[{"ID":"1","attribute1":"123","subDocument":[{"ID":"2","attribute1":"456",},{"ID":"3","attribute1":"567",}]},{"ID":"4","attribute1":"123","subDocument":[{"ID":"5","attribute1":"456",}]}]

db.collection.aggregate([{$project:{"ID":1,"attribute1":1}},{"$unionWith":{"coll":"collection","pipeline":[{"$unwind":"$subDocument"},{"$replaceRoot":{"newRoot":"$subDocument"}}]}},{$match:{"ID":"2","attribute1":"456",}}])