[{"id":"dc4b9a2f-12b3-42f8-b0b3-dd1bff19fccc","name":"name 1","fields":[{"id":2},{"id":1},{"id":3}],"order":[1,3,2]},{"id":"dc4b9a2f-12b3-42f8-b0b3-dd1bff19fccd","name":"name 2","fields":[{"id":1},{"id":2},{"id":3}],"order":[1,4,2]}]

db.collection.aggregate([{$unwind:"$fields"},{$sort:{"fields.id":1,"order":1}},{$group:{_id:"$_id",name:{$first:"$name"},fields:{$push:"$fields"},order:{$first:"$order"}}},{$project:{_id:1,name:1,fields:1,order:1}}])