Fixed #6785 -- Made QuerySet.get() fetch a limited number of rows.

Thanks Patryk Zawadzki.

django/db/models/query.py

@@ -19,6 +19,10 @@ from django.utils.functional import partition
 from django.utils import six
 from django.utils import timezone
 
+# The maximum number (one less than the max to be precise) of results to fetch
+# in a get() query
+MAX_GET_RESULTS = 20
+
 # The maximum number of items to display in a QuerySet.__repr__
 REPR_OUTPUT_SIZE = 20
 
@@ -297,6 +301,7 @@ class QuerySet(object):
         clone = self.filter(*args, **kwargs)
         if self.query.can_filter():
             clone = clone.order_by()
+        clone = clone[:MAX_GET_RESULTS + 1]
         num = len(clone)
         if num == 1:
             return clone._result_cache[0]
@@ -305,8 +310,11 @@ class QuerySet(object):
                 "%s matching query does not exist." %
                 self.model._meta.object_name)
         raise self.model.MultipleObjectsReturned(
-            "get() returned more than one %s -- it returned %s!" %
-            (self.model._meta.object_name, num))
+            "get() returned more than one %s -- it returned %s!" % (
+                self.model._meta.object_name,
+                num if num <= MAX_GET_RESULTS else 'more than %s' % MAX_GET_RESULTS
+            )
+        )
 
     def create(self, **kwargs):
         """

tests/basic/tests.py

@@ -6,7 +6,7 @@ import threading
 from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.db.models.fields import Field, FieldDoesNotExist
-from django.db.models.query import QuerySet, EmptyQuerySet, ValuesListQuerySet
+from django.db.models.query import QuerySet, EmptyQuerySet, ValuesListQuerySet, MAX_GET_RESULTS
 from django.test import TestCase, TransactionTestCase, skipIfDBFeature, skipUnlessDBFeature
 from django.utils import six
 from django.utils.translation import ugettext_lazy
@@ -155,6 +155,28 @@ class ModelTest(TestCase):
             pub_date__month=7,
         )
 
+    def test_multiple_objects_max_num_fetched(self):
+        """
+        #6785 - get() should fetch a limited number of results.
+        """
+        Article.objects.bulk_create(
+            Article(headline='Area %s' % i, pub_date=datetime(2005, 7, 28))
+            for i in range(MAX_GET_RESULTS)
+        )
+        six.assertRaisesRegex(self,
+            MultipleObjectsReturned,
+            "get\(\) returned more than one Article -- it returned %d!" % MAX_GET_RESULTS,
+            Article.objects.get,
+            headline__startswith='Area',
+        )
+        Article.objects.create(headline='Area %s' % MAX_GET_RESULTS, pub_date=datetime(2005, 7, 28))
+        six.assertRaisesRegex(self,
+            MultipleObjectsReturned,
+            "get\(\) returned more than one Article -- it returned more than %d!" % MAX_GET_RESULTS,
+            Article.objects.get,
+            headline__startswith='Area',
+        )
+
     def test_object_creation(self):
         # Create an Article.
         a = Article(