diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py index 099831fe..fe1285c6 100644 --- a/mongoengine/queryset/base.py +++ b/mongoengine/queryset/base.py @@ -157,7 +157,13 @@ class BaseQuerySet(object): def _bool(self): """ Avoid to open all records in an if stmt """ - return False if self.first() is None else True + queryset = self.clone() + queryset._ordering = [] + try: + queryset[0] + return True + except IndexError: + return False def __nonzero__(self): """ Same behaviour in Py2 """ diff --git a/tests/queryset/queryset.py b/tests/queryset/queryset.py index f6adaf39..65f7255b 100644 --- a/tests/queryset/queryset.py +++ b/tests/queryset/queryset.py @@ -3837,6 +3837,59 @@ class QuerySetTest(unittest.TestCase): if not queryset: raise AssertionError('There is data, cursor must return True') + def test_bool_performance(self): + + class Person(Document): + name = StringField() + + Person.drop_collection() + for i in xrange(100): + Person(name="No: %s" % i).save() + + with query_counter() as q: + if Person.objects: + pass + + self.assertEqual(q, 1) + op = q.db.system.profile.find({"ns": + {"$ne": "%s.system.indexes" % q.db.name}})[0] + + self.assertEqual(op['nreturned'], 1) + + + def test_bool_with_ordering(self): + + class Person(Document): + name = StringField() + + Person.drop_collection() + Person(name="Test").save() + + qs = Person.objects.order_by('name') + + with query_counter() as q: + + if qs: + pass + + op = q.db.system.profile.find({"ns": + {"$ne": "%s.system.indexes" % q.db.name}})[0] + + self.assertFalse('$orderby' in op['query'], + 'BaseQuerySet cannot use orderby in if stmt') + + with query_counter() as p: + + for x in qs: + pass + + op = p.db.system.profile.find({"ns": + {"$ne": "%s.system.indexes" % q.db.name}})[0] + + + self.assertTrue('$orderby' in op['query'], + 'BaseQuerySet cannot remove orderby in for loop') + if __name__ == '__main__': unittest.main()