Yet another approach to provide soft (logical) delete or masking (thrashing) django models instead of deleting them physically from db.

To create non-deletable model just inherit it form the PermanentModel.:

class MyModel(PermanentModel):
    pass

It automatically changes delete behaviour, to hide model instead of deleting. restore() method.:

>>> a = MyModel.objects.create(pk=1)
>>> b = MyModel.objects.create(pk=2)
>>> MyModel.objects.count()
2
>>> a.delete()
>>> MyModel.objects.count()
1

To recover model just call its restore method.:

>>> a.restore()
>>> MyModel.objects.count()
2

User Force kwarg to enforce physical deletion.:

>>> a.delete(force=True) # Will act as the default django delete
>>> MyModel._base_manager.count()
0

It changes default model manager to ignore deleted objects. And adds deleted_objects manager to find the last ones.:

>>> MyModel.objects.count()
2
>>> a.delete()
>>> MyModel.objects.count()
1
>>> MyModel.deleted_objects.count()
1
>>> MyModel.all_objects.count()
2
>>> MyModel._base_manager.count()
2

Query set delete method will act as the default django delete, with the one exception - all related PermanentModel children will be marked as deleted, the usual models will be deleted physically:

>>> MyModel.objects.all().delete()

You can still force django query set physical deletion:

>>> MyModel.objects.all().delete(force=True)

1. Inherit your query set from PermanentQuerySet:

   class ServerFileQuerySet(PermanentQuerySet)
       pass

2. Wrap it in the permanent_queryset or deleted_queryset in you model manager declaration:

   class MyModel(PermanentModel)
       objects = MultiPassThroughManager(ServerFileQuerySet, NonDeletedQuerySet)
       deleted_objects = MultiPassThroughManager(ServerFileQuerySet, DeletedQuerySet)
       all_objects = MultiPassThroughManager(ServerFileQuerySet, PermanentQuerySet)

1. Check existence of the object.
2. Restore it was deleted.
3. Create new one, if it wasn't ever created.

By default field is named removed, but you can override it by PERMANENT_FIELD variable in you settings.py.:

PERMANENT_FIELD = 'deleted'

Django 1.6.x required. To cover Django 1.5 needs use 0.1.4 branch.