misc: use BEGIN IMMEDIATE to start transactions (#89314)

debian/debian_config.py

@@ -13,7 +13,7 @@ MEDIA_ROOT = os.path.join(VAR_DIR, 'media')
 
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
+        'ENGINE': 'ants_hub.sqlite3_backend',
         'NAME': os.path.join(VAR_DIR, 'db.sqlite3'),
     }
 }

debian/settings.py

@@ -15,7 +15,7 @@
 # Databases
 # DATABASES = {
 #     'default': {
-#         'ENGINE': 'django.db.backends.sqlite3',
+#         'ENGINE': 'ants_hub.sqlite3_backend',
 #         'NAME': os.path.join(VAR_DIR, 'db.sqlite3'),
 #     }
 # }

src/ants_hub/settings.py

@@ -63,7 +63,7 @@ WSGI_APPLICATION = 'ants_hub.wsgi.application'
 
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
+        'ENGINE': 'ants_hub.sqlite3_backend',
         'NAME': 'db.sqlite3',
         # Keep database open
         'CONN_MAX_AGE': None,

src/ants_hub/sqlite3_backend/base.py

@@ -0,0 +1,14 @@
+# ANTS-Hub - Copyright (C) Entr'ouvert
+
+from django.db.backends.sqlite3 import base
+
+
+class DatabaseWrapper(base.DatabaseWrapper):
+    def _start_transaction_under_autocommit(self):
+        """
+        Start a transaction explicitly in autocommit mode.
+
+        Staying in autocommit mode works around a bug of sqlite3 that breaks
+        savepoints when autocommit is disabled.
+        """
+        self.cursor().execute('BEGIN IMMEDIATE')