the name of the output field which has the count as its value
(count: StringAdd).self
(count: StringFormat).self
(count: ArrowAssoc[Count]).x
(Since version 2.10.0) Use leftOfArrow
instead
(count: Ensuring[Count]).x
(Since version 2.10.0) Use resultOfEnsuring
instead
$count of the number of documents input.
the name of the output field which has the count as its value
MongoDB 3.4