Insert code generated by models using multiple inheritance is incorrect and fails in postgresql

[Arthur Pemberton]

When a model with multiple concrete parents is saved (inserted) the parents are saved first. Currently, the first parent is saved and its primary key is also set as the primary key of the yet unsaved top model. Any parent following uses the new primary key of 'self' and explicitly inserts the PK into the parent models table

There is no reason to explicitly set the PK of any of the parent classes, the code already handles retrieval of the DB assigned PK.

While other DBs let this pass, PostgreSQL does not. The problem comes not on the offending .save() but subsequent inserts to the table, this time without an explicit PK. The DB's internal counter has not advanced, so the next chosen PK already exists and yields a database error due to duplicate of a key field.

There is no apparent need to explicitly set any of the PK on insert. I believe that changing the following code block within source:django/trunk/django/db/models/base.py#13538 , line 533 , Model.save_base(...) can solve the problem:

from

                if update_pk:
                    setattr(self, meta.pk.attname, result)

to

                if update_pk and cls == self.__class__:
                    setattr(self, meta.pk.attname, result)

I have attached a sample site ('minherit') with app ('data') and a test case in a ZIP file.

[Arthur Pemberton]

same site with test case

[Arthur Pemberton]

sample site, fewer models, two tests cases

[Russell Keith-Magee]

(In [13579]) Fixed #14096 -- Corrected Python 2.4 syntax issue. Thanks to PaulM for the report.

[Russell Keith-Magee]

Fat fingers; [13579] closed #14086.

[Arthur Pemberton]

more complete, tested patch

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[la_iscla@…]

I'm experiencing the same issue here. Annoying. Any chance to see this fixed?

[Tim Graham]

Update the patch and add a test if you'd like to get it fixed.

[la_iscla@…]

Well, I've made a workaround with Postgres by having the model tables rely on the same SEQUENCE counter:

ALTER TABLE mymodule_a ALTER COLUMN id SET DEFAULT nextval('mymodule_c_id_seq');

I'll dig further into this issue whenever I have more time.

[Tim Graham]

Closing as invalid given the provided models don't validate:

data.Company: (models.E005) The field 'id' from parent model 'data.account' clashes with the field 'id' from parent model 'data.contact'.
data.Employee.company: (models.E006) The field 'company' clashes with the field 'company' from model 'data.contact'.