Django提交评论触发FOREIGN KEY constraint failed报错求助

我正在编写一个允许用户提交商品评论的功能，但提交时触发FOREIGN KEY constraint failed错误。以下是报错回溯及相关代码：

报错回溯 #

Traceback (most recent call last):
  File "/workspace/webster00/products/views.py", line 84, in submit_review
    review = ReviewRating.objects.get(user=request.user.userprofile, product_id=product_id)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/query.py", line 435, in get
    raise self.model.DoesNotExist(

During handling of the above exception (ReviewRating matching query does not exist.), another exception occurred:
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/sqlite3/base.py", line 423, in execute
    return Database.Cursor.execute(self, query, params)

The above exception (FOREIGN KEY constraint failed) was the direct cause of the following exception:
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/workspace/webster00/products/views.py", line 99, in submit_review
    data.save()
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/base.py", line 726, in save
    self.save_base(using=using, force_insert=force_insert,
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/base.py", line 763, in save_base
    updated = self._save_table(
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/base.py", line 868, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/base.py", line 906, in _do_insert
    return manager._insert(
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/query.py", line 1270, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/models/sql/compiler.py", line 1410, in execute_sql
    cursor.execute(sql, params)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 98, in execute
    return super().execute(sql, params)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/workspace/.pip-modules/lib/python3.8/site-packages/django/db/backends/sqlite3/base.py", line 423, in execute
    return Database.Cursor.execute(self, query, params)

Exception Type: IntegrityError at /products/submit_review/6/
Exception Value: FOREIGN KEY constraint failed

相关代码 #

views.py #

def product_detail(request, product_id):
    """ A view to show individual product details """

    product = get_object_or_404(Product, pk=product_id)
    product = Product.objects.get(id=product_id)
    reviews = ReviewRating.objects.filter(product_id=product.id, status=True)
    
    context = {
        'product': product,
        'reviews': reviews,
    }

    return render(request, 'products/product_detail.html', context)


def submit_review(request, product_id):
    url = request.META.get('HTTP_REFERER')
    if request.method == 'POST':
        try:
            review = ReviewRating.objects.get(user=request.user.userprofile, product=product_id)
            form = ReviewForm(request.POST, instance=reviews)
            form.save()
            messages.success(request, 'Thank you! Your review has been updated')
            return redirect(url)
        except ReviewRating.DoesNotExist:
            form = ReviewForm(request.POST)
            if form.is_valid():
                data = ReviewRating()
                data.subject = form.cleaned_data['subject']
                data.rating = form.cleaned_data['rating']
                data.review = form.cleaned_data['review']
                data.ip = request.META.get('REMOTE_ADDR')
                data.product_id = product_id
                data.user_id = request.user.id
                data.save()
                messages.success(request, 'Thank you! Your review has been submited.')
                return redirect(url)

models.py #

class Product(models.Model):
    category = models.ForeignKey('Category', null=True, blank=True, on_delete=models.SET_NULL)
    sku = models.CharField(max_length=254, null=True, blank=True)
    name = models.CharField(max_length=254)
    description = models.TextField()
    price = models.DecimalField(max_digits=6, decimal_places=2)
    wheight = models.DecimalField(max_digits=6, decimal_places=1)
    rating = models.DecimalField(max_digits=6, decimal_places=2, null=True, blank=True)
    image_url = models.URLField(max_length=1024, null=True, blank=True)
    image = models.ImageField(null=True, blank=True)

    def __str__(self):
        return self.name


class ReviewRating(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    user = models.ForeignKey(UserProfile, on_delete=models.CASCADE)
    subject = models.CharField(max_length=100, blank=True)
    review = models.TextField(max_length=500, blank=True)
    rating = models.FloatField()
    ip = models.CharField(max_length=20, blank=True)
    status = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    def __str__(self):
        return self.subject

外键约束失败的核心原因是关联外键时使用了错误的对象或字段，以下是具体问题和修正方法：

1. 新增评论时用户外键关联错误 #

在submit_review的except块中，你设置了data.user_id = request.user.id，但ReviewRating模型的user字段关联的是UserProfile而非默认User模型。直接传入User的ID会导致外键找不到对应UserProfile记录，触发约束错误。

修正代码：

# 替换 data.user_id = request.user.id
data.user = request.user.userprofile

2. 查询已有评论时的字段与变量错误 #

在try块中，查询ReviewRating时用了product=product_id，但product是外键字段，需用product_id=product_id来匹配ID；同时表单实例化时写错了变量名，instance=reviews应为instance=review。

修正代码：

# 修正查询语句
review = ReviewRating.objects.get(user=request.user.userprofile, product_id=product_id)
# 修正表单实例化
form = ReviewForm(request.POST, instance=review)

3. 可选优化：提前验证产品存在性 #

为避免传入不存在的product_id导致外键错误，可在submit_review开头先获取产品对象：

# 添加在函数开头
product = get_object_or_404(Product, id=product_id)
# 替换 data.product_id = product_id
data.product = product

内容的提问来源于stack exchange，提问作者Cyborg sonny