title: Django Haystack add additional input to search
body: <p>I've a haystack search currently works well searching on the following model:</p>
  
  <pre><code>class AdminEntry(models.Model):
      product = models.ForeignKey('Product')
      number_entries = models.IntegerField(max_length=3,  null=True)
  </code></pre>
  
  <p>My <code>search_indexes.py</code>:</p>
  
  <pre><code>class AdminEntryIndex(SearchIndex):
      text = CharField(document=True, use_template=True)
      author = CharField(model_attr='product__author')
      title = CharField(model_attr='product__title')
      desc = CharField(model_attr='product__desc')
  
      def get_queryset(self):
          return AdminEntry.objects.all()
  
  site.register(AdminEntry, AdminEntryIndex)
  </code></pre>
  
  <p>but now I want to add additional search parameter in dropdown in my search form with 2 values <code>['Admin', 'Staff']</code> since I've added another model:</p>
  
  <pre><code>class StaffEntry(models.Model):
      product = models.ForeignKey('Product')
      number_entries = models.IntegerField(max_length=3,  null=True)
  </code></pre>
  
  <p>I want to my search to search on <code>StaffEntry</code> if the dropdown selected is 'Staff', and <code>AdminEntry</code> is 'Admin' is selected. Can someone help me on how to achieve this using Haystack with Whoosh? Thanks in advance.</p>