with a :class:`.SchemaType` implementation, typically :class:`.Enum`
or :class:`.Boolean` with regards to ensuring that the per-table
events are propagated from the implementation type to the outer type.
These events are used
to ensure that the constraints or Postgresql types (e.g. ENUM)
are correctly created (and possibly dropped) along with the parent
table.
fixes #2919

all DBs now support ON UPDATE CASCADE other than Oracle, there's no need
to try to reimplement more functionality here and users should be encouraged
to forego natural PKs unless their target platform supports them.
references #2666

ARRAY type, references #3132

``<function> WITHIN GROUP (ORDER BY <criteria>)``, using the
method :class:`.FunctionElement.within_group`.  A series of common
set-aggregate functions with return types derived from the set have
been added. This includes functions like :class:`.percentile_cont`,
:class:`.dense_rank` and others.
fixes #1370
- make sure we use func.name for all _literal_as_binds in functions.py
so we get consistent naming behavior for parameters.

which automatically returns an :class:`.Array` of the correct type
and supports index / slice operations.   As arrays are only
supported on Postgresql at the moment, only actually works on
Postgresql. fixes #3132

- any/all work for Array as well as subqueries, accepted by MySQL
- Postgresql ARRAY now subclasses Array
- fixes #3516

could encounter empty history, and where a column keyed to an alternate
attribute name would fail to track properly.  Fixes courtesy
Alex Fraser.

or mapped instances into contexts where they are interpreted as
SQL bound parameters; a new exception is raised for this.
fixes #3321