Lazy object id fetch on object initialization.

[Bartłomiej Nowak]

Let's assume I am using the Postgres database, so the flag can_return_ids_from_bulk_insert is True.

I would like to do this:

class ModelA:
      pass

class ModelB:
      a = models.ForeginKey(ModelA)

a_to_create = []
b_to_create = []
for _ in some_data:
    a = ModelA(...)
    a_to_create.append(a)
    b_to_create.append(
          ModelB(a=a, ...)
     )

ModelA.objects.bulk_create(a_to_create)
# all objects in the a_to_create list have now ids, becouse of can_return_ids_from_bulk_insert flag. a_to_create[0].id will return int. 
ModelA.objects.bulk_create(b_to_create)

But when I initialize ModelB(a=a), Django immediately fetches id from object a, which is None in this line, and using this latter, instead of fetching it (id) from the provided object, when it's going to create. Why do not fetch this id lazy?

Because of this situation, I have to do an additional loop for every additional model.

Thank you

[Mariusz Felisiak]

Duplicate of #29497, fixed in 10f8b82d195caa3745ba37d9424893763f89653e.