adapter.rb

require 'sunspot'

module SunspotAdapter

  class InstanceAdapter < Sunspot::Adapters::InstanceAdapter
    def id
      @instance.id
    end
  end

  class DataAccessor < Sunspot::Adapters::DataAccessor
    def load(id)
      Team.find(BSON::ObjectId.from_string(id))
    end

    def load_all(ids)
      Team.where(:_id.in => ids.map{|id| BSON::ObjectId.from_string(id)})
    end
  end

end

foo.rb

require 'sunspot'

module SunspotAdapter

  class InstanceAdapter < Sunspot::Adapters::InstanceAdapter
    def id
      @instance.id
    end
  end

  class DataAccessor < Sunspot::Adapters::DataAccessor
    def load(id)
      @klass.find(BSON::ObjectId.from_string(id))
    end

    def load_all(ids)
      @klass.where(:_id.in => ids.map{|id| BSON::ObjectId.from_string(id)})
    end
  end

end

initializer_sunspot.rb

require 'sunspot'
require 'sunspot_adapter'
Sunspot::Adapters::InstanceAdapter.register(SunspotAdapter::InstanceAdapter, Team)
Sunspot::Adapters::DataAccessor.register(SunspotAdapter::DataAccessor, Team)