postgres_macros.rs

macro_rules! query {
    ($db:ident, $query:expr, [$($param:expr),*], {$($out_field:ident: $ty:ty),+ }) => ({
        #[derive(Debug, Clone)]
        #[allow(non_snake_case)]
        struct Output {
            $(
                $out_field: $ty,
            )+
        }

        let stmt = $db.prepare_cached($query).unwrap();
        let rows = stmt.query(&[$($param),*]).unwrap();
        rows.into_iter()
            .map(|row| {
                Output {
                    $(
                        $out_field: match row.get_opt(stmt.columns().iter().position(|c| c.name() == stringify!($out_field)).expect(&format!("no field named {}", stringify!($out_field)))) {
                            Some(Ok(f)) => f,
                            Some(Err(err)) => panic!("Error while executing {:?}: {:?}", $query, err),
                            None => panic!("Index doesn't reference a column"),
                        }
                    ),+
                }
            })
            .collect::<Vec<_>>()
    });
}

macro_rules! query_single {
    ($db:ident, $query:expr, [$($param:expr),*], {$($out_field:ident:$ty:ty),+ }) => ({
        query!($db, $query, [$($param),*], {$($out_field:$ty),+}).into_iter().next()
    });
}

macro_rules! query_one_field {
    ($db:ident, $query:expr, [$($param:expr),*]) => ({
        let stmt = match $db.prepare_cached($query) {
            Ok(stmt) => stmt,
            Err(err) => panic!("Error while executing {:?}: {:?}", $query, err)
        };
        let rows = stmt.query(&[$($param),*]).unwrap();
        rows.into_iter()
            .map(|row| match row.get_opt(0) {
                Some(Ok(v)) => v,
                Some(Err(err)) => panic!("Error while reading result of {:?}: {:?}", $query, err),
                None => panic!("No column in the query output")
            })
            .collect::<Vec<_>>()
    });
}

macro_rules! query_single_one_field {
    ($db:ident, $query:expr, [$($param:expr),*]) => ({
        query_one_field!($db, $query, [$($param),*]).into_iter().next()
    });
}


// Example usages:

let user: Option<_> = query_single!(database, r#"
        SELECT name, email FROM users WHERE id = $1 LIMIT 1
        "#, [&id], { name: Option<String>, email: String });
let user = match user { Some(u) => u, None => return err_404!("User doesn't exist") };
println!("user's email: ", user.email);



let users = query!(database, r#"SELECT id FROM users"#, [], { id: i32 });
for user in users {
    let id = user.id;
}


let email: Option<String> = query_single_one_field!(database, r#"SELECT email FROM users WHERE id = $1"#, [&id]);



let emails: Vec<String> = query_single_one_field!(database, r#"SELECT email FROM users"#, []);