Fixed #19896 -- Committed after clearing cache in the database.

django/core/cache/backends/db.py

@@ -184,6 +184,7 @@ def clear(self):
         table = connections[db].ops.quote_name(self._table)
         cursor = connections[db].cursor()
         cursor.execute('DELETE FROM %s' % table)
+        transaction.commit_unless_managed(using=db)
 
 # For backwards compatibility
 class CacheClass(DatabaseCache):

tests/regressiontests/cache/tests.py

@@ -18,7 +18,7 @@
 from django.core.cache import get_cache
 from django.core.cache.backends.base import (CacheKeyWarning,
     InvalidCacheBackendError)
-from django.db import router
+from django.db import router, transaction
 from django.http import (HttpResponse, HttpRequest, StreamingHttpResponse,
     QueryDict)
 from django.middleware.cache import (FetchFromCacheMiddleware,
@@ -836,6 +836,13 @@ def test_second_call_doesnt_crash(self):
                 interactive=False
             )
 
+    def test_clear_commits_transaction(self):
+        # Ensure the database transaction is committed (#19896)
+        self.cache.set("key1", "spam")
+        self.cache.clear()
+        transaction.rollback()
+        self.assertEqual(self.cache.get("key1"), None)
+
 
 @override_settings(USE_TZ=True)
 class DBCacheWithTimeZoneTests(DBCacheTests):