Group using Sunspot/Solr?

I'm having some problem searching by group when using Sunspot.

Here is an example:

# == Schema Information
#
# Table name: movies
#
#  id              :integer(4)      not null, primary key
#  title           :string(255)

class Movie < ActiveRecord::Base
  has_and_belongs_to_many :actors

  searchable do
    text :title

    integer :ages, multiple: true do
      actors.map(&:age)
    end

    text :names, multiple: true do
      actors.map(&:name)
    end
  end
end

# == Schema Information
#
# Table name: actors
#
#  id              :integer(4)      not null, primary key
#  name            :string(255)
#  age             :integer(30)

class Actor < ActiveRecord::Base
  has_and_belongs_to_many :movies

  searchable do
    integer :age
    text :name
  end
end

I want to find every movie that has an actor named John at age 30.

Movie.search do
  with(:names).equal_to("John")
  with(:ages).equal_to(30)
  with(:title).equal_to("...")
  # ...
end

The problem is here that it may find a movie that has two actors; one named John and one at age 30. Is there a way to somehow group this together so that the movie found have an actor named John at age 30?

The solution, just like Maurício Linhares wrote in his comment, is to go through the actors model and group by movies.

The problem is that Sunspot doesn't support Solr 3.3 or 4.0, which is the only Solr versions that support grouping.

Here is my solution using Sunspot 1.2.1 and Solr 3.3.

In my example movie_id is placed in the actors table, this isn't done in my real application.

# == Schema Information
#
# Table name: actors
#
#  id              :integer(4)      not null, primary key
#  name            :string(255)
#  created_at      :datetime
#  updated_at      :datetime
#  movie_id        :integer(4)
#

class Actor < ActiveRecord::Base
  searchable do

    # We need to store the movie_id as an string
    # So it can be sorted. We also need to pass the
    # stored: true params
    string :movie_id, stored: true do
      movie_id.to_s
    end
  end

  def search_using_solr
    scoped = Sunspot.new_search(Actor)

    scoped.build do      
      adjust_solr_params do |params|
        params[:group]          = true
        params[:"group.field"]  = "movie_id_s"
        params[:"group.format"] = "simple"
      end
    end

    # Sunspot 1.2.1 doesn't support grouping, so we need to do some hacking.
    def scoped.hits
      @hits ||= @solr_result["grouped"].values.first["doclist"]["docs"].map do |doc|
        Sunspot::Search::Hit.new(doc, nil, self)
      end
    end

    def scoped.total
      @total ||= @solr_result["grouped"]["movie_id_s"]["matches"] || 0
    end

    # Here we'll only fetch the stored data from Solr it self, 
    # and then pass it manualy to ActiveRecord.
    Movie.where({
      id: scoped.execute.hits.map{ |h| h.stored(:movie_id) }
    })
  end
end

Cred to alindeman for his example gist.