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copied!<p>You could either do it in python (as suggested above) or let the DB do the dirty work for you.</p> <p>You would need to construct a QuerySet containing all threads with a deleted message for a particular user and then a second QuerySet that gets all threads not contained in the first:</p> <pre><code>delthreads = MessageThread.objects.filter(messagerecipient__recipient=user, messagerecipient__status='deleted').distinct() result = MessageThread.objects.filter(messagerecipient_recipient=user) .exclude(messagethread_in=delthreads).distinct() </code></pre> <p>However, performance wise (especially on large tables) this will hurt you. Your model needs some restructuring to allow for more efficient queries. Consider:</p> <pre><code>class MessageThread(models.Model): subject = models.CharField(max_length=256, blank=False) class Message(models.Model): thread = models.ForeignKey(MessageThread) content = models.CharField(max_length=5000, blank=False) timestamp = models.DateTimeField(auto_now_add=True, blank=False) sender = models.ForeignKey(User) recipient = models.ForeignKey(User) status = models.CharField(max_length=20, choices=MESSAGE_STATUS, default="unread") </code></pre> <p>If you anticipate you will execute this query often, you could add a cache field to MessageThread which you can update whenever someone deletes a message in that thread:</p> <pre><code>class MessageThread(models.Model): subject = models.CharField(max_length=256, blank=False) dirty = models.BooleanField(default=False) </code></pre> <p>Then, it would be very easy to extract a list of threads with no deleted messages.</p> <pre><code>nondelthreads = MessageThread.objects.filter(message__recipient=user, dirty=True).distinct() </code></pre>

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