""" QuerySet for PolymorphicModel """ import copy import heapq from collections import defaultdict from django.contrib.contenttypes.models import ContentType from django.core.exceptions import FieldDoesNotExist from django.db import connections, models from django.db.models import FilteredRelation from django.db.models.query import ModelIterable, Q, QuerySet from .query_translate import ( translate_polymorphic_field_path, translate_polymorphic_filter_definitions_in_args, translate_polymorphic_filter_definitions_in_kwargs, translate_polymorphic_Q_object, ) from .utils import concrete_descendants, route_to_ancestor Polymorphic_QuerySet_objects_per_request = 2000 """ The maximum number of objects requested per db-request by the polymorphic queryset.iterator() implementation """ class _Inconsistent: """ A marker class indicating that there is a mismatch between the content type and the actual class of an object retrieved from the database. """ pass class PolymorphicModelIterable(ModelIterable): """ ModelIterable for PolymorphicModel Yields real instances if qs.polymorphic_disabled is False, otherwise acts like a regular ModelIterable. """ def __iter__(self): base_iter = super().__iter__() if self.queryset.polymorphic_disabled: return base_iter return self._polymorphic_iterator(base_iter) def _polymorphic_iterator(self, base_iter): """ Here we do the same as:: real_results = queryset._get_real_instances(list(base_iter)) for o in real_results: yield o but it requests the objects in chunks from the database, with QuerySet.iterator(chunk_size) per chunk """ # some databases have a limit on the number of query parameters, we must # respect this for generating get_real_instances queries because those # queries do a large WHERE IN clause with primary keys max_chunk = connections[self.queryset.db].features.max_query_params sql_chunk = self.chunk_size if self.chunked_fetch else None if max_chunk: sql_chunk = ( max_chunk if not self.chunked_fetch # chunk_size was not provided else min(max_chunk, self.chunk_size or max_chunk) ) sql_chunk = sql_chunk or Polymorphic_QuerySet_objects_per_request while True: base_result_objects = [] reached_end = False # Fetch in chunks for _ in range(sql_chunk): try: o = next(base_iter) base_result_objects.append(o) except StopIteration: reached_end = True break yield from self.queryset._get_real_instances(base_result_objects) if reached_end: return def transmogrify(cls, obj): """ Upcast a class to a different type without asking questions. """ if "__init__" not in obj.__class__.__dict__: # Just assign __class__ to a different value. new = obj new.__class__ = cls else: # Run constructor, reassign values new = cls() for k, v in obj.__dict__.items(): new.__dict__[k] = v return new ################################################################################### # PolymorphicQuerySet class PolymorphicQuerySet(QuerySet): """ QuerySet for PolymorphicModel Contains the core functionality for PolymorphicModel Usually not explicitly needed, except if a custom queryset class is to be used. """ def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self._iterable_class = PolymorphicModelIterable self.polymorphic_disabled = False # A parallel structure to django.db.models.query.Query.deferred_loading, # which we maintain with the untranslated field names passed to # .defer() and .only() in order to be able to retranslate them when # retrieving the real instance (so that the deferred fields apply # to that queryset as well). self.polymorphic_deferred_loading = (set(), True) def _clone(self, *args, **kwargs): # Django's _clone only copies its own variables, so we need to copy ours here new = super()._clone(*args, **kwargs) new.polymorphic_disabled = self.polymorphic_disabled new.polymorphic_deferred_loading = ( copy.copy(self.polymorphic_deferred_loading[0]), self.polymorphic_deferred_loading[1], ) return new def as_manager(cls): """ Override base :meth:`~django.db.models.query.QuerySet.as_manager` to return a manager extended from :class:`polymorphic.managers.PolymorphicManager`. """ from .managers import PolymorphicManager manager = PolymorphicManager.from_queryset(cls)() manager._built_with_as_manager = True return manager as_manager.queryset_only = True as_manager = classmethod(as_manager) def bulk_create(self, objs, batch_size=None, ignore_conflicts=False): objs = list(objs) for obj in objs: obj.pre_save_polymorphic() return super().bulk_create(objs, batch_size, ignore_conflicts=ignore_conflicts) def non_polymorphic(self): """switch off polymorphic behaviour for this query. When the queryset is evaluated, only objects of the type of the base class used for this query are returned.""" qs = self._clone() qs.polymorphic_disabled = True if issubclass(qs._iterable_class, PolymorphicModelIterable): qs._iterable_class = ModelIterable return qs def instance_of(self, *args): """Filter the queryset to only include the classes in args (and their subclasses).""" # Implementation in _translate_polymorphic_filter_defnition. return self.filter(instance_of=args) def not_instance_of(self, *args): """Filter the queryset to exclude the classes in args (and their subclasses).""" # Implementation in _translate_polymorphic_filter_defnition.""" return