Improve $lookup explain to indicate query plan on the "from" collection

db.goods.drop();

db.persons.drop();

db.goods_persons.drop();

db.goods.insert({'id': 1, 'name': 'good1'});

db.goods.insert({'id': 2, 'name': 'good2'});

db.persons.insert({'id': 1, 'name': 'john'});

db.persons.insert({'id': 2, 'name': 'tom'});

db.goods_persons.insert({'good': 1, 'person': 1});

db.goods_persons.insert({'good': 2, 'person': 1});

db.goods_persons.insert({'good': 1, 'person': 2});

//create all probably indexes

db.goods.ensureIndex({'id':1});

db.persons.ensureIndex({'id':1});

db.goods_perons.ensureIndex({'good':1});

db.goods_perons.ensureIndex({'person':1});

db.goods.ensureIndex({'goods_persons.person':1});

db.goods.ensureIndex({'goods_persons.good':1});

//get buyers

db.goods.aggregate(

[

    {$lookup:{

        from: "goods_persons",

        localField: "id",

        foreignField: "good",

        as: "goods_persons"

    }},

    {$match:{

        "goods_persons.person": 1

    }}

], {'explain': true}); //COLLSCAN   -  index not used