Commit 056ace0f authored by Aymeric Augustin's avatar Aymeric Augustin
Browse files

[1.5.x] Fixed #19547 -- Caching of related instances. 

When &'ing or |'ing querysets, wrong values could be cached, and crashes
could happen.

Thanks Marc Tamlyn for figuring out the problem and writing the patch.

Backport of 07fbc6ae.
parent da2cdd3a

django/db/models/fields/related.py

+1 −1
Original line number Diff line number Diff line
@@ -497,7 +497,7 @@ class ForeignRelatedObjectsDescriptor(object): 
                except (AttributeError, KeyError):

                    db = self._db or router.db_for_read(self.model, instance=self.instance)

                    qs = super(RelatedManager, self).get_query_set().using(db).filter(**self.core_filters)

                    qs._known_related_object = (rel_field.name, self.instance)

                    qs._known_related_objects = {rel_field: {self.instance.pk: self.instance}}

                    return qs



            def get_prefetch_query_set(self, instances):

django/db/models/query.py

+22 −7
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ class QuerySet(object): 
        self._for_write = False

        self._prefetch_related_lookups = []

        self._prefetch_done = False

        self._known_related_object = None       # (attname, rel_obj)

        self._known_related_objects = {}        # {rel_field, {pk: rel_obj}}



    ########################

    # PYTHON MAGIC METHODS #
@@ -221,6 +221,7 @@ class QuerySet(object): 
        if isinstance(other, EmptyQuerySet):

            return other._clone()

        combined = self._clone()

        combined._merge_known_related_objects(other)

        combined.query.combine(other.query, sql.AND)

        return combined
@@ -229,6 +230,7 @@ class QuerySet(object): 
        combined = self._clone()

        if isinstance(other, EmptyQuerySet):

            return combined

        combined._merge_known_related_objects(other)

        combined.query.combine(other.query, sql.OR)

        return combined
@@ -289,10 +291,9 @@ class QuerySet(object): 
                    init_list.append(field.attname)

            model_cls = deferred_class_factory(self.model, skip)



        # Cache db, model and known_related_object outside the loop

        # Cache db and model outside the loop

        db = self.db

        model = self.model

        kro_attname, kro_instance = self._known_related_object or (None, None)

        compiler = self.query.get_compiler(using=db)

        if fill_cache:

            klass_info = get_klass_info(model, max_depth=max_depth,
@@ -323,9 +324,16 @@ class QuerySet(object): 
                for i, aggregate in enumerate(aggregate_select):

                    setattr(obj, aggregate, row[i + aggregate_start])



            # Add the known related object to the model, if there is one

            if kro_instance:

                setattr(obj, kro_attname, kro_instance)

            # Add the known related objects to the model, if there are any

            if self._known_related_objects:

                for field, rel_objs in self._known_related_objects.items():

                    pk = getattr(obj, field.get_attname())

                    try:

                        rel_obj = rel_objs[pk]

                    except KeyError:

                        pass               # may happen in qs1 | qs2 scenarios

                    else:

                        setattr(obj, field.name, rel_obj)



            yield obj
@@ -902,7 +910,7 @@ class QuerySet(object): 
        c = klass(model=self.model, query=query, using=self._db)

        c._for_write = self._for_write

        c._prefetch_related_lookups = self._prefetch_related_lookups[:]

        c._known_related_object = self._known_related_object

        c._known_related_objects = self._known_related_objects

        c.__dict__.update(kwargs)

        if setup and hasattr(c, '_setup_query'):

            c._setup_query()
@@ -942,6 +950,13 @@ class QuerySet(object): 
        """

        pass



    def _merge_known_related_objects(self, other):

        """

        Keep track of all known related objects from either QuerySet instance.

