Ch6 Last quiz for Pipeline Optimization Part 2

The last statement of the quiz is “The query in a $match stage can be entirely covered by an index”, and this statement is marked as true which I don’t understand.

If “can be” means “is supposed/better to be”, it’s fine because the statement then serves as a piece of good advice.

However, if “can be entirely” means, for a given $match stage, there should be an index entirely covering it, I can’t see how the statement is true.


It does not mean that you should or shouldn’t have an index entirely covering it, it just means that it can be a covered query.

José Carlos