Howdy all,
There are tangential references to this on the list archives and
elsewhere, but I haven't found any describing this specific situation:
In short, if I have a model object type with both 'simple' sub-
objects (objects with a single ForeignKey to the main object and no
other references) and 'complex' foreign key relations with peer
objects (which are not wholly owned by the main object, but do have a
ForeignKey reference to it somewhere), and I try delete()-ing my main
object, I end up with the simple objects being fully deleted, but my
main object is _not_ deleted due to the 'complex' relational
integrity constraints.
The end result is that an attempt to delete the record ultimately
fails--which is what I want, due to the constraints--but because the
overall deletion process "half-occurred", I have lost data in the
process! This is bad.
Since transactions aren't in yet, I can't think of another way to
prevent this from happening--don't know if I am doing something
incorrectly, or what :)
That's the gist of it; the concrete example follows, if you're
interested (unnecessary info stripped out):
==== apps/contacts/models/contacts.py ====
class Contact(meta.Model):
[....]
# Reference to employee who provided the firm with this
contact's info
provider = meta.ForeignKey('self',null=True,limit_choices_to=
{'company__name__exact':OUR_COMPANY})
# Reference to user/employee who last updated this contact record
mod_user = meta.ForeignKey('self',blank=True,null=True)
[....]
class Address(meta.Model):
# 'Parent' reference to the contact this address belongs to
contact = meta.ForeignKey
(Contact,edit_inline=meta.STACKED,max_num_in_admin=3,min_num_in_admin=3)
[....]
==== ipython session ====
In [1]: from django.models.contacts import contacts
In [2]: me = contacts.get_object
(first__exact='Jeffrey',last__exact='Forcier')
In [3]: me
Out[3]: Forcier, Jeffrey E.
In [4]: me.get_address_list
------> me.get_address_list()
Out[4]: [home address, business address]
In [5]: [x.id for x in me.get_address_list()]
Out[5]: [1231, 1232]
In [6]: me.delete()
##### These 3 lines are from a debug statement I had inserted into
delete() ####
DELETE FROM "contacts_addresses" WHERE "id"=%s [1231]
DELETE FROM "contacts_addresses" WHERE "id"=%s [1232]
DELETE FROM "contacts_contacts" WHERE "id"=%s [1247]
------------------------------------------------------------------------
---
psycopg.IntegrityError Traceback (most
recent call last)
[...traceback was here...]
IntegrityError: ERROR: update or delete on "contacts_contacts"
violates foreign key constraint "contacts_contacts_provider_id_fkey"
on "contacts_contacts"
DETAIL: Key (id)=(1247) is still referenced from table
"contacts_contacts".
DELETE FROM "contacts_contacts" WHERE "id"=1247
Thanks, sorry for the length,
Jeff
--
Jeffrey E. Forcier
Junior Developer, Research and Development
Stroz Friedberg, LLC
15 Maiden Lane, 12th Floor
New York, NY 10038
[main]212-981-6540 [direct]212-981-6546
http://www.strozllc.com
This message is for the named person's use only. It may contain
confidential, proprietary or legally privileged information. No right to
confidential or privileged treatment of this message is waived or lost
by any error in transmission. If you have received this message in
error, please immediately notify the sender by e-mail or by telephone at
212.981.6540, delete the message and all copies from your system and
destroy any hard copies. You must not, directly or indirectly, use,
disclose, distribute, print or copy any part of this message if you are
not the intended recipient.
