Pin sqlalchemy to latest version 1.3.5

[pyup-bot]

This PR pins SQLAlchemy to the latest release 1.3.5.

Changelog

1.3.5

:released: June 17, 2019

 .. change::
     :tags: bug, mysql
     :tickets: 4715

     Fixed bug where MySQL ON DUPLICATE KEY UPDATE would not accommodate setting
     a column to the value NULL.  Pull request courtesy Lukáš Banič.

 .. change::
     :tags: bug, orm
     :tickets: 4723

     Fixed a series of related bugs regarding joined table inheritance more than
     two levels deep, in conjunction with modification to primary key values,
     where those primary key columns are also linked together in a foreign key
     relationship as is typical for joined table inheritance.  The intermediary
     table in a  three-level inheritance hierachy will now get its UPDATE if
     only the primary key value has changed and passive_updates=False (e.g.
     foreign key constraints not being enforced), whereas before it would be
     skipped; similarly, with passive_updates=True (e.g. ON UPDATE  CASCADE in
     effect), the third-level table will not receive an UPDATE statement as was
     the case earlier which would fail since CASCADE already modified it.   In a
     related issue, a relationship linked to a three-level inheritance hierarchy
     on the primary key of an intermediary table of a joined-inheritance
     hierarchy will also correctly have its foreign key column updated when the
     parent object's primary key is modified, even if that parent object is a
     subclass of the linked parent class, whereas before these classes would
     not be counted.

 .. change::
     :tags: bug, orm
     :tickets: 4729

     Fixed bug where the :attr:`.Mapper.all_orm_descriptors` accessor would
     return an entry for the :class:`.Mapper` itself under the declarative
     ``__mapper___`` key, when this is not a descriptor.  The ``.is_attribute``
     flag that's present on all :class:`.InspectionAttr` objects is now
     consulted, which has also been modified to be ``True`` for an association
     proxy, as it was erroneously set to False for this object.

 .. change::
     :tags: bug, orm
     :tickets: 4704

     Fixed regression in :meth:`.Query.join` where the ``aliased=True`` flag
     would not properly apply clause adaptation to filter criteria, if a
     previous join were made to the same entity.  This is because the adapters
     were placed in the wrong order.   The order has been reversed so that the
     adapter for the most recent ``aliased=True`` call takes precedence as was
     the case in 1.2 and earlier.  This broke the "elementtree" examples among
     other things.

 .. change::
     :tags: bug, orm, py3k
     :tickets: 4674

     Replaced the Python compatbility routines for ``getfullargspec()`` with a
     fully vendored version from Python 3.3.  Originally, Python was emitting
     deprecation warnings for this function in Python 3.8 alphas.  While this
     change was reverted, it was observed that Python 3 implementations for
     ``getfullargspec()`` are an order of magnitude slower as of the 3.4 series
     where it was rewritten against ``Signature``.  While Python plans to
     improve upon this situation, SQLAlchemy projects for now are using a simple
     replacement to avoid any future issues.

 .. change::
     :tags: bug, orm
     :tickets: 4694

     Reworked the attribute mechanics used by :class:`.AliasedClass` to no
     longer rely upon calling ``__getattribute__`` on the MRO of the wrapped
     class, and to instead resolve the attribute normally on the wrapped class
     using getattr(), and then unwrap/adapt that.  This allows a greater range
     of attribute styles on the mapped class including special ``__getattr__()``
     schemes; but it also makes the code simpler and more resilient in general.

 .. change::
     :tags: usecase, postgresql
     :tickets: 4717

     Added support for column sorting flags when reflecting indexes for
     PostgreSQL, including ASC, DESC, NULLSFIRST, NULLSLAST.  Also adds this
     facility to the reflection system in general which can be applied to other
     dialects in future releases.  Pull request courtesy Eli Collins.

 .. change::
     :tags: bug, postgresql
     :tickets: 4701

     Fixed bug where PostgreSQL dialect could not correctly reflect an ENUM
     datatype that has no members, returning a list with ``None`` for the
     ``get_enums()`` call and raising a TypeError when reflecting a column which
     has such a datatype.   The inspection now returns an empty list.

 .. change::
     :tags: bug, sql
     :tickets: 4730

     Fixed a series of quoting issues which all stemmed from the concept of the
     :func:`.literal_column` construct, which when being "proxied" through a
     subquery to be referred towards by a label that matches its text, the label
     would not have quoting rules applied to it, even if the string in the
     :class:`.Label` were set up as a :class:`.quoted_name` construct.  Not
     applying quoting to the text of the :class:`.Label` is a bug because this
     text is strictly a SQL identifier name and not a SQL expression, and the
     string should not have quotes embedded into it already unlike the
     :func:`.literal_column` which it may be applied towards.   The existing
     behavior of a non-labeled :func:`.literal_column` being propagated as is on
     the outside of a subquery is maintained in order to help with manual
     quoting schemes, although it's not clear if valid SQL can be generated for
     such a construct in any case.

.. changelog::

1.3.4

:released: May 27, 2019

 .. change::
     :tags: feature, mssql
     :tickets: 4657

     Added support for SQL Server filtered indexes, via the ``mssql_where``
     parameter which works similarly to that of the ``postgresql_where`` index
     function in the PostgreSQL dialect.

