I've implemented some code already to de-reference (SET_NULL) on
delete, in a view which first presents a list of objects which will be
deleted and a list of objects which will be de-referenced. It might
not be the most efficient approach, but it could be a starting point.
def _clear(instance):
"""
recursively clear related models before deleting `instance`.
"""
cleared = []
deleted = []
for related_set in (getattr(instance, elem) for elem in dir(instance)
if re.search(r'_set$', elem)):
if hasattr(related_set, 'clear'):
cleared.extend(elem for elem in related_set.all())
related_set.clear()
elif hasattr(related_set, 'all'):
for related_instance in related_set.all():
_cleared, _deleted = _clear(related_instance)
deleted.extend(_deleted)
return cleared, ((instance, deleted), )
@user_is_authenticated()
@request_passes_test(lambda r: r.user.is_superuser)
@transaction.commit_manually
def delete(request, app_label, model_name, pk, template='base/
delete.html', next='/base/'):
try:
model = get_model(app_label, model_name)
instance = model.objects.get(pk=pk)
except model.DoesNotExist:
raise Http404
if request.method == 'POST':
alert = '<b>%s</b> successfully deleted.' % instance
_clear(instance)
instance.delete()
transaction.commit()
# set alert and redirect.
context = RequestContext(request, {
})
request.session['alert'] = alert
request.session['alert_class'] = 'good'
return HttpResponseRedirect(context['base']['next'] or next)
cleared, deleted = _clear(instance)
transaction.rollback()
# set context and render template.
context = RequestContext(request, {
'cleared': cleared,
'deleted': deleted,
})
return render_to_response(template, context)
One other thing that you might need to consider is how any change here
will affect post_delete and post_save triggers. Will they still fire
when a supported database executes a cascading delete or SET_NULL, or
will they only fire when a delete/update is implemented through the
Django ORM?
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