Ticket #7539: on_delete_on_update-r11620.diff

django/db/models/base.py

@@ -13 +13 @@
 from django.db.models.fields import AutoField, FieldDoesNotExist
 from django.db.models.fields.related import OneToOneRel, ManyToOneRel, OneToOneField
 from django.db.models.query import delete_objects, Q
-from django.db.models.query_utils import CollectedObjects, DeferredAttribute
+from django.db.models.query_utils import CollectedFields, CollectedObjects, DeferredAttribute
 from django.db.models.options import Options
-from django.db import connection, transaction, DatabaseError
+from django.db import connection, transaction, DatabaseError, IntegrityError
 from django.db.models import signals
+from django.db.models.fields.related import CASCADE, PROTECT, SET_NULL, SET_DEFAULT
 from django.db.models.loading import register_models, get_model
 from django.utils.functional import curry
 from django.utils.encoding import smart_str, force_unicode, smart_unicode
@@ -507 +508 @@
 
     save_base.alters_data = True
 
-    def _collect_sub_objects(self, seen_objs, parent=None, nullable=False):
+    def _collect_sub_objects(self, seen_objs, fields_to_set, parent=None, nullable=False):
         """
         Recursively populates seen_objs with all objects related to this
         object.
@@ -519 +520 @@
         pk_val = self._get_pk_val()
         if seen_objs.add(self.__class__, pk_val, self, parent, nullable):
             return
+            
+        def _handle_sub_obj(related, sub_obj):
+            on_delete = related.field.rel.on_delete
+            if on_delete is None:
+                #If no explicit on_delete option is specified, use the old
+                #django behavior as the default: SET_NULL if the foreign
+                #key is nullable, otherwise CASCADE.
+                if related.field.null:
+                    on_delete = SET_NULL
+                else:
+                    on_delete = CASCADE
+                
+            if on_delete == CASCADE:
+                sub_obj._collect_sub_objects(seen_objs, fields_to_set, self.__class__)
+            elif on_delete == PROTECT:
+                msg = '[Django] Cannot delete a parent object: a foreign key constraint fails (ForeignKey `%s` (pk=`%s`) references `%s` (pk=`%s`))' % (
+                    sub_obj.__class__,
+                    sub_obj._get_pk_val(),
+                    self.__class__,
+                    pk_val,
+                    )
+                raise IntegrityError(msg)
+            elif on_delete == SET_NULL:
+                if not related.field.null:
+                    msg = '[Django] Cannot delete a parent object: foreign key constraint on_delete=SET_NULL is specified for a non-nullable foreign key (ForeignKey `%s` (pk=`%s`) references `%s` (pk=`%s`))' % (
+                        sub_obj.__class__,
+                        sub_obj._get_pk_val(),
+                        self.__class__,
+                        pk_val,
+                        )
+                    raise IntegrityError(msg)
+                fields_to_set.add(sub_obj.__class__, sub_obj._get_pk_val(), sub_obj, related.field.name, None)
+            elif on_delete == SET_DEFAULT:
+                if not related.field.has_default():
+                    msg = '[Django] Cannot delete a parent object: foreign key constraint on_delete=SET_DEFAULT is specified for a foreign key with no default value (ForeignKey `%s` (pk=`%s`) references `%s` (pk=`%s`))' % (
+                        sub_obj.__class__,
+                        sub_obj._get_pk_val(),
+                        self.__class__,
+                        pk_val,
+                        )
+                    raise IntegrityError(msg)
+                fields_to_set.add(sub_obj.__class__, sub_obj._get_pk_val(), sub_obj, related.field.name, related.field.get_default())
+            else:
+                raise AttributeError('Unexpected value for on_delete')
 
