val KProperty<*>.count: BsonField (source)
Gets a field name for a $group operation representing the count of the values of the given expression when applied to all members of the group.
Return
the field
fun <T> KProperty<T>.count(): Bson (source)
Creates a $count pipeline stage using the named field to store the result
field - the field in which to store the count
Return
the $count pipeline stage
Mongodb
.driver.manual reference/operator/aggregation/count/ $count