     .. seealso::

         :ref:`mssql_index_where`

 .. change::
    :tags: bug, misc
    :tickets: 4625

    Removed errant "sqla_nose.py" symbol from MANIFEST.in which created an
    undesirable warning message.

 .. change::
     :tags: bug, sql
     :tickets: 4653

     Fixed that the :class:`.GenericFunction` class was inadvertently
     registering itself as one of the named functions.  Pull request courtesy
     Adrien Berchet.

 .. change::
    :tags: bug, engine, postgresql
    :tickets: 4663

    Moved the "rollback" which occurs during dialect initialization so that it
    occurs after additional dialect-specific initialize steps, in particular
    those of the psycopg2 dialect which would inadvertently leave transactional
    state on the first new connection, which could interfere with some
    psycopg2-specific APIs which require that no transaction is started.  Pull
    request courtesy Matthew Wilkes.


 .. change::
     :tags: bug, orm
     :tickets: 4695

     Fixed issue where the :paramref:`.AttributeEvents.active_history` flag
     would not be set for an event listener that propgated to a subclass via the
     :paramref:`.AttributeEvents.propagate` flag.   This bug has been present
     for the full span of the :class:`.AttributeEvents` system.


 .. change::
     :tags: bug, orm
     :tickets: 4690

     Fixed regression where new association proxy system was still not proxying
     hybrid attributes when they made use of the ``hybrid_property.expression``
     decorator to return an alternate SQL expression, or when the hybrid
     returned an arbitrary :class:`.PropComparator`, at the expression level.
     This involved futher generalization of the heuristics used to detect the
     type of object being proxied at the level of :class:`.QueryableAttribute`,
     to better detect if the descriptor ultimately serves mapped classes or
     column expressions.

 .. change::
     :tags: bug, orm
     :tickets: 4686

     Applied the mapper "configure mutex" against the declarative class mapping
     process, to guard against the race which can occur if mappers are used
     while dynamic module import schemes are still in the process of configuring
     mappers for related classes.  This does not guard against all possible race
     conditions, such as if the concurrent import has not yet encountered the
     dependent classes as of yet, however it guards against as much as possible
     within the SQLAlchemy declarative process.

 .. change::
     :tags: bug, mssql
     :tickets: 4680

     Added error code 20047 to "is_disconnect" for pymssql.  Pull request
     courtesy Jon Schuff.


 .. change::
    :tags: bug, postgresql, orm
    :tickets: 4661

    Fixed an issue where the "number of rows matched" warning would emit even if
    the dialect reported "supports_sane_multi_rowcount=False", as is the case
    for psycogp2 with ``use_batch_mode=True`` and others.


 .. change::
     :tags: bug, sql
     :tickets: 4618

     Fixed issue where double negation of a boolean column wouldn't reset
     the "NOT" operator.

 .. change::
     :tags: mysql, bug
     :tickets: 4650

     Added support for DROP CHECK constraint which is required by MySQL 8.0.16
     to drop a CHECK constraint; MariaDB supports plain DROP CONSTRAINT.  The
     logic distinguishes between the two syntaxes by checking the server version
     string for MariaDB presence.    Alembic migrations has already worked
     around this issue by implementing its own DROP for MySQL / MariaDB CHECK
     constraints, however this change implements it straight in Core so that its
     available for general use.   Pull request courtesy Hannes Hansen.

 .. change::
    :tags: bug, orm
    :tickets: 4647

    A warning is now emitted for the case where a transient object is being
    merged into the session with :meth:`.Session.merge` when that object is
    already transient in the :class:`.Session`.   This warns for the case where
    the object would normally be double-inserted.


 .. change::
     :tags: bug, orm
     :tickets: 4676

     Fixed regression in new relationship m2o comparison logic first introduced
     at :ref:`change_4359` when comparing to an attribute that is persisted as
     NULL and is in an un-fetched state in the mapped instance.  Since the
     attribute has no explicit default, it needs to default to NULL when
     accessed in a persistent setting.


 .. change::
     :tags: bug, sql
     :tickets: 4569

     The :class:`.GenericFunction` namespace is being migrated so that function
     names are looked up in a case-insensitive manner, as SQL  functions do not
     collide on case sensitive differences nor is this something which would
     occur with user-defined functions or stored procedures.   Lookups for
     functions declared with :class:`.GenericFunction` now use a case
     insensitive scheme,  however a deprecation case is supported which allows
     two or more :class:`.GenericFunction` objects with the same name of
     different cases to exist, which will cause case sensitive lookups to occur
     for that particular name, while emitting a warning at function registration
     time.  Thanks to Adrien Berchet for a lot of work on this complicated
     feature.


.. changelog::

1.3.3

:released: April 15, 2019

 .. change::
     :tags: bug, postgresql
     :tickets: 4601

     Fixed regression from release 1.3.2 caused by :ticket:`4562` where a URL
     that contained only a query string and no hostname, such as for the
     purposes of specifying a service file with connection information, would no
     longer be propagated to psycopg2 properly.   The change in :ticket:`4562`
     has been adjusted to further suit psycopg2's exact requirements, which is
     that if there are any connection parameters whatsoever, the "dsn" parameter
     is no longer required, so in this case the query string parameters are
     passed alone.

