Modified UOW so that a Row Switch scenario will not attempt to update the Primary Key.

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 0dc346532..1e257f9a4 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -1318,6 +1318,9 @@ class Mapper(object):
                                         params[col._label] = prop.get_col_value(col, history.deleted[0])
                                     else:
                                         # row switch logic can reach us here
+                                        # remove the pk from the update params so the update doesn't
+                                        # attempt to include the pk in the update statement
+                                        del params[col.key]
                                         params[col._label] = prop.get_col_value(col, history.added[0])
                                 hasdata = True
                             elif col in pks: