id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
7539	Add ON DELETE and ON UPDATE support to Django	glassfordm	Carl Meyer	"The attached patch adds two levels of ON DELETE and ON UPDATE
support to Django.

A. Just applying the patch changes nothing: Django should continue
to behave exactly as before, emulating ON DELETE CASCADE behavior
just as it has all along.
However:
1) Adding on_delete=RESTRICT or on_delete=SET_NULL to a ForeignKey
definition will cause Django to emulate the specified behavior 
for that particular foreign key. Django will continue to emulate 
CASCADE behavior for ForeignKeys which have no on_delete behavior 
specified; it will also emulate CASCADE behavior for foreign keys
having on_delete=CASCADE defined, of course.
2) The new setting, settings.ON_DELETE_NONE_HANDLING = <option>,
specifies the behavior of foreign keys that have no on_delete
option specified. It defaults to CASCADE (because this is what 
Django has done in the past), but can be set to RESTRICT (essentially
the default for SQL) or SET_NULL as well (although SET_NULL is not
recommended: it will cause errors for ForeignKeys that are not nullable).
3) Finally, the patch does not provide any Django emulation for 
ON UPDATE behavior, so, while the on_update option can be added to 
foreign key definitions, it does nothing (but see below).

B. Defining settings.ON_DELETE_HANDLED_BY_DB = True changes Django's
ON DELETE behavior completely: 
1) It disables Django emulation of ON DELETE behavior entirely.
2) It adds appropriate ON DELETE statements to the SQL generated 
by Django (by ""python manage.py sqlall"", for instance).

C. Defining settings.ON_UPDATE_HANDLED_BY_DB = True adds appropriate
ON UPDATE statements to the SQL generated by Django
(by ""python manage.py sqlall"", for instance)."	Uncategorized	closed	Database layer (models, ORM)	dev	Normal	fixed	feature	miracle2k mathijs@… matthubb diegobz road Sergey Belov Marinho Brandão me@… findepi gabor@… dnordberg@… ehs@… Jani Tiainen hanne.moa@… aaron@… groby@… Ilya Semenov ales.zoulek@… plandry@… lukasz.korzybski@… preston@… eschler@… paluho@… gorsky.exe@… ego@… Gonzalo Saavedra l.dziedzia@… cgieringer t.django@… goliath.mailinglist@… jdunck@… mlong@… erikrose paulc@… jakub@… david@… jbauer@… luc.saffre@…	Accepted	1	1	0	1	0	0