Opened 15 years ago

Closed 15 years ago

#10262 closed (duplicate)

Allow to clear object before deleting to avoid data loss because delete cascade behaviour

Reported by: Manuel Saelices Owned by: nobody
Component: Database layer (models, ORM) Version: 1.0
Severity: Keywords:
Cc: Carl Meyer Triage Stage: Design decision needed
Has patch: yes Needs documentation: yes
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

Imaging a model like this:

class Master(models.Model):
    name = models.CharField(max_length=100)
        

class Slave(models.Model):
    name = models.CharField(max_length=100)
    master = models.ForeignKey(Master, null=True)

And this object creation:

>>> m1 = Master.objects.create(name="master1")
>>> s1 = Slave.objects.create(name="slave1", master=m1)

>>> m1.delete() # this will also delete s1

Django by default, delete in cascade all related objects... even with null=True.

If you want to avoid this, you can do this:

>>> m1.slave_set.clear()
>>> m1.delete()

This is ok, but it was wonderful if I can change behaviour to not delete cascade. You can think in admin site for example. If you want to delete a Category object you have previously to enter in maybe a hundred objects to set null by hand.

I propose a definition like this:

class Slave(models.Model):
    name = models.CharField(max_length=100)
    master = models.ForeignKey(Master, null=True, delete_cascade=False)

With delete_cascade=False (by default would be True), delete() method will clear this relation previously deletion.

I've attached a patch that implements this idea.

Attachments (3)

delete_cascade_option_r9832.diff (3.1 KB ) - added by Manuel Saelices 15 years ago.
delete_cascade_option_with_admin_r9834.diff (3.7 KB ) - added by Manuel Saelices 15 years ago.
Updated admin to not display objects not deleted (because delete_cascade was False)
delete_cascade_option_with_tests_r9834.diff (7.1 KB ) - added by Manuel Saelices 15 years ago.
With unit tests and with delete_cascade for OneToOneRel

Download all attachments as: .zip

Change History (8)

by Manuel Saelices, 15 years ago

by Manuel Saelices, 15 years ago

Updated admin to not display objects not deleted (because delete_cascade was False)

by Manuel Saelices, 15 years ago

With unit tests and with delete_cascade for OneToOneRel

comment:1 by Mikhail Korobov, 15 years ago

Triage Stage: UnreviewedDesign decision needed

comment:2 by Mikhail Korobov, 15 years ago

Needs documentation: set

comment:3 by Carl Meyer, 15 years ago

Cc: Carl Meyer added

comment:4 by Erin Kelly, 15 years ago

This looks like a duplicate of #7539.

comment:5 by Jacob, 15 years ago

Resolution: duplicate
Status: newclosed

Duplicate of #7539

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