From 1b6670dd590ef8f235166ce966d28ac49f322c54 Mon Sep 17 00:00:00 2001
From: Luke Plant <L.Plant.98@cantab.net>
Date: Tue, 26 Apr 2011 11:28:50 +0000
Subject: [PATCH] Fixed #15904 - render_comment_form executes unnecessary query
 for object

Thanks to stefanw for report and patch!

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16103 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 .../contrib/comments/templatetags/comments.py   | 17 ++++++++++++++---
 .../comment_tests/tests/templatetag_tests.py    |  5 +++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/django/contrib/comments/templatetags/comments.py b/django/contrib/comments/templatetags/comments.py
index 42691c63e459b..8bc61cd44565a 100644
--- a/django/contrib/comments/templatetags/comments.py
+++ b/django/contrib/comments/templatetags/comments.py
@@ -122,12 +122,23 @@ class CommentFormNode(BaseCommentNode):
     """Insert a form for the comment model into the context."""
 
     def get_form(self, context):
-        ctype, object_pk = self.get_target_ctype_pk(context)
-        if object_pk:
-            return comments.get_form()(ctype.get_object_for_this_type(pk=object_pk))
+        obj = self.get_object(context)
+        if obj:
+            return comments.get_form()(obj)
         else:
             return None
 
+    def get_object(self, context):
+        if self.object_expr:
+            try:
+                return self.object_expr.resolve(context)
+            except template.VariableDoesNotExist:
+                return None
+        else:
+            object_pk = self.object_pk_expr.resolve(context,
+                    ignore_failures=True)
+            return self.ctype.get_object_for_this_type(pk=object_pk)
+
     def render(self, context):
         context[self.as_varname] = self.get_form(context)
         return ''
diff --git a/tests/regressiontests/comment_tests/tests/templatetag_tests.py b/tests/regressiontests/comment_tests/tests/templatetag_tests.py
index 4c90d9d208bf3..0ead6c2257a63 100644
--- a/tests/regressiontests/comment_tests/tests/templatetag_tests.py
+++ b/tests/regressiontests/comment_tests/tests/templatetag_tests.py
@@ -40,6 +40,11 @@ def testRenderCommentFormFromLiteral(self):
     def testRenderCommentFormFromObject(self):
         self.testRenderCommentForm("{% render_comment_form for a %}")
 
+    def testRenderCommentFormFromObjectWithQueryCount(self):
+        def test():
+            self.testRenderCommentFormFromObject()
+        self.assertNumQueries(1, test)
+
     def testGetCommentCount(self, tag=None):
         self.createSomeComments()
         t = "{% load comments %}" + (tag or "{% get_comment_count for comment_tests.article a.id as cc %}") + "{{ cc }}"