Envuelto para legibilidad:
connection.query({
sql : "SELECT \
users.users_id, \
users.users_firstname, \
rides.rides_latitude, \
rides.rides_longitude \
FROM \
users \
RIGHT JOIN rides ON users.id = rides.id_user \
WHERE \
users.id = ?",
nestTables: '_',
values : [id]
}, function (err, rows) {
var result = [], index = {};
if (err) throw err;
rows.forEach(function (row) {
if ( !(row.users_id in index) ) {
index[row.users_id] = {
users_id: row.users_id,
users_firstname: row.users_firstname,
rides: []
};
result.push(index[row.users_id]);
}
index[row.users_id].rides.push({
rides_latitude: row.rides_latitude,
rides_longitude: row.rides_longitude
});
});
console.log(result);
});