 .. change::
    :tags: bug, pool
    :tickets: 4585

    Fixed behavioral regression as a result of deprecating the "use_threadlocal"
    flag for :class:`.Pool`, where the :class:`.SingletonThreadPool` no longer
    makes use of this option which causes the "rollback on return" logic to take
    place when the same :class:`.Engine` is used multiple times in the context
    of a transaction to connect or implicitly execute, thereby cancelling the
    transaction.   While this is not the recommended way to work with engines
    and connections, it is nonetheless a confusing behavioral change as when
    using :class:`.SingletonThreadPool`, the transaction should stay open
    regardless of what else is done with the same engine in the same thread.
    The ``use_threadlocal`` flag remains deprecated however the
    :class:`.SingletonThreadPool` now implements its own version of the same
    logic.


 .. change::
    :tags: bug, orm
    :tickets: 4584

    Fixed 1.3 regression in new "ambiguous FROMs" query logic introduced in
    :ref:`change_4365` where a :class:`.Query` that explicitly places an entity
    in the FROM clause with :meth:`.Query.select_from` and also joins to it
    using :meth:`.Query.join` would later cause an "ambiguous FROM" error if
    that entity were used in additional joins, as the entity appears twice in
    the "from" list of the :class:`.Query`.  The fix resolves this ambiguity by
    folding the standalone entity into the join that it's already a part of in
    the same way that ultimately happens when the SELECT statement is rendered.

 .. change::
     :tags: bug, ext
     :tickets: 4603

     Fixed bug where using ``copy.copy()`` or ``copy.deepcopy()`` on
     :class:`.MutableList` would cause the items within the list to be
     duplicated, due to an inconsistency in how Python pickle and copy both make
     use of ``__getstate__()`` and ``__setstate__()`` regarding lists.  In order
     to resolve, a ``__reduce_ex__`` method had to be added to
     :class:`.MutableList`.  In order to maintain backwards compatibility with
     existing pickles based on ``__getstate__()``, the ``__setstate__()`` method
     remains as well; the test suite asserts that pickles made against the old
     version of the class can still be deserialized by the pickle module.

 .. change::
    :tags: bug, orm
    :tickets: 4606

    Adjusted the :meth:`.Query.filter_by` method to not call :func:`.and()`
    internally against multiple criteria, instead passing it off to
    :meth:`.Query.filter` as a series of criteria, instead of a single criteria.
    This allows :meth:`.Query.filter_by` to defer to :meth:`.Query.filter`'s
    treatment of variable numbers of clauses, including the case where the list
    is empty.  In this case, the :class:`.Query` object will not have a
    ``.whereclause``, which allows subsequent "no whereclause" methods like
    :meth:`.Query.select_from` to behave consistently.

 .. change::
    :tags: bug, mssql
    :tickets: 4587

    Fixed issue in SQL Server dialect where if a bound parameter were present in
    an ORDER BY expression that would ultimately not be rendered in the SQL
    Server version of the statement, the parameters would still be part of the
    execution parameters, leading to DBAPI-level errors.  Pull request courtesy
    Matt Lewellyn.

.. changelog::

1.3.2

:released: April 2, 2019

 .. change::
    :tags: bug, documentation, sql
    :tickets: 4580

    Thanks to :ref:`change_3981`, we no longer need to rely on recipes that
    subclass dialect-specific types directly, :class:`.TypeDecorator` can now
    handle all cases.   Additionally, the above change made it slightly less
    likely that a direct subclass of a base SQLAlchemy type would work as
    expected, which could be misleading.  Documentation has been updated to use
    :class:`.TypeDecorator` for these examples including the PostgreSQL
    "ArrayOfEnum" example datatype and direct support for the "subclass a type
    directly" has been removed.

 .. change::
    :tags: bug, postgresql
    :tickets: 4550

    Modified the :paramref:`.Select.with_for_update.of` parameter so that if a
    join or other composed selectable is passed, the individual :class:`.Table`
    objects will be filtered from it, allowing one to pass a join() object to
    the parameter, as occurs normally when using joined table inheritance with
    the ORM.  Pull request courtesy Raymond Lu.


 .. change::
     :tags: feature, postgresql
     :tickets: 4562

     Added support for parameter-less connection URLs for the psycopg2 dialect,
     meaning, the URL can be passed to :func:`.create_engine` as
     ``"postgresql+psycopg2://"`` with no additional arguments to indicate an
     empty DSN passed to libpq, which indicates to connect to "localhost" with
     no username, password, or database given. Pull request courtesy Julian
     Mehnle.

 .. change::
    :tags: bug, orm, ext
    :tickets: 4574, 4573

    Restored instance-level support for plain Python descriptors, e.g.
    ``property`` objects, in conjunction with association proxies, in that if
    the proxied object is not within ORM scope at all, it gets classified as
    "ambiguous" but is proxed directly.  For class level access, a basic class
    level``__get__()`` now returns the
    :class:`.AmbiguousAssociationProxyInstance` directly, rather than raising
    its exception, which is the closest approximation to the previous behavior
    that returned the :class:`.AssociationProxy` itself that's possible.  Also
    improved the stringification of these objects to be more descriptive of
    current state.

