Fixed regression caused by the fix in :ticket:`3807` (version 1.1.0)
where we ensured that the tablename was qualified in the WHERE clause
of the DO UPDATE portion of PostgreSQL's ON CONFLICT, however you
*cannot* put the table name in the  WHERE clause in the actual ON
CONFLICT itself.   This was an incorrect assumption, so that portion
of the change in :ticket:`3807` is rolled back.

Change-Id: I442d8629496a8e405b54711cfcf487761810ae8a
Fixes: #3846
Fixes: #3807

Options like uselist and backref can be determined from
within _register_attribute based on parent_property
given; move this logic inside so that individual strategies
have less responsibility.  Also don't require that
_register_attribute consider the "strategy" itself
at all; it would be better if we could no longer require
that Joined/Subquery/etc loaders call upon the "lazy" strategy
in order to initialize attribute instrumentation and
this could be done more generically.

Fixes long-standing bug where the "noload" relationship loading
strategy would cause backrefs and/or back_populates options to be
ignored.   There is concern that some application that uses
"noload" might be surprised at a back-populating attribute
appearing suddenly, which may have side effects.  However,
"noload" itself must be extremely seldom used since as a
strategy, it already disables loading, population of attributes
is the only behavior that is even supported, so that this issue has existed
for at least through 0.7 four years ago without ever being
reported indicates extremely low use of this option.

Change-Id: Icffb9c83ac5782b76ce882ed1df4361a1efbfba3
Fixes: #3845

MySQL's native ENUM type supports any non-valid value being sent, and
in response will return a blank string.  A hardcoded rule to check for
"is returning the blank string" has been added to the  MySQL
implementation for ENUM so that this blank string is returned to the
application rather than being rejected as a non-valid value.  Note that
if your MySQL enum is linking values to objects, you still get the
blank string back.

Change-Id: I61f85c20293a48b0c11a31f2a19f6756c206bd20
Fixes: #3841

Fixed regression caused by :ticket:`2677` whereby calling
:meth:`.Session.delete` on an object that was already flushed as
deleted in that session would fail to set up the object in the
identity map (or reject the object), causing flush errors as the
object were in a state not accommodated by the unit of work.
The pre-1.1 behavior in this case has been restored, which is that
the object is put back into the identity map so that the DELETE
statement will be attempted again, which emits a warning that the number
of expected rows was not matched (unless the row were restored outside
of the session).

Change-Id: I9a8871f82cb1ebe67a7ad54d888d5ee835a9a40a
Fixes: #3839

_ColumnEntity didn't seem to have .mapper present, which
due to the way _mapper_zero() worked didn't tend to come
across it.   With :ticket:`3608` _mapper_zero() has
been simplified so make sure this is now present.
Also ensure that _select_from_entity is an entity and
not a mapped class, though this does not seem to matter
at the moment.

Fixes: #3836

Change-Id: Id6dae8e700269b97de3b01562edee95ac1e01f80

Postgresql table reflection will ensure that the
:paramref:`.Column.autoincrement` flag is set to False when reflecting
a primary key column that is not of an :class:`.Integer` datatype,
even if the default is related to an integer-generating sequence.
This can happen if a column is created as SERIAL and the datatype
is changed.  The autoincrement flag can only be True if the datatype
is of integer affinity in the 1.1 series.

This bug is related to a test failure in downstream sqlalchemy_migrate.

Change-Id: I40260e47e1927a1ac940538408983c943bbdba28
Fixes: #3835

Fixed bug involving new value translation and validation feature
in :class:`.Enum` whereby using the enum object in a string
concatenation would maintain the :class:`.Enum` type as the type
of the expression overall, producing missing lookups.  A string
concatenation against an :class:`.Enum`-typed column now uses
:class:`.String` as the datatype of the expression itself.

Change-Id: Id402054e3ef008e0250c740dbb7e1c80f339fe78
Fixes: #3833

Ensure TypeDecorator delegates _set_parent_with_dispatch as well as
_set_parent to itself as well as its impl, as the TypeDecorator
class itself may have an active SchemaType implementation as well.

Fixed regression which occurred as a side effect of :ticket:`2919`,
which in the less typical case of a user-defined
:class:`.TypeDecorator` that was also itself an instance of
:class:`.SchemaType` (rather than the implementation being such)
would cause the column attachment events to be skipped for the
type itself.

Change-Id: I0afb498fd91ab7d948e4439e7323a89eafcce0bc
Fixes: #3832

Changed the naming convention used when generating bound parameters
for a multi-VALUES insert statement, so that the numbered parameter
names don't conflict with the anonymized parameters of a WHERE clause,
as is now common in a PostgreSQL ON CONFLICT construct.

Change-Id: I3188d100fe4d322a47d344d6a63d3e40b915f228
Fixes: #3828

The Boolean and Enum types both place SchemaType second in the
inheritance hierarchy.  In the case of Enum, this works
out that the copy() method is called from the base TypeEngine
which fails to transfer _create_events.   The test suite
doesn't seem to work with the inhertance hierarchy set up like
this as the event listeners don't work out, the _on_metadata_create
and _on_table_create hooks cause the production of an adapted type
which then adds event listeners that cause deque changed while
iteration.  It's not clear why Enum /Boolean don't have this problem.
But in any case it seems like the class mechanics for these types
remains fragile and would benefit from yet another refactor someday.

Change-Id: Ib641a5d2321b00f58bbe98dd0c5e789374db32b2
Fixes: #3827