How to get the size of single document in Mongodb?

Question

I encountered a strange behavior of mongo and I would like to clarify it a bit...
My request is simple as that: I would like to get a size of single document in collect

Answer 1

With mongodb 4.4 (upcoming), You can use bsonSize operator to get the document size.

db.test.aggregate([
  {
    "$project": {
      "name": 1,
      "object_size": { "$bsonSize": "$$ROOT" }
    }
  }
])