Mongo DB Change Streams - is there a way to fetch the relationship data of a document?

Question

I'm migrating from Legacy Realm and its Realm.Sync listeners to Change Streams and I'm trying to figure out how to easily fetch the full objects returned on update.

 case "update": {
      const { documentKey, fullDocument } = change;
      console.log(`updated document: ${documentKey}`, fullDocument);
      break;
    }

Is there a way to fetch the full document with the relationship data?

For example the fullDocument:

{
  "_id": "b03dcd5d-94dc-7254-6aff-44d5818390ca",
  "_partition": "test"
  "Message": "Test",
  "Sender": "51f717ad-afbc-c3d6-779a-72db53f8b708",
  "SeenBy": [
    "51f717ad-afbc-c3d6-779a-72db53f8b708"
  ],
}

Instead of the Sender id, I want to get the sender document, same thing in SeenBy.

{
  "_id": "b03dcd5d-94dc-7254-6aff-44d5818390ca",
  "_partition": "test"
  "Message": "Test",
  "Sender": {"_id": "51f717ad-afbc-c3d6-779a-72db53f8b708", "Name":"John"},
  "SeenBy": [
    {"_id": "51f717ad-afbc-c3d6-779a-72db53f8b708", "Name":"John"}
  ],
}

Answer 1

If you want to bring in data from other collections, you need to retrieve it separately from the change stream. Change stream allows specifying several aggregation pipeline stages but $lookup is not one of them.