included, with no per-connection hook:

unsafe { sqlite_predict::register()?; }   // once, before connecting

// then through any rusqlite-based stack:
let doc: String = conn.query_row(
    "SELECT forecast(ts, value, 24) FROM readings WHERE city = ?1",
    ["SF"], |r| r.get(0))?;

If a migration tool manages your schema, exclude sqlite-predict’s model registry (_predict_* tables) from diffs so it doesn’t get dropped.

Next: Operations.