Wenn ich alles tun, unten ohne benutzerdefinierten Manager, alles funktioniert wie erwartet:Custom Manager in Django Zerstört Caching für prefetch_related
class Content(models.Model):
name = models.CharField(max_length=200)
def __str__(self):
return self.name
class Meta:
app_label = 'game'
class Requirement(models.Model):
content = models.ForeignKey(Content, on_delete=models.CASCADE, related_name = 'requirements')
value = models.IntegerField(default=0)
def __str__(self):
return "{} requires value {}".format(self.content,self.value)
class Meta:
app_label = 'game'
def testPrefetchOrig():
contents = Content.objects.filter(name__startswith = 'a').prefetch_related('requirements')
for c in contents:
for r in c.requirements.all():
print r
logging.warning(r)
logging.warning("Done with query")
Diese Prefetch-Vorgänge für die Daten einmal und nie wieder:
DEBUG:django.db.backends:(0.001) SELECT "game_content"."id", "game_content"."name", "game_content"."deleted" FROM "game_content" WHERE "game_content"."name"::text LIKE 'a%'; args=(u'a%',)
DEBUG:django.db.backends:(0.001) SELECT "game_requirement"."id", "game_requirement"."content_id", "game_requirement"."value", "game_requirement"."deleted" FROM "game_requirement" WHERE "game_requirement"."content_id" IN (5, 6); args=(5, 6)
alphabet requires value 5
WARNING:root:alphabet requires value 5
alphabet requires value 3
WARNING:root:alphabet requires value 3
albatross requires value 1
WARNING:root:albatross requires value 1
albatross requires value 0
WARNING:root:albatross requires value 0
WARNING:root:Done with query
Ich möchte jedoch einen benutzerdefinierten Manager verwenden, um das Filtern von "gelöschten" Einträgen zu handhaben, indem ein gelöschtes Flag gesetzt wird.
class DeletedItemsQuerySet(models.query.QuerySet):
def get(self, *args, **kwargs):
kwargs['deleted']=False
return models.query.QuerySet.get(self, *args, **kwargs)
def all(self):
return self.filterNoDeleted()
def filterNoDeleted(self, *args, **kwargs):
kwargs['deleted']=False
return models.query.QuerySet.filter(self, *args, **kwargs)
def getDeleted(self, *args, **kwargs):
return models.query.QuerySet.get(self, *args, **kwargs)
def filterDeleted(self, *args, **kwargs):
return models.query.QuerySet.filter(self, *args, **kwargs)
class DeletedItemsManager(models.Manager.from_queryset(DeletedItemsQuerySet)):
def all(self):
return super(models.Manager,self).all().filterNoDeleted()
Und dann ändern wir unsere Modelle diese verwenden:
class Content(models.Model):
name = models.CharField(max_length=200)
objects = DeletedItemsManager()
deleted = models.BooleanField(default=False)
def __str__(self):
return self.name
class Meta:
app_label = 'game'
class Requirement(models.Model):
content = models.ForeignKey(Content, on_delete=models.CASCADE, related_name = 'requirements')
value = models.IntegerField(default=0)
deleted = models.BooleanField(default=False)
objects = DeletedItemsManager()
def __str__(self):
return "{} requires value {}".format(self.content,self.value)
class Meta:
app_label = 'game'
def testPrefetchOrig():
contents = Content.objects.filter(name__startswith = 'a').prefetch_related('requirements')
for c in contents:
for r in c.requirements.all():
print r
logging.warning(r)
logging.warning("Done with query")
Diese Prefetch-Vorgänge für die Daten, aber immer noch fragt er:
DEBUG:django.db.backends:(0.001) SELECT "game_content"."id", "game_content"."name", "game_content"."deleted" FROM "game_content" WHERE "game_content"."name"::text LIKE 'a%'; args=(u'a%',)
DEBUG:django.db.backends:(0.001) SELECT "game_requirement"."id", "game_requirement"."content_id", "game_requirement"."value", "game_requirement"."deleted" FROM "game_requirement" WHERE "game_requirement"."content_id" IN (5, 6); args=(5, 6)
DEBUG:django.db.backends:(0.000) SELECT "game_requirement"."id", "game_requirement"."content_id", "game_requirement"."value", "game_requirement"."deleted" FROM "game_requirement" WHERE ("game_requirement"."content_id" = 5 AND "game_requirement"."deleted" = false); args=(5, False)
alphabet requires value 5
WARNING:root:alphabet requires value 5
alphabet requires value 3
WARNING:root:alphabet requires value 3
DEBUG:django.db.backends:(0.001) SELECT "game_requirement"."id", "game_requirement"."content_id", "game_requirement"."value", "game_requirement"."deleted" FROM "game_requirement" WHERE ("game_requirement"."content_id" = 6 AND "game_requirement"."deleted" = false); args=(6, False)
albatross requires value 1
WARNING:root:albatross requires value 1
albatross requires value 0
WARNING:root:albatross requires value 0
WARNING:root:Done with query
Wie ich den benutzerdefinierten Manager verwenden Sie und noch prefetch_related Arbeit haben?
Warten. Ich verstehe, was passiert. Die all() -Methode des Managers enthält einen Filter, der gelöschte Objekte herausfiltert, aber dieser Filter zerstört den Cache. – user8168634