Index: django/db/models/base.py =================================================================== --- django/db/models/base.py (revision 5737) +++ django/db/models/base.py (working copy) @@ -15,6 +15,7 @@ from django.utils.encoding import smart_str, force_unicode from django.conf import settings from itertools import izip +from weakref import WeakValueDictionary import types import sys import os @@ -76,6 +77,21 @@ # should only be one class for each model, so we must always return the # registered version. return get_model(new_class._meta.app_label, name, False) + + def __call__(cls, *args, **kwargs): + if not kwargs.pop("disable_instance_cache", False) \ + and cls._meta.has_auto_field: + key = cls._get_cache_key(args, kwargs) + if key is not None: + obj = cls.__instance_cache__.get(key) + if obj is None: + obj = super(ModelBase, cls).__call__(*args, **kwargs) + cls.__instance_cache__[key] = obj + else: + obj = super(ModelBase, cls).__call__(*args, **kwargs) + else: + obj = super(ModelBase, cls).__call__(*args, **kwargs) + return obj class Model(object): __metaclass__ = ModelBase @@ -96,6 +112,23 @@ def __ne__(self, other): return not self.__eq__(other) + + def _get_cache_key(cls, args, kwargs): + # this should be calculated *once*, but isn't atm + pk_index = cls._meta.fields.index(cls._meta.pk) + if len(args) > pk_index: + return args[pk_index] + pk = cls._meta.pk + if pk.name in kwargs: + return kwargs[pk.name] + elif pk.attname in kwargs: + return kwargs[pk.attname] + return None + _get_cache_key = classmethod(_get_cache_key) + + def get_cached_instance(cls, key): + return cls.__instance_cache__.get(key) + get_cached_instance = classmethod(get_cached_instance) def __init__(self, *args, **kwargs): dispatcher.send(signal=signals.pre_init, sender=self.__class__, args=args, kwargs=kwargs) @@ -196,6 +229,8 @@ if hasattr(cls, 'get_absolute_url'): cls.get_absolute_url = curry(get_absolute_url, opts, cls.get_absolute_url) + + cls.__instance_cache__ = WeakValueDictionary() dispatcher.send(signal=signals.class_prepared, sender=cls) @@ -254,6 +289,10 @@ if self._meta.has_auto_field and not pk_set: setattr(self, self._meta.pk.attname, backend.get_last_insert_id(cursor, self._meta.db_table, self._meta.pk.column)) transaction.commit_unless_managed() + + # write this instance into cache if not already present + if self._meta.has_auto_field: + self.__instance_cache__[self._get_pk_val()] = self # Run any post-save hooks. dispatcher.send(signal=signals.post_save, sender=self.__class__, instance=self) @@ -315,6 +354,10 @@ self._collect_sub_objects(seen_objs) # Actually delete the objects + if self._meta.has_auto_field: + pk = self._get_pk_val() + if pk is not None: + self.__instance_cache__.pop(pk, None) delete_objects(seen_objs) delete.alters_data = True Index: django/db/models/fields/related.py =================================================================== --- django/db/models/fields/related.py (revision 5737) +++ django/db/models/fields/related.py (working copy) @@ -165,12 +165,14 @@ if self.field.null: return None raise self.field.rel.to.DoesNotExist - other_field = self.field.rel.get_related_field() - if other_field.rel: - params = {'%s__pk' % self.field.rel.field_name: val} - else: - params = {'%s__exact' % self.field.rel.field_name: val} - rel_obj = self.field.rel.to._default_manager.get(**params) + rel_obj = self.field.rel.to.get_cached_instance(val) + if rel_obj is None: + other_field = self.field.rel.get_related_field() + if other_field.rel: + params = {'%s__pk' % self.field.rel.field_name: val} + else: + params = {'%s__exact' % self.field.rel.field_name: val} + rel_obj = self.field.rel.to._default_manager.get(**params) setattr(instance, cache_name, rel_obj) return rel_obj Index: django/db/models/query.py =================================================================== --- django/db/models/query.py (revision 5737) +++ django/db/models/query.py (working copy) @@ -1109,12 +1109,19 @@ for cls in ordered_classes: seen_objs[cls] = seen_objs[cls].items() seen_objs[cls].sort() + clean_instance_cache = cls.__instance_cache__.pop # Pre notify all instances to be deleted for pk_val, instance in seen_objs[cls]: dispatcher.send(signal=signals.pre_delete, sender=cls, instance=instance) pk_list = [pk for pk,instance in seen_objs[cls]] + # we wipe the cache now; it's *possible* some form of a __get__ lookup + # may reintroduce an item after the fact with the same pk, however + # it is extremely unlikely + for x in pk_list: + clean_instance_cache(x, None) + for related in cls._meta.get_all_related_many_to_many_objects(): if not isinstance(related.field, generic.GenericRelation): for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE): @@ -1148,6 +1155,8 @@ for cls in ordered_classes: seen_objs[cls].reverse() pk_list = [pk for pk,instance in seen_objs[cls]] + for x in pk_list: + clean_instance_cache(x, None) for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE): cursor.execute("DELETE FROM %s WHERE %s IN (%s)" % \ (qn(cls._meta.db_table), qn(cls._meta.pk.column), Index: django/core/serializers/xml_serializer.py =================================================================== --- django/core/serializers/xml_serializer.py (revision 5737) +++ django/core/serializers/xml_serializer.py (working copy) @@ -177,6 +177,7 @@ value = field.to_python(getInnerText(field_node).strip()) data[field.name] = value + data["disable_instance_cache"] = True # Return a DeserializedObject so that the m2m data has a place to live. return base.DeserializedObject(Model(**data), m2m_data) Index: django/core/serializers/python.py =================================================================== --- django/core/serializers/python.py (revision 5737) +++ django/core/serializers/python.py (working copy) @@ -88,7 +88,8 @@ # Handle all other fields else: data[field.name] = field.to_python(field_value) - + + data["disable_instance_cache"] = True yield base.DeserializedObject(Model(**data), m2m_data) def _get_model(model_identifier): Index: tests/modeltests/select_related/models.py =================================================================== --- tests/modeltests/select_related/models.py (revision 5737) +++ tests/modeltests/select_related/models.py (working copy) @@ -107,13 +107,13 @@ 1 # select_related() also of course applies to entire lists, not just items. -# Without select_related() +# Without select_related() (note instance caching still reduces this from 9 to 5) >>> db.reset_queries() >>> world = Species.objects.all() >>> [o.genus.family for o in world] [, , , ] >>> len(db.connection.queries) -9 +5 # With select_related(): >>> db.reset_queries() @@ -129,23 +129,23 @@ >>> pea.genus.family.order.klass.phylum.kingdom.domain -# Notice: one few query than above because of depth=1 +# Notice: instance caching saves the day; would be 7 without. >>> len(db.connection.queries) -7 +1 >>> db.reset_queries() >>> pea = Species.objects.select_related(depth=5).get(name="sativum") >>> pea.genus.family.order.klass.phylum.kingdom.domain >>> len(db.connection.queries) -3 +1 >>> db.reset_queries() >>> world = Species.objects.all().select_related(depth=2) >>> [o.genus.family.order for o in world] [, , , ] >>> len(db.connection.queries) -5 +1 # Reset DEBUG to where we found it. >>> settings.DEBUG = False