         for related in self._meta.get_all_related_objects():
             rel_opts_name = related.get_accessor_name()
             if isinstance(related.field.rel, OneToOneRel):
                 try:
+                    # delattr(self, rel_opts_name) #Delete first to clear any stale cache 
+                        #TODO: the above line is a bit of a hack
+                        #It's one way (not a very good one) to work around stale cache data causing
+                        #spurious RESTRICT errors, etc; it would be better to prevent the cache from
+                        #becoming stale in the first place.
                     sub_obj = getattr(self, rel_opts_name)
                 except ObjectDoesNotExist:
                     pass
                 else:
-                    sub_obj._collect_sub_objects(seen_objs, self.__class__, related.field.null)
+                    _handle_sub_obj(related, sub_obj)
             else:
                 # To make sure we can access all elements, we can't use the
                 # normal manager on the related object. So we work directly
@@ -541 +591 @@
                     raise AssertionError("Should never get here.")
                 delete_qs = rel_descriptor.delete_manager(self).all()
                 for sub_obj in delete_qs:
-                    sub_obj._collect_sub_objects(seen_objs, self.__class__, related.field.null)
+                    _handle_sub_obj(related, sub_obj)
 
         # Handle any ancestors (for the model-inheritance case). We do this by
         # traversing to the most remote parent classes -- those with no parents
@@ -556 +606 @@
                 continue
             # At this point, parent_obj is base class (no ancestor models). So
             # delete it and all its descendents.
-            parent_obj._collect_sub_objects(seen_objs)
+            parent_obj._collect_sub_objects(seen_objs, fields_to_set)
 
     def delete(self):
         assert self._get_pk_val() is not None, "%s object can't be deleted because its %s attribute is set to None." % (self._meta.object_name, self._meta.pk.attname)
 
         # Find all the objects than need to be deleted.
         seen_objs = CollectedObjects()
-        self._collect_sub_objects(seen_objs)
+        fields_to_set = CollectedFields()
+        self._collect_sub_objects(seen_objs, fields_to_set)
 
         # Actually delete the objects.
-        delete_objects(seen_objs)
-
+        delete_objects(seen_objs, fields_to_set)
     delete.alters_data = True
 
     def _get_FIELD_display(self, field):

django/db/models/fields/related.py

@@ -20 +20 @@
 
 pending_lookups = {}
 
+class CASCADE(object):
+    pass
+class PROTECT(object):
+    pass
+class SET_NULL(object):
+    pass
+class SET_DEFAULT(object):
+    pass
+ALLOWED_ON_DELETE_ACTION_TYPES = set([None, CASCADE, PROTECT, SET_NULL, SET_DEFAULT])
+
 def add_lazy_relation(cls, field, relation, operation):
     """
     Adds a lookup on ``cls`` when a related field is defined using a string,
@@ -218 +228 @@
         # object you just set.
         setattr(instance, self.cache_name, value)
         setattr(value, self.related.field.get_cache_name(), instance)
+        
+    #TODO: the following function is a bit of a hack
+        #It's one way (not a very good one) to work around stale cache data causing
+        #spurious RESTRICT errors, etc; it would be better to prevent the cache from
+        #becoming stale in the first place.
+    # def __delete__(self, instance):
+    #     try:
+    #         return delattr(instance, self.cache_name)
+    #     except AttributeError:
+    #         pass
 
 class ReverseSingleRelatedObjectDescriptor(object):
     # This class provides the functionality that makes the related-object
@@ -628 +648 @@
 
 class ManyToOneRel(object):
     def __init__(self, to, field_name, related_name=None,
-            limit_choices_to=None, lookup_overrides=None, parent_link=False):
+            limit_choices_to=None, lookup_overrides=None, parent_link=False,
+            on_delete=None):
         try:
             to._meta
         except AttributeError: # to._meta doesn't exist, so it must be RECURSIVE_RELATIONSHIP_CONSTANT
@@ -641 +662 @@
         self.lookup_overrides = lookup_overrides or {}
         self.multiple = True
         self.parent_link = parent_link
+        self.on_delete = on_delete
 
