Ticket #8044: random.diff

django/template/defaultfilters.py

@@ -12 +12 @@
 from django.utils.translation import ugettext, ungettext
 from django.utils.encoding import force_unicode, iri_to_uri
 from django.utils.safestring import mark_safe, SafeData
-
+from django.db.models.query import QuerySet
 register = Library()
 
 #######################
@@ -475 +475 @@
 length_is.is_safe = True
 
 def random(value):
-    """Returns a random item from the list."""
-    return random_module.choice(value)
+    """
+    Returns a random item from the list.
+    
+    If the value is a queryset, limits the queryset instead of evaluating
+    and then choosing.
+    """
+    if isinstance(value, QuerySet):
+        object_count = value.count()
+        if not object_count:
+            return None
+        else:
+            random_index = random_module.randint(0, object_count-1)
+            return value[random_index]
+    else:
+        return random_module.choice(value)
 random.is_safe = True
 
 def slice_(value, arg):

docs/templates.txt

@@ -1641 +1641 @@
 
 Returns a random item from the given list.
 
+If the list is really a queryset, will limit the queryset to a random item
+instead of evaluating it. See the `DB API documentation`_ on `limiting querysets`_.
+
+.. _DB API documentation: ../db-api/
+.. _limiting querysets: ../db-api/#limiting-querysets
+
 For example::
 
     {{ value|random }}