django.db.utils.IntegrityError：关系“shop_book”的“genre_id”列中的空值违反非空约束答案

【问题标题】：django.db.utils.IntegrityError: null value in column "genre_id" of relation "shop_book" violates not-null constraintdjango.db.utils.IntegrityError：关系“shop_book”的“genre_id”列中的空值违反非空约束
【发布时间】：2021-12-06 20:27:46
【问题描述】：

我正在构建微服务，我在仓库中有 2 个项目/1 个数据库，在商店中有 1 个数据库。当我在仓库中有一本新书时，我已经更新了商店中的数据库 - celery 完成了这项任务并完成了

Warehouse 和 Shop 中的模型相同。

我遇到了一个奇怪的错误，我找不到相关信息。

型号：

from django.db import models
from django.urls import reverse


class Author(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)

    def __str__(self):
        return f'{self.first_name} {self.last_name}'


class Genre(models.Model):
    name = models.CharField(max_length=50, db_index=True)
    slug = models.SlugField(max_length=50, unique=True)

    class Meta:
        ordering = ('name',)
        verbose_name = 'genre'
        verbose_name_plural = 'genres'

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('shop:book_list_by_genre', args=[self.slug])


class Book(models.Model):
    author = models.ForeignKey('Author', on_delete=models.CASCADE)
    genre = models.ForeignKey(Genre,
                              related_name='books',
                              on_delete=models.CASCADE)
    title = models.CharField(max_length=255)
    description = models.TextField(blank=True)
    language = models.CharField("language", max_length=20)
    pages = models.IntegerField()
    image = models.ImageField(upload_to='products/%Y/%m/%d')
    slug = models.SlugField(max_length=255)
    price = models.DecimalField(max_digits=10, decimal_places=2)

    isbn = models.CharField('ISBN', max_length=13,
                            unique=True)
    created = models.DateTimeField(auto_now_add=True)
    available = models.BooleanField(default=True)
    quantity = models.IntegerField()

    class Meta:
        ordering = ('title',)
        index_together = (('id', 'slug'),)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('shop:book_detail',
                       args=[self.id, self.slug])

芹菜：

from celery import shared_task

from django.core.mail import send_mail

import requests

from .models import Author, Book, Genre


@shared_task
def send_mail_task(subject, message, email):
    send_mail(subject, message, email, ['admin@example.com'])


@shared_task
def shop_sync():
    print('Starting update from warehouse api for database')
    print('Getting data from api...')

    url = 'http://warehouse:8001/warehouse/authors/'
    print('Clearing data...')

    response_author = requests.get(url)
    if response_author.status_code != 200:
        return
    response_data_author = response_author.json()
    while 1:
        for counter, data in enumerate(response_data_author['results']):
            Author.objects.get_or_create(
                id=data['id'],
                defaults={
                    'id': data['id'],
                    'first_name': data['first_name'],
                    'last_name': data['last_name']
                }
            )

        if response_data_author['next']:
            response_data_author = requests.get(response_data_author['next']).json()
        else:
            break

    url = 'http://warehouse:8001/warehouse/genres/'
    print('Clearing data...')

    response_genre = requests.get(url)
    if response_genre.status_code != 200:
        return
    response_data_genre = response_genre.json()

    while 1:
        for counter, data in enumerate(response_data_genre['results']):
            Genre.objects.get_or_create(
                id=data['id'],

                defaults={
                    'slug': data['slug'],
                    'name': data['name'],
                }
            )

        if response_data_genre['next']:
            response_data_genre = requests.get(
                response_data_genre['next']
            ).json()
        else:
            break

    url = 'http://warehouse:8001/warehouse/books/'
    print('Clearing data...')

    response_book = requests.get(url)
    if response_book.status_code != 200:
        return
    response_data_book = response_book.json()
    while 1:
        for counter, data in enumerate(response_data_book['results']):
            book, created = Book.objects.get_or_create(
                id=data['id'],
                defaults={
                    'id': data['id'],
                    "title": data['title'],
                    "description": data['description'],
                    "language": data['language'],
                    "pages": data['pages'],
                    "image": data['image'],
                    'slug': data['slug'],
                    "price": data['price'],
                    "isbn": data['isbn'],
                    "created": data['created'],
                    "available": data['available'],
                    "quantity": data['quantity'],
                    "author": Author.objects.get(id=data['author'])
                }
            )

            if not created:
                book.title = data['title']
                book.description = data['description']
                book.language = data['language']
                book.pages = data['pages']
                book.image = data['image']
                book.slug = data['slug']
                book.price = data['price']
                book.isbn = data['isbn']
                book.created = data['created']
                book.available = data['available']
                book.quantity = data['quantity']
                book.author = Author.objects.get(id=data['author'])
                book.save()

            for i in data['genre']:
                genre = Genre.objects.get(id=i)
                book.genre.add(genre)

        if response_data_book['next']:
            response_data_book = requests.get(response_data_book['next']).json()
        else:
            break
        print('Database was updated from warehouse api')

