diff options
Diffstat (limited to 'lib/sqlalchemy/orm/mapper.py')
| -rw-r--r-- | lib/sqlalchemy/orm/mapper.py | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py index cd2fa62d5..8b4a140f2 100644 --- a/lib/sqlalchemy/orm/mapper.py +++ b/lib/sqlalchemy/orm/mapper.py @@ -360,11 +360,13 @@ class Mapper(_InspectionAttr): """ polymorphic_on = None - """The :class:`.Column` specified as the ``polymorphic_on`` column + """The :class:`.Column` or SQL expression specified as the + ``polymorphic_on`` argument for this :class:`.Mapper`, within an inheritance scenario. - This attribute may also be of other types besides :class:`.Column` - in a future SQLAlchemy release. + This attribute is normally a :class:`.Column` instance but + may also be an expression, such as one derived from + :func:`.cast`. This is a *read only* attribute determined during mapper construction. Behavior is undefined if directly modified. |