[{"collection":"collection","count":5,"content":{"field_1":{"type":"object","objectContent":{"A":{"type":"enum","values":[1,2,3,4,5]},"B":{"type":"enum","values":[6,7,8,9,0]}}}},"indexes":[{"name":"field_1_index","key":{"field_1":1}}]}]

db.collection.find({"field_1":{A:123}}).explain()