带有 querset User.objects.all() 的 ListAPIView 在测试数据库中仅对两个用户进行 7 次查询？

Question

我正在使用 drf 创建端点来列出用户。在测试代码时，我意识到它调用了 7 个查询。

models.py:(我觉得用django的User模型会达到同样的效果）

class CustomUserManager(BaseUserManager):
    """
    Custom user model manager where email is the unique identifiers
    for authentication instead of usernames.
    """

    def create_user(self, email, password, **extra_fields):
        """
        Create and save a User with the given email and password.
        """
        if not email:
            raise ValueError(_("The Email must be set"))
        email = self.normalize_email(email)
        user = self.model(email=email, **extra_fields)
        user.set_password(password)
        user.save()
        return user

    def create_superuser(self, email, password, **extra_fields):
        """
        Create and save a SuperUser with the given email and password.
        """
        extra_fields.setdefault("is_staff", True)
        extra_fields.setdefault("is_superuser", True)
        extra_fields.setdefault("is_active", True)

        if extra_fields.get("is_staff") is not True:
            raise ValueError(_("Superuser must have is_staff=True."))
        if extra_fields.get("is_superuser") is not True:
            raise ValueError(_("Superuser must have is_superuser=True."))
        return self.create_user(email, password, **extra_fields)
class BaseUser(AbstractUser):
    email = models.EmailField(_("email address"), unique=True)
    id_number = models.CharField(max_length=MID_LENGTH)
    username = None

    USERNAME_FIELD = "email"
    REQUIRED_FIELDS = [email]

    objects = CustomUserManager()

    def __str__(self) -> str:
        return self.email

serializers.py:

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.BaseUser
        fields = "__all__"

api.py:

class ListUserView(ListAPIView):
    permission_classes = [IsAdminUser]
    queryset = models.BaseUser.objects.all().order_by("id")
    serializer_class = serializers.UserSerializer

test.py:

from . import models
from django.db import connection
from django.test.utils import CaptureQueriesContext
from django.urls import reverse
from django_seed import Seed
from rest_framework.test import APIClient, APITestCase


seeder = Seed.seeder()

CREDENTIALS = ["test@email.com", "12345678"]


class UserViewsTest(APITestCase):
    def setUp(self) -> None:
        #   Create user and login
        self.user = models.BaseUser.objects.create(email=CREDENTIALS[0], is_staff=True)
        self.user.set_password(CREDENTIALS[1])
        self.user.save()

        self.assertTrue(
            self.client.login(email=CREDENTIALS[0], password=CREDENTIALS[1])
        )

        #   Seed users
        seeder.add_entity(models.BaseUser, 1)
        seeder.execute()

    def tearDown(self) -> None:
        self.client.logout()

    def test_list_users(self):
        """
        7 queries:
            1. Logged in user session
            2. 2 of each of:
                i.   1 query for base user
                ii.  1 query for base user's group
                iii. 1 query for base user's permission
        """
        with CaptureQueriesContext(connection) as queries:
            response = self.client.get(reverse("accounts-list-users"))

            self.assertEqual(200, response.status_code)
            self.assertIsNotNone(response.content)

        print(queries.captured_queries)

