[{field1:1,field2:2,name:"ABC"},{field1:1,field2:2,name:"ABC"},{field1:2,field2:3,name:"ABC"}]

db.collection.aggregate([{$group:{_id:{field1:"$field1",field2:"$field2"},data:{$push:{name:"$name"}}}},{$group:{_id:"$_id.field1",data:{$push:{field1:"$field1",data:"$data"}}}},{$project:{_id:0,data:1,field1:"$_id"}}])