- The primary :class:`.Mapper` of a :class:`.Query` is now passed to the

- The primary :class:`.Mapper` of a :class:`.Query` is now passed to the
:meth:`.Session.get_bind` method when calling upon
:meth:`.Query.count`, :meth:`.Query.update`, :meth:`.Query.delete`,
as well as queries against mapped columns,
:obj:`.column_property` objects, and SQL functions and expressions
derived from mapped columns.   This allows sessions that rely upon
either customized :meth:`.Session.get_bind` schemes or "bound" metadata
to work in all relevant cases.
fixes #3227 fixes #3242 fixes #1326