Question

我的模型包含ManyToManyField到django.contrib.auth.models.Permission

问题是当我打开以在admin中编辑我的模型记录时，数据库请求的数量是241

class RoleManager(models.Manager):

    def get_query_set(self):
        return super(RoleManager, self).get_query_set().select_related('organization')

class Role(models.Model):

    name = models.CharField(u'Name', max_length = 80)
    organization = models.ForeignKey(Organization)
    permissions = models.ManyToManyField(Permission, blank = True)

    objects = RoleManager()

    def __unicode__(self):
        return u'{name} in {organization}'.format(name = self.name, organization = self.organization.name)

235个SELECT是：

SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 8
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 8
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 8
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 68
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 69
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 69
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 69
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 9
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 9
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 9
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 10
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 10
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 10
SELECT ••• FROM "django_content_type" WHERE "django_content_type"."id" = 17

可能我必须使用经理来解决这个问题吗？

我看了https://github.com/django/django/blob/master/django/contrib/auth/models.py

并看到Permission正在使用一些PermissionManager，但不确定究竟发生了什么，以及如何在我的经理中进行此操作

Answer 1

是的，你可以使用prefetch_related QuerySet method，这是它的预期用途！

这应该将查询开销减少到只有一个查询所有相关对象。

Answer 2

如果您正在使用它，调试工具栏可以发出此请求。

Django ManyToManyField到权限

2 个答案: