from operator import attrgetter from django.db import connections, transaction, IntegrityError from django.db.models import signals, sql from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE from django.utils.datastructures import SortedDict from django.utils.functional import wraps class ProtectedError(IntegrityError): def __init__(self, msg, protected_objects): self.protected_objects = protected_objects # TODO change this to use super() when we drop Python 2.4 IntegrityError.__init__(self, msg, protected_objects) def CASCADE(collector, field, sub_objs, using): collector.collect(sub_objs, source=field.rel.to, source_attr=field.name, nullable=field.null) if field.null and not connections[using].features.can_defer_constraint_checks: collector.add_field_update(field, None, sub_objs) def PROTECT(collector, field, sub_objs, using): raise ProtectedError("Cannot delete some instances of model '%s' because " "they are referenced through a protected foreign key: '%s.%s'" % ( field.rel.to.__name__, sub_objs[0].__class__.__name__, field.name ), sub_objs ) def SET(value): if callable(value): def set_on_delete(collector, field, sub_objs, using): collector.add_field_update(field, value(), sub_objs) else: def set_on_delete(collector, field, sub_objs, using): collector.add_field_update(field, value, sub_objs) return set_on_delete SET_NULL = SET(None) def SET_DEFAULT(collector, field, sub_objs, using): collector.add_field_update(field, field.get_default(), sub_objs) def DO_NOTHING(collector, field, sub_objs, using): pass def force_managed(func): @wraps(func) def decorated(self, *args, **kwargs): if not transaction.is_managed(using=self.using): transaction.enter_transaction_management(using=self.using) forced_managed = True else: forced_managed = False try: func(self, *args, **kwargs) if forced_managed: transaction.commit(using=self.using) else: transaction.commit_unless_managed(using=self.using) finally: if forced_managed: transaction.leave_transaction_management(using=self.using) return decorated class Collector(object): def __init__(self, using): self.using = using # Initially, {model: set([instances])}, later values become lists. self.data = {} self.batches = {} # {model: {field: set([instances])}} self.field_updates = {} # {model: {(field, value): set([instances])}} self.dependencies = {} # {model: set([models])} def add(self, objs, source=None, nullable=False, reverse_dependency=False): """ Adds 'objs' to the collection of objects to be deleted. If the call is the result of a cascade, 'source' should be the model that caused it, and 'nullable' should be set to True if the relation can be null. Returns a list of all objects that were not already collected. """ if not objs: return [] new_objs = [] model = objs[0].__class__ instances = self.data.setdefault(model, set()) for obj in objs: if obj not in instances: new_objs.append(obj) instances.update(new_objs) # Nullable relationships can be ignored -- they are nulled out before # deleting, and therefore do not affect the order in which objects have # to be deleted. if source is not None and not nullable: if reverse_dependency: source, model = model, source self.dependencies.setdefault(source, set()).add(model) return new_objs def add_batch(self, model, field, objs): """ Schedules a batch delete. Every instance of 'model' that is related to an instance of 'obj' through 'field' will be deleted. """ self.batches.setdefault(model, {}).setdefault(field, set()).update(objs) def add_field_update(self, field, value, objs): """ Schedules a field update. 'objs' must be a homogenous iterable collection of model instances (e.g. a QuerySet). """ if not objs: return model = objs[0].__class__ self.field_updates.setdefault( model, {}).setdefault( (field, value), set()).update(objs) def collect(self, objs, source=None, nullable=False, collect_related=True, source_attr=None, reverse_dependency=False): """ Adds 'objs' to the collection of objects to be deleted as well as all parent instances. 'objs' must be a homogenous iterable collection of model instances (e.g. a QuerySet). If 'collect_related' is True, related objects will be handled by their respective on_delete handler. If the call is the result of a cascade, 'source' should be the model that caused it and 'nullable' should be set to True, if the relation can be null. If 'reverse_dependency' is True, 'source' will be deleted before the current model, rather than after. (Needed for cascading to parent models, the one case in which the cascade follows the forwards direction of an FK rather than the reverse direction.) """ new_objs = self.add(objs, source, nullable, reverse_dependency=reverse_dependency) if not new_objs: return model = new_objs[0].__class__ # Recursively collect parent models, but not their related objects. # These will be found by meta.get_all_related_objects() for parent_model, ptr in model._meta.parents.iteritems(): if ptr: parent_objs = [getattr(obj, ptr.name) for obj in new_objs] self.collect(parent_objs, source=model, source_attr=ptr.rel.related_name, collect_related=False, reverse_dependency=True) if collect_related: for related in model._meta.get_all_related_objects(include_hidden=True): field = related.field if related.model._meta.auto_created: self.add_batch(related.model, field, new_objs) else: sub_objs = self.related_objects(related, new_objs) if not sub_objs: continue field.rel.on_delete(self, field, sub_objs, self.using) # TODO This entire block is only needed as a special case to # support cascade-deletes for GenericRelation. It should be # removed/fixed when the ORM gains a proper abstraction for virtual # or composite fields, and GFKs are reworked to fit into that. for relation in model._meta.many_to_many: if not relation.rel.through: sub_objs = relation.bulk_related_objects(new_objs, self.using) self.collect(sub_objs, source=model, source_attr=relation.rel.related_name, nullable=True) def related_objects(self, related, objs): """ Gets a QuerySet of objects related to ``objs`` via the relation ``related``. """ return related.model._base_manager.using(self.using).filter( **{"%s__in" % related.field.name: objs} ) def instances_with_model(self): for model, instances in self.data.iteritems(): for obj in instances: yield model, obj def sort(self): sorted_models = [] models = self.data.keys() while len(sorted_models) < len(models): found = False for model in models: if model in sorted_models: continue dependencies = self.dependencies.get(model) if not (dependencies and dependencies.difference(sorted_models)): sorted_models.append(model) found = True if not found: return self.data = SortedDict([(model, self.data[model]) for model in sorted_models]) @force_managed def delete(self): # sort instance collections for model, instances in self.data.items(): self.data[model] = sorted(instances, key=attrgetter("pk")) # if possible, bring the models in an order suitable for databases that # don't support transactions or cannot defer contraint checks until the # end of a transaction. self.sort() # send pre_delete signals for model, obj in self.instances_with_model(): if not model._meta.auto_created: signals.pre_delete.send( sender=model, instance=obj, using=self.using ) # update fields for model, instances_for_fieldvalues in self.field_updates.iteritems(): query = sql.UpdateQuery(model) for (field, value), instances in instances_for_fieldvalues.iteritems(): query.update_batch([obj.pk for obj in instances], {field.name: value}, self.using) # reverse instance collections for instances in self.data.itervalues(): instances.reverse() # delete batches for model, batches in self.batches.iteritems(): query = sql.DeleteQuery(model) for field, instances in batches.iteritems(): query.delete_batch([obj.pk for obj in instances], self.using, field) # delete instances for model, instances in self.data.iteritems(): query = sql.DeleteQuery(model) pk_list = [obj.pk for obj in instances] query.delete_batch(pk_list, self.using) # send post_delete signals for model, obj in self.instances_with_model(): if not model._meta.auto_created: signals.post_delete.send( sender=model, instance=obj, using=self.using ) # update collected instances for model, instances_for_fieldvalues in self.field_updates.iteritems(): for (field, value), instances in instances_for_fieldvalues.iteritems(): for obj in instances: setattr(obj, field.attname, value) for model, instances in self.data.iteritems(): for instance in instances: setattr(instance, model._meta.pk.attname, None)