if true updates all the matching documents
the query that matches the documents to update
the modifications to apply
if true perform an insert if no documents match the query
(updateElement: StringAdd).self
(updateElement: StringFormat).self
(updateElement: ArrowAssoc[UpdateElement]).x
(Since version 2.10.0) Use leftOfArrow instead
(updateElement: Ensuring[UpdateElement]).x
(Since version 2.10.0) Use resultOfEnsuring instead
the query that matches the documents to update
the modifications to apply
if true perform an insert if no documents match the query
if true updates all the matching documents