Counting all documents in a FaunaDB collection

Question

Is there a way to count all documents in a collection in FaunaDB?

Say I have a users collection and I have defined an all_users index. What is the best way to count all documents in the users collection in the database?

Update: expanding on @Keston's answer below

1. The all_users index is no longer needed. Fauna now automatically maintains a built-in default index for each collection, and you can access it via Documents(Collection('<collection>')).

2. You can count all users like so:

Count(Documents(Collection('users')))

Answer 1

Now faunadb offers the count() function in the most recent release which is another option to maintaining an aggregate

https://docs.fauna.com/fauna/current/api/fql/functions/count

Answer 2

The best way is to maintain your own aggregate in transaction with your data updates, so update a counter document when you write your new users. I wrote a blog post about how to do that here: https://blog.fauna.com/using-acid-transactions-to-combine-queries-and-ensure-integrity (See the last example)