[{prices:{id:"a",ops:[{id:"a1",},{id:"a2"}]}},{prices:{id:"b",ops:[{id:"b2"},{id:"a1"}]}},{prices:[{id:"c",ops:[]}]}]

db.collection.find({"prices.id":"a","prices.ops.id":"a1"},{addOp:{$first:{"$filter":{"input":"$prices.ops","as":"gro","cond":{"$eq":["$$gro.id","a1"]}}}}})