Fixed #35996 -- Fixed database serialization crash when serializing a many-to-many field that had a prefetch.

1 files changed, 8 insertions, 7 deletions

diff --git a/django/core/serializers/python.py b/django/core/serializers/python.py
index 57edebbb70..807d4b3977 100644
--- a/django/core/serializers/python.py
+++ b/django/core/serializers/python.py
@@ -74,7 +74,11 @@ class Serializer(base.Serializer):
                     return value.natural_key()
 
                 def queryset_iterator(obj, field):
-                    return getattr(obj, field.name).iterator()
+                    attr = getattr(obj, field.name)
+                    chunk_size = (
+                        2000 if getattr(attr, "prefetch_cache_name", None) else None
+                    )
+                    return attr.iterator(chunk_size)
 
             else:
 
@@ -82,12 +86,9 @@ class Serializer(base.Serializer):
                     return self._value_from_field(value, value._meta.pk)
 
                 def queryset_iterator(obj, field):
-                    return (
-                        getattr(obj, field.name)
-                        .select_related(None)
-                        .only("pk")
-                        .iterator()
-                    )
+                    query_set = getattr(obj, field.name).select_related(None).only("pk")
+                    chunk_size = 2000 if query_set._prefetch_related_lookups else None
+                    return query_set.iterator(chunk_size=chunk_size)
 
             m2m_iter = getattr(obj, "_prefetched_objects_cache", {}).get(
                 field.name,