 .. change::
    :tags: bug, orm
    :tickets: 4537

    Fixed bug where use of :func:`.with_polymorphic` or other aliased construct
    would not properly adapt when the aliased target were used as the
    :meth:`.Select.correlate_except` target of a subquery used inside of a
    :func:`.column_property`. This required a fix to the clause adaption
    mechanics to properly handle a selectable that shows up in the "correlate
    except" list, in a similar manner as which occurs for selectables that show
    up in the "correlate" list.  This is ultimately a fairly fundamental bug
    that has lasted for a long time but it is hard to come across it.


 .. change::
    :tags: bug, orm
    :tickets: 4566

    Fixed regression where a new error message that was supposed to raise when
    attempting to link a relationship option to an AliasedClass without using
    :meth:`.PropComparator.of_type` would instead raise an ``AttributeError``.
    Note that in 1.3, it is no longer valid to create an option path from a
    plain mapper relationship to an :class:`.AliasedClass` without using
    :meth:`.PropComparator.of_type`.

.. changelog::

1.3.1

:released: March 9, 2019

 .. change::
    :tags: bug, mssql
    :tickets: 4525

    Fixed regression in SQL Server reflection due to :ticket:`4393` where the
    removal of open-ended ``**kw`` from the :class:`.Float` datatype caused
    reflection of this type to fail due to a "scale" argument being passed.

 .. change::
    :tags: bug, orm, ext
    :tickets: 4522

    Fixed regression where an association proxy linked to a synonym would no
    longer work, both at instance level and at class level.

.. changelog::

1.3.0

:released: March 4, 2019

 .. change::
    :tags: feature, schema
    :tickets: 4517

    Added new parameters :paramref:`.Table.resolve_fks` and
    :paramref:`.MetaData.reflect.resolve_fks` which when set to False will
    disable the automatic reflection of related tables encountered in
    :class:`.ForeignKey` objects, which can both reduce SQL overhead for omitted
    tables as well as avoid tables that can't be reflected for database-specific
    reasons.  Two :class:`.Table` objects present in the same :class:`.MetaData`
    collection can still refer to each other even if the reflection of the two
    tables occurred separately.


 .. change::
    :tags: feature, orm
    :tickets: 4316

    The :meth:`.Query.get` method can now accept a dictionary of attribute keys
    and values as a means of indicating the primary key value to load; is
    particularly useful for composite primary keys.  Pull request courtesy
    Sanjana S.

 .. change::
    :tags: feature, orm
    :tickets: 3133

    A SQL expression can now be assigned to a primary key attribute for an ORM
    flush in the same manner as ordinary attributes as described in
    :ref:`flush_embedded_sql_expressions` where the expression will be evaulated
    and then returned to the ORM using RETURNING, or in the case of pysqlite,
    works using the cursor.lastrowid attribute.Requires either a database that
    supports RETURNING (e.g. Postgresql, Oracle, SQL Server) or pysqlite.

 .. change::
    :tags: bug, sql
    :tickets: 4509

    The :class:`.Alias` class and related subclasses :class:`.CTE`,
    :class:`.Lateral` and :class:`.TableSample` have been reworked so that it is
    not possible for a user to construct the objects directly.  These constructs
    require that the standalone construction function or selectable-bound method
    be used to instantiate new objects.


 .. change::
    :tags: feature, engine
    :tickets: 4500

    Revised the formatting for :class:`.StatementError` when stringified. Each
    error detail is broken up over multiple newlines instead of spaced out on a
    single line.  Additionally, the SQL representation now stringifies the SQL
    statement rather than using ``repr()``, so that newlines are rendered as is.
    Pull request courtesy Nate Clark.

    .. seealso::

         :ref:`change_4500`

.. changelog::

1.3.0b3

:released: March 4, 2019
 :released: February 8, 2019

 .. change::
    :tags: bug, ext
    :tickets: 2642

    Implemented a more comprehensive assignment operation (e.g. "bulk replace")
    when using association proxy with sets or dictionaries.  Fixes the problem
    of redundant proxy objects being created to replace the old ones, which
    leads to excessive events and SQL and in the case of unique constraints
    will cause the flush to fail.

    .. seealso::

       :ref:`change_2642`

 .. change::
     :tags: bug, postgresql
     :tickets: 4473

     Fixed issue where using an uppercase name for an index type (e.g. GIST,
     BTREE, etc. ) or an EXCLUDE constraint would treat it as an identifier to
     be quoted, rather than rendering it as is. The new behavior converts these
     types to lowercase and ensures they contain only valid SQL characters.

 .. change::
    :tags: bug, orm
    :tickets: 4469

    Improved the behavior of :func:`.orm.with_polymorphic` in conjunction with
    loader options, in particular wildcard operations as well as
    :func:`.orm.load_only`.  The polymorphic object will be more accurately
    targeted so that column-level options on the entity will correctly take
    effect.The issue is a continuation of the same kinds of things fixed in
    :ticket:`4468`.


 .. change::
    :tags: bug, sql
    :tickets: 4481

    Fully removed the behavior of strings passed directly as components of a
    :func:`.select` or :class:`.Query` object being coerced to :func:`.text`
    constructs automatically; the warning that has been emitted is now an
    ArgumentError or in the case of order_by() / group_by() a CompileError.
    This has emitted a warning since version 1.0 however its presence continues
    to create concerns for the potential of mis-use of this behavior.