self.filter(not_instance_of=args) def _filter_or_exclude(self, negate, args, kwargs): # We override this internal Django function as it is used for all filter member functions. q_objects = translate_polymorphic_filter_definitions_in_args( queryset_model=self.model, args=args, using=self.db ) # filter_field='data' additional_args = translate_polymorphic_filter_definitions_in_kwargs( queryset_model=self.model, kwargs=kwargs, using=self.db ) args = list(q_objects) + additional_args return super()._filter_or_exclude(negate=negate, args=args, kwargs=kwargs) def order_by(self, *field_names): """translate the field paths in the args, then call vanilla order_by.""" field_names = [ translate_polymorphic_field_path(self.model, a) if isinstance(a, str) else a # allow expressions to pass unchanged for a in field_names ] return super().order_by(*field_names) def defer(self, *fields): """ Translate the field paths in the args, then call vanilla defer. Also retain a copy of the original fields passed, which we'll need when we're retrieving the real instance (since we'll need to translate them again, as the model will have changed). """ new_fields = [translate_polymorphic_field_path(self.model, a) for a in fields] clone = super().defer(*new_fields) clone._polymorphic_add_deferred_loading(fields) return clone def only(self, *fields): """ Translate the field paths in the args, then call vanilla only. Also retain a copy of the original fields passed, which we'll need when we're retrieving the real instance (since we'll need to translate them again, as the model will have changed). """ new_fields = {translate_polymorphic_field_path(self.model, a) for a in fields} new_fields.add("polymorphic_ctype_id") clone = super().only(*new_fields) clone._polymorphic_add_immediate_loading(fields) return clone def _polymorphic_add_deferred_loading(self, field_names): """ Follows the logic of django.db.models.query.Query.add_deferred_loading(), but for the non-translated field names that were passed to self.defer(). """ existing, defer = self.polymorphic_deferred_loading if defer: # Add to existing deferred names. self.polymorphic_deferred_loading = existing.union(field_names), True else: # Remove names from the set of any existing "immediate load" names. self.polymorphic_deferred_loading = existing.difference(field_names), False def _polymorphic_add_immediate_loading(self, field_names): """ Follows the logic of django.db.models.query.Query.add_immediate_loading(), but for the non-translated field names that were passed to self.only() """ existing, defer = self.polymorphic_deferred_loading field_names = set(field_names) if "pk" in field_names: field_names.remove("pk") field_names.add(self.model._meta.pk.name) if defer: # Remove any existing deferred names from the current set before # setting the new names. self.polymorphic_deferred_loading = field_names.difference(existing), False else: # Replace any existing "immediate load" field names. self.polymorphic_deferred_loading = field_names, False def _process_aggregate_args(self, args, kwargs): """for aggregate and annotate kwargs: allow ModelX___field syntax for kwargs, forbid it for args. Modifies kwargs if needed (these are Aggregate objects, we translate the lookup member variable) """ ___lookup_assert_msg = "PolymorphicModel: annotate()/aggregate(): ___ model lookup supported for keyword arguments only" def patch_lookup(a): # The field on which the aggregate operates is # stored inside a complex query expression. if isinstance(a, Q): # modify in place - this should be fixed if we want immutable # aggregate/annotation expressions a.children = translate_polymorphic_Q_object(self.model, a).children elif isinstance(a, FilteredRelation): patch_lookup(a.condition) elif isinstance(a, models.F): a.name = translate_polymorphic_field_path(self.model, a.name) elif hasattr(a, "get_source_expressions"): for source_expression in a.get_source_expressions(): if source_expression is not None: patch_lookup(source_expression) else: a.name = translate_polymorphic_field_path(self.model, a.name) def test___lookup(a): """*args might be complex expressions too in django 1.8 so the testing for a '___' is rather complex on this one""" if isinstance(a, Q): def tree_node_test___lookup(my_model, node): "process all children of this Q node" for i in range(len(node.children)): child = node.children[i] if type(child) is tuple: # this Q object child is a tuple => a kwarg like Q( instance_of=ModelB ) assert "___" not in child[0], ___lookup_assert_msg else: # this Q object child is another Q object, recursively process this as well tree_node_test___lookup(my_model, child) tree_node_test___lookup(self.model, a) elif hasattr(a, "get_source_expressions"): for source_expression in a.get_source_expressions(): if source_expression is not None: test___lookup(source_expression) elif a is not None: assert "___" not in a.name, ___lookup_assert_msg for a in args: test___lookup(a) for a in kwargs.values(): patch_lookup(a) def annotate(self, *args, **kwargs): """translate the polymorphic field paths in the kwargs, then call vanilla annotate. _get_real_instances will do the rest of the job after executing the query.""" self._process_aggregate_args(args, kwargs) return