title: django foreignkey contains query
body: <p>I have the following model</p>
  
  <pre><code>class Command(models.Model):
      server = models.ForeignKey(Server)
      user_login = models.CharField(max_length=100)
      user_run = models.CharField(max_length=100)
      host = models.CharField(max_length=100)
      ip = models.CharField(max_length=100)
      session = models.CharField(max_length=100)
      command = models.TextField()
      ts = models.DateTimeField(auto_now_add=True)
      version = models.CharField(max_length=100)
      type = models.CharField(max_length=100)
  </code></pre>
  
  <p>I have the following search query</p>
  
  <pre><code>cmds = Command.objects.filter(Q(user_login__contains=form.cleaned_data['loguser']),
                                Q(user_run__contains=form.cleaned_data['runuser']),
                                Q(host__contains=form.cleaned_data['loghost']),
                                Q(command__contains=form.cleaned_data['command']),
                                Q(server__contains=form.cleaned_data['host']),
                                Q(session__contains=form.cleaned_data['session'])) \
                        .order_by('-id')[:100]
  </code></pre>
  
  <p>I need to search by the following string for server.host</p>
  
  <p>If I try to add the following I get an error</p>
  
  <pre><code>Q(server__contains=form.cleaned_data['host']),
  
  Exception Type:     TypeError
  Exception Value:    
  
  Related Field has invalid lookup: contains
  
  Exception Location:     /usr/lib/python2.5/site-packages/django/db/models/fields/related.py in get_db_prep_lookup, line 156
  </code></pre>
  
  <p>form.cleaned_data['host'] will contain a text string for a hostname.</p>