ListAPIView與quersetUser.objects.all()在測驗資料庫中只有兩個用戶進行7次查詢？

我正在使用 drf 創建一個端點來列出用戶。在測驗代??碼時，我意識到它呼叫了 7 個查詢。

models.py：（我認為使用django的User模型會達到同樣的效果）

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

序列化程式.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

測驗.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 = ["[email protected]", "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)

它進行 7 次查詢的原因可能是什么？我知道一個查詢是針對會話內容的。此外，有沒有辦法可以減少查詢的數量？

下面是 print(queries.captured_queries) 的輸出：

[
    {
        "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",
    },
]

uj5u.com熱心網友回復：

7個查詢：

1. 獲取會話。為避免此查詢，您可以使用例如session cached_dbbackend。
2. 從資料庫中獲取登錄用戶的詳細資訊。這也可以通過從快取（或者可能是會話物件本身）獲取資料的不同會話后端來避免（但您必須小心例如快取失效）。
3. 列出用戶。由于您要列出用戶，因此這是意料之中的。
4. 獲取用戶 1 的分配組。
5. 獲取用戶 1 的分配權限。
6. 獲取用戶 2 的分配組。
7. 獲取用戶 2 的分配權限。

可以通過以下方式避免從 4 到 7 的查詢：

• 從序列化器中洗掉資料。（您當前正在使用fields = "__all__".）如果您的序列化程式不序列化權限和組，它們也不會被獲取。
• 在視圖集的查詢集中添加一個合適的.prefetch_related()（因為這些是 M2M）子句，所以這些是在 2 個查詢中完成的，而不是 2N 個查詢。

標籤：Python django 测试 django-rest-framework

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