joins of :ticket:`3222` takes place inappropriately
for a JOIN along explicit join criteria with a single-inheritance
subclass that does not make use of any discriminator, resulting
in an additional "AND NULL" clause.
fixes #3462

it to prevent excess memory usage with yield_per

to suit #3451 exclude these columns from the "params"
dictionary in the first place, revises pr github:181

Suppose you have a model class with a primary key.

Base = declarative_base()
class User(Base):
  id = Column(BigInteger, primary_key=True)
  name = Column(String)

Previously, running
`bulk_update_mappings(User, {'id': 1, 'name': 'hello'})`
would emit the following:

```UPDATE users SET id=1, name='hello' WHERE id=1```

This is contrary to the stated behaviour, where primary keys are omitted
from the SET clause. Furthermore, this behaviour is harmful, as it
can cause the db engine to lock over-aggresively (at least in Postgres).

With this change, the emitted SQL is:

```UPDATE users SET name='hello' WHERE id=1```

objects that made use of the ``__clause_element__()`` method and
returned an object that was an ORM-mapped
:class:`.InstrumentedAttribute` and not explicitly a
:class:`.ColumnElement` would fail to be correctly
handled when passed as an expression to :meth:`.Session.query`.
The logic in 0.9 happened to succeed on this, so this use case is now
supported. fixes #3448

as a result of the bugfix for :ticket:`3167`,
where attribute and validation events are no longer
called within the flush process.  The mutable
extension was relying upon this behavior in the case where a column
level Python-side default were responsible for generating the new value
on INSERT or UPDATE, or when a value were fetched from the RETURNING
clause for "eager defaults" mode.  The new value would not be subject
to any event when populated and the mutable extension could not
establish proper coercion or history listening.  A new event
:meth:`.InstanceEvents.refresh_flush` is added which the mutable
extension now makes use of for this use case.
fixes #3427
- Added new event :meth:`.InstanceEvents.refresh_flush`, invoked
when an INSERT or UPDATE level default value fetched via RETURNING
or Python-side default is invoked within the flush process.  This
is to provide a hook that is no longer present as a result of
:ticket:`3167`, where attribute and validation events are no longer
called within the flush process.
- Added a new semi-public method to :class:`.MutableBase`
:meth:`.MutableBase._get_listen_keys`.  Overriding this method
is needed in the case where a :class:`.MutableBase` subclass needs
events to propagate for attribute keys other than the key to which
the mutable type is associated with, when intercepting the
:meth:`.InstanceEvents.refresh` or
:meth:`.InstanceEvents.refresh_flush` events.  The current example of
this is composites using :class:`.MutableComposite`.

primaryjoin of a relationship involved comparison to an unhashable
type such as an HSTORE, lazy loads would fail due to a hash-oriented
check on the statement parameters, modified in 1.0 as a result of
:ticket:`3061` to use hashing and modified in :ticket:`3368`
to occur in cases more common than "load on pending".
The values are now checked for the ``__hash__`` attribute beforehand.
fixes #3416

to protect against unknown conditions when splicing inner joins
together within joined eager loads with ``innerjoin=True``; if
some of the joins use a "secondary" table, the assertion needs to
unwrap further joins in order to pass.
fixes #3412

as failing with the new 'entity' key value added to
:attr:`.Query.column_descriptions`, the logic to discover the "from"
clause is again reworked to accommodate columns from aliased classes,
as well as to report the correct value for the "aliased" flag in these
cases.
fixes #3409