How do I properly use select_related() and prefetch_related() in Django?
I'm working on a Django project and encountering an issue with Django REST API. Here's my current implementation:
# models.py
class Article(models.Model):
title = models.CharField(max_length=200)
author = models.ForeignKey(User, on_delete=models.CASCADE)
def save(self, *args, **kwargs):
# This is causing issues
super().save(*args, **kwargs)
The specific error I'm getting is: "django.db.utils.OperationalError: no such table: django_session"
I've already tried the following approaches:
- Checked Django documentation and Stack Overflow
- Verified my database schema and migrations
- Added debugging prints to trace the issue
- Tested with different data inputs
Environment details:
- Django version: 5.0.1
- Python version: 3.11.0
- Database: PostgreSQL 15
- Operating system: Windows 11
Has anyone encountered this before? Any guidance would be greatly appreciated!
Comments
michael_code: Have you considered using Django's async views for this use case? Might be more efficient for I/O operations. 2 months ago
azzani: This Django transaction approach worked perfectly for my payment processing system. Thanks! 2 months ago
2 Answers
Here's a comprehensive approach to implementing JWT authentication in Django REST Framework:
# settings.py
INSTALLED_APPS = [
'rest_framework',
'rest_framework_simplejwt',
]
REST_FRAMEWORK = {
'DEFAULT_AUTHENTICATION_CLASSES': (
'rest_framework_simplejwt.authentication.JWTAuthentication',
),
'DEFAULT_PERMISSION_CLASSES': [
'rest_framework.permissions.IsAuthenticated',
],
}
from datetime import timedelta
SIMPLE_JWT = {
'ACCESS_TOKEN_LIFETIME': timedelta(minutes=60),
'REFRESH_TOKEN_LIFETIME': timedelta(days=7),
'ROTATE_REFRESH_TOKENS': True,
}# urls.py
from rest_framework_simplejwt.views import (
TokenObtainPairView,
TokenRefreshView,
)
urlpatterns = [
path('api/token/', TokenObtainPairView.as_view()),
path('api/token/refresh/', TokenRefreshView.as_view()),
]# Custom serializer for additional user data
from rest_framework_simplejwt.serializers import TokenObtainPairSerializer
class CustomTokenObtainPairSerializer(TokenObtainPairSerializer):
@classmethod
def get_token(cls, user):
token = super().get_token(user)
token['username'] = user.username
token['email'] = user.email
return tokenThe RecursionError occurs when Python's recursion limit is exceeded. Here are several solutions:
1. Increase recursion limit (temporary fix):
import sys
sys.setrecursionlimit(10000) # Default is usually 10002. Convert to iterative approach (recommended):
# Recursive (problematic for large inputs)
def factorial_recursive(n):
if n <= 1:
return 1
return n * factorial_recursive(n - 1)
# Iterative (better)
def factorial_iterative(n):
result = 1
for i in range(2, n + 1):
result *= i
return result3. Use memoization for recursive algorithms:
from functools import lru_cache
@lru_cache(maxsize=None)
def fibonacci(n):
if n < 2:
return n
return fibonacci(n-1) + fibonacci(n-2)4. Tail recursion optimization (manual):
def factorial_tail_recursive(n, accumulator=1):
if n <= 1:
return accumulator
return factorial_tail_recursive(n - 1, n * accumulator)Comments
michael_code: I'm getting a similar error but with PostgreSQL instead of SQLite. Any differences in the solution? 2 months ago
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