回溯：

Traceback（最近一次调用最后一次）：文件“/usr/local/lib/python3.10/site-packages/celery/app/trace.py”，行
450，在 trace_task 中 R = retval = fun(*args, **kwargs) 文件“/usr/local/lib/python3.10/site-packages/celery/app/trace.py”，行
731，在 protected_call 返回 self.run(*args, **kwargs) shop_sync 中的文件“/code/shop/tasks.py”，第 78 行书，创建 = Book.objects.get_or_create( 文件“/usr/local/lib/python3.10/site-packages/django/db/models/manager.py”，第 85 行，在 manager_method 中返回 getattr(self.get_queryset(), name)(*args, **kwargs) 文件“/usr/local/lib/python3.10/site-packages/django/db/models/query.py”，
第 588 行，在 get_or_create 返回 self.create(**params), True 文件“/usr/local/lib/python3.10/site-packages/django/db/models/query.py”，
第 453 行，在创建中 obj.save（force_insert=True，使用=self.db）文件“/usr/local/lib/python3.10/site-packages/django/db/models/base.py”，
第 726 行，保存中 self.save_base（使用=使用，force_insert=force_insert，文件“/usr/local/lib/python3.10/site-packages/django/db/models/base.py”，
第 763 行，在 save_base 更新 = self._save_table( 文件“/usr/local/lib/python3.10/site-packages/django/db/models/base.py”，
第 868 行，在 _save_table 中结果 = self._do_insert（cls._base_manager，使用，字段，返回字段，原始）文件“/usr/local/lib/python3.10/site-packages/django/db/models/base.py”，
第 906 行，在 _do_insert 返回经理._插入（文件“/usr/local/lib/python3.10/site-packages/django/db/models/manager.py”，第 85 行，在 manager_method 中返回 getattr(self.get_queryset(), name)(*args, **kwargs) 文件“/usr/local/lib/python3.10/site-packages/django/db/models/query.py”，
第 1270 行，在 _insert return query.get_compiler(using=using).execute_sql(returning_fields) 文件“/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py”，第 1416 行，在 execute_sql 中 cursor.execute（sql，参数）文件“/usr/local/lib/python3.10/site-packages/django/db/backends/utils.py”，第 98 行，在执行中返回 super().execute(sql, 参数) 文件“/usr/local/lib/python3.10/site-packages/django/db/backends/utils.py”，第 66 行，在执行中 return self._execute_with_wrappers(sql, params, many=False, executor=self._execute) 文件“/usr/local/lib/python3.10/site-packages/django/db/backends/utils.py”，第 75 行，在 _execute_with_wrappers 中返回执行程序（sql，参数，许多，上下文）文件“/usr/local/lib/python3.10/site-packages/django/db/backends/utils.py”，第 79 行，在 _execute 使用 self.db.wrap_database_errors：文件“/usr/local/lib/python3.10/site-packages/django/db/utils.py”，行
90，在退出从 exc_value 提高 dj_exc_value.with_traceback(traceback) 文件“/usr/local/lib/python3.10/site-packages/django/db/backends/utils.py”，第 84 行，在 _execute 返回 self.cursor.execute(sql, params) django.db.utils.IntegrityError：关系“shop_book”的“genre_id”列中的空值违反非空约束细节：失败的行包含（7，INFERNO，发现自己在最神秘的意大利小镇 - 佛罗伦萨，...，英语，472，
http://warehouse:8001/media/products/2021/09/15/cover-50.jpg,
地狱, 445.00, 9780307736925, 2021-10-19 23:38:08.910299+00, t, 8,
1，空）。

【问题讨论】：

标签： python django celery

【解决方案1】：

您的Book 模型与Genre 具有强制性的一对多关系

class Book(models.Model):
genre = models.ForeignKey(Genre,
                          related_name='books',
                          on_delete=models.CASCADE)

这意味着如果创建新的Book，则必须在defaults 中为genre 提供价值

book, created = Book.objects.get_or_create(
            id=data['id'],
            defaults={
                'id': data['id'],
                'genre': # value needs to be provided here

后面有一段代码尝试添加流派

for i in data['genre']:
    genre = Genre.objects.get(id=i)
    book.genre.add(genre)

但该代码为时已晚，它预计 Book 到 Genre 是多对多关系，而事实上 Book 到 Genre 定义为一对多关系

必须更改数据模型或同步脚本。

【讨论】：