Sunspot: How to filter?

BusinessStore.rb

class BusinessStore < ActiveRecord::Base
  attr_accessible :website, :name, :address,  :phone_number, :online_store
  has_many :products
end

create_business_stores.rb

class CreateBusinessStores < ActiveRecord::Migration
  def self.up
    create_table :business_stores do |t|
      t.string :name
      t.string :address
      t.string :website
      t.string :phone_number
      t.boolean :online_store

      t.timestamps
    end
  end
end

Product.rb

class Product < ActiveRecord::Base
  attr_accessible :price, :name, :purchase_date, :store
  belongs_to :business_store
  attr_accessor :store # for finding particular ID of business_store

  searchable do
    text :name
    time :purchase_date
    float :price
    boolean :online_store
  end

  def online_store
    # I'm assuming all products have a business_store otherwise you
    # might want this business_store.try(:online_store) or take a look
    # at the delegate method that's included in ActiveRecord::Base.
    business_store.online_store
  end

end

search_controller.rb

class SearchController < ApplicationController

  def index
    # Pass a block variable or else you won't be able to access the
    # params here.
    @search = Product.search do |q|
      q.fulltext params[:search]
      q.with(:online_store, params[:online_store] == 1)
      q.paginate(:per_page => 10, :page => params[:page])
      q.order_by(:purchase_date, :desc)
      q.order_by(:price,:asc)
    end

    @products = @search.results
  end

end

search_index.html.erb

<%= form_tag search_path, :method => 'get' do %>
  <%= text_field_tag :search, params[:search] %>
  <%= submit_tag "Search", :name => nil %>
<%end%>

<% @products.each do |p| %>
  <%= p.name %>
  <%= p.price %>
  <%= p.purchase_date. %>
  <%= p.store %>
  <% if p.business_store.online_store %>
    <%= "Online Store" if p.business_store.online_store %>
  <% end %>
<% end %>