of ``entity`` to the :attr:`.Query.column_descriptions` accessor
would fail if the target entity was produced from a core selectable
such as a :class:`.Table` or :class:`.CTE` object.
fixes #3403  references #3320

which is now consumed by Alembic migrations as of 0.7.6.  User-defined
types can implement this method to assist in the comparison of
a type against one reflected from the database.

set to a SQL expression for an UPDATE, and the SQL expression when
compared to the previous value of the attribute would produce a SQL
comparison other than ``==`` or ``!=``, the exception "Boolean value
of this clause is not defined" would raise.   The fix ensures that
the unit of work will not interpret the SQL expression in this way.
fixes #3402

on an relationship->scalar non-object attribute comparison would fail,
e.g.
``filter(Parent.some_collection_to_attribute.any(Child.attr == 'foo'))``
fixes #3397

a label that overlapped another label that is not truncated; this
because the length threshhold for truncation was greater than
the portion of the label that remains after truncation.  These
two values have now been made the same; label_length - 6.
The effect here is that shorter column labels will be "truncated"
where they would not have been truncated before.
fixes #3396

now skip textual label references when copying ORDER BY elements
to the joined-eager-load subquery, as we can't know that these
expressions are compatible with this placement;  either because
they are meant for text(), or because they refer to label names
already stated and aren't bound to a table. fixes #3392

passed as a keyword argument to the :meth:`.DDLEvents.before_create`,
:meth:`.DDLEvents.after_create`, :meth:`.DDLEvents.before_drop`, and
:meth:`.DDLEvents.after_drop` events would no longer be a list
of tables, but instead a list of tuples which contained a second
entry with foreign keys to be added or dropped.  As the ``tables``
collection, while documented as not necessarily stable, has come
to be relied upon, this change is considered a regression.
Additionally, in some cases for "drop", this collection would
be an iterator that would cause the operation to fail if
prematurely iterated.   The collection is now a list of table
objects in all cases and test coverage for the format of this
collection is now added.
fixes #3391

event where its invocation was moved to be after the class manager's
instrumentation of the class, which is the opposite of what the
documentation for the event explicitly states.  The rationale for the
switch was due to Declarative taking the step of setting up
the full "instrumentation manager" for a class before it was mapped
for the purpose of the new ``@declared_attr`` features
described in :ref:`feature_3150`, but the change was also made
against the classical use of :func:`.mapper` for consistency.
However, SQLSoup relies upon the instrumentation event happening
before any instrumentation under classical mapping.
The behavior is reverted in the case of classical and declarative
mapping, the latter implemented by using a simple memoization
without using class manager.
fixes #3388