title: Django queryset filter filefield not empty
body: <p>I'm trying to filter a queryset, to exclude the one with no file. And I can't get it work, except by numberless iterations.</p>
  <pre><code>class Something(models.Model):
      name = models.CharField(max_length=512)
      file = models.FieldField(upload_to=&quot;files&quot;, null=True, blank=True)
  </code></pre>
  <p>Then, to get the one with a file</p>
  <pre><code> # this give me all objects
   Something.objects.exclude(file__exact='')
   
   # this is a valid solution, but hell, something easier should exist, 
   something_with_files = set()
   for s in Something.objects.all():
      if s.file:
          something_with_files.add(s)
  </code></pre>
  <p>What is the real solution to this?</p>
  <p>PS: working on PostGres, I don't know if that can change anything at that point.</p>