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Change: Fix DB_ENGINE=postgres being silently ignored

Date: 2026-09-11

Goal

Make DB_ENGINE=postgres actually select PostgreSQL, regardless of DEBUG. Previously the Postgres branch was gated on not DEBUG, so with DEBUG true (the default, and the state inside the Docker container) the app fell back to SQLite even though DB_ENGINE=postgres and DATABASE_URL were set.

What changed

Area Change
Database selection config/settings.py now chooses the backend from DB_ENGINE alone (if DB_ENGINE in ("postgres", "postgresql")); the not DEBUG and condition was removed.
Error message With DB_ENGINE=postgres and no DATABASE_URL, startup raises a clear ImproperlyConfigured instead of a bare KeyError.
Compose env loading docker-compose.yml web now declares an optional env_file: .env (required: false), so the whole .env (DEBUG, SECRET_KEY, SSO, MCP, search tuning, ...) reaches the container. Explicit environment entries still take precedence, and Coolify can still deploy with no .env file.
Compose DEBUG web.environment sets DJANGO_DEBUG: ${DJANGO_DEBUG:-0}, so the container's DEBUG reflects .env and defaults off in Docker.

Notes

  • The SQLite fallback is still the default only when DB_ENGINE is unset or set to sqlite, so local development without a .env is unchanged.
  • This corrects the earlier production-Docker plan's locked decision, which specified DB_ENGINE as the sole selector (no DEBUG coupling).
  • env_file.required needs Docker Compose v2.24+; older hosts must keep a real .env or rely on Coolify-injected variables.
  • No model, migration, or schema changes.

User validation

  1. With DB_ENGINE=postgres and DATABASE_URL set: python manage.py shell -c "from django.conf import settings; print(settings.DATABASES['default']['ENGINE'])" prints django.db.backends.postgresql.
  2. Same command with DJANGO_DEBUG=1 still prints the Postgres backend.
  3. With DB_ENGINE=postgres and no DATABASE_URL, startup raises the clear ImproperlyConfigured message.
  4. With DB_ENGINE unset, the backend is django.db.backends.sqlite3.
  5. Set DJANGO_DEBUG=1 in .env, run docker compose config (shows DJANGO_DEBUG: "1"), then docker compose exec web python manage.py shell -c "from django.conf import settings; print(settings.DEBUG)" prints True; set it to 0 and confirm False.