Added mget method to base backend to fetch all keys in one fell swoop, instead of one by one. Especially useful in the admin.

constance/admin.py

@@ -61,8 +61,13 @@ class ConstanceAdmin(admin.ModelAdmin):
 
     @csrf_protect_m
     def changelist_view(self, request, extra_context=None):
-        form = ConstanceForm(initial=dict((name, getattr(config, name))
-                             for name in settings.CONFIG))
+        # First load a mapping between config name and default value
+        default_initial = ((name, default)
+            for name, (default, help_text) in settings.CONFIG.iteritems())
+        # Then update the mapping with actually values from the backend
+        initial = dict(default_initial,
+            **dict(config._backend.mget(settings.CONFIG.iterkeys())))
+        form = ConstanceForm(initial=initial)
         if request.method == 'POST':
             form = ConstanceForm(request.POST)
             if form.is_valid():
@@ -79,7 +84,11 @@ class ConstanceAdmin(admin.ModelAdmin):
             'media': self.media + form.media,
         }
         for name, (default, help_text) in settings.CONFIG.iteritems():
-            value = getattr(config, name)
+            # First try to load the value from the actual backend
+            value = initial.get(name)
+            # Then if the returned value is None, get the default
+            if value is None:
+                value = getattr(config, name)
             context['config'].append({
                 'name': name,
                 'default': localize(default),

constance/backends/__init__.py

@@ -1,16 +1,25 @@
+"""
+Defines the base constance backend
+"""
 
 class Backend(object):
 
     def get(self, key):
         """
-        Get the key from the backend store and return it.
+        Get the key from the backend store and return the value.
         Return None if not found.
         """
         raise NotImplementedError
 
+    def mget(self, keys):
+        """
+        Get the keys from the backend store and return a list of the values.
+        Return an empty list if not found.
+        """
+        raise NotImplementedError
+
     def set(self, key, value):
         """
         Add the value to the backend store given the key.
         """
         raise NotImplementedError
-

constance/backends/redisd.py

@@ -1,3 +1,5 @@
+import itertools
+
 from django.core.exceptions import ImproperlyConfigured
 
 from constance import settings, utils
@@ -34,5 +36,10 @@ class RedisBackend(Backend):
             return loads(value)
         return None
 
+    def mget(self, keys):
+        prefixed_keys = (self.add_prefix(key) for key in keys)
+        values = (loads(value) for value in self._rd.mget(prefixed_keys))
+        return itertools.izip(keys, values)
+
     def set(self, key, value):
         self._rd.set(self.add_prefix(key), dumps(value))

tests/testproject/test_app/redis_mockup.py

@@ -2,4 +2,10 @@ class Connection(dict):
     def set(self, key, value):
         self[key] = value
 
-    
+    def mget(self, keys):
+        values = []
+        for key in keys:
+            value = self.get(key, None)
+            if value is not None:
+                values.append(value)
+        return values