Hi guys,
I'm new to Django but otherwise quite a seasoned python and sql
programmer. I'm baffled by django's foreign key id behaviour and as a
result stuck in my current coding project. Let me start immediately
with an example of what I'm trying to do. Assume two very simple
models:
class A(models.Model):
pass
class B(models.Model):
a = models.ForeignKey(A)
Now I need to create an instance of A and B without saving either of
them (I'm parsing a whack load of data and only want to commit objects
to the db once successfully parsed):
from test.models import A,B
instA = A()
instB = B(a=instA)
Now I'm done with my parsing and am happy to save them to my database:
instA.save() # all good
instB.save() # fails with IntegrityError: null value in column "a_id"
violates not-null constraint
On closer inspection the second line above fails because instB.a_id is
None, even though instB.a.id is defined. Why does django throw in a
duplicate, now stale instB.a_id field which, to make matters worse, is
used in generating the underlying SQL for instB.save() to result in
failure????
Perhaps I'm just to n00b to use the correct semantics which avoid the
above issues... excuse me if that's the case.
Gunther
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