/*

 RESTAURANT COLLECTION SINGLE DOCUMENT SCHEMA FOR REFERENCE
{
    "_id" : ObjectId("5d83eb456e04f8d82b8a8363"),
        "address" : {
        "building" : "2780",
            "coord" : [
                -73.98242,
                40.579505
            ],
                "street" : "Stillwell Avenue",
                    "zipcode" : "11224"
    },
    "borough" : "Brooklyn",
        "cuisine" : "American ",
            "grades" : [
                {
                    "date": ISODate("2014-06-10T00:00:00.000Z"),
                    "grade": "A",
                    "score": 5
                },
                {
                    "date": ISODate("2013-06-05T00:00:00.000Z"),
                    "grade": "A",
                    "score": 7
                },
                {
                    "date": ISODate("2012-04-13T00:00:00.000Z"),
                    "grade": "A",
                    "score": 12
                },
                {
                    "date": ISODate("2011-10-12T00:00:00.000Z"),
                    "grade": "A",
                    "score": 12
                }
            ],
                "name" : "Riviera Caterer",
                    "restaurant_id" : "40356018"
}
 */





db.getCollection('restaurants').aggregate([
    {
        "$project": {
            "filtered_grades": {
                "$filter": {
                    "input": "$grades",
                    "as": "grade",
                    "cond": { "$in": [ "$$grade.score", [ 12, 2 ] ] }
                }
            }
        }
    }
])
/*
result

filters only the selected subdocuments from the array of subdocuments 'grades'


*/



// just queries
/*

db.getCollection('vendors').aggregate([
{
				"$match": {
					"category": { $in: ['onion'] }
				}
},

{
				"$lookup": {
					"from": "products",
					"localField": "products",
					"foreignField": "_id",


					"as": "productObjects"
				}
},

{
        "$project": {
            "filtered_products": {
                "$filter": {
                    "input": "$productObjects",
                    "as": "products",
                    "cond": { "$in": [ "$$products.productname", ["onion","tomato"] ] }
                }
            }
        }
},

{
        "$project": {
            "prods":"$filtered_products" ,
             "total":{$size:"$filtered_products"}
        }
}

]);





*/