- xmin example requires a server default declaration to function

correctly

Change-Id: I1cc50da6fe1c0eeef1d00201b45d998daddfd8ac

diff --git a/doc/build/orm/versioning.rst b/doc/build/orm/versioning.rst
index a2f1635c903c176e1ac28bbd6c00e58228bfcdf0..563185604d042b882db62b53b3b809ed74daf8b8 100644 (file)
--- a/doc/build/orm/versioning.rst
+++ b/doc/build/orm/versioning.rst
@@ -142,12 +142,14 @@ which provides UPDATE versioning.  We can make use
 of the PostgreSQL ``xmin`` column to version our ``User``
 class as follows::
 
+    from sqlalchemy import FetchedValue
+
     class User(Base):
         __tablename__ = 'user'
 
         id = Column(Integer, primary_key=True)
         name = Column(String(50), nullable=False)
-        xmin = Column("xmin", Integer, system=True)
+        xmin = Column("xmin", Integer, system=True, server_default=FetchedValue())
 
         __mapper_args__ = {
             'version_id_col': xmin,