How to select, groupBy, and join in Waterline or MongoDB

Question

I have three models: user, noun, and usernoun (user_noun in PHP/Eloquent). There is a many to many relationship between user and noun. The "pivot" table has an extra attribute score. I can use this query with Eloquent to sum the scores of each noun a user has to get the user's total score:

$users = User::leftJoin('noun_user', 'user.id', 'noun_user.user_id')
    ->groupBy('user.id')
    ->select('user.*', DB::raw('sum(noun_user.score) as score'))
    ->orderBy('score', 'desc')
    ->get();

But I can't figure out how to get this to work in Waterline. This works, but not when I uncomment the .populate('user') line. I need user to be populated.

UserNoun
    .find({})
    //.populate('user')
    .groupBy('user')
    .sum('score')
    .sort({ score: 'desc' })
    .exec((err, usernouns) => {
    return res.json(usernouns)
})

here is a .native() query that works:

UserNoun.native(function(err, collection) {
    collection.aggregate([
        {
            $lookup: {
                from: 'user',
                localField: 'user',
                foreignField: '_id',
                as: 'user'
            }
        },
        {
            $group: { _id: '$user', total: { $sum: '$score' } }
        },
        {
            $sort : { total: -1 }
        }
    ]).toArray(function (err, results) {
        return res.json(results)
    })
})

Can this native query be rewritten in Waterline with groupBy and populate and sum?

Answer 1

As of [email protected], the only way to do that is to use native queries.

By the way, you can export your method inside the User model:

// User.js
module.exports = {

    // ...

    findTotalScores: function (callback) {
        UserNoun.native(function(err, collection) {
            if (err) {
                return callback(err);
            }

            collection.aggregate([
                {
                    $lookup: {
                        from: 'user',
                        localField: 'user',
                        foreignField: '_id',
                        as: 'user'
                    }
                },
                {
                    $group: { _id: '$user', total: { $sum: '$score' } }
                },
                {
                    $sort : { total: -1 }
                }
            ]).toArray(callback);
        });
    }

};

And you can use it in your controller by calling:

User.findTotalScores(function (err, results) {
    return res.json(results);
});