super().annotate(*args, **kwargs) def aggregate(self, *args, **kwargs): """translate the polymorphic field paths in the kwargs, then call vanilla aggregate. We need no polymorphic object retrieval for aggregate => switch it off.""" self._process_aggregate_args(args, kwargs) qs = self.non_polymorphic() return super(PolymorphicQuerySet, qs).aggregate(*args, **kwargs) # Starting with Django 1.9, the copy returned by 'qs.values(...)' has the # same class as 'qs', so our polymorphic modifications would apply. # We want to leave values queries untouched, so we set 'polymorphic_disabled'. def _values(self, *args, **kwargs): clone = super()._values(*args, **kwargs) clone.polymorphic_disabled = True return clone # Since django_polymorphic 'V1.0 beta2', extra() always returns polymorphic results. # The resulting objects are required to have a unique primary key within the result set # (otherwise an error is thrown). # The "polymorphic" keyword argument is not supported anymore. # def extra(self, *args, **kwargs): def _get_real_instances(self, base_result_objects): """ Polymorphic object loader Does the same as: return [ o.get_real_instance() for o in base_result_objects ] but more efficiently. The list base_result_objects contains the objects from the executed base class query. The class of all of them is self.model (our base model). Some, many or all of these objects were not created and stored as class self.model, but as a class derived from self.model. We want to re-fetch these objects from the db as their original class so we can return them just as they were created/saved. We identify these objects by looking at o.polymorphic_ctype, which specifies the real class of these objects (the class at the time they were saved). First, we sort the result objects in base_result_objects for their subclass (from o.polymorphic_ctype), and then we execute one db query per subclass of objects. Here, we handle any annotations from annotate(). Finally we re-sort the resulting objects into the correct order and return them as a list. """ resultlist = [] # polymorphic list of result-objects # dict contains one entry per unique model type occurring in result, # in the format idlist_per_model[modelclass]=[list-of-object-ids] idlist_per_model = defaultdict(list) indexlist_per_model = defaultdict(list) # priority queue holding the query order of concrete classes # we need this so we can retry fetching objects further up the hierarchy with # stale content types - this can happen in some legitimate cases (deletion) # we build up and pop classes off this queue to ensure we process in tree # traversal order (leaves first) - this allows us to retry fetching as parent # classes if child class retrieval fails classes_to_query = [] # use the pk attribute for the base model type used in the query to identify # objects pk_name = self.model._meta.pk.attname # - sort base_result_object ids into idlist_per_model lists, depending on their real class; # - store objects that already have the correct class into "results" content_type_manager = ContentType.objects.db_manager(self.db) self_model_class_id = content_type_manager.get_for_model( self.model, for_concrete_model=False ).pk self_concrete_model_class_id = content_type_manager.get_for_model( self.model, for_concrete_model=True ).pk class_priorities = { mdl: idx + 1 for idx, mdl in enumerate((*reversed(concrete_descendants(self.model)), self.model)) } for i, base_object in enumerate(base_result_objects): if base_object.polymorphic_ctype_id == self_model_class_id: # Real class is exactly the same as base class, go straight to results resultlist.append(base_object) else: real_concrete_class = base_object.get_real_instance_class() real_concrete_class_id = base_object.get_real_concrete_instance_class_id() if real_concrete_class_id is None: # Dealing with a stale content type continue elif real_concrete_class_id == self_concrete_model_class_id: # Real and base classes share the same concrete ancestor, # upcast it and put it in the results resultlist.append(transmogrify(real_concrete_class, base_object)) else: # This model has a concrete derived class, track it for bulk retrieval. real_concrete_class = content_type_manager.get_for_id( real_concrete_class_id ).model_class() if real_concrete_class not in idlist_per_model: # Maintain a priority queue to process the model classes # in order of their occurrence in the inheritance tree - leafs # first heapq.heappush( classes_to_query, (class_priorities.get(real_concrete_class, 0), real_concrete_class), ) idlist_per_model[real_concrete_class].append(getattr(base_object, pk_name)) indexlist_per_model[real_concrete_class].append((i, len(resultlist))) resultlist.append(None) # For each model in "idlist_per_model" request its objects (the real model) # from the db and store them in results[]. # Then we copy the annotate fields from the base objects to the real objects. # Then we copy the extra() select fields from the base objects to the real objects. # TODO: defer(), only(): support for these would be around here while classes_to_query: _, real_concrete_class = heapq.heappop(classes_to_query) idlist = idlist_per_model.pop(real_concrete_class) indices = indexlist_per_model.pop(real_concrete_class) real_objects = real_concrete_class._base_objects.db_manager(self.db).filter( **{(f"{pk_name}__in"): idlist} ) # copy select related configuration to new qs real_objects.query.select_related = self.query.select_related # Copy deferred fields configuration to the new queryset deferred_loading_fields = [] existing_fields = self.polymorphic_deferred_loading[0] for field in existing_fields: try: translated_field_name = translate_polymorphic_field_path( real_concrete_class, field ) except AssertionError: if "___" in field: # The originally passed argument to .defer() or .only() # was in the form Model2B___field2, where Model2B is # now a superclass of real_concrete_class. Thus it's # sufficient to just use the field name. translated_field_name = field.rpartition("___")[-1] # Check if the field does exist. # Ignore deferred fields that don't exist in this subclass type. try: real_concrete_class._meta.get_field(translated_field_name) except FieldDoesNotExist: continue else: raise deferred_loading_fields.append(translated_field_name) real_objects.query.deferred_loading = ( set(deferred_loading_fields), self.query.deferred_loading[1], ) real_objects_dict = { getattr(real_object, pk_name): real_object for real_object in real_objects } for base_idx, result_idx in indices: base_object = base_result_objects[base_idx] o_pk = getattr(base_object, pk_name) real_object = real_objects_dict.get(o_pk) if real_object is None: # Our content type is pointing to a row that does not exist anymore # We try to find the next best available parent row inheritance_path = route_to_ancestor(real_concrete_class, self.model) if not inheritance_path or inheritance_path[0].model is self.model: resultlist[result_idx] = base_object else: next_best_class = inheritance_path[0].model if next_best_class not in idlist_per_model: # add this class to the priority try queue heapq.heappush( classes_to_query, (class_priorities.get(next_best_class, 0), next_best_class), ) idlist_per_model[next_best_class].append(o_pk) indexlist_per_model[next_best_class].append((base_idx, result_idx)) resultlist[result_idx] = _Inconsistent continue # need shallow copy to avoid duplication in caches (see PR #353) real_object = copy.copy(real_object) real_class = ( real_concrete_class if resultlist[result_idx] is _Inconsistent else real_object.get_real_instance_class() ) # If the real class is a proxy, upcast it if real_class != real_concrete_class: real_object = transmogrify(real_class, real_object) if self.query.annotations: # New in Django 3.2+: annotation_select contains only the selected annotations # (excluding aliases). Fallback for older Django versions if needed. annotation_select = getattr( self.query, "annotation_select", self.query.annotations ) for anno_field_name in annotation_select.keys(): if hasattr(base_object, anno_field_name): attr = getattr(base_object, anno_field_name) setattr(real_object, anno_field_name, attr) if self.query.extra_select: for select_field_name in self.query.extra_select.keys(): attr = getattr(base_object, select_field_name) setattr(real_object, select_field_name, attr) resultlist[result_idx] = real_object resultlist = [i for i in resultlist if i and i is not _Inconsistent] # set polymorphic_annotate_names in all objects (currently just used for debugging/printing) if self.query.annotations: # get annotate field list annotation_select = getattr(self.query, "annotation_select", self.query.annotations) annotate_names = list(annotation_select.keys()) for real_object in resultlist: real_object.polymorphic_annotate_names = annotate_names # set polymorphic_extra_select_names in all objects (currently just used for debugging/printing) if self.query.extra_select: # get extra select field list extra_select_names = list(self.query.extra_select.keys()) for real_object in resultlist: real_object.polymorphic_extra_select_names = extra_select_names return resultlist def __repr__(self, *args, **kwargs): if self.model.polymorphic_query_multiline_output: result = ",\n ".join(repr(o) for o in self.all()) return f"[ {result} ]" else: return super().__repr__(*args, **kwargs) class _p_list_class(list): def __repr__(self, *args, **kwargs): result = ",\n ".join(repr(o) for o in self) return f"[ {result} ]" def get_real_instances(self, base_result_objects=None): """ Cast a list of objects to their actual classes. This does roughly the same as:: return [ o.get_real_instance() for o in base_result_objects ] but more efficiently. :rtype: PolymorphicQuerySet """ "same as _get_real_instances, but make sure that __repr__ for ShowField... creates correct output" if base_result_objects is None: base_result_objects = self olist = self._get_real_instances(base_result_objects) if not self.model.polymorphic_query_multiline_output: return olist clist = PolymorphicQuerySet._p_list_class(olist) return clist def delete(self): """ Deletion will be done non-polymorphically because Django's multi-table deletion mechanism is already walking the class hierarchy and producing a correct deletion graph. Introducing polymorphic querysets into the deletion process disrupts the model hierarchy/relationship traversal. """ return QuerySet.delete(self.non_polymorphic())