Class AliasedClass

lib/sqlalchemy/orm/util.py:635–834

r"""Represents an "aliased" form of a mapped class for usage with Query. The ORM equivalent of a :func:`~sqlalchemy.sql.expression.alias` construct, this object mimics the mapped class using a ``__getattr__`` scheme and maintains a reference to a real :class:`~sqlalchemy.sql.express

class AliasedClass(
    inspection.Inspectable["AliasedInsp[_O]"], ORMColumnsClauseRole[_O]
):
    r"""Represents an "aliased" form of a mapped class for usage with Query.

    The ORM equivalent of a :func:`~sqlalchemy.sql.expression.alias`
    construct, this object mimics the mapped class using a
    ``__getattr__`` scheme and maintains a reference to a
    real :class:`~sqlalchemy.sql.expression.Alias` object.

    A primary purpose of :class:`.AliasedClass` is to serve as an alternate
    within a SQL statement generated by the ORM, such that an existing
    mapped entity can be used in multiple contexts.   A simple example::

        # find all pairs of users with the same name
        user_alias = aliased(User)
        session.query(User, user_alias).join(
            (user_alias, User.id > user_alias.id)
        ).filter(User.name == user_alias.name)

    :class:`.AliasedClass` is also capable of mapping an existing mapped
    class to an entirely new selectable, provided this selectable is column-
    compatible with the existing mapped selectable, and it can also be
    configured in a mapping as the target of a :func:`_orm.relationship`.
    See the links below for examples.

    The :class:`.AliasedClass` object is constructed typically using the
    :func:`_orm.aliased` function.   It also is produced with additional
    configuration when using the :func:`_orm.with_polymorphic` function.

    The resulting object is an instance of :class:`.AliasedClass`.
    This object implements an attribute scheme which produces the
    same attribute and method interface as the original mapped
    class, allowing :class:`.AliasedClass` to be compatible
    with any attribute technique which works on the original class,
    including hybrid attributes (see :ref:`hybrids_toplevel`).

    The :class:`.AliasedClass` can be inspected for its underlying
    :class:`_orm.Mapper`, aliased selectable, and other information
    using :func:`_sa.inspect`::

        from sqlalchemy import inspect

        my_alias = aliased(MyClass)
        insp = inspect(my_alias)

    The resulting inspection object is an instance of :class:`.AliasedInsp`.


    .. seealso::

        :func:`.aliased`

        :func:`.with_polymorphic`

        :ref:`relationship_aliased_class`

        :ref:`relationship_to_window_function`