When I run makemigrations error is occurred. Here is models.py
def unique_order_id():
not_unique = True
while not_unique:
uo_id = random.randint(1000000000, 9999999999)
if not Order.objects.filter(order_id=uo_id):
not_unique = False
return uo_id
class Product(models.Model):
#product code, name, category, unit price, current stock
product_code = models.IntegerField(unique=True)
name = models.CharField(max_length=100)
category = models.CharField(max_length=100)
unit_price = models.FloatField()
current_stock = models.IntegerField()
def __str__(self):
return self.name
class Order(models.Model):
order_id = models.IntegerField(unique=True,
default=unique_order_id)
customer_name = models.CharField(max_length=100)
phone = models.CharField(max_length=14)
email = models.EmailField()
qr_code = models.ImageField(upload_to='qr_codes', blank=True)
def __str__(self):
return self.customer_name
#override ths save method for creating qrcode based on fields on this model.
def save(self, *args, **kwargs):
qr_info = "Invoice No : "+ str(self.order_id)+" Name : "+self.customer_name +" Phone : "+str(self.phone)+ " Email : "+ self.email
qrcode_img = qrcode.make(qr_info)
#canvas = Image.new('RGB', (290, 290), 'white')
canvas = Image.new('RGB', (qrcode_img.pixel_size, qrcode_img.pixel_size), 'white')
canvas.paste(qrcode_img)
fname = f'qr_code-{self.customer_name}.png'
buffer = BytesIO()
canvas.save(buffer,'PNG')
self.qr_code.save(fname, File(buffer), save=False)
canvas.close()
super().save(*args, **kwargs)
class OrderItem(models.Model):
qty = models.IntegerField(default=0)
product = models.ForeignKey(Product, on_delete=models.SET_NULL, null=True)
order = models.ForeignKey(Order, on_delete=models.SET_NULL, null=True)
#this will return total price of product(unit_price*quntity)
@property
def get_total(self):
total = self.product.unit_price * self.qty
return total
This is forms.py codes
class ItemSelectForm(forms.Form):
p_name = forms.ChoiceField(label='Select Product',choices=list ((obj.product_code,obj.name) for obj in Product.objects.all()))
qty = forms.IntegerField()
#function for checking product avaiability
def clean_qty(self):
data = self.cleaned_data['qty']
product_code = self.cleaned_data['p_name']
product = Product.objects.get(product_code = product_code)
if data > product.current_stock:
raise forms.ValidationError(('Insufficient Stock'), code='ins_stock')
# Always return a value to use as the new cleaned data, even if
# this method didn't change it.
return data
This code works fine on my environment, but when i run this on another environment and run makamigrations this error shows up. After searching online, my understanding is, the p_name field in the form is causing the error, the query is running even before creating the table.
p_name = forms.ChoiceField(label='Select Product',choices=list ((obj.product_code,obj.name) for obj in Product.objects.all()))
How can i get out of this situation and solve the error !
You are executing a query when the p_name field on the ItemSelectForm is initialised, this initialisation happens when your application is parsed/loaded/started. Executing queries at start-up of your application is bad practice and in this case preventing you from running migrations as the query you are running is for a model that has not been migrated.
Use a ModelChoiceField instead and pass it a queryset, this queryset will not be executed on start-up and should alleviate this issue
class ItemSelectForm(forms.Form):
product = forms.ModelChoiceField(Product.objects.all(), label='Select Product')
qty = forms.IntegerField()
#function for checking product availability
def clean_qty(self):
data = self.cleaned_data['qty']
product = self.cleaned_data['product']
if data > product.current_stock:
raise forms.ValidationError(('Insufficient Stock'), code='ins_stock')
# Always return a value to use as the new cleaned data, even if
# this method didn't change it.
return data