title: Is it possible to persist a joined field in Djangos SearchVectorField?
body: <p>Is it possible to persist a joined field with Djangos SearchVectorField for full text search?</p>
  
  <p>For example:</p>
  
  <pre><code>class P(models.Model):
      brand = models.ForeignKey(Brand, on_delete=models.CASCADE)
      search_vector = SearchVectorField(null=True, blank=True)
  </code></pre>
  
  <p>code:</p>
  
  <pre><code>p = P.objects.get(id=1)
  p.search_vector = SearchVector('brand__name')
  p.save()
  </code></pre>
  
  <p>raises this exception:</p>
  
  <pre><code>FieldError: Joined field references are not permitted in this query
  </code></pre>
  
  <p>If this is not possible how can you increase the performance of joined annotated queries? </p>