#12339: ContentType update could cascade deletes to generic foreign keys,
causing
data loss
-----------------------------------+----------------------------------------
Reporter: kcarnold | Owner: nobody
Status: closed | Milestone:
Component: Contrib apps | Version: 1.1
Resolution: duplicate | Keywords: contenttype, delete,
cascade
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by kmtracey):
* status: new => closed
* needs_better_patch: => 0
* resolution: => duplicate
* needs_tests: => 0
* needs_docs: => 0
Comment:
Starting with "Imagine that you change the name of a model" we're off in
territory that Django does not yet claim to support: schema migration.
Given that, what it looks like to Django when you change the name of a
model is that the old model has been deleted. Django then correctly
deletes the content type for that model, and yes that will cascade to any
rows in other tables that referenced that content type. You do not lose
the admin log, but you lose any entries in it that refer to the old model.
To omit the cascade would be wrong, because that would leave pointers to
nowhere hanging around. The current behavior is correct for the case where
a model has been deleted. True, it does not account for the case where
you are renaming the model, not actually deleting it, but that is not a
problem that will be fixed individually. The correct way to fix that
problem would be to implement general schema migration, which is covered
by #5934. Presumably a good schema migration would handle updating the
content type on a rename instead of deleting it, and so avoid the cascade
delete (though I don't know the details of how any of the existing
external apps that do migration handle this, I've not had any need to use
them). At any rate I'm going to close this as a duplicate of the migration
ticket, since this won't be "fixed" except as part of the larger effort to
incorporate migrations into the base.
--
Ticket URL: <http://code.djangoproject.com/ticket/12339#comment:1>
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