How can I detect number of mached and changed documents in an UPDATE statement?
The number of documents selected for update. If the update operation results in no change to the document, e.g.
$set expression updates the value to the current value,
nMatched can be greater than
The number of existing documents updated. If the update/replacement operation results in no change to the document, such as setting the value of the field to its current value,
nModified can be less than