    Note that public CVEs have been posted for order_by() / group_by() which
    are resolved by this commit:  CVE-2019-7164  CVE-2019-7548


    .. seealso::

     :ref:`change_4481`

 .. change::
    :tags: bug, sql
    :tickets: 4467

    Quoting is applied to :class:`.Function` names, those which are usually but
    not necessarily generated from the :attr:`.sql.func` construct,  at compile
    time if they contain illegal characters, such as spaces or punctuation. The
    names are as before treated as case insensitive however, meaning if the
    names contain uppercase or mixed case characters, that alone does not
    trigger quoting. The case insensitivity is currently maintained for
    backwards compatibility.


 .. change::
    :tags: bug, sql
    :tickets: 4481

    Added "SQL phrase validation" to key DDL phrases that are accepted as plain
    strings, including :paramref:`.ForeignKeyConstraint.on_delete`,
    :paramref:`.ForeignKeyConstraint.on_update`,
    :paramref:`.ExcludeConstraint.using`,
    :paramref:`.ForeignKeyConstraint.initially`, for areas where a series of SQL
    keywords only are expected.Any non-space characters that suggest the phrase
    would need to be quoted will raise a :class:`.CompileError`.   This change
    is related to the series of changes committed as part of :ticket:`4481`.

 .. change::
    :tags: bug, orm, declarative
    :tickets: 4470

    Added some helper exceptions that invoke when a mapping based on
    :class:`.AbstractConcreteBase`, :class:`.DeferredReflection`, or
    :class:`.AutoMap` is used before the mapping is ready to be used, which
    contain descriptive information on the class, rather than falling through
    into other failure modes that are less informative.


 .. change::
    :tags: change, tests
    :tickets: 4460

    The test system has removed support for Nose, which is unmaintained for
    several years and is producing warnings under Python 3. The test suite is
    currently standardized on Pytest.  Pull request courtesy Parth Shandilya.

.. changelog::

1.3.0b2

:released: March 4, 2019
 :released: January 25, 2019

 .. change::
    :tags: bug, ext
    :tickets: 4401

    Fixed a regression in 1.3.0b1 caused by :ticket:`3423` where association
    proxy objects that access an attribute that's only present on a polymorphic
    subclass would raise an ``AttributeError`` even though the actual instance
    being accessed was an instance of that subclass.

 .. change::
     :tags: bug, orm
     :tickets: 1103

     Fixed long-standing issue where duplicate collection members would cause a
     backref to delete the association between the member and its parent object
     when one of the duplicates were removed, as occurs as a side effect of
     swapping two objects in one statement.

     .. seealso::

         :ref:`change_1103`

 .. change::
    :tags: bug, mssql
    :tickets: 4442

    The ``literal_processor`` for the :class:`.Unicode` and
    :class:`.UnicodeText` datatypes now render an ``N`` character in front of
    the literal string expression as required by SQL Server for Unicode string
    values rendered in SQL expressions.

 .. change::
    :tags: feature, orm
    :tickets: 4423

    Implemented a new feature whereby the :class:`.AliasedClass` construct can
    now be used as the target of a :func:`.relationship`.  This allows the
    concept of "non primary mappers" to no longer be necessary, as the
    :class:`.AliasedClass` is much easier to configure and automatically inherits
    all the relationships of the mapped class, as well as preserves the
    ability for loader options to work normally.

    .. seealso::

         :ref:`change_4423`

 .. change::
    :tags: bug, orm
    :tickets: 4373

    Extended the fix first made as part of :ticket:`3287`, where a loader option
    made against a subclass using a wildcard would extend itself to include
    application of the wildcard to attributes on the super classes as well, to a
    "bound" loader option as well, e.g. in an expression like
    ``Load(SomeSubClass).load_only('foo')``.  Columns that are part of the
    parent class of ``SomeSubClass`` will also be excluded in the same way as if
    the unbound option ``load_only('foo')`` were used.

 .. change::
    :tags: bug, orm
    :tickets: 4433

    Improved error messages emitted by the ORM in the area of loader option
    traversal.  This includes early detection of mis-matched loader strategies
    along with a clearer explanation why these strategies don't match.


 .. change::
    :tags: change, orm
    :tickets: 4412

    Added a new function :func:`.close_all_sessions` which takes
    over the task of the :meth:`.Session.close_all` method, which
    is now deprecated as this is confusing as a classmethod.
    Pull request courtesy Augustin Trancart.

 .. change::
    :tags: feature, orm
    :tickets: 4397

    Added new :meth:`.MapperEvents.before_mapper_configured` event.   This
    event complements the other "configure" stage mapper events with a per
    mapper event that receives each :class:`.Mapper` right before its
    configure step, and additionally may be used to prevent or delay the
    configuration of specific :class:`.Mapper` objects using a new
    return value :attr:`.orm.interfaces.EXT_SKIP`.  See the
    documentation link for an example.

    .. seealso::

       :meth:`.MapperEvents.before_mapper_configured`



 .. change::
    :tags: bug, orm

    The "remove" event for collections is now called before the item is removed
    in the case of the ``collection.remove()`` method, as is consistent with the
    behavior for most other forms of collection item removal (such as
    ``__delitem__``, replacement under ``__setitem__``).  For ``pop()`` methods,
    the remove event still fires after the operation.

