{"_id": "id1", "contacts": [{"phone": "xxx", "email":"id1@gmail.com"}, {"phone":"yyy"}, {"phone":"zzz", "email":"id1_1@gmail.com"}] }
{"_id": "id2", "contacts": [{"phone": "aaa", "email":"id2@gmail.com"}, {"phone":"bbb"}, {"phone":"ccc"}] }

{"_id": "id1", "contacts": ["xxx", "yyy", "zzz"] }
{"_id": "id2", "contacts": ["aaa", "bbb", "ccc"] }