mirror of https://github.com/django/django.git
Fixed #16649 -- Refactored save_base logic
Model.save() will use UPDATE - if not updated - INSERT instead of SELECT - if found UPDATE else INSERT. This should save a query when updating, but will cost a little when inserting model with PK set. Also fixed #17341 -- made sure .save() commits transactions only after the whole model has been saved. This wasn't the case in model inheritance situations. The save_base implementation was refactored into multiple methods. A typical chain for inherited save is: save_base() _save_parents(self) for each parent: _save_parents(parent) _save_table(parent) _save_table(self)
This commit is contained in:
Anssi Kääriäinen
parent
8a2f5300b2
commit
6b4834952d
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@ -545,125 +545,139 @@ class Model(six.with_metaclass(ModelBase)):
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force_update=force_update, update_fields=update_fields)
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save.alters_data = True
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def save_base(self, raw=False, cls=None, origin=None, force_insert=False,
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def save_base(self, raw=False, force_insert=False,
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force_update=False, using=None, update_fields=None):
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"""
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Does the heavy-lifting involved in saving. Subclasses shouldn't need to
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override this method. It's separate from save() in order to hide the
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need for overrides of save() to pass around internal-only parameters
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('raw', 'cls', and 'origin').
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Handles the parts of saving which should be done only once per save,
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yet need to be done in raw saves, too. This includes some sanity
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checks and signal sending.
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The 'raw' argument is telling save_base not to save any parent
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models and not to do any changes to the values before save. This
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is used by fixture loading.
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"""
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using = using or router.db_for_write(self.__class__, instance=self)
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assert not (force_insert and (force_update or update_fields))
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assert update_fields is None or len(update_fields) > 0
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if cls is None:
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cls = self.__class__
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cls = origin = self.__class__
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# Skip proxies, but keep the origin as the proxy model.
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if cls._meta.proxy:
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cls = cls._meta.concrete_model
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meta = cls._meta
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if not meta.proxy:
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origin = cls
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else:
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meta = cls._meta
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if origin and not meta.auto_created:
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if not meta.auto_created:
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signals.pre_save.send(sender=origin, instance=self, raw=raw, using=using,
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update_fields=update_fields)
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# If we are in a raw save, save the object exactly as presented.
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# That means that we don't try to be smart about saving attributes
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# that might have come from the parent class - we just save the
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# attributes we have been given to the class we have been given.
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# We also go through this process to defer the save of proxy objects
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# to their actual underlying model.
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if not raw or meta.proxy:
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if meta.proxy:
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org = cls
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else:
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org = None
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for parent, field in meta.parents.items():
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# At this point, parent's primary key field may be unknown
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# (for example, from administration form which doesn't fill
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# this field). If so, fill it.
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if field and getattr(self, parent._meta.pk.attname) is None and getattr(self, field.attname) is not None:
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setattr(self, parent._meta.pk.attname, getattr(self, field.attname))
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self.save_base(cls=parent, origin=org, using=using,
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update_fields=update_fields)
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if field:
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setattr(self, field.attname, self._get_pk_val(parent._meta))
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# Since we didn't have an instance of the parent handy, we
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# set attname directly, bypassing the descriptor.
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# Invalidate the related object cache, in case it's been
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# accidentally populated. A fresh instance will be
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# re-built from the database if necessary.
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cache_name = field.get_cache_name()
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if hasattr(self, cache_name):
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delattr(self, cache_name)
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if meta.proxy:
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return
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if not meta.proxy:
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non_pks = [f for f in meta.local_fields if not f.primary_key]
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if update_fields:
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non_pks = [f for f in non_pks if f.name in update_fields or f.attname in update_fields]
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with transaction.commit_on_success_unless_managed(using=using):
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# First, try an UPDATE. If that doesn't update anything, do an INSERT.
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pk_val = self._get_pk_val(meta)
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pk_set = pk_val is not None
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record_exists = True
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manager = cls._base_manager
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if pk_set:
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# Determine if we should do an update (pk already exists, forced update,
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# no force_insert)
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if ((force_update or update_fields) or (not force_insert and
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manager.using(using).filter(pk=pk_val).exists())):
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if force_update or non_pks:
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values = [(f, None, (raw and getattr(self, f.attname) or f.pre_save(self, False))) for f in non_pks]
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if values:
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rows = manager.using(using).filter(pk=pk_val)._update(values)
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if force_update and not rows:
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raise DatabaseError("Forced update did not affect any rows.")
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if update_fields and not rows:
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raise DatabaseError("Save with update_fields did not affect any rows.")
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else:
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record_exists = False
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if not pk_set or not record_exists:
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if meta.order_with_respect_to:
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# If this is a model with an order_with_respect_to
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# autopopulate the _order field
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field = meta.order_with_respect_to
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order_value = manager.using(using).filter(**{field.name: getattr(self, field.attname)}).count()
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self._order = order_value
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fields = meta.local_fields
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if not pk_set:
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if force_update or update_fields:
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raise ValueError("Cannot force an update in save() with no primary key.")
