implemented right before the release of 0.9.3 affected the case where
a UNION contained nested joins in it.   "Join rewriting" is a feature
with a wide range of possibilities and is the first intricate
"SQL rewriting" feature we've introduced in years, so we're sort of
going through a lot of iterations with it (not unlike eager loading
back in the 0.2/0.3 series, polymorphic loading in 0.4/0.5). We should
be there soon so thanks for bearing with us :).
fixes #2969   re: #2967
- solve the issue of join rewriting inspecting various types of
from objects without using isinstance(), by adding some new
underscored inspection flags to the FromClause hierarchy.

on the columns clause of the SELECT statement if the targets were
aliased tables, as opposed to individual aliased columns.

would fail to be rewritten properly, such as when the exists is
mapped to a column_property in an intricate nested-join scenario. #2967

Have also considered linking column.label() to the "column" itself being
in the result map but this reveals some naming collision problems (that
also seem to be very poorly tested...).   This should be as far as
we want to go right now with [ticket:2932].

constructs would fail if the bind were constructed with a callable,
rather than a direct value.  This prevented ORM expressions
from being rendered with the "literal_binds" compiler flag.

such as "literal binds" into a CAST expression.
- Fixed bug whereby binary type would fail in some cases
if used with a "test" dialect, such as a DefaultDialect or other
dialect with no DBAPI.
- Fixed bug where "literal binds" wouldn't work with a bound parameter
that's a binary type.  A similar, but different, issue is fixed
in 0.8.

MySQL, to correctly render the SET clause among multiple columns
with the same name across tables.  This also changes the name used for
the bound parameter in the SET clause to "<tablename>_<colname>" for
the non-primary table only; as this parameter is typically specified
using the :class:`.Column` object directly this should not have an
impact on applications.   The fix takes effect for both
:meth:`.Table.update` as well as :meth:`.Query.update` in the ORM.
[ticket:2912]

yet the column is not the "auto increment" column, either because
it has a foreign key constraint or ``autoincrement=False`` set,
would attempt to fire the Sequence on INSERT for backends that don't
support sequences, when presented with an INSERT missing the primary
key value.  This would take place on non-sequence backends like
SQLite, MySQL. [ticket:2896]