I have a single Document in my mongoDb collection:

{
  "_id": {
    "$oid": "f8cc66adc6b5ce1fc99a2f59"
  },
  "isFlat": true,
  "schema": {
    "type": "record",
    "name": "topLevelRecord",
    "fields": Array[]
  },
  "userId": "4d18fa67-c4ca-4d89-8e52-506774a8b12c",
  "filenames": [],
  "createdAt": {
    "$date": "2024-08-02T12:04:40.551Z"
  }
}

Now, I’d like to retrieve the field “schema”.

Up till now I have done it with the toArray() function of the cursor like this:

await collection
    .aggregate([
      { $match: { _id: new ObjectId(`${fileId}`) }},
      { $project: { _id: 0, schema: 1}}
    ])
    .toArray()

This approach appears to be very time consuming. I some because the Array in the schema field can be very nested.

In the official documentation (https://www.mongodb.com/docs/drivers/node/current/fundamentals/crud/read-operations/cursor/) I learned about the other functions of the Cursor Object.

I tried the following:

cursor.stream().on("data", doc => console.log(doc));

which perfectly prints me the result I want in a very time-efficient manner but when I try to change it so that the result will be returned and attached to result, like so:

let schema = cursor.stream().on("data", doc => doc);

I get the whole Cursor Object attached to the schema variable.

Why is this the case? How to achieve the same result to be bounded to a variable then what is printed out on the console?