Fixed bug where a :class:`.Sequence` would be dropped explicitly before any
:class:`.Table` that refers to it, which breaks in the case when the
sequence is also involved in a server-side default for that table, when
using :meth:`.MetaData.drop_all`.   The step which processes sequences
to be dropped via non server-side column default functions is now invoked
after the table itself is dropped.

Change-Id: I185f2cc76d2011ad4dd3ba9bde5d8aef0ec335ae
Fixes: #4300

Fixed a reference leak issue where the values of the parameter dictionary
used in a statement execution would remain referenced by the "compiled
cache", as a result of storing the key view used by Python 3 dictionary
keys().  Pull request courtesy Olivier Grisel.

Change-Id: Icfb0f38111a165780f6dd3e4e3382a03df79ce26
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/441

Fixed regression caused in 1.2.3 due to fix from :ticket:`4181` where
the changes to the event system involving :class:`.Engine` and
:class:`.OptionEngine` did not accommodate for event removals, which
would raise an ``AttributeError`` when invoked at the class
level.

Change-Id: I1c9083829d74dd710716d28b0eaca4fa15e86313
Fixes: #4190

Fixed bug where events associated with an :class:`Engine`
at the class level would be doubled when the
:meth:`.Engine.execution_options` method were used.  To
achieve this, the semi-private class :class:`.OptionEngine`
no longer accepts events directly at the class level
and will raise an error; the class only propagates class-level
events from its parent :class:`.Engine`.   Instance-level
events continue to work as before.

The comments present another way of doing this where we would
copy events from the parent engine at option time rather
than linking the event listeners, but this would be a behavioral
change that adding new events to the parent engine would not
take effect for an already-created OptionEngine.

Change-Id: Id128516f54103fbad9a2210d6571eceb59c8b0cb
Fixes: #4181

Fixed bug in cx_Oracle disconnect detection, used by pre_ping and other
features, where an error could be raised as DatabaseError which includes a
numeric error code; previously we weren't checking in this case for a
disconnect code.

Change-Id: I359bb5ede25a4726ea632b81af83c6391f405ae1
Fixes: #4182

Change-Id: Ida0d01ae9bcc0573b86e24fddea620a38c962822

Fixed bug where a SQL-oriented Python-side column default could fail to
be executed properly upon INSERT in the "pre-execute" codepath, if the
SQL itself were an untyped expression, such as plain text.  The "pre-
execute" codepath is fairly uncommon however can apply to non-integer
primary key columns with SQL defaults when RETURNING is not used.

Tests exist here to ensure typing is applied to
a typed expression for default, but in the case of
an untyped SQL value, we know the type from the column,
so apply this.

Change-Id: I5d8b391611c137b9f700115a50a2bf5b30abfe94
Fixes: #3923

Added an exception handler that will warn for the "cause" exception on
Py2K when the "autorollback" feature of :class:`.Connection` itself
raises an exception. In Py3K, the two exceptions are naturally reported
by the interpreter as one occurring during the handling of the other.
This is continuing with the series of changes for rollback failure
handling that were last visited as part of :ticket:`2696` in 1.0.12.

Change-Id: I600ba455a14ebaea27c6189889181f97c632f179
Fixes: #3946

Fixed bug where in the unusual case of passing a
:class:`.Compiled` object directly to :meth:`.Connection.execute`,
the dialect with which the :class:`.Compiled` object were generated
was not consulted for the paramstyle of the string statement, instead
assuming it would match the dialect-level paramstyle, causing
mismatches to occur.

Change-Id: I114e4db2183fbb75bb7c0b0641f5a161855696ee
Fixes: #3938