How to check all documents in a collection for uniqueness?

Question

MongoDB

There is a collection with ~1kk documents of the form {_id: ObjectId, "id": "ID"}, you need to check all of them with each other to find out if all IDs are unique in this collection.
What is the best way to do this?

Answer 1

db.collection.find({}).count() must be equal to db.collection.distinct({"ID"}).length