$nin with the $expr

Question

I have a query to find if a user CreatedBy is in a SharedWith. I want to inverse the query to check if the CreatedBy is not in S

Answer 1

$nin is an query operator not an aggregation operator and also $expr only supports the aggregation operators not the query ones. So, You should probably use $not $in with the $expr expression in this manner

{
  "$match": {
    "$and": [
      {
        "$or": [
          {
            "Multi_User": {
              "$exists": False
            }
          },
          {
            "$expr": {
              "$not": { "$in": ["$CreatedBy", "$Multi_User"] }
            }
          }
        ]
      }
    ]
  }
}