     def get_related_field(self):
         """
@@ -655 +677 @@
 
 class OneToOneRel(ManyToOneRel):
     def __init__(self, to, field_name, related_name=None,
-            limit_choices_to=None, lookup_overrides=None, parent_link=False):
+            limit_choices_to=None, lookup_overrides=None, parent_link=False, 
+            on_delete=None):
         super(OneToOneRel, self).__init__(to, field_name,
                 related_name=related_name, limit_choices_to=limit_choices_to,
-                lookup_overrides=lookup_overrides, parent_link=parent_link)
+                lookup_overrides=lookup_overrides, parent_link=parent_link,
+                on_delete=on_delete)
         self.multiple = False
 
 class ManyToManyRel(object):
@@ -697 +721 @@
             related_name=kwargs.pop('related_name', None),
             limit_choices_to=kwargs.pop('limit_choices_to', None),
             lookup_overrides=kwargs.pop('lookup_overrides', None),
-            parent_link=kwargs.pop('parent_link', False))
+            parent_link=kwargs.pop('parent_link', False),
+            on_delete=kwargs.pop('on_delete', None))
         Field.__init__(self, **kwargs)
 
         self.db_index = True
@@ -742 +767 @@
             target = self.rel.to._meta.db_table
         cls._meta.duplicate_targets[self.column] = (target, "o2m")
 
+        on_delete = self.rel.on_delete
+        if on_delete not in ALLOWED_ON_DELETE_ACTION_TYPES:
+            raise ValueError("Invalid value 'on_delete=%s' specified for %s %s.%s." % (on_delete, type(self).__name__, cls.__name__, name))
+        if on_delete == SET_NULL and not self.null:
+            specification = "'on_delete=SET_NULL'"
+            raise ValueError("%s specified for %s '%s.%s', but the field is not nullable." % (specification, type(self).__name__, cls.__name__, name))
+        if on_delete == SET_DEFAULT and not self.has_default():
+            specification = "'on_delete=SET_DEFAULT'"
+            raise ValueError("%s specified for %s '%s.%s', but the field has no default value." % (specification, type(self).__name__, cls.__name__, name))
+
     def contribute_to_related_class(self, cls, related):
         setattr(cls, related.get_accessor_name(), ForeignRelatedObjectsDescriptor(related))
 

django/db/models/__init__.py

@@ -11 +11 @@
 from django.db.models.fields.subclassing import SubfieldBase
 from django.db.models.fields.files import FileField, ImageField
 from django.db.models.fields.related import ForeignKey, OneToOneField, ManyToManyField, ManyToOneRel, ManyToManyRel, OneToOneRel
+from django.db.models.fields.related import CASCADE, PROTECT, SET_NULL, SET_DEFAULT
 from django.db.models import signals
 
 # Admin stages.

django/db/models/query.py

@@ -11 +11 @@
 
 from django.db import connection, transaction, IntegrityError
 from django.db.models.aggregates import Aggregate
+from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE
 from django.db.models.fields import DateField
-from django.db.models.query_utils import Q, select_related_descend, CollectedObjects, CyclicDependency, deferred_class_factory
+from django.db.models.query_utils import Q, select_related_descend, CollectedFields, CollectedObjects, CyclicDependency, deferred_class_factory
 from django.db.models import signals, sql
 
 
@@ -391 +392 @@
             # Collect all the objects to be deleted in this chunk, and all the
             # objects that are related to the objects that are to be deleted.
             seen_objs = CollectedObjects(seen_objs)
+            fields_to_set = CollectedFields()
             for object in del_query[:CHUNK_SIZE]:
-                object._collect_sub_objects(seen_objs)
+                object._collect_sub_objects(seen_objs, fields_to_set)
 
             if not seen_objs:
                 break
-            delete_objects(seen_objs)
+            delete_objects(seen_objs, fields_to_set)
 
         # Clear the result cache, in case this QuerySet gets reused.
         self._result_cache = None
@@ -1002 +1004 @@
                 setattr(obj, f.get_cache_name(), rel_obj)
     return obj, index_end
 
