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