Takes two sets and returns an array containing the elements that only exist in the first set; i.e. performs a relative complement of the second set relative to the first.
https://www.mongodb.com/docs/manual/reference/operator/aggregation/setDifference/#mongodb-expression-exp.-setDifference
Takes two sets and returns an array containing the elements that only exist in the first set; i.e. performs a relative complement of the second set relative to the first.