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fields = [f for f in fields if not isinstance(f, AutoField)]
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record_exists = False
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update_pk = bool(meta.has_auto_field and not pk_set)
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result = manager._insert([self], fields=fields, return_id=update_pk, using=using, raw=raw)
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if update_pk:
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setattr(self, meta.pk.attname, result)
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with transaction.commit_on_success_unless_managed(using=using, savepoint=False):
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if not raw:
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self._save_parents(cls, using, update_fields)
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updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
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# Store the database on which the object was saved
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self._state.db = using
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# Once saved, this is no longer a to-be-added instance.
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self._state.adding = False
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# Signal that the save is complete
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if origin and not meta.auto_created:
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signals.post_save.send(sender=origin, instance=self, created=(not record_exists),
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if not meta.auto_created:
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signals.post_save.send(sender=origin, instance=self, created=(not updated),
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update_fields=update_fields, raw=raw, using=using)
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save_base.alters_data = True
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def _save_parents(self, cls, using, update_fields):
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"""
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Saves all the parents of cls using values from self.
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"""
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meta = cls._meta
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for parent, field in meta.parents.items():
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# Make sure the link fields are synced between parent and self.
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if (field and getattr(self, parent._meta.pk.attname) is None
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and getattr(self, field.attname) is not None):
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setattr(self, parent._meta.pk.attname, getattr(self, field.attname))
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self._save_parents(cls=parent, using=using, update_fields=update_fields)
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self._save_table(cls=parent, using=using, update_fields=update_fields)
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# Set the parent's PK value to self.
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if field:
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setattr(self, field.attname, self._get_pk_val(parent._meta))
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# Since we didn't have an instance of the parent handy set
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# attname directly, bypassing the descriptor. Invalidate
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# the related object cache, in case it's been accidentally
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# populated. A fresh instance will be re-built from the
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# database if necessary.
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cache_name = field.get_cache_name()
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if hasattr(self, cache_name):
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delattr(self, cache_name)
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def _save_table(self, raw=False, cls=None, force_insert=False,
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force_update=False, using=None, update_fields=None):
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"""
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Does the heavy-lifting involved in saving. Updates or inserts the data
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for a single table.
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"""
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meta = cls._meta
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non_pks = [f for f in meta.local_fields if not f.primary_key]
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if update_fields:
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non_pks = [f for f in non_pks
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if f.name in update_fields or f.attname in update_fields]
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pk_val = self._get_pk_val(meta)
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pk_set = pk_val is not None
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if not pk_set and (force_update or update_fields):
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raise ValueError("Cannot force an update in save() with no primary key.")
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updated = False
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# If possible, try an UPDATE. If that doesn't update anything, do an INSERT.
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if pk_set and not force_insert:
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base_qs = cls._base_manager.using(using)
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values = [(f, None, (raw and getattr(self, f.attname) or f.pre_save(self, False)))
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for f in non_pks]
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if not values:
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# We can end up here when saving a model in inheritance chain where
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# update_fields doesn't target any field in current model. In that
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# case we just say the update succeeded. Another case ending up here
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# is a model with just PK - in that case check that the PK still
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# exists.
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updated = update_fields is not None or base_qs.filter(pk=pk_val).exists()
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else:
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updated = self._do_update(base_qs, using, pk_val, values)
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if force_update and not updated:
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raise DatabaseError("Forced update did not affect any rows.")
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if update_fields and not updated:
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raise DatabaseError("Save with update_fields did not affect any rows.")
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if not updated:
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if meta.order_with_respect_to:
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# If this is a model with an order_with_respect_to
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# autopopulate the _order field
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field = meta.order_with_respect_to
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order_value = cls._base_manager.using(using).filter(
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**{field.name: getattr(self, field.attname)}).count()
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self._order = order_value
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fields = meta.local_fields
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if not pk_set:
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fields = [f for f in fields if not isinstance(f, AutoField)]
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update_pk = bool(meta.has_auto_field and not pk_set)
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result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
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if update_pk:
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setattr(self, meta.pk.attname, result)
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return updated
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def _do_update(self, base_qs, using, pk_val, values):
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"""
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This method will try to update the model. If the model was updated (in
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the sense that an update query was done and a matching row was found
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from the DB) the method will return True.
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"""
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return base_qs.filter(pk=pk_val)._update(values) > 0
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def _do_insert(self, manager, using, fields, update_pk, raw):
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"""
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Do an INSERT. If update_pk is defined then this method should return
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the new pk for the model.
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"""
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return manager._insert([self], fields=fields, return_id=update_pk,
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using=using, raw=raw)
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def delete(self, using=None):
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using = using or router.db_for_write(self.__class__, instance=self)
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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)
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@ -292,12 +292,13 @@ follows this algorithm:
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* If the object's primary key attribute is set to a value that evaluates to
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``True`` (i.e., a value other than ``None`` or the empty string), Django
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executes a ``SELECT`` query to determine whether a record with the given
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primary key already exists.
