interface readwrite {
    use types.{statement, row, error, connection};

    /// query is optimized for querying data, and 
    /// implementors can make use of that fact to optimize 
    /// the performance of query execution (e.g., using
    /// indexes).
    query: func(c: borrow<connection>, q: borrow<statement>) -> result<list<row>, error>;

    /// exec is for modifying data in the database.
    exec: func(c: borrow<connection>, q: borrow<statement>) -> result<u32, error>;
}