I am referring to the * [Lecture: Aggregation Framework] when the lecturer managed to get countries that exist in the listing.
However, I am wondering if the database is bigger, there will be more countries in the listings. Is there a way for me to count the number of distinct countries using mongo shell? From what I understand, I can only get the number of listing for each country but I am not sure how to count the no. of distinct countries in the listings.