We currently have this batched code using MongoMapper which is still taking longer than we would like:

```
User.find_each(conditions: {is_active: true}, batch_size: 500) do |user|
  # simple stuff that only requires a couple fields from user
end

```

Is there some way to tell it to only return the fields we need from the User model like you can do with a non-batched find?

```
User.where(is_active:true).fields(:field1, :field2).all

```

Changing the batch size hasn't helped so we're looking for other ideas.

Thanks!