Is there a way to create a named scope that groups?

I have the following using searchlogic:

@todos = Todo.contact_user_id_is(current_user).
              contact_campaign_id_is(@campaign).
              current_date_lte(Date.today).
              done_date_null.
              ascend_by_current_date

I only want @todos to contain a Todo record for a single contact_id (contact_id is an attribute on Todo).

Question: how can I group so that I there is only one record per contact_id in the @todos array?

named_scope supports grouping. Something like this should work:

class Todo < ActiveRecord::Base

  belongs_to :contact

  named_scope :one_per_contact, lambda{ |user, campaign|
    {
      :joins => :contact,
      :conditions => ['contacts.user_id = ? AND contacts.campaign_id = ? AND todos.current_date <= ? AND todos.done_date IS NULL', user.id, campaign.id, Date.today],
      :group => 'todos.contact_id'
      :order => :current_date
    }
  }

end

Then just put this in your controller:

@todos = Todo.one_per_contact(current_user, @campaign)

The code may not be exactly right for your app, but you get the idea.