#29085: Possible data loss on .save() with unsaved related model
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Reporter: Jonas Haag | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Matthew Schinckel):
I believe I hit the same issue today.
I have a set of related objects that I want to construct all of the forms
for, validate all of them, and then save.
However, the reference to the primary object (which is still "connected"
to the child instances) is removed when saving.
I _think_ it's got to do with `Field.pre_save(self, model_instance, add)`
being called before saving: which uses `field.attname`, which is
necessarily empty initially (because we don't have a primary key on the
reference object, yet).
I'm going to play around, but I think it could be that a ForeignKey can
have slightly different behaviour, where it falls back to the related (in-
memory) object, if one exists, and `field.attname` is None.
--
Ticket URL: <https://code.djangoproject.com/ticket/29085#comment:6>
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