它进行 7 次查询的原因可能是什么？我知道一个查询是针对会话内容的。此外，有什么方法可以减少查询次数？

下面是 print(queries.captured_queries) 的输出：

[
    {
        "sql": "SELECT `django_session`.`session_key`, `django_session`.`session_data`, `django_session`.`expire_date` FROM `django_session` WHERE (`django_session`.`expire_date` > '2022-02-22 08:41:16.815976' AND `django_session`.`session_key` = 'hebjioxebumhz0y1mumtafwk3lfoj81h') LIMIT 21",
        "time": "0.001",
    },
    {
        "sql": "SELECT `accounts_baseuser`.`id`, `accounts_baseuser`.`password`, `accounts_baseuser`.`last_login`, `accounts_baseuser`.`is_superuser`, `accounts_baseuser`.`first_name`, `accounts_baseuser`.`last_name`, `accounts_baseuser`.`is_staff`, `accounts_baseuser`.`is_active`, `accounts_baseuser`.`date_joined`, `accounts_baseuser`.`email`, `accounts_baseuser`.`id_number` FROM `accounts_baseuser` WHERE `accounts_baseuser`.`id` = 1 LIMIT 21",
        "time": "0.000",
    },
    {
        "sql": "SELECT `accounts_baseuser`.`id`, `accounts_baseuser`.`password`, `accounts_baseuser`.`last_login`, `accounts_baseuser`.`is_superuser`, `accounts_baseuser`.`first_name`, `accounts_baseuser`.`last_name`, `accounts_baseuser`.`is_staff`, `accounts_baseuser`.`is_active`, `accounts_baseuser`.`date_joined`, `accounts_baseuser`.`email`, `accounts_baseuser`.`id_number` FROM `accounts_baseuser` ORDER BY `accounts_baseuser`.`id` ASC",
        "time": "0.000",
    },
    {
        "sql": "SELECT `auth_group`.`id`, `auth_group`.`name` FROM `auth_group` INNER JOIN `accounts_baseuser_groups` ON (`auth_group`.`id` = `accounts_baseuser_groups`.`group_id`) WHERE `accounts_baseuser_groups`.`baseuser_id` = 1",
        "time": "0.001",
    },
    {
        "sql": "SELECT `auth_permission`.`id`, `auth_permission`.`name`, `auth_permission`.`content_type_id`, `auth_permission`.`codename` FROM `auth_permission` INNER JOIN `accounts_baseuser_user_permissions` ON (`auth_permission`.`id` = `accounts_baseuser_user_permissions`.`permission_id`) INNER JOIN `django_content_type` ON (`auth_permission`.`content_type_id` = `django_content_type`.`id`) WHERE `accounts_baseuser_user_permissions`.`baseuser_id` = 1 ORDER BY `django_content_type`.`app_label` ASC, `django_content_type`.`model` ASC, `auth_permission`.`codename` ASC",
        "time": "0.001",
    },
    {
        "sql": "SELECT `auth_group`.`id`, `auth_group`.`name` FROM `auth_group` INNER JOIN `accounts_baseuser_groups` ON (`auth_group`.`id` = `accounts_baseuser_groups`.`group_id`) WHERE `accounts_baseuser_groups`.`baseuser_id` = 2",
        "time": "0.000",
    },
    {
        "sql": "SELECT `auth_permission`.`id`, `auth_permission`.`name`, `auth_permission`.`content_type_id`, `auth_permission`.`codename` FROM `auth_permission` INNER JOIN `accounts_baseuser_user_permissions` ON (`auth_permission`.`id` = `accounts_baseuser_user_permissions`.`permission_id`) INNER JOIN `django_content_type` ON (`auth_permission`.`content_type_id` = `django_content_type`.`id`) WHERE `accounts_baseuser_user_permissions`.`baseuser_id` = 2 ORDER BY `django_content_type`.`app_label` ASC, `django_content_type`.`model` ASC, `auth_permission`.`codename` ASC",
        "time": "0.000",
    },
]

Answer 1

7 个查询：

获取会话。为避免此查询，您可以使用例如the cached_db session backend.
从数据库中获取登录用户的详细信息。这也可以通过不同的会话后端从缓存（或者可能是会话对象本身）获取数据来避免（但是你必须小心，例如缓存失效）。
列出用户。由于您要列出用户，这是可以预料的。
获取用户 1 的分配组。
获取用户 1 的分配权限。
获取用户 2 的分配组。
获取用户 2 的分配权限。

可以通过以下方式避免查询 4 到 7：

正在从序列化程序中删除数据。（您当前正在使用 fields = "__all__"。）如果您的序列化程序未序列化权限和组，则也不会获取它们。
向视图集的查询集添加合适的 .prefetch_related()（因为这些是 M2M）子句，因此这些是在 2 个查询中完成的，而不是 2N 个查询。

带有 querset User.objects.all() 的 ListAPIView 在测试数据库中仅对两个用户进行 7 次查询？

ListAPIView with the querset User.objects.all() makes 7 queries with only two users in the test database?

python

testing

django

django-rest-framework