 .. change::
     :tags: bug, orm declarative
     :tickets: 4372

    Added a ``__clause_element__()`` method to :class:`.ColumnProperty` which
    can allow the usage of a not-fully-declared column or deferred attribute in
    a declarative mapped class slightly more friendly when it's used in a
    constraint or other column-oriented scenario within the class declaration,
    though this still can't work in open-ended expressions; prefer to call the
    :attr:`.ColumnProperty.expression` attribute if receiving ``TypeError``.

 .. change::
    :tags: bug, orm, engine
    :tickets: 4464

    Added accessors for execution options to Core and ORM, via
    :meth:`.Query.get_execution_options`,
    :meth:`.Connection.get_execution_options`,
    :meth:`.Engine.get_execution_options`, and
    :meth:`.Executable.get_execution_options`.  PR courtesy Daniel Lister.

 .. change::
    :tags: bug, orm
    :tickets: 4446

    Fixed issue in association proxy due to :ticket:`3423` which caused the use
    of custom :class:`.PropComparator` objects with hybrid attribites, such as
    the one demonstrated in  the ``dictlike-polymorphic`` example to not
    function within an association proxy.  The strictness that was added in
    :ticket:`3423` has been relaxed, and additional logic to accomodate for
    an association proxy that links to a custom hybrid have been added.

 .. change::
    :tags: change, general
    :tickets: 4393

    A large change throughout the library has ensured that all objects,
    parameters, and behaviors which have been noted as deprecated or legacy now
    emit ``DeprecationWarning`` warnings when invoked.As the Python 3
    interpreter now defaults to displaying deprecation warnings, as well as that
    modern test suites based on tools like tox and pytest tend to display
    deprecation warnings, this change should make it easier to note what API
    features are obsolete. A major rationale for this change is so that long-
    deprecated features that nonetheless still see continue to see real world
    use can  finally be removed in the near future; the biggest example of this
    are the :class:`.SessionExtension` and :class:`.MapperExtension` classes as
    well as a handful of other pre-event extension hooks, which have been
    deprecated since version 0.7 but still remain in the library.  Another is
    that several major longstanding behaviors are to be deprecated as well,
    including the threadlocal engine strategy, the convert_unicode flag, and non
    primary mappers.

    .. seealso::

       :ref:`change_4393_general`


 .. change::
    :tags: change, engine
    :tickets: 4393

    The "threadlocal" engine strategy which has been a legacy feature of
    SQLAlchemy since around version 0.2 is now deprecated, along with the
    :paramref:`.Pool.threadlocal` parameter of :class:`.Pool` which has no
    effect in most modern use cases.

    .. seealso::

       :ref:`change_4393_threadlocal`

 .. change::
    :tags: change, sql
    :tickets: 4393

    The :paramref:`.create_engine.convert_unicode` and
    :paramref:`.String.convert_unicode` parameters have been deprecated.  These
    parameters were built back when most Python DBAPIs had little to no support
    for Python Unicode objects, and SQLAlchemy needed to take on the very
    complex task of marshalling data and SQL strings between Unicode and
    bytestrings throughout the system in a performant way.  Thanks to Python 3,
    DBAPIs were compelled to adapt to Unicode-aware APIs and today all DBAPIs
    supported by SQLAlchemy support Unicode natively, including on Python 2,
    allowing this long-lived and very complicated feature to finally be (mostly)
    removed.  There are still of course a few Python 2 edge cases where
    SQLAlchemy has to deal with Unicode however these are handled automatically;
    in modern use, there should be no need for end-user interaction with these
    flags.

    .. seealso::

       :ref:`change_4393_convertunicode`

 .. change::
    :tags: bug, orm
    :tickets: 3777

    Implemented the ``.get_history()`` method, which also implies availability
    of :attr:`.AttributeState.history`, for :func:`.synonym` attributes.
    Previously, trying to access attribute history via a synonym would raise an
    ``AttributeError``.

 .. change::
    :tags: feature, engine
    :tickets: 3689

    Added public accessor :meth:`.QueuePool.timeout` that returns the configured
    timeout for a :class:`.QueuePool` object.  Pull request courtesy Irina Delamare.

 .. change::
    :tags: feature, sql
    :tickets: 4386

    Amended the :class:`.AnsiFunction` class, the base of common SQL
    functions like ``CURRENT_TIMESTAMP``, to accept positional arguments
    like a regular ad-hoc function.  This to suit the case that many of
    these functions on specific backends accept arguments such as
    "fractional seconds" precision and such.  If the function is created
    with arguments, it renders the parenthesis and the arguments.  If
    no arguments are present, the compiler generates the non-parenthesized form.

.. changelog::

1.3.0b1

:released: March 4, 2019
 :released: November 16, 2018

 .. change::
    :tags: bug, ext
    :tickets: 3423

    Reworked :class:`.AssociationProxy` to store state that's specific to a
    parent class in a separate object, so that a single
    :class:`.AssocationProxy` can serve for multiple parent classes, as is
    intrinsic to inheritance, without any ambiguity in the state returned by it.
    A new method :meth:`.AssociationProxy.for_class` is added to allow
    inspection of class-specific state.

    .. seealso::

         :ref:`change_3423`


 .. change::
    :tags: bug, oracle
    :tickets: 4369

    Updated the parameters that can be sent to the cx_Oracle DBAPI to both allow
    for all current parameters as well as for future parameters not added yet.
    In addition, removed unused parameters that were deprecated in version 1.2,
    and additionally we are now defaulting "threaded" to False.

    .. seealso::

       :ref:`change_4369`

 .. change::
     :tags: bug, oracle
     :tickets: 4242

     The Oracle dialect will no longer use the NCHAR/NCLOB datatypes
     represent generic unicode strings or clob fields in conjunction with
     :class:`.Unicode` and :class:`.UnicodeText` unless the flag
     ``use_nchar_for_unicode=True`` is passed to :func:`.create_engine` -
     this includes CREATE TABLE behavior as well as ``setinputsizes()`` for
     bound parameters.   On the read side, automatic Unicode conversion under
     Python 2 has been added to CHAR/VARCHAR/CLOB result rows, to match the
     behavior of cx_Oracle under Python 3.  In order to mitigate the performance
     hit under Python 2, SQLAlchemy's very performant (when C extensions
     are built) native Unicode handlers are used under Python 2.

     .. seealso::

         :ref:`change_4242`

 .. change::
     :tags: bug, orm
     :tickets: 3844

     Fixed issue regarding passive_deletes="all", where the foreign key
     attribute of an object is maintained with its value even after the object
     is removed from its parent collection.  Previously, the unit of work would
     set this to NULL even though passive_deletes indicated it should not be
     modified.

     .. seealso::

         :ref:`change_3844`

 .. change::
     :tags: bug, ext
     :tickets: 4268

     The long-standing behavior of the association proxy collection maintaining
     only a weak reference to the parent object is reverted; the proxy will now
     maintain a strong reference to the parent for as long as the proxy
     collection itself is also in memory, eliminating the "stale association
     proxy" error. This change is being made on an experimental basis to see if
     any use cases arise where it causes side effects.

     .. seealso::

         :ref:`change_4268`


 .. change::
     :tags: bug, sql
     :tickets: 4302

     Added "like" based operators as "comparison" operators, including
     :meth:`.ColumnOperators.startswith` :meth:`.ColumnOperators.endswith`
     :meth:`.ColumnOperators.ilike` :meth:`.ColumnOperators.notilike` among many
     others, so that all of these operators can be the basis for an ORM
     "primaryjoin" condition.


 .. change::
     :tags: feature, sqlite
     :tickets: 3850

     Added support for SQLite's json functionality via the new
     SQLite implementation for :class:`.types.JSON`, :class:`.sqlite.JSON`.
     The name used for the type is ``JSON``, following an example found at
     SQLite's own documentation. Pull request courtesy Ilja Everilä.

     .. seealso::

         :ref:`change_3850`

 .. change::
    :tags: feature, engine

    Added new "lifo" mode to :class:`.QueuePool`, typically enabled by setting
    the flag :paramref:`.create_engine.pool_use_lifo` to True.   "lifo" mode
    means the same connection just checked in will be the first to be checked
    out again, allowing excess connections to be cleaned up from the server
    side during periods of the pool being only partially utilized.  Pull request
    courtesy Taem Park.

    .. seealso::

       :ref:`change_pr467`

 .. change::
    :tags: bug, orm
    :tickets: 4359

    Improved the behavior of a relationship-bound many-to-one object expression
    such that the retrieval of column values on the related object are now
    resilient against the object being detached from its parent
    :class:`.Session`, even if the attribute has been expired.  New features
    within the :class:`.InstanceState` are used to memoize the last known value
    of a particular column attribute before its expired, so that the expression
    can still evaluate when the object is detached and expired at the same
    time.  Error conditions are also improved using modern attribute state
    features to produce more specific messages as needed.

    .. seealso::

         :ref:`change_4359`

 .. change::
     :tags: feature, mysql
     :tickets: 4219

     Support added for the "WITH PARSER" syntax of CREATE FULLTEXT INDEX
     in MySQL, using the ``mysql_with_parser`` keyword argument.  Reflection
     is also supported, which accommodates MySQL's special comment format
     for reporting on this option as well.  Additionally, the "FULLTEXT" and
     "SPATIAL" index prefixes are now reflected back into the ``mysql_prefix``
     index option.



 .. change::
     :tags: bug, orm, mysql, postgresql
     :tickets: 4246

     The ORM now doubles the "FOR UPDATE" clause within the subquery that
     renders in conjunction with joined eager loading in some cases, as it has
     been observed that MySQL does not lock the rows from a subquery.   This
     means the query renders with two FOR UPDATE clauses; note that on some
     backends such as Oracle, FOR UPDATE clauses on subqueries are silently
     ignored since they are unnecessary.  Additionally, in the case of the "OF"
     clause used primarily with PostgreSQL, the FOR UPDATE is rendered only on
     the inner subquery when this is used so that the selectable can be targeted
     to the table within the SELECT statement.

     .. seealso::

         :ref:`change_4246`

 .. change::
     :tags: feature, mssql
     :tickets: 4158

     Added ``fast_executemany=True`` parameter to the SQL Server pyodbc dialect,
     which enables use of pyodbc's new performance feature of the same name
     when using Microsoft ODBC drivers.

     .. seealso::

         :ref:`change_4158`

 .. change::
     :tags: bug, ext
     :tickets: 4308

     Fixed multiple issues regarding de-association of scalar objects with the
     association proxy.  ``del`` now works, and additionally a new flag
     :paramref:`.AssociationProxy.cascade_scalar_deletes` is added, which when
     set to True indicates that setting a scalar attribute to ``None`` or
     deleting via ``del`` will also set the source association to ``None``.

