Fixed #18087 -- Prevented date-based generic views from loading entire tables in memory when pagination is enabled.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17893 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/views/generic/dates.py

@@ -190,11 +190,16 @@ class BaseDateListView(MultipleObjectMixin, DateMixin, View):
         date_field = self.get_date_field()
         allow_future = self.get_allow_future()
         allow_empty = self.get_allow_empty()
+        paginate_by = self.get_paginate_by(qs)
 
         if not allow_future:
             qs = qs.filter(**{'%s__lte' % date_field: timezone.now()})
 
-        if not allow_empty and not qs:
+        if not allow_empty:
+            # When pagination is enabled, it's better to do a cheap query
+            # than to load the unpaginated queryset in memory.
+            is_empty = not bool(qs) if paginate_by is None else not qs.exists()
+            if is_empty:
                 raise Http404(_(u"No %(verbose_name_plural)s available") % {
                         'verbose_name_plural': force_unicode(qs.model._meta.verbose_name_plural)
                 })

tests/regressiontests/generic_views/dates.py

@@ -78,6 +78,15 @@ class ArchiveIndexViewTests(TestCase):
         self.assertEqual(res.context['page_obj'].number, 2)
         self.assertEqual(list(res.context['latest']), list(Book.objects.all()[10:20]))
 
+    def test_paginated_archive_view_does_not_load_entire_table(self):
+        # Regression test for #18087
+        self._make_books(20, base_date=datetime.date.today())
+        # 1 query for years list + 1 query for books
+        with self.assertNumQueries(2):
+            self.client.get('/dates/books/')
+        # same as above + 1 query to test if books exist
+        with self.assertNumQueries(3):
+            self.client.get('/dates/books/paginated/')
 
 class YearArchiveViewTests(TestCase):
     fixtures = ['generic-views-test-data.json']