title: Query prefetched objects without using the db?
body: <p>I'm getting multiple objects with prefetched relations from my db:</p>
  
  <pre><code>datei_logs = DateiLog.objects.filter(user=request.user)
                               .order_by("-pk")
                               .prefetch_related('transfer_logs')
  </code></pre>
  
  <p><code>transfer_logs</code> refers to this:</p>
  
  <pre><code>class TransferLog(models.Model):
    datei_log = models.ForeignKey("DateiLog", related_name="transfer_logs")
    status = models.CharField(
                      max_length=1,
                      choices=LOG_STATUS_CHOICES,
                      default='Good'
                      ) 
    server_name = models.CharField(max_length=100, blank=True, default="(no server)")
    server = models.ForeignKey('Server')
  
    class Meta:
      verbose_name_plural = "Transfer-Logs"
  
    def __unicode__(self):
      return self.server_name
  </code></pre>
  
  <p>Now I want to get all the <code>TransferLogs</code> that have a status of <code>"Good"</code>. But I think if I do this:</p>
  
  <pre><code>datei_logs[0].transfer_logs.filter(...)
  </code></pre>
  
  <p>It queries the db again! Since this happens on a website with many log entries I end up with 900 Queries!</p>
  
  <p>I use:</p>
  
  <pre><code>datei_logs[0].transfer_logs.count()
  </code></pre>
  
  <p>As well and it causes lots of queries to the db too!</p>
  
  <p>What can I do to "just get everything" and then just query an object that holds all the information instead of the db?</p>