Small startup detection thing

src/manage.py

@@ -3,7 +3,12 @@ import os
 import sys
 
 if __name__ == "__main__":
-    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
+    try:
+        from paperless_migration.detect import choose_settings_module
+
+        os.environ.setdefault("DJANGO_SETTINGS_MODULE", choose_settings_module())
+    except Exception:
+        os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
 
     from django.core.management import execute_from_command_line
 

src/paperless/asgi.py

@@ -1,12 +1,18 @@
 import os
 
+try:
+    from paperless_migration.detect import choose_settings_module
+
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", choose_settings_module())
+except Exception:
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
+
 from django.core.asgi import get_asgi_application
 
 # Fetch Django ASGI application early to ensure AppRegistry is populated
 # before importing consumers and AuthMiddlewareStack that may import ORM
 # models.
 
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
 django_asgi_app = get_asgi_application()
 
 from channels.auth import AuthMiddlewareStack  # noqa: E402

src/paperless/wsgi.py

@@ -9,9 +9,14 @@ https://docs.djangoproject.com/en/1.10/howto/deployment/wsgi/
 
 import os
 
-from django.core.wsgi import get_wsgi_application
+try:
+    from paperless_migration.detect import choose_settings_module
 
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", choose_settings_module())
+except Exception:
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "paperless.settings")
+
+from django.core.wsgi import get_wsgi_application
 
 application = get_wsgi_application()
 

src/paperless_migration/detect.py

@@ -0,0 +1,150 @@
+"""Lightweight detection to decide if we should boot migration mode."""
+
+from __future__ import annotations
+
+import logging
+import os
+import sqlite3
+from pathlib import Path
+from typing import Any
+
+logger = logging.getLogger(__name__)
+
+BASE_DIR = Path(__file__).resolve().parent.parent
+
+_DOC_EXISTS_QUERY = "SELECT 1 FROM documents_document LIMIT 1;"
+
+
+def _get_db_config() -> dict[str, Any]:
+    data_dir = Path(os.getenv("PAPERLESS_DATA_DIR", BASE_DIR.parent / "data")).resolve()
+    if not os.getenv("PAPERLESS_DBHOST"):
+        return {
+            "ENGINE": "sqlite",
+            "NAME": data_dir / "db.sqlite3",
+        }
+
+    engine = "mariadb" if os.getenv("PAPERLESS_DBENGINE") == "mariadb" else "postgres"
+    cfg = {
+        "ENGINE": engine,
+        "HOST": os.getenv("PAPERLESS_DBHOST"),
+        "PORT": os.getenv("PAPERLESS_DBPORT"),
+        "NAME": os.getenv("PAPERLESS_DBNAME", "paperless"),
+        "USER": os.getenv("PAPERLESS_DBUSER", "paperless"),
+        "PASSWORD": os.getenv("PAPERLESS_DBPASS", "paperless"),
+    }
+    return cfg
+
+
+def _probe_sqlite(path: Path) -> bool:
+    if not path.exists():
+        return False
+    try:
+        conn = sqlite3.connect(path, timeout=1)
+        cur = conn.cursor()
+        cur.execute(_DOC_EXISTS_QUERY)
+        cur.fetchone()
+        return True
+    except sqlite3.Error:
+        return False
+    finally:
+        try:
+            conn.close()
+        except Exception:
+            pass
+
+
+def _probe_postgres(cfg: dict[str, Any]) -> bool:
+    try:
+        import psycopg
+    except ImportError:  # pragma: no cover
+        logger.debug("psycopg not installed; skipping postgres probe")
+        return False
+
+    try:
+        conn = psycopg.connect(
+            host=cfg["HOST"],
+            port=cfg["PORT"],
+            dbname=cfg["NAME"],
+            user=cfg["USER"],
+            password=cfg["PASSWORD"],
+            connect_timeout=2,
+        )
+        with conn, conn.cursor() as cur:
+            cur.execute(_DOC_EXISTS_QUERY)
+            cur.fetchone()
+        return True
+    except Exception:
+        return False
+    finally:
+        try:
+            conn.close()
+        except Exception:
+            pass
+
+
+def _probe_mariadb(cfg: dict[str, Any]) -> bool:
+    try:
+        import MySQLdb  # type: ignore
+    except ImportError:  # pragma: no cover
+        logger.debug("mysqlclient not installed; skipping mariadb probe")
+        return False
+
+    try:
+        conn = MySQLdb.connect(
+            host=cfg["HOST"],
+            port=int(cfg["PORT"] or 3306),
+            user=cfg["USER"],
+            passwd=cfg["PASSWORD"],
+            db=cfg["NAME"],
+            connect_timeout=2,
+        )
+        cur = conn.cursor()
+        cur.execute("SELECT 1 FROM documents_document LIMIT 1;")
+        cur.fetchone()
+        return True
+    except Exception:
+        return False
+    finally:
+        try:
+            conn.close()
+        except Exception:
+            pass
+
+
+def is_v2_database() -> bool:
+    cfg = _get_db_config()
+    if cfg["ENGINE"] == "sqlite":
+        return _probe_sqlite(cfg["NAME"])
+    if cfg["ENGINE"] == "postgres":
+        return _probe_postgres(cfg)
+    if cfg["ENGINE"] == "mariadb":
+        return _probe_mariadb(cfg)
+    return False
+
+
+def choose_settings_module() -> str:
+    # ENV override
+    toggle = os.getenv("PAPERLESS_MIGRATION_MODE")
+    if toggle is not None:
+        chosen = (
+            "paperless_migration.settings"
+            if str(toggle).lower() in ("1", "true", "yes", "on")
+            else "paperless.settings"
+        )
+        os.environ["PAPERLESS_MIGRATION_MODE"] = "1" if "migration" in chosen else "0"
+        return chosen
+
+    # Auto-detect via DB probe
+    if is_v2_database():
+        logger.warning("Detected v2 schema; booting migration mode.")
+        os.environ["PAPERLESS_MIGRATION_MODE"] = "1"
+        return "paperless_migration.settings"
+
+    os.environ["PAPERLESS_MIGRATION_MODE"] = "0"
+    return "paperless.settings"
+
+
+if __name__ == "__main__":  # pragma: no cover
+    logger.info(
+        "v2 database detected" if is_v2_database() else "v2 database not detected",
+    )