Question

Say I have a MongoDB collection with documents like—

{
  "name": "Hawaiian",
  "toppings": ['cheese', 'ham', 'pineapple'],
}

How could I get a list of all the collection’s toppings?

I assume I’d have to use MapReduce or the new aggregation framework (ideally MapReduce as I can’t use the new aggregation framework), but I’m not sure how to do it.

Thanks!

Edit: And, is there a way to count the number of distinct toppings at the database level?

Answer 1

MongoDB supports DISTINCT aggregation. This should do the trick.