Fixed #11402: added a `QuerySet.exists()` method. Thanks, Alex Gaynor.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11646 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 2 insertions, 6 deletions

diff --git a/django/forms/models.py b/django/forms/models.py
index cc43612bf5..37fce6824c 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -319,9 +319,7 @@ class BaseModelForm(BaseForm):
             if self.instance.pk is not None:
                 qs = qs.exclude(pk=self.instance.pk)
 
-            # This cute trick with extra/values is the most efficient way to
-            # tell if a particular query returns any results.
-            if qs.extra(select={'a': 1}).values('a').order_by():
+            if qs.exists():
                 if len(unique_check) == 1:
                     self._errors[unique_check[0]] = ErrorList([self.unique_error_message(unique_check)])
                 else:
@@ -354,9 +352,7 @@ class BaseModelForm(BaseForm):
             if self.instance.pk is not None:
                 qs = qs.exclude(pk=self.instance.pk)
 
-            # This cute trick with extra/values is the most efficient way to
-            # tell if a particular query returns any results.
-            if qs.extra(select={'a': 1}).values('a').order_by():
+            if qs.exists():
                 self._errors[field] = ErrorList([
                     self.date_error_message(lookup_type, field, unique_for)
                 ])