Mongoose Query to filter array and populate content

Question

I am trying to request a property that is an array of both links to another schema and some additional data. For better clarification, here is the diagram:

    var orderSchema = new Schema({
        orderDate: Date,
        articles: [{
            article: {
                type: Schema.Types.ObjectId,
                ref: 'Article'
            },
            quantity: 'Number'
        }]
    }),
    Order = mongoose.model('Order', orderSchema);

So far, I have been able to successfully request the link, that is:

Order.find({}).populate('articles.article', null, {
    price: {
        $lte: 500
    }
}).exec(function(err, data) {
    for (var order of data) {
        for (var article of order.articles) {
            console.log(article);
        }
    }
});

I have some questions asking for an attribute quantity, i.e. this does not work:

Order.find({}).where({
    'articles.quantity': {
        $gte: 5
    }
}).populate('articles.article', null, {
    /*price: {
        $lte: 500
    }*/
}).exec(function(err, data) {
    for (var order of data) {
        for (var article of order.articles) {
            console.log(article);
        }
    }
});

Is it even possible to ask for a request quantity? And if so, what would be the best approach?

Thank!

UPDATE:

The problem is that the result is either a full array or nothing (see the updated question). I want to get only those records, the number of which is greater than or equal to 5. With your (and my) approach, I get either no records at all (if I install $ gte: 5001), or both records (if I set $ gte: 5000)

{
    "_id": ObjectId('56fe76c12f7174ac5018054f'),
    "orderDate": ISODate('2016-04-01T13:25:21.055Z'),
    "articles": [
        {
            "article": ObjectId('56fe76c12f7174ac5018054b'),
            "quantity": 5000,
            "_id": ObjectId('56fe76c12f7174ac50180551')
        },
        {
            "article": ObjectId('56fe76c12f7174ac5018054c'),
            "quantity": 1,
            "_id": ObjectId('56fe76c12f7174ac50180552')
        }
    ],
    "__v": 1
}

Answer 1

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Order.find({ "articles.quantity": { "$gte": 5 } })
    .select({ "articles.$": 1 })
    .populate({
        "path": "articles.article",
        "match": { "price": { "$lte": 500 } }
    }).exec(function(err,orders) {
       // populated and filtered twice
    }
)

"" , , , - "articles".

.aggregate() . MongoDB 3.2 $filter. .populate():

Order.aggregate(
    [
        { "$match": { "artciles.quantity": { "$gte": 5 } } },
        { "$project": {
            "orderdate": 1,
            "articles": {
                "$filter": {
                    "input": "$articles",
                    "as": "article",
                    "cond": {
                       "$gte": [ "$$article.quantity", 5 ]
                    }
                }
            },
            "__v": 1
        }}
    ],
    function(err,orders) {
        Order.populate(
            orders.map(function(order) { return new Order(order) }),
            {
                "path": "articles.article",
                "match": { "price": { "$lte": 500 } }
            },
            function(err,orders) {
                // now it all populated and mongoose documents
            }
        )
    }
)

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MongoDB 2.6. $map $setDifference. "", , mongoose _id :

    [
        { "$match": { "artciles.quantity": { "$gte": 5 } } },
        { "$project": {
            "orderdate": 1,
            "articles": {
                "$setDiffernce": [
                   { "$map": {
                      "input": "$articles",
                      "as": "article",
                      "in": {
                         "$cond": [
                             { "$gte": [ "$$article.price", 5 ] },
                             "$$article",
                             false
                         ]
                      }
                   }},
                   [false]
                ]
            },
            "__v": 1
        }}
    ],

, $unwind:

    [
        { "$match": { "artciles.quantity": { "$gte": 5 } }},
        { "$unwind": "$articles" },
        { "$match": { "artciles.quantity": { "$gte": 5 } }},
        { "$group": {
          "_id": "$_id",
          "orderdate": { "$first": "$orderdate" },
          "articles": { "$push": "$articles" },
          "__v": { "$first": "$__v" }
        }}
    ],

$lookup Alternative

- "". $lookup MongoDB 3.2 :

Order.aggregate(
    [
        { "$match": { "artciles.quantity": { "$gte": 5 } }},
        { "$project": {
            "orderdate": 1,
            "articles": {
                "$filter": {
                    "input": "$articles",
                    "as": "article",
                    "cond": {
                       "$gte": [ "$$article.quantity", 5 ]
                    }
                }
            },
            "__v": 1
        }},
        { "$unwind": "$articles" },
        { "$lookup": {
            "from": "articles",
            "localField": "articles.article",
            "foreignField": "_id",
            "as": "articles.article"
        }},
        { "$unwind": "$articles.article" },
        { "$group": {
          "_id": "$_id",
          "orderdate": { "$first": "$orderdate" },
          "articles": { "$push": "$articles" },
          "__v": { "$first": "$__v" }
        }},
        { "$project": {
            "orderdate": 1,
            "articles": {
                "$filter": {
                    "input": "$articles",
                    "as": "article",
                    "cond": {
                       "$lte": [ "$$article.article.price", 500 ]
                    }
                }
            },
            "__v": 1
        }}
    ],
    function(err,orders) {

    }
)

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Order.find({ "articles.quantity": { "$gte": 5 } })
    .populate({
        "path": "articles.article",
        "match": { "price": { "$lte": 500 } }
    }).exec(function(err,orders) {
        orders = orders.filter(function(order) {
            order.articles = order.articles.filter(function(article) {
                return (
                    ( article.quantity >= 5 ) &&
                    ( article.article != null )
                )
            });
            return order.aricles.length > 0;
        })

        // orders has non matching entries removed            
    }
)