django-nplus1 0.2.0

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"]

# tests.py
@pytest.mark.nplus1
class TestMyView:
    def test_list_books(self, books):
        response = client.get("/books/")  # raises NPlus1Error if view has N+1

Tests marked with @pytest.mark.nplus1 will fail if the code under test triggers an N+1 query. Fix the N+1, or use nplus1_allow() in helper functions that intentionally defer prefetching to their callers.

See examples/ for a working project and the docs for full configuration.

Celery Integration

Detect N+1 queries inside Celery tasks, using the same per-execution scoping as the HTTP middleware.

pip install django-nplus1[celery]

# settings.py
NPLUS1_CELERY = True

Each task execution gets its own detection scope. 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