MongoObservable aggregate


i’m trying to use Mongo’s aggregate functions in Meteor but it seems not to work… I’ve installed the aggregate package ( and i’m calling it from the server side but still no luck…

This is my error message:

Exception while invoking method 'findMyTodos' TypeError: todos_collection_1.Todos.aggregate is not a function

I’m using the MongoObservable package so maybe thats the problem?


I have this working now by switching to Mongo.Collection instead of MongoObservable.Collection

However since I have to do the query from the server side it seems to be returning bson objectIDs that look like this:

_id : Object
   _bsontype : "ObjectID"
      id : Uint8Array[12]

Is there a way to get it to return normal hex objectIDs?
Or is there a way to convert this to a hex objectID?

I have my mongo collection set to ‘MONGO’ id generation, i.e:

export const Todos = new Mongo.Collection<Todo>('todos', {idGeneration: 'MONGO'});

If I remove the idGeneration parameter I get back normal strings (not in an ObjectID) but I need to keep the idGeneration (for other areas in my app)


Talking to myself here… but I found a solution.

You can convert the bson id (which contains Uint8Array) to a hex string with:


I’d still like to know why I was getting bson object ids anyway, is that normal behaviour when querying form the server side?


No - you get whatever the _id is defined as, but as you’re using MongoDB aggregation you get to define the _id with the $group operator. If you’re not using $group, or you’re using null as the _id in $group you probably get the default MongoDB objectId form.


Did anyone ever find a solution for this?


I had the same issue, which was resolved using Buffer. Seems like Meteor Aggregate returns a different object for ObjectID

import Buffer from 'buffer';

Hi @ruloweb could you explain how you were able to fix this? I cant convert the ObjectId in aggregate.