db={"User":[{"_id":"1","name":"Robert"},{"_id":"2","name":"David"},{"_id":"3","name":"Sam"},{"_id":"4","name":"Michael"}]}

db.User.aggregate([{$limit:1},{$project:{_id:["1","3","5","7"]}},{"$unwind":"$_id"},{"$lookup":{"from":"User","localField":"_id","foreignField":"_id","as":"userLookup"}},{"$project":{matched:{$gt:[{$size:"$userLookup"},0]}}}])