[{"name":"def","partners":{"address":{"country":"int","state":0,"street":10},"partnerName":"abc",xyz:111,abc:1}},{"name":"def2","partners":{"address":{"country":"int2","state":1,"street":101},"partnerName":"abc2",xyz:222,abc:2}}]

db.collection.aggregate({$project:{name:1,"partners.country":"$partners.address.country","partners.partnerName":1}})