        """

        for field, objects in other._known_related_objects.items():

            self._known_related_objects.setdefault(field, {}).update(objects)



    def _setup_aggregate_query(self, aggregates):

        """

        Prepare the query for computing a result that contains aggregate annotations.

tests/modeltests/known_related_objects/fixtures/tournament.json

+11 −0
Original line number Diff line number Diff line
@@ -13,11 +13,19 @@ 
            "name": "Tourney 2"

            }

        },

    {

        "pk": 1,

        "model": "known_related_objects.organiser",

        "fields": {

            "name": "Organiser 1"

            }

        },

    {

        "pk": 1,

        "model": "known_related_objects.pool",

        "fields": {

            "tournament": 1,

            "organiser": 1,

            "name": "T1 Pool 1"

            }

        },
@@ -26,6 +34,7 @@ 
        "model": "known_related_objects.pool",

        "fields": {

            "tournament": 1,

            "organiser": 1,

            "name": "T1 Pool 2"

            }

        },
@@ -34,6 +43,7 @@ 
        "model": "known_related_objects.pool",

        "fields": {

            "tournament": 2,

            "organiser": 1,

            "name": "T2 Pool 1"

            }

        },
@@ -42,6 +52,7 @@ 
        "model": "known_related_objects.pool",

        "fields": {

            "tournament": 2,

            "organiser": 1,

            "name": "T2 Pool 2"

            }

        },

tests/modeltests/known_related_objects/models.py

+4 −0
Original line number Diff line number Diff line
@@ -9,9 +9,13 @@ from django.db import models 
class Tournament(models.Model):

    name = models.CharField(max_length=30)



class Organiser(models.Model):

    name = models.CharField(max_length=30)



class Pool(models.Model):

    name = models.CharField(max_length=30)

    tournament = models.ForeignKey(Tournament)

    organiser = models.ForeignKey(Organiser)



class PoolStyle(models.Model):

    name = models.CharField(max_length=30)

tests/modeltests/known_related_objects/tests.py

+41 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ from __future__ import absolute_import 


from django.test import TestCase



from .models import Tournament, Pool, PoolStyle

from .models import Tournament, Organiser, Pool, PoolStyle



class ExistingRelatedInstancesTests(TestCase):

    fixtures = ['tournament.json']
@@ -27,6 +27,46 @@ class ExistingRelatedInstancesTests(TestCase): 
            pool2 = tournaments[1].pool_set.all()[0]

            self.assertIs(tournaments[1], pool2.tournament)



    def test_queryset_or(self):

        tournament_1 = Tournament.objects.get(pk=1)

        tournament_2 = Tournament.objects.get(pk=2)

        with self.assertNumQueries(1):

            pools = tournament_1.pool_set.all() | tournament_2.pool_set.all()

            related_objects = set(pool.tournament for pool in pools)

            self.assertEqual(related_objects, set((tournament_1, tournament_2)))



    def test_queryset_or_different_cached_items(self):

        tournament = Tournament.objects.get(pk=1)

        organiser = Organiser.objects.get(pk=1)

        with self.assertNumQueries(1):

            pools = tournament.pool_set.all() | organiser.pool_set.all()

            first = pools.filter(pk=1)[0]

            self.assertIs(first.tournament, tournament)

            self.assertIs(first.organiser, organiser)



    def test_queryset_or_only_one_with_precache(self):

        tournament_1 = Tournament.objects.get(pk=1)

        tournament_2 = Tournament.objects.get(pk=2)

        # 2 queries here as pool id 3 has tournament 2, which is not cached

        with self.assertNumQueries(2):

            pools = tournament_1.pool_set.all() | Pool.objects.filter(pk=3)

            related_objects = set(pool.tournament for pool in pools)

            self.assertEqual(related_objects, set((tournament_1, tournament_2)))

        # and the other direction

        with self.assertNumQueries(2):

            pools = Pool.objects.filter(pk=3) | tournament_1.pool_set.all()

            related_objects = set(pool.tournament for pool in pools)

            self.assertEqual(related_objects, set((tournament_1, tournament_2)))



    def test_queryset_and(self):

        tournament = Tournament.objects.get(pk=1)

        organiser = Organiser.objects.get(pk=1)

        with self.assertNumQueries(1):

            pools = tournament.pool_set.all() & organiser.pool_set.all()

            first = pools.filter(pk=1)[0]

            self.assertIs(first.tournament, tournament)

            self.assertIs(first.organiser, organiser)



    def test_one_to_one(self):

        with self.assertNumQueries(2):

            style = PoolStyle.objects.get(pk=1)