db={"contacts":[{_id:1,name:"John legend",age:35},{_id:2,name:"michael Ava",age:40},{_id:3,name:"Tom holand",age:20},{_id:4,name:"Frido pex",age:25},{_id:5,name:"Daniel Gunava",age:30},{_id:6,name:"Mert Brava",age:30}]}

db.contacts.aggregate([{"$facet":{"contains":[{"$match":{name:{$regex:"ava",$options:"i"}}},{"$group":{_id:"$name",count:{$sum:1}}}],notContains:[{"$match":{$expr:{$eq:[null,{"$regexFind":{"input":"$name","regex":"ava","options":"i"}}]}}},{"$group":{_id:"$name",count:{$sum:1}}}]}}])