[{"_id":"61717cafd351f3ae8b6d205a","restaurant":"Hogwarts","purchasedAt":"2021-10-20T17:47:40.166Z","products":[{"name":"Meat Samosa","price":3.95,"quantity":1,"_id":"61717cafd351f3ae8b6d205b"},{"name":"Pilau Rice","price":2.95,"quantity":1,"_id":"61717cafd351f3ae8b6d205f"}]},{"_id":"61717cb2d351f3ae8b6dd05b","restaurant":"Hogwarts","purchasedAt":"2021-10-20T03:14:11.111Z","products":[{"name":"Pilau Rice","price":2.95,"quantity":1,"_id":"61717cb2d351f3ae8b6dd05d"}]}]

db.collection.aggregate([{$project:{_id:0,products:1}},{$unwind:"$products"},{$group:{_id:"$products.name",price:{$first:"$products.price"},quantity:{$sum:"$products.quantity"}}},{$project:{_id:0,name:"$_id",price:1,quantity:1}}])