Fixed #34865 -- Released memory earlier than garbage collection on database wrapping layers.

Thank you Florian Apolloner, Jake Howard and Patryk Zawadzki for
the clarifying comments and reviews.

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/backends/base/test_base.py b/tests/backends/base/test_base.py
index 4418d010ea..8f47e30172 100644
--- a/tests/backends/base/test_base.py
+++ b/tests/backends/base/test_base.py
@@ -1,3 +1,4 @@
+import gc
 from unittest.mock import MagicMock, patch
 
 from django.db import DEFAULT_DB_ALIAS, connection, connections, transaction
@@ -60,6 +61,36 @@ class DatabaseWrapperTests(SimpleTestCase):
         with patch.object(connection.features, "minimum_database_version", None):
             connection.check_database_version_supported()
 
+    def test_release_memory_without_garbage_collection(self):
+        # Schedule the restore of the garbage collection settings.
+        self.addCleanup(gc.set_debug, 0)
+        self.addCleanup(gc.enable)
+
+        # Disable automatic garbage collection to control when it's triggered,
+        # then run a full collection cycle to ensure `gc.garbage` is empty.
+        gc.disable()
+        gc.collect()
+
+        # The garbage list isn't automatically populated to avoid CPU overhead,
+        # so debugging needs to be enabled to track all unreachable items and
+        # have them stored in `gc.garbage`.
+        gc.set_debug(gc.DEBUG_SAVEALL)
+
+        # Create a new connection that will be closed during the test, and also
+        # ensure that a `DatabaseErrorWrapper` is created for this connection.
+        test_connection = connection.copy()
+        with test_connection.wrap_database_errors:
+            self.assertEqual(test_connection.queries, [])
+
+        # Close the connection and remove references to it. This will mark all
+        # objects related to the connection as garbage to be collected.
+        test_connection.close()
+        test_connection = None
+
+        # Enforce garbage collection to populate `gc.garbage` for inspection.
+        gc.collect()
+        self.assertEqual(gc.garbage, [])
+
 
 class DatabaseWrapperLoggingTests(TransactionTestCase):
     available_apps = ["backends"]