Prevented initialization of unused database connections.

django/contrib/postgres/apps.py

@@ -51,7 +51,7 @@ class PostgresConfig(AppConfig):
     def ready(self):
         setting_changed.connect(uninstall_if_needed)
         # Connections may already exist before we are called.
-        for conn in connections.all():
+        for conn in connections.all(initialized_only=True):
             if conn.vendor == "postgresql":
                 conn.introspection.data_types_reverse.update(
                     {

django/core/cache/__init__.py

@@ -51,14 +51,6 @@ class CacheHandler(BaseConnectionHandler):
             ) from e
         return backend_cls(location, params)
 
-    def all(self, initialized_only=False):
-        return [
-            self[alias]
-            for alias in self
-            # If initialized_only is True, return only initialized caches.
-            if not initialized_only or hasattr(self._connections, alias)
-        ]
-
 
 caches = CacheHandler()
 

django/core/handlers/base.py

@@ -344,16 +344,13 @@ class BaseHandler:
 
     def make_view_atomic(self, view):
         non_atomic_requests = getattr(view, "_non_atomic_requests", set())
-        for db in connections.all():
+        for alias, settings_dict in connections.settings.items():
-            if (
+            if settings_dict["ATOMIC_REQUESTS"] and alias not in non_atomic_requests:
-                db.settings_dict["ATOMIC_REQUESTS"]
-                and db.alias not in non_atomic_requests
-            ):
                 if asyncio.iscoroutinefunction(view):
                     raise RuntimeError(
                         "You cannot use ATOMIC_REQUESTS with async views."
                     )
-                view = transaction.atomic(using=db.alias)(view)
+                view = transaction.atomic(using=alias)(view)
         return view
 
     def process_exception_by_middleware(self, exception, request):

django/db/__init__.py

@@ -43,7 +43,7 @@ connection = ConnectionProxy(connections, DEFAULT_DB_ALIAS)
 
 # Register an event to reset saved queries when a Django request is started.
 def reset_queries(**kwargs):
-    for conn in connections.all():
+    for conn in connections.all(initialized_only=True):
         conn.queries_log.clear()
 
 
@@ -53,7 +53,7 @@ signals.request_started.connect(reset_queries)
 # Register an event to reset transaction state and close connections past
 # their lifetime.
 def close_old_connections(**kwargs):
-    for conn in connections.all():
+    for conn in connections.all(initialized_only=True):
         conn.close_if_unusable_or_obsolete()
 
 

django/test/signals.py

@@ -70,7 +70,7 @@ def update_connections_time_zone(*, setting, **kwargs):
 
     # Reset the database connections' time zone
     if setting in {"TIME_ZONE", "USE_TZ"}:
-        for conn in connections.all():
+        for conn in connections.all(initialized_only=True):
             try:
                 del conn.timezone
             except AttributeError:

django/test/testcases.py

@@ -1197,7 +1197,7 @@ class TransactionTestCase(SimpleTestCase):
                 # tests (e.g., losing a timezone setting causing objects to be
                 # created with the wrong time). To make sure this doesn't
                 # happen, get a clean connection at the start of every test.
-                for conn in connections.all():
+                for conn in connections.all(initialized_only=True):
                     conn.close()
         finally:
             if self.available_apps is not None:
@@ -1378,7 +1378,7 @@ class TestCase(TransactionTestCase):
     def tearDownClass(cls):
         if cls._databases_support_transactions():
             cls._rollback_atomics(cls.cls_atomics)
-            for conn in connections.all():
+            for conn in connections.all(initialized_only=True):
                 conn.close()
         super().tearDownClass()
 

django/utils/connection.py

@@ -72,5 +72,10 @@ class BaseConnectionHandler:
     def __iter__(self):
         return iter(self.settings)
 
-    def all(self):
+    def all(self, initialized_only=False):
-        return [self[alias] for alias in self]
+        return [
+            self[alias]
+            for alias in self
+            # If initialized_only is True, return only initialized connections.
+            if not initialized_only or hasattr(self._connections, alias)
+        ]

tests/utils_tests/test_connection.py

@@ -8,3 +8,7 @@ class BaseConnectionHandlerTests(SimpleTestCase):
         msg = "Subclasses must implement create_connection()."
         with self.assertRaisesMessage(NotImplementedError, msg):
             handler.create_connection(None)
+
+    def test_all_initialized_only(self):
+        handler = BaseConnectionHandler({"default": {}})
+        self.assertEqual(handler.all(initialized_only=True), [])