While doing some testing with the notablescan feature, I discovered that even with this flag set a mongod will still allow queries with empty predicates. For example, db.foo.find() works, while

db.foo.find({a:{$gt:10}}) 

will throw an exception.

Since some customers use this feature to test that their applications are not doing any COLLSCAN's, I think it would be good to update the doc to explicitly state this behavior.

https://docs.mongodb.org/manual/reference/parameters/#param.notablescan