diff options
Diffstat (limited to 'lib/sqlalchemy/ext/declarative/api.py')
| -rw-r--r-- | lib/sqlalchemy/ext/declarative/api.py | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/lib/sqlalchemy/ext/declarative/api.py b/lib/sqlalchemy/ext/declarative/api.py index ee13a90f3..0773922d0 100644 --- a/lib/sqlalchemy/ext/declarative/api.py +++ b/lib/sqlalchemy/ext/declarative/api.py @@ -199,11 +199,24 @@ class declared_attr(interfaces._MappedAttribute, property): or MapperProperty-based declared attribute should be configured distinctly per mapped subclass, within a mapped-inheritance scenario. - .. note:: + .. warning:: - The :attr:`.declared_attr.cascading` modifier **only** applies - to the use of :class:`.declared_attr` on declarative mixin classes - and ``__abstract__`` classes. + The :attr:`.declared_attr.cascading` modifier has several + limitations: + + * The flag **only** applies to the use of :class:`.declared_attr` + on declarative mixin classes and ``__abstract__`` classes; it + currently has no effect when used on a mapped class directly. + + * The flag **only** applies to normally-named attributes, e.g. + not any special underscore attributes such as ``__tablename__``. + On these attributes it has **no** effect. + + * The flag currently **does not allow further overrides** down + the class hierarchy; if a subclass tries to override the + attribute, a warning is emitted and the overridden attribute + is skipped. This is a limitation that it is hoped will be + resolved at some point. Below, both MyClass as well as MySubClass will have a distinct ``id`` Column object established:: |