Detect no params w/ manual version_id counter and set to itself

Fixed bug where programmatic version_id counter in conjunction with
joined table inheritance would fail if the version_id counter
were not actually incremented and no other values on the base table
were modified, as the UPDATE would have an empty SET clause.  Since
programmatic version_id where version counter is not incremented
is a documented use case, this specific condition is now detected
and the UPDATE now sets the version_id value to itself, so that
concurrency checks still take place.

Change-Id: I80e385bffeed4851cc20131cbe983c173a46f655
Fixes: #3996

1 files changed, 62 insertions, 0 deletions

diff --git a/test/orm/test_versioning.py b/test/orm/test_versioning.py
index 40b373097..4c339d3bb 100644
--- a/test/orm/test_versioning.py
+++ b/test/orm/test_versioning.py
@@ -1284,3 +1284,65 @@ class ManualVersionTest(fixtures.MappedTest):
         sess.commit()
 
         eq_(a1.vid, 2)
+
+
+class ManualInheritanceVersionTest(fixtures.MappedTest):
+    run_define_tables = 'each'
+    __backend__ = True
+
+    @classmethod
+    def define_tables(cls, metadata):
+        Table(
+            "a", metadata,
+            Column(
+                'id', Integer, primary_key=True,
+                test_needs_autoincrement=True),
+            Column('data', String(30)),
+            Column('vid', Integer, nullable=False)
+        )
+
+        Table(
+            "b", metadata,
+            Column(
+                'id', Integer, ForeignKey('a.id'), primary_key=True),
+            Column('b_data', String(30)),
+        )
+
+    @classmethod
+    def setup_classes(cls):
+        class A(cls.Basic):
+            pass
+
+        class B(A):
+            pass
+
+    @classmethod
+    def setup_mappers(cls):
+        mapper(
+            cls.classes.A, cls.tables.a, version_id_col=cls.tables.a.c.vid,
+            version_id_generator=False)
+
+        mapper(
+            cls.classes.B, cls.tables.b, inherits=cls.classes.A)
+
+    def test_no_increment(self):
+        sess = Session()
+        b1 = self.classes.B()
+
+        b1.vid = 1
+        b1.data = 'd1'
+        sess.add(b1)
+        sess.commit()
+
+        # change col on subtable only without
+        # incrementing version id
+        b1.b_data = 'bd2'
+        sess.commit()
+
+        eq_(b1.vid, 1)
+
+        b1.b_data = 'd3'
+        b1.vid = 2
+        sess.commit()
+
+        eq_(b1.vid, 2)