Retrieve all fields when using $project

I’m using the following specification in $project but I’ve to use field: 1 to retrieve the fields that I want in the final document but instead what I want is to do is include all the fields in the final document.

  "newField": {
    "$filter": {
      "input": "$example",
      "as": "example",
      cond: {
        "$and": [
            {"$eq": ["$$", "1234"]}


  example: [{_id:: 12314}]

Is there any way to retrieve all the fields?

Thank you so much.

If you using $project to simply add a field while you want all other fields you should take a look at introduced in 3.4.

There is one extra thing that need to be tested. It is to use $project but to exclude a non-existent, which in principle will include all existing fields.