Django-过滤prefetch_related

Question

I am having trouble with filtering one of my views. It is a DetailView, that also display lots of additional tables. I have my models as such:

 class Pipeline(models.Model):

 class Stage(models.Model):
     pipeline = models.ForeignKey(Pipeline, related_name='stages')

 class Opportunity(models.Model):
     status = ....
     stage = models.ForeignKey(Stage, related_name='opportunities')

 class EstateActivity(models.Model):
      time = models.DateTimeField(...)
      opportunity = models.ForeignKey(EstateOpportunity, related_name='activities')

Now, I am displaying Pipeline DetailView. In this DetailView I use prefetch related on all these models

qs.filter(users=self.request.user).prefetch_related('stages__opportunities__activities')

One pipeline contains many stages, and each stage containst many opportunities etc. However, I need to filter out firstly opportunities by their status(which can be obtained from URL). And to each opportunity I need to filter one specific activity (most recent activity and if such doesn't exist, then most recent from the past). So far, I tried using extra, however this doesn't work. I fail to come up with a solution that doesn't involve hitting database each time. Also, I can't just select it each model one by one

context['opportunities'] = Opportunity.objects.filter(user=..., ..pipeline=self.object, status=.....)

because I need to have the relations with Stage for template. If I just iterate over context['opportunities'] and add the desired Activity to each one, it's gonna hit database each time. Sadly, the prefetch_related filtering is only in the development version, with stable release in about 5 months.

Answer 1

Would select_related work for you instead?

qs.filter(users=self.request.user).select_related('stages')

Alternatively, work backwards:

opportunities = EstateActivity.objects.filter(opportunity__stage__pipeline__users=self.request.user)