CODEWITHSUNDEEP
djangodjango-orm
coderDude
coderDude

Reputation: 904

Quickly get query set of objects related to 2 other objects by a Foreign key

Here are my models: 

class A(models.Model):
  #Some fields

class B(models.Model):
  #Some fields

class C(models.Model):
  a = models.ForeignKey(A)
  b = models.ForeignKey(B)
  #Some more fields

  class Meta:
     unique_together = ['a', 'b']

Now based on some object of A (say 'a') , I want set of all 'b' for which C.a = 'a' and C.b = 'b' .
In other words, get a set of objects of B for which entries exist in a.c_set

Currently the way I am doing this is:

qset_c = C.objects.filter(a='a')    
qset_b = [c.b for c in qset_c]

First of all this gives me a list (a queryset would be preferred).
Second, I am concerned about line 2 having list comprehension , as it may take a lot of time for huge data.

Is there a better way to achieve this?

Note: I understand , the statement is a bit unclear. If someone can edit it to make it more clear, it will be a lot helpful

Upvotes: 0

Views: 30

Answers (1)

ger.s.brett
ger.s.brett

Reputation: 3308

Would this do what you want?

set_c = C.objects.filter(a=a).values_list('b', flat=True)

Upvotes: 1

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