django-nplus1 0.3.5

N+1 query detection for Django

django-nplus1

N+1 query detection for Django. Beta - API may still change before 1.0.

Quick Start

pip install django-nplus1

# settings.py
INSTALLED_APPS = [..., "django_nplus1"]

# settings/testing.py
MIDDLEWARE = [..., "django_nplus1.NPlus1Middleware"]
NPLUS1_RAISE = True

Adding the middleware to your test settings means every view test that goes through the Django test client will fail on N+1 queries. This catches real problems in actual request paths without false positives from helper functions or scripts that intentionally defer prefetching.

For existing projects, introducing django-nplus1 will likely surface many N+1 queries at once. Whitelist the known issues and fix them over time:

# settings/testing.py
NPLUS1_WHITELIST = [
    {"model": "myapp.Author", "field": "books"},
    {"model": "myapp.Book", "field": "publisher"},
]

The middleware can also run in development or production settings to log warnings instead of raising — see the docs for all options, including the pytest plugin and the Profiler context manager.

See examples/ for a working project.

Celery Integration

The equivalent of the middleware for Celery tasks — each task execution gets its own detection scope.

pip install django-nplus1[celery]

# settings.py (or settings/testing.py)
NPLUS1_CELERY = True

Lazy loads, .get()-in-a-loop, unused eager loads, and duplicate queries are all detected per-task, just as they are per-request. nplus1_allow() works inside tasks the same way it does in views.

Limitations:

• nplus1_allow() context does not propagate across task boundaries. If a view calls task.delay() inside an nplus1_allow() block, the allow rules do not carry into the worker (ContextVars don't survive serialization).
• Scope nesting for synchronous subtasks (.apply() inside a task) creates a separate scope for the inner task.

Credits

This project builds on the work of:

• nplusone by Joshua Carp - the original automatic N+1 detection library for Python ORMs. django-nplus1 started as a Django-specific fork of nplusone's architecture.
• django-zeal by Tao Bojlen - inspired several features including deferred field detection, .get()-in-a-loop detection, ContextVar-based async safety, call-site tracking, and configurable thresholds.

License

MIT