-def delete_objects(seen_objs):
+def delete_objects(seen_objs, fields_to_set):
     """
     Iterate through a list of seen classes, and remove any instances that are
     referred to.
@@ -1023 +1025 @@
 
     obj_pairs = {}
     try:
+        for cls, cls_dct in fields_to_set.iteritems():
+            #TODO: batch these, similar to UpdateQuery.clear_related?
+            #(Note that it may be harder to do here because the default value
+            #for a given field may be different for each instance,
+            #while UpdateQuery.clear_related always uses the value None).
+            query = sql.UpdateQuery(cls, connection)
+            for instance, field_names_and_values in cls_dct.itervalues():
+                query.where = query.where_class()
+                pk = query.model._meta.pk
+                query.where.add((sql.where.Constraint(None, pk.column, pk), 'exact', instance.pk), sql.where.AND)
+                query.add_update_values(field_names_and_values)
+                query.execute_sql()
+                    
         for cls in ordered_classes:
             items = seen_objs[cls].items()
             items.sort()
@@ -1032 +1047 @@
             for pk_val, instance in items:
                 signals.pre_delete.send(sender=cls, instance=instance)
 
+            # Handle related GenericRelation and ManyToManyField instances
             pk_list = [pk for pk,instance in items]
             del_query = sql.DeleteQuery(cls, connection)
             del_query.delete_batch_related(pk_list)
 
-            update_query = sql.UpdateQuery(cls, connection)
-            for field, model in cls._meta.get_fields_with_model():
-                if (field.rel and field.null and field.rel.to in seen_objs and
-                        filter(lambda f: f.column == field.rel.get_related_field().column,
-                        field.rel.to._meta.fields)):
-                    if model:
-                        sql.UpdateQuery(model, connection).clear_related(field,
-                                pk_list)
-                    else:
-                        update_query.clear_related(field, pk_list)
-
-        # Now delete the actual data.
         for cls in ordered_classes:
             items = obj_pairs[cls]
             items.reverse()
-
             pk_list = [pk for pk,instance in items]
             del_query = sql.DeleteQuery(cls, connection)
             del_query.delete_batch(pk_list)
 
-            # Last cleanup; set NULLs where there once was a reference to the
-            # object, NULL the primary key of the found objects, and perform
-            # post-notification.
+        #Last cleanup; set NULLs and default values where there once was a 
+        #reference to the object, NULL the primary key of the found objects, 
+        #and perform post-notification.
+        for cls, cls_dct in fields_to_set.iteritems():
+            for instance, field_names_and_values in cls_dct.itervalues():
+                for field_name, field_value in field_names_and_values.iteritems():
+                    field = cls._meta.get_field_by_name(field_name)[0]
+                    setattr(instance, field.attname, field_value)
+        for cls in ordered_classes:
+            items = obj_pairs[cls]
+            items.reverse()
             for pk_val, instance in items:
                 for field in cls._meta.fields:
                     if field.rel and field.null and field.rel.to in seen_objs:

django/db/models/query_utils.py

@@ -124 +124 @@
         """
         return self.data.keys()
 
+class CollectedFields(object):
+    """
+    A container that stores the model object and field name
+    for fields that need to  be set to enforce on_delete=SET_NULL
+    and on_delete=SET_DEFAULT ForeigKey constraints.
+    """
+
+    def __init__(self):
+        self.data = {}
+
+    def add(self, model, pk, obj, field_name, field_value):
+        """
+        Adds an item.
+        model is the class of the object being added,
+        pk is the primary key, obj is the object itself, 
+        field_name is the name of the field to be set,
+        field_value is the value it needs to be set to.
+        """
+        d = self.data.setdefault(model, SortedDict())
+        obj, field_names_and_values = d.setdefault(pk, (obj, dict()))
+        assert field_name not in field_names_and_values or field_names_and_values[field_name] == field_value
+        field_names_and_values[field_name] = field_value
+
+    def __contains__(self, key):
+        return self.data.__contains__(key)
+
+    def __getitem__(self, key):
+        return self.data[key]
+
+    def __nonzero__(self):
+        return bool(self.data)
+
+    def iteritems(self):
+        return self.data.iteritems()
+
+    def iterkeys(self):
+        return self.data.iterkeys()
+
+    def itervalues(self):
+        return self.data.itervalues()
+
+    def items(self):
+        return self.data.items()
+
+    def keys(self):
+        return self.data.keys()
+
+    def values(self):
+        return self.data.values()
+
 class QueryWrapper(object):
     """
     A type that indicates the contents are an SQL fragment and the associate

