Sometimes it might be useful to have 'native' autocommit support
provided by a DB API driver rather than rely on SQLAlchemy autocommit
emulation.

many-to-one ``!= None`` would fail if the source were an aliased
class, or if the query needed to apply special aliasing to the
expression due to aliased joins or polymorphic querying; also fixed
bug in the case where comparing a many-to-one to an object state
would fail if the query needed to apply special aliasing
due to aliased joins or polymorphic querying.
fixes #3310

an ``after_rollback()`` handler for a :class:`.Session` incorrectly
adds state to that :class:`.Session` within the handler, and the task
to warn and remove this state (established by :ticket:`2389`) attempts
to proceed.
fixes #3309

asserting.

in callcounts specific to the "expiration" of objects, as in
the "auto expire" feature of :meth:`.Session.commit` and
for :meth:`.Session.expire_all`, as well as in the "cleanup" step
which occurs when object states are garbage collected.
fixes #3307

as :class:`.TypeDecorator` objects.

dialect on a type where MySQL does not support CAST; MySQL only
supports CAST on a subset of datatypes.   SQLAlchemy has for a long
time just omitted the CAST for unsupported types in the case of
MySQL.  While we don't want to change this now, we emit a warning
to show that it's taken place.   A warning is also emitted when
a CAST is used with an older MySQL version (< 4) that doesn't support
CAST at all, it's skipped in this case as well.
fixes #3237

when using the :paramref:`.Column.server_default` parameter, will
now be rendered using the "inline" compiler, so that they are rendered
as-is, rather than as bound parameters.
fixes #3087