label.rb

class Label < ActiveRecord::Base
  searchable do
    text :user_name do |label| 
      label.user.name
    end

    string :tracking_number
    string :status
    
    date :created_at
  end
end

labels_controller.rb

class Admin::LabelsController < ApplicationController
  def index
    @search = Sunspot.new_search(Label) 
    @search.build do |q|
      q.keywords(params[:keywords]) if params[:keywords].present?
      q.with(:tracking_number, params[:tracking_number]) if params[:tracking_number].present?
      q.with(:status, params[:status]) if params[:status].present?

      q.order_by(:created_at, :desc)
      q.facet :status
      
      q.data_accessor_for(Label).include = {:collection => [:brigade, :team]}
    end
    
    respond_to do |format|
      format.html { @search.execute! }
      format.csv do

        render :text => proc {|resp, output|
          output.write FasterCSV.generate_line(
            ["User Name", "Tracking Number", "Status", "Created At"]
          )
          
          # Ugly, but given will_paginate's collection API, this seems to the best option.
          page = 1
          while page
            @search.build do |q|
              q.paginate(:per_page => 10000, :page => page)
            end
            @search.execute!
            
            @search.hits.each do |hit|
              output.write FasterCSV.generate_line([
                [
                  :user_name
                  :status, 
                  :tracking_number, 
                  :created_at
                ].map {|col| hit.stored(col)}
              ])
            end
            
            page = @search.results.next_page
          end
        }
        
      end
    end
  end
end