[1.9.x] Fixed #25496 -- Made ModelChoiceField respect prefetch_related().

Backport of 6afa6818fcf25665bbf61f0921c8c8c6fa8f223e from master

1 files changed, 3 insertions, 1 deletions

diff --git a/django/forms/models.py b/django/forms/models.py
index ac8bd1c860..938535bf6a 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -1102,7 +1102,9 @@ class ModelChoiceIterator(object):
     def __iter__(self):
         if self.field.empty_label is not None:
             yield ("", self.field.empty_label)
-        for obj in self.queryset.iterator():
+        # Can't use iterator() when queryset uses prefetch_related()
+        method = 'all' if self.queryset._prefetch_related_lookups else 'iterator'
+        for obj in getattr(self.queryset, method)():
             yield self.choice(obj)
 
     def __len__(self):