MongoDB: how to return specific fields and specific subdocuments in JSON

Question

If I have the following collection:

{
    "restaurant": {
        "_id": "5c0711f23533ef13a3e53d8b",
        "name": "burger king",
        "description": "american",
        "reservations": [
            {
                "_id": "5c0712503533ef13a3e53d8c",
                "time": "1:00 pm",
                "people": 3
            },
            {
                "_id": "5c0717129a8d7213e46d92da",
                "time": "9:30 am",
                "people": 10
            },
            {
                "_id": "5c071960160f2a13f647e100",
                "time": "12:30 am",
                "people": 25
            }
        ],
        "__v": 0
    }
}

and if I want to POST return only a specific reservation with restaurant's _id, name, description, like:

{
    "restaurant": {
        "_id": "5c0711f23533ef13a3e53d8b",
        "name": "burger king",
        "description": "american",
        "reservations": [
            {
                "_id": "5c0717129a8d7213e46d92da",
                "time": "9:30 am",
                "people": 10
            }
        ],
        "__v": 0
    }
}

What would be the best way?

I tried:

Restaurant.find( {_id: ObjectID(id)}, {reservations : { $elemMatch: {time: time} }, {$elemMatch: {people: people}} } )
.then( (restaurant)=> {
    res.send({restaurant})
})

but not working. Any help would be appreciated

Answer 1

Your query is incorrect .

The match should look like this:

Restaurant.find( {_id: ObjectID(id)}, {
   name: 1, 
   description: 1, 
   reservations : { $elemMatch: {time: time, people: people} } } )
.then( (restaurant)=> {
    res.send({restaurant})
})

And make sure _id is actually of type ObjectID and not of type String

The following query works fine(testing locally):

db.getCollection('test').find({_id: '5c0711f23533ef13a3e53d8b'}, {name:1, description: 1, reservations: {$elemMatch: {people: 3, time: '1:00 pm'}}})

Please notice that I'm using string _id and not object id.