create autofill_values dict with full_cachekey straight away

constance/backends/database.py

@@ -53,8 +53,7 @@ def autofill(self):
         full_cachekey = self.add_prefix(self._autofill_cachekey)
         if self._cache.get(full_cachekey):
             return
-        autofill_values = {}
-        autofill_values[full_cachekey] = 1
+        autofill_values = {full_cachekey: 1}
         for key, value in self.mget(settings.CONFIG):
             autofill_values[self.add_prefix(key)] = value
         self._cache.set_many(autofill_values, timeout=self._autofill_timeout)

tests/backends/test_database.py

@@ -25,3 +25,30 @@ def test_database_queries(self):
 
     def tearDown(self):
         settings.BACKEND = self.old_backend
+
+
+class TestDatabaseWithCache(StorageTestsMixin, TestCase):
+    def setUp(self):
+        self.old_backend = settings.BACKEND
+        settings.BACKEND = "constance.backends.database.DatabaseBackend"
+        self.old_cache_backend = settings.DATABASE_CACHE_BACKEND
+        settings.DATABASE_CACHE_BACKEND = "default"
+        super().setUp()
+        self.config._backend._cache.clear()
+
+    def test_database_queries(self):
+        # Read and set to default value
+        with self.assertNumQueries(6):
+            self.assertEqual(self.config.INT_VALUE, 1)
+
+        # Read again
+        with self.assertNumQueries(0):
+            self.assertEqual(self.config.INT_VALUE, 1)
+
+        # Set value
+        with self.assertNumQueries(3):
+            self.config.INT_VALUE = 15
+
+    def tearDown(self):
+        settings.BACKEND = self.old_backend
+        settings.DATABASE_CACHE_BACKEND = self.old_cache_backend

tests/cache_mockup.py

@@ -0,0 +1,12 @@
+from django.core.cache.backends.base import BaseCache
+from django.core.cache.backends.locmem import LocMemCache
+
+
+class Cache(BaseCache):
+    def __init__(self, name, params):
+        self._cache = LocMemCache(name, params)
+        self.add = self._cache.add
+        self.delete = self._cache.delete
+        self.set = self._cache.set
+        self.get = self._cache.get
+        self.clear = self._cache.clear

tests/settings.py

@@ -29,6 +29,13 @@
     },
 }
 
+CACHES = {
+    "default": {
+        "BACKEND": "tests.cache_mockup.Cache",
+        "LOCATION": "locmem",
+    }
+}
+
 INSTALLED_APPS = (
     "django.contrib.admin",
     "django.contrib.staticfiles",