Ensure attribute keys used for bulk update pk set

Fixed bug in :meth:`.Session.bulk_update_mappings` where an alternate-named
primary key attribute would not track properly into the UPDATE statement.

Change-Id: I33e9140f45827772768fa548adcfeb4dbfc2208d
Fixes: #3849

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 60848097c..87f2a24b0 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -2020,6 +2020,16 @@ class Mapper(InspectionAttr):
         )
 
     @_memoized_configured_property
+    def _pk_attr_keys_by_table(self):
+        return dict(
+            (
+                table,
+                frozenset([self._columntoproperty[col].key for col in pks])
+            )
+            for table, pks in self._pks_by_table.items()
+        )
+
+    @_memoized_configured_property
     def _server_default_cols(self):
         return dict(
             (