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* If the record with the given primary key does already exist, Django
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executes an ``UPDATE`` query.
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* If the object's primary key attribute is *not* set, or if it's set but a
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record doesn't exist, Django executes an ``INSERT``.
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executes an ``UPDATE``.
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* If the object's primary key attribute is *not* set or if the ``UPDATE``
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didn't update anything, Django executes an ``INSERT``.
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.. versionchanged:: 1.6
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Previously Django used ``SELECT`` - if not found ``INSERT`` else ``UPDATE``
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algorithm. The old algorithm resulted in one more query in ``UPDATE`` case.
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The one gotcha here is that you should be careful not to specify a primary-key
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value explicitly when saving new objects, if you cannot guarantee the
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@ -150,6 +150,10 @@ Minor features
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* Generic :class:`~django.contrib.gis.db.models.GeometryField` is now editable
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with the OpenLayers widget in the admin.
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* The :meth:`Model.save() <django.db.models.Model.save()>` will do
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``UPDATE`` - if not updated - ``INSERT`` instead of ``SELECT`` - if not
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found ``INSERT`` else ``UPDATE`` in case the model's primary key is set.
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Backwards incompatible changes in 1.6
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=====================================
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@ -1,11 +1,13 @@
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from __future__ import absolute_import, unicode_literals
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from datetime import datetime
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import threading
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from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, FieldError
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from django.db import connections, DEFAULT_DB_ALIAS
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from django.db.models.fields import Field, FieldDoesNotExist
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from django.db.models.query import QuerySet, EmptyQuerySet, ValuesListQuerySet
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from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
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from django.test import TestCase, TransactionTestCase, skipIfDBFeature, skipUnlessDBFeature
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from django.utils import six
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from django.utils.translation import ugettext_lazy
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@ -691,3 +693,28 @@ class ModelTest(TestCase):
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qs = Article.objects.order_by('invalid_column')
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self.assertRaises(FieldError, list, qs)
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self.assertRaises(FieldError, list, qs)
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class ConcurrentSaveTests(TransactionTestCase):
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@skipUnlessDBFeature('test_db_allows_multiple_connections')
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def test_concurrent_delete_with_save(self):
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"""
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Test fetching, deleting and finally saving an object - we should get
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an insert in this case.
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"""
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a = Article.objects.create(headline='foo', pub_date=datetime.now())
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exceptions = []
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def deleter():
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try:
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# Do not delete a directly - doing so alters its state.
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Article.objects.filter(pk=a.pk).delete()
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connections[DEFAULT_DB_ALIAS].commit_unless_managed()
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except Exception as e:
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exceptions.append(e)
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finally:
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connections[DEFAULT_DB_ALIAS].close()
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self.assertEqual(len(exceptions), 0)
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t = threading.Thread(target=deleter)
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t.start()
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t.join()
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a.save()
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self.assertEqual(Article.objects.get(pk=a.pk).headline, 'foo')
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@ -294,7 +294,7 @@ class ModelInheritanceTests(TestCase):
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rating=4,
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chef=c
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)
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with self.assertNumQueries(6):
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with self.assertNumQueries(3):
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ir.save()
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def test_update_parent_filtering(self):
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@ -4,6 +4,8 @@ from django.db import models
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class Mod(models.Model):
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fld = models.IntegerField()
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class SubMod(Mod):
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cnt = models.IntegerField(unique=True)
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class M2mA(models.Model):
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others = models.ManyToManyField('M2mB')
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@ -1,6 +1,7 @@
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from __future__ import absolute_import
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from django.db import connection, connections, transaction, DEFAULT_DB_ALIAS, DatabaseError
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from django.db import (connection, connections, transaction, DEFAULT_DB_ALIAS, DatabaseError,
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IntegrityError)
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from django.db.transaction import commit_on_success, commit_manually, TransactionManagementError
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from django.test import TransactionTestCase, skipUnlessDBFeature
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from django.test.utils import override_settings
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@ -8,8 +9,25 @@ from django.utils.unittest import skipIf, skipUnless
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from transactions.tests import IgnorePendingDeprecationWarningsMixin
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from .models import Mod, M2mA, M2mB
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from .models import Mod, M2mA, M2mB, SubMod
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class ModelInheritanceTests(TransactionTestCase):
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def test_save(self):
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# First, create a SubMod, then try to save another with conflicting
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# cnt field. The problem was that transactions were committed after
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# every parent save when not in managed transaction. As the cnt
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# conflict is in the second model, we can check if the first save
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# was committed or not.
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SubMod(fld=1, cnt=1).save()
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# We should have committed the transaction for the above - assert this.
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connection.rollback()
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self.assertEqual(SubMod.objects.count(), 1)
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try:
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SubMod(fld=2, cnt=1).save()
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except IntegrityError:
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connection.rollback()
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self.assertEqual(SubMod.objects.count(), 1)
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self.assertEqual(Mod.objects.count(), 1)
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class TestTransactionClosing(IgnorePendingDeprecationWarningsMixin, TransactionTestCase):
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"""
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