Using Django bulk_create objects in foreign keys?

Question

I was reading up on Django bulk_create and a few of its "flaws":

"
This has a number of caveats though:

1. The model's save() method will not be called, and the pre_save and post_save signals will not be sent.
2. It does not work with child models in a multi-table inheritance scenario.
3. If the model's primary key is an AutoField it does not retrieve and set the primary key attribute, as save() does.
"

I didn't fully understand it. So if I have a list of objects, pass it into bulk_create:

objList = [a, b, c,] #none are saved
model.objects.bulk_create(objList)

Could I still use these objects in foreign keys fine?

for obj in objList:
    o = otherModel(something='asdfasdf', fkey=obj)
    o.save() # will this be fine given the caveats stated above?

So will the foreignKey relation be okay? Also when it says 2. It does not work with child models in a multi-table inheritance scenario, it means that any model that inherits from another model(abstract or not) cannot use bulk_create?

Answer 1

Try setting the ids manually. To prevent race conditions, make sure to wrap the function as a single transaction.

from django.db import transaction, models

@transaction.commit_on_success
def bulk_create_with_manual_ids(foo_list):
    id_start = (Foo.objects.all().aggregate(models.Max('id'))['id__max'] or 0) + 1
    for i,foo in enumerate(foo_list): foo.id = id_start + i
    return Foo.objects.bulk_create(foo_list)

objList = [Foo(),Foo(),Foo()]
foo_objects = bulk_create_with_manual_ids(objList)
Bar(foo=foo_objects[0]).save()

Note that this approach is unsuitable for any table that has a serial field or other auto-incrementing in-database generated key. The key will not be incremented by the bulk create since IDs are being generated on the Django side.

Answer 2

For the first question, no you won't be able to do that, because obj won't have its primary key set so couldn't be used as a foreign key.

The second question, no that's not what it says at all. It specifically mentions "multi-table inheritance": inheriting from an abstract model is not multi-table inheritance.