the query that documents must satisfy to be in the stream
(match: StringAdd).self
(match: StringFormat).self
(match: ArrowAssoc[Match]).x
(Since version 2.10.0) Use leftOfArrow instead
(match: Ensuring[Match]).x
(Since version 2.10.0) Use resultOfEnsuring instead
Filters out documents from the stream that do not match the predicate. http://docs.mongodb.org/manual/reference/aggregation/match/#_S_match
the query that documents must satisfy to be in the stream