title: Django view queryset - how to remove duplicate queries
body: <p>This is my <strong>view</strong> I filter the table by user, the model as a ForeignKey to another table.</p>
  
  <pre><code>class LaListaView(ListView):
      def get_queryset(self, **kwargs):
          qs = super(OraListView, self).get_queryset()
          qs= qs.filter(Q(cod_operatore=self.request.user.username) ).prefetch_related()
          qs= qs.select_related()
          return qs
  </code></pre>
  
  <p>from django debug toolbar I get:</p>
  
  <blockquote>
    <p>SELECT ••• FROM "mat_app_materiale" WHERE
    "mat_app_materiale"."rapp_rif_id" = 282 LIMIT 1 Duplicated 50 times.</p>
  </blockquote>
  
  <p>The Duplicated  50 times action can be removed ? If yes how?</p>