when loading mapped entities.   The function overhead of applying
a per-object deferred callable to an instance at load time was
significantly higher than that of just loading the data from the row
(note that ``defer()`` is meant to reduce DB/network overhead, not
necessarily function call count); the function call overhead is now
less than that of loading data from the column in all cases.  There
is also a reduction in the number of "lazy callable" objects created
per load from N (total deferred values in the result) to 1 (total
number of deferred cols).
[ticket:2778]

to worry about it too much

labeled columns when apply_labels() is used; this mode
produces a SELECT where each column is labeled as in
<tablename>_<columnname>, to remove column name collisions
for a multiple table select.   The fix is that if two labels
collide when combined with the table name, i.e.
"foo.bar_id" and "foo_bar.id", anonymous aliasing will be
applied to one of the dupes.  This allows the ORM to handle
both columns independently; previously, 0.7
would in some cases silently emit a second SELECT for the
column that was "duped", and in 0.8 an ambiguous column error
would be emitted.   The "keys" applied to the .c. collection
of the select() will also be deduped, so that the "column
being replaced" warning will no longer emit for any select()
that specifies use_labels, though the dupe key will be given
an anonymous label which isn't generally user-friendly.
[ticket:2702]

whereas the other do_rollback_twophase(), savepoint etc. work with
:class:`.Connection`.  the context on these are different as twophase/savepoint
are available at the :class:`.Connection` level, whereas commit/rollback are needed
at a lower level as well.  Rename the argument to "dbapi_connection" when the conneciton
is in fact the DBAPI interface.
- start thinking about being able to track "autocommit" vs. "commit", but not sure
we have a need for this yet.
- have Pool call out to a Dialect for all rollback/commit/close operations now.  Pool
no longer calls DBAPI methods directly.  May use this for a workaround for [ticket:2611]
- add a new Pool event reset() to allow the pool's reset of the connection to be intercepted.
- remove methods in Informix dialect which appear to be hardcoding some isolation
settings on new Transaction only; the isolation API should be implemented for Informix.
also removed "flag" for transaction commit/rollback being not available; this should
be based on server/DBAPI version and we will need someone with test access in order
to help determine how this should work