[5.2.x] Fixed #36416 -- Made QuerySet.in_bulk() account for composite pks in id_list.

Backport of 26313bc21932d0d3af278ab387549d63b1f64575 from main.

1 files changed, 3 insertions, 1 deletions

diff --git a/django/db/models/query.py b/django/db/models/query.py
index bb5462037c..1270141619 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -1149,7 +1149,9 @@ class QuerySet(AltersData):
             if not id_list:
                 return {}
             filter_key = "{}__in".format(field_name)
-            batch_size = connections[self.db].features.max_query_params
+            max_params = connections[self.db].features.max_query_params or 0
+            num_fields = len(opts.pk_fields) if field_name == "pk" else 1
+            batch_size = max_params // num_fields
             id_list = tuple(id_list)
             # If the database has a limit on the number of query parameters
             # (e.g. SQLite), retrieve objects in batches if necessary.