GraphQL更新子对象

Question

const Photo = new GraphQLObjectType({
  name: 'Photo',
  description: 'Photo',
  fields: () => ({
    upload: {type: GraphQLString},
    facebook: {type: GraphQLString},
    linkedin: {type: GraphQLString}
  })
});

const Account = new GraphQLObjectType({
  name: 'Account',
  description: 'Account',
  fields: () => ({
    _id: {type: new GraphQLNonNull(GraphQLString)},
    created_on: {type: GraphQLDate},
    username: {type: GraphQLString},
    password: {type: GraphQLString},
    photo: {type: Photo},
  })
});

export default Account;

我有一个变异查询来更新记录：

mutation { updateAccountById(id: "587c84c713742bf421f3fa4e", update: {photo: {upload: "test1"}}) { photo { upload facebook linkedin } } }

在：

photo{
 upload:"test1"
 facebook: "test2"
 linkedin: "test3"
}

在： 这会将照片属性更新为

photo{
 upload:"test1"
}

有没有办法只更新照片字段？任何帮助，将不胜感激。提前谢谢。

突变：

const Mutation = new GraphQLObjectType({
    name: 'Mutation',
    fields: {
        updateAccountById:{
            type: Account,
            args: {
                id:{type: new GraphQLNonNull(GraphQLString)},
                update: {
                  type: new GraphQLInputObjectType({
                    name: 'update_account_byId',
                    fields: Account.getFields()
                  })
                }
            },
            resolve: function(rootValue, args) {
                let update = Object.assign({}, args.update);
                db.account.update({ _id: pmongo.ObjectId(args.id.toString())}, {$set: update},{multi:true});
            }
        }
    }
});