I'm trying to use the fields option on the find method as explained here:
https://github.com/mongodb/mongo-ruby-driver/wiki/Tutorial#selecting-a-subset-of-fields-for-a-query

On my Rails console I do something like:
client = Mongoid::Clients.default
client[:entities].find({},:fields=>["_id"]).to_a

and the result includes all fields from the Entity model. Same result as when I don't add the :fields parameter.

Is this an issue in how I'm requesting the fields to be returned or the option is being ignored and it's actually a bug?