Use only one query to count items in a collection

[trekdemo]

Hi Guys,

Is there a reason for firing 3 queries to count items in a collection?

The previous version caused 3 queries:

1. collection.empty? #=> load an item to ensure there are items in the collection
2. collection.first ... #=> load an item again to be sure about we querying mongo
3. collection.count(true) #=> actual count command