db.data.aggregate([{'$sort': {'_id': 1}}, {'$group': {'_id': '$key',
    'first': {'$first': '$$ROOT'}}}, {'$project': {'_id': 0, 'id':
    '$first.id', 'key': '$first.key', 'name': '$first.name', 'country':
    '$first.country'}}])
Mongo Distinct Query with full row object