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

Backport of 6afa6818fcf25665bbf61f0921c8c8c6fa8f223e from master

1 files changed, 4 insertions, 2 deletions

diff --git a/django/forms/models.py b/django/forms/models.py
index 2137e9f4a6..1036e9b288 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -1092,15 +1092,17 @@ class ModelChoiceIterator(object):
     def __iter__(self):
         if self.field.empty_label is not None:
             yield ("", self.field.empty_label)
+        method = 'all' if self.queryset._prefetch_related_lookups else 'iterator'
+        queryset = getattr(self.queryset, method)
         if self.field.cache_choices:
             if self.field.choice_cache is None:
                 self.field.choice_cache = [
-                    self.choice(obj) for obj in self.queryset.iterator()
+                    self.choice(obj) for obj in queryset()
                 ]
             for choice in self.field.choice_cache:
                 yield choice
         else:
-            for obj in self.queryset.iterator():
+            for obj in queryset():
                 yield self.choice(obj)
 
     def __len__(self):