added options to change database backend

paperless.conf.example

@@ -3,6 +3,16 @@
 # As this file contains passwords it should only be readable by the user
 # running paperless.
 
+###############################################################################
+####                        Database Settings                              ####
+###############################################################################
+
+# By default, sqlite is used as the database backend. This can be changed here.
+#PAPERLESS_DBENGINE="django.db.backends.postgresql_psycopg2"
+#PAPERLESS_DBNAME="paperless"
+#PAPERLESS_DBUSER="paperless"
+#PAPERLESS_DBPASS="paperless"
+
 
 ###############################################################################
 ####                         Paths & Folders                               ####

src/documents/checks.py

@@ -2,7 +2,7 @@ import textwrap
 
 from django.conf import settings
 from django.core.checks import Error, register
-from django.db.utils import OperationalError
+from django.db.utils import OperationalError, ProgrammingError
 
 
 @register()
@@ -14,7 +14,7 @@ def changed_password_check(app_configs, **kwargs):
     try:
         encrypted_doc = Document.objects.filter(
             storage_type=Document.STORAGE_TYPE_GPG).first()
-    except OperationalError:
+    except (OperationalError, ProgrammingError):
         return []  # No documents table yet
 
     if encrypted_doc:

src/paperless/settings.py

@@ -133,9 +133,9 @@ DATABASES = {
     }
 }
 
-if os.getenv("PAPERLESS_DBUSER") and os.getenv("PAPERLESS_DBPASS"):
+if os.getenv("PAPERLESS_DBENGINE"):
     DATABASES["default"] = {
-        "ENGINE": "django.db.backends.postgresql_psycopg2",
+        "ENGINE": os.getenv("PAPERLESS_DBENGINE"),
         "NAME": os.getenv("PAPERLESS_DBNAME", "paperless"),
         "USER": os.getenv("PAPERLESS_DBUSER"),
         "PASSWORD": os.getenv("PAPERLESS_DBPASS")