[1.11.x] Fixed #28091 -- Re-raised original exception when closing cursor cleanup fails

django/db/models/sql/compiler.py

@@ -874,7 +874,7 @@ class SQLCompiler(object):
             cursor = self.connection.cursor()
         try:
             cursor.execute(sql, params)
-        except Exception:
+        except Exception as original_exception:
             try:
                 # Might fail for server-side cursors (e.g. connection closed)
                 cursor.close()
@@ -883,7 +883,7 @@ class SQLCompiler(object):
                 # Python 2 doesn't chain exceptions. Remove this error
                 # silencing when dropping Python 2 compatibility.
                 pass
-            raise
+            raise original_exception
 
         if result_type == CURSOR:
             # Caller didn't specify a result_type, so just give them back the

docs/releases/1.11.1.txt

@@ -42,3 +42,7 @@ Bugfixes
   ``ModelAdmin.radio_fields`` with ``admin.HORIZONTAL`` (:ticket:`28059`).
 
 * Fixed crash in ``BaseGeometryWidget.subwidgets()`` (:ticket:`28039`).
+
+* Re-raised the original exception when ``cursor.execute()`` fails and the
+  cleanup code ``cursor.close()`` fails as well, instead of raising the cleanup
+  code failure (:ticket:28091).

tests/backends/tests.py

@@ -682,6 +682,25 @@ class BackendTestCase(TransactionTestCase):
             self.create_squares(args, 'pyformat', multiple=True)
         self.assertEqual(Square.objects.count(), 9)
 
+    def test_cursor_close_failure_does_not_mask_original_exception(self):
+        persons = Person.objects.iterator()
+
+        def raise_original_exception(*args, **kwargs):
+            raise Exception('Real exception raised by the database on cursor.execute')
+
+        def raise_close_exception():
+            raise Exception(
+                'Error when attempting to close the cursor, this exception should not mask the original exception'
+            )
+
+        mock_cursor = connection.chunked_cursor()
+        mock_cursor.execute = mock.MagicMock(side_effect=raise_original_exception)
+        mock_cursor.close = mock.MagicMock(side_effect=raise_close_exception)
+
+        with self.assertRaisesMessage(Exception, 'Real exception raised by the database on cursor.execute'):
+            with mock.patch('django.db.connection.create_cursor', return_value=mock_cursor):
+                list(persons)
+
     def test_unicode_fetches(self):
         # fetchone, fetchmany, fetchall return strings as unicode objects #6254
         qn = connection.ops.quote_name