Mongoose specifying an _id on upsert (Query)

Question

In my chat application, every user has a dictionary of unread messages which looks like this :

Unread Dictionary

{
    _id: // reference to their user_id,
    events: [] // array of ObjectIds
}

I want to make a mongoose findByIdAndUpdate query where ) search by ID and $push a new ObjectId into the events array.

If the document doesn't exist, I would like for it to upsert the document assigning it the _id used for the update query and initializing the array with the element being $push ed in the update query.

EDIT:

Here is an example of the query I would like to make:

Model.findByIdAndUpdate(user_id, {$push: {events: event_id}}, {upsert: true}, function (err, updatedDoc) {});

If the document doesn't exist and it decides to upsert, will it use the user_id I used to search to assign the _id on the upserted document? OR will mongo assign it's own _id? I'm looking for something that does the former.

Sounds like a standard upsert, did it not work when you tried it? — JohnnyHK, Aug 14 '14 at 15:11
@JohnnyHK I assumed mongoose would assign it's own _id if it was unable to find the document, and upserted it. Is this not true? — Jorge Olivero, Aug 14 '14 at 15:21
It's probably best if you add some code to your question that better illustrates exactly what you're looking to do. — JohnnyHK, Aug 14 '14 at 15:24
I would expect that will do what you're looking for. Just try it. — JohnnyHK, Aug 14 '14 at 15:41

score 1 · Answer 1 · answered Sep 09 '20 at 03:10

1

The question is too long, but I hope my answer will help someone. We can use $setOnInsert to specify field only used on insert:

const idUsedOnInsert = new mongoose.Types.ObjectID();

const document = await Model.findByIdAndUpdate(
      user_id,
      { $push: { events: event_id }, $setOnInsert: { _id: idUsedOnInsert } },
      { upsert: true }
    );

if(document){
    console.log('Update');
} else {
    console.log('Insert');
}

answered Sep 09 '20 at 03:10

Akkien

84
11

I think it would be easier to add the generated _id to the object before running findByIdAndUpdate. – user2495085 Apr 23 '21 at 16:36

score 0 · Answer 2 · answered Jan 22 '19 at 22:34

Mongoose will use the _id you passed as the object _id when upserting.

You can try that on your console.

Create an ObjectId: const id = ObjectId(), then query with <Model>.findByIdAndUpdate(id, { name: 'Albert' }, { upsert: true }).

And also, if you want to receive the object when it's upsert, you need to pass new: true within the query options, or else you will receive null for upserts*

*that's because by default, mongoose/MongoDB returns the find query's result instead the update's result, if you'd have queried an update on an existing object, you'd receive the old object in case you didn't pass the new: true option.

https://docs.mongodb.com/manual/reference/method/db.collection.update/#upsert-option

Mongoose specifying an _id on upsert (Query)

2 Answers2