Question

I have to models:

class A(Model):
    b = models.ManyToManyField(B)

class B(Model):
    # fields

What is the most efficient way to add a large number of existing instances of B to the relationship?

Answer 1

As of django 1.4, you can make use of a bulk_create method to create numerous B objects in one go, then add them to the A.b ManyToMany

So create a list of B objects, bulk create them, then add them (all at once) to the ManyToMany relationship of your A instance(s):

l = [
    B(...),
    B(...),
    B(...),
    ...
]
B.objects.bulk_create(l)
a.b.add(*o)