With Django's ORM, I have a simple Question and Topic model like so:
class Topic(models.Model):
name = models.CharField(max_length=200)
class Question(models.Model):
topic_items = models.ManyToManyField(Topic, blank=True)
date_asked = models.DateField()
Suppose I have four Questions asked each on separate dates, with the fourth sharing two topics 'topic1', 'topic2'
If I do the following query with topics_restrict a list of the two topic ids for 'topic1' and 'topic2'...
q_filter = Question.objects.filter(topic_items__in=topics_restrict).distinct()
Then I get four results (instead of five, which would have resulted without the distinct)
Now if I do the following:
return q_filter.annotate(
total=Count('date_asked')
).values_list('total', flat=True)
I get the result [2,1,1,1] instead of [1,1,1,1] - ie, as if the distinct() had never been applied.
The only way to get around it is to do...
q_filter = Question.objects.filter(pk__in=q_filter.values_list('pk', flat=True))
... and then annotate on that q_filter.
But there has to be a better way?