tests/modeltests/delete/models.py

@@ -46 +46 @@
 
 ## First, test the CollectedObjects data structure directly
 
->>> from django.db.models.query import CollectedObjects
+>>> from django.db.models.query_utils import CollectedFields, CollectedObjects
 
 >>> g = CollectedObjects()
 >>> g.add("key1", 1, "item1", None)
@@ -112 +112 @@
 >>> d1 = D(c=c1, a=a1)
 >>> d1.save()
 
->>> o = CollectedObjects()
->>> a1._collect_sub_objects(o)
+>>> o, f = CollectedObjects(), CollectedFields()
+>>> a1._collect_sub_objects(o, f)
 >>> o.keys()
 [<class 'modeltests.delete.models.D'>, <class 'modeltests.delete.models.C'>, <class 'modeltests.delete.models.B'>, <class 'modeltests.delete.models.A'>]
+>>> f.keys()
+[]
 >>> a1.delete()
 
 # Same again with a known bad order
@@ -131 +133 @@
 >>> d2 = D(c=c2, a=a2)
 >>> d2.save()
 
->>> o = CollectedObjects()
->>> a2._collect_sub_objects(o)
+>>> o, f = CollectedObjects(), CollectedFields()
+>>> a2._collect_sub_objects(o, f)
 >>> o.keys()
 [<class 'modeltests.delete.models.D'>, <class 'modeltests.delete.models.C'>, <class 'modeltests.delete.models.B'>, <class 'modeltests.delete.models.A'>]
+>>> f.keys()
+[]
 >>> a2.delete()
 
 ### Tests for models E,F - nullable related fields ###
@@ -163 +167 @@
 # Since E.f is nullable, we should delete F first (after nulling out
 # the E.f field), then E.
 
->>> o = CollectedObjects()
->>> e1._collect_sub_objects(o)
+>>> o, f = CollectedObjects(), CollectedFields()
+>>> e1._collect_sub_objects(o, f)
 >>> o.keys()
 [<class 'modeltests.delete.models.F'>, <class 'modeltests.delete.models.E'>]
+>>> f.keys()
+[<class 'modeltests.delete.models.E'>]
 
-# temporarily replace the UpdateQuery class to verify that E.f is actually nulled out first
->>> import django.db.models.sql
->>> class LoggingUpdateQuery(django.db.models.sql.UpdateQuery):
-...     def clear_related(self, related_field, pk_list):
-...         print "CLEARING FIELD",related_field.name
-...         return super(LoggingUpdateQuery, self).clear_related(related_field, pk_list)
->>> original_class = django.db.models.sql.UpdateQuery
->>> django.db.models.sql.UpdateQuery = LoggingUpdateQuery
 >>> e1.delete()
-CLEARING FIELD f
 
 >>> e2 = E()
 >>> e2.save()
@@ -188 +185 @@
 
 # Same deal as before, though we are starting from the other object.
 
->>> o = CollectedObjects()
->>> f2._collect_sub_objects(o)
+>>> o, f = CollectedObjects(), CollectedFields()
+>>> f2._collect_sub_objects(o, f)
 >>> o.keys()
-[<class 'modeltests.delete.models.F'>, <class 'modeltests.delete.models.E'>]
+[<class 'modeltests.delete.models.F'>]
+>>> f.keys()
+[<class 'modeltests.delete.models.E'>]
 
 >>> f2.delete()
-CLEARING FIELD f
-
-# Put this back to normal
->>> django.db.models.sql.UpdateQuery = original_class
 """
 }