Python: Django ORM

Runs Django migrations (introspection, django_migrations, constraints) and the ORM against the database. The code is the same against the original database and against MachSQL; only the address changes.

The only change

DB_HOST=old-postgres
DB_HOST=machsql-host

Nothing else changes: not the code, not the driver, not its version, not the SQL.

Versions

• Python 3.15
• Django 6.1.2
• psycopg 3.3.6

Run

python3 -m venv .venv && . .venv/bin/activate
pip install -r requirements.txt
export DB_HOST=machsql-host DB_PASSWORD=...
python manage.py migrate
python manage.py demo

Expected output: inserted todo <id>, <n> open.

Source

The program as it is kept and tested in the Mach Database for PostgreSQL repository; highlighted lines read the connection setting.

project/settings.py

"""Minimal settings: one app, the database from the environment."""

import os

SECRET_KEY = os.environ.get("DJANGO_SECRET_KEY", "example-only-not-a-secret")
DEBUG = False
ALLOWED_HOSTS: list[str] = []
INSTALLED_APPS = ["todos"]
USE_TZ = True
DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"

DATABASES = {
    "default": {
        "ENGINE": "django.db.backends.postgresql",
        "HOST": os.environ["DB_HOST"],  # the only value that changes
        "PORT": os.environ.get("DB_PORT", "5432"),
        "NAME": os.environ.get("DB_NAME", "app"),
        "USER": os.environ.get("DB_USER", "app"),
        "PASSWORD": os.environ["DB_PASSWORD"],
    }
}

manage.py

#!/usr/bin/env python3
"""Django's command-line utility."""

import os
import sys

if __name__ == "__main__":
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "project.settings")
    from django.core.management import execute_from_command_line

    execute_from_command_line(sys.argv)

project/__init__.py

requirements.txt

Django==6.1.2
psycopg[binary]==3.3.6

todos/__init__.py

todos/apps.py

from django.apps import AppConfig


class TodosConfig(AppConfig):
    name = "todos"

todos/management/__init__.py

todos/management/commands/__init__.py

todos/management/commands/demo.py

from django.core.management.base import BaseCommand

from todos.models import Todo


class Command(BaseCommand):
    help = "Insert a todo and count the open ones."

    def handle(self, *args, **options):
        todo = Todo.objects.create(title="write the examples")
        open_count = Todo.objects.filter(done=False).count()
        self.stdout.write(f"inserted todo {todo.id}, {open_count} open")

todos/migrations/__init__.py

todos/migrations/0001_initial.py

from django.db import migrations, models


class Migration(migrations.Migration):
    initial = True
    dependencies: list[tuple[str, str]] = []

    operations = [
        migrations.CreateModel(
            name="Todo",
            fields=[
                ("id", models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name="ID")),
                ("title", models.CharField(max_length=200)),
                ("done", models.BooleanField(default=False)),
            ],
        ),
    ]

todos/models.py

from django.db import models


class Todo(models.Model):
    title = models.CharField(max_length=200)
    done = models.BooleanField(default=False)