Django objection creation failing due to FOREIGN KEY constraint failure (IntegrityError ) - django

Question

My website has a comment section where user can leave comments on a product . The comments on the product page will be stored in a model called 'ProductReview'. Here is the code for the model :
class ProductReview(models.Model):
product = models.ForeignKey(Product, related_name='reviews', on_delete=models.CASCADE)
name = models.CharField(blank=True,max_length=20)
stars = models.IntegerField()
content = models.TextField(blank=True)
date_added = models.DateTimeField(auto_now_add=True)
created_by = models.OneToOneField(User, on_delete=models.CASCADE)
Now the view associated with the model are as follows Note:The entire view isnt relevant to the error. The part relevant to the saving comment is the second 'request.POST' which I have denoted with a python
comment using # :
def product(request, category_slug, product_slug):
cart = Cart(request)
product = get_object_or_404(Product, category__slug=category_slug, slug=product_slug)
if request.method == 'POST':
form = AddToCartForm(request.POST)
if form.is_valid():
quantity = form.cleaned_data['quantity']
cart.add(product_id=product.id, quantity=quantity, update_quantity=False)
messages.success(request, 'The product was added to the cart')
return redirect('product', category_slug=category_slug, product_slug=product_slug)
similar_products = list(product.category.products.exclude(id=product.id))
# this part is for saving of the user comments to productreview model
if request.method == 'POST':
stars = request.POST.get('stars', 3)
content = request.POST.get('content', '')
name = request.POST.get('name', '')
created_by = request.user
review = ProductReview.objects.create(product=product, name=name, stars=stars, content=content, created_by=created_by)
return HttpResponseRedirect(request.META.get('HTTP_REFERER'))
# this marks the end of the code relevant to saving the user comment
if len(similar_products) >= 4:
similar_products = random.sample(similar_products, 4)
user_type = 0
if request.user.is_authenticated:
user_type = UserType.objects.filter(created_by=request.user.id).values_list('user_type', flat=True)
user_type = int(user_type[0])
return render(request, 'product.html', {'product': product, 'similar_products': similar_products, 'user_type': user_type})
And finally the relevant part of the template 'product.html' which is referenced in the view
{% if request.user.is_authenticated %}
{% if user_type == 2 %}
<div class="notification space-below">
<form method="post" action=".">
{% csrf_token %}
<div class="field">
<label>Name</label>
<div class="control">
<input class="text" name="name" value="{{ request.user }}" readonly>
</div>
</div>
<div class="field">
<label>Stars</label>
<div class="control">
<div class="select">
<select name="stars">
<option value="1">1</option>
<option value="2">2</option>
<option value="3" selected>3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</div>
</div>
</div>
<div class="field">
<label>Content</label>
<div class="control">
<textarea class="textarea" name="content"></textarea>
</div>
</div>
<div class="field">
<div class="control">
<button class="button is-success">Submit</button>
</div>
</div>
</form>
</div>
{% else %}
<div>sign in with a buyer account to leave review</div>
{% endif %}
{% endif %}
Now when I try to fill the form in the product.html page and try to submit it ,I get the following error:
FOREIGN KEY constraint failed
IntegrityError at /smartwatch/apple-watch/
Can anyone tell what exactly is the issue with my code?

Answer 1

Pretty sure this all comes to your model, especially to this single line:
created_by = models.OneToOneField(User, on_delete=models.CASCADE)
You are using OneToOneField. This means a single user will be able to leave a single review in your entire application. You are getting integrity errors probably because this user you've selected already has a review on a different product.
If this isn't what you want, use normal ForeignKey instead.
I think your intention was to ensure that a single user can leave only one review per product. In that case, you should try setting UniqueConstraint between the product and created_by fields