[{"houses":[{"from":"mine","codekey":"123"},{"from":"Giuglio","codekey":"Giuglio010193"},{"from":"Francesco","codekey":"vatican"}]}]

db.collection.update({/**this will not match documents*/houses:{$exists:false}},{/**if document does not exist, can't use dot notation*/$setOnInsert:{"houses":{codekey:"apple"}}},{upsert:true})