[{name:"name1",age:19},{name:"name2",age:20},{name:"name3",age:18},{name:"name4",age:22},{name:"name5",age:25}]

db.collection.aggregate([{$facet:{"gt20":[{$match:{age:{$gt:20}}}],"NOTgt20":[{$match:{age:{$not:{$gt:20}}}}],}}])