     .. seealso::

         :ref:`change_4308`


 .. change::
     :tags: feature, ext
     :tickets: 4318

     Added new feature :meth:`.BakedQuery.to_query`, which allows for a
     clean way of using one :class:`.BakedQuery` as a subquery inside of another
     :class:`.BakedQuery` without needing to refer explicitly to a
     :class:`.Session`.


 .. change::
    :tags: feature, sqlite
    :tickets: 4360

    Implemented the SQLite ``ON CONFLICT`` clause as understood at the DDL
    level, e.g. for primary key, unique, and CHECK constraints as well as
    specified on a :class:`.Column` to satisfy inline primary key and NOT NULL.
    Pull request courtesy Denis Kataev.

    .. seealso::

       :ref:`change_4360`

 .. change::
    :tags: feature, postgresql
    :tickets: 4237

    Added rudimental support for reflection of PostgreSQL
    partitioned tables, e.g. that relkind='p' is added to reflection
    queries that return table information.

    .. seealso::

         :ref:`change_4237`

 .. change::
    :tags: feature, ext
    :tickets: 4351

    The :class:`.AssociationProxy` now has standard column comparison operations
    such as :meth:`.ColumnOperators.like` and
    :meth:`.ColumnOperators.startswith` available when the target attribute is a
    plain column - the EXISTS expression that joins to the target table is
    rendered as usual, but the column expression is then use within the WHERE
    criteria of the EXISTS.  Note that this alters the behavior of the
    ``.contains()`` method on the association proxy to make use of
    :meth:`.ColumnOperators.contains` when used on a column-based attribute.

    .. seealso::

       :ref:`change_4351`


 .. change::
     :tags: feature, orm

     Added new flag :paramref:`.Session.bulk_save_objects.preserve_order` to the
     :meth:`.Session.bulk_save_objects` method, which defaults to True. When set
     to False, the given mappings will be grouped into inserts and updates per
     each object type, to allow for greater opportunities to batch common
     operations together.  Pull request courtesy Alessandro Cucci.

 .. change::
     :tags: bug, orm
     :tickets: 4365

     Refactored :meth:`.Query.join` to further clarify the individual components
     of structuring the join. This refactor adds the ability for
     :meth:`.Query.join` to determine the most appropriate "left" side of the
     join when there is more than one element in the FROM list or the query is
     against multiple entities.  If more than one FROM/entity matches, an error
     is raised that asks for an ON clause to be specified to resolve the
     ambiguity.  In particular this targets the regression we saw in
     :ticket:`4363` but is also of general use.   The codepaths within
     :meth:`.Query.join` are now easier to follow and the error cases are
     decided more specifically at an earlier point in the operation.

     .. seealso::

         :ref:`change_4365`

 .. change::
     :tags: bug, sql
     :tickets: 3981

     Fixed issue with :meth:`.TypeEngine.bind_expression` and
     :meth:`.TypeEngine.column_expression` methods where these methods would not
     work if the target type were part of a :class:`.Variant`, or other target
     type of a :class:`.TypeDecorator`.  Additionally, the SQL compiler now
     calls upon the dialect-level implementation when it renders these methods
     so that dialects can now provide for SQL-level processing for built-in
     types.

     .. seealso::

         :ref:`change_3981`


 .. change::
     :tags: bug, orm
     :tickets: 4304

     Fixed long-standing issue in :class:`.Query` where a scalar subquery such
     as produced by :meth:`.Query.exists`, :meth:`.Query.as_scalar` and other
     derivations from :attr:`.Query.statement` would not correctly be adapted
     when used in a new :class:`.Query` that required entity adaptation, such as
     when the query were turned into a union, or a from_self(), etc. The change
     removes the "no adaptation" annotation from the :func:`.select` object
     produced by the :attr:`.Query.statement` accessor.

 .. change::
     :tags: bug, orm, declarative
     :tickets: 4133

     Fixed bug where declarative would not update the state of the
     :class:`.Mapper` as far as what attributes were present, when additional
     attributes were added or removed after the mapper attribute collections had
     already been called and memoized.  Addtionally, a ``NotImplementedError``
     is now raised if a fully mapped attribute (e.g. column, relationship, etc.)
     is deleted from a class that is currently mapped, since the mapper will not
     function correctly if the attribute has been removed.

 .. change::
    :tags: bug, mssql
    :tickets: 4362

    Deprecated the use of :class:`.Sequence` with SQL Server in order to affect
    the "start" and "increment" of the IDENTITY value, in favor of new
    parameters ``mssql_identity_start`` and ``mssql_identity_increment`` which
    set these parameters directly.  :class:`.Sequence` will be used to generate
    real ``CREATE SEQUENCE`` DDL with SQL Server in a future release.

    .. seealso::

         :ref:`change_4362`


 .. change::
     :tags: feature, mysql

     Added support for the parameters in an ON DUPLICATE KEY UPDATE statement on
     MySQL to be ordered, since parameter order in a MySQL UPDATE clause is
     significant, in a similar manner as that described at
     :ref:`updates_order_parameters`.  Pull request courtesy Maxim Bublis.

     .. seealso::

         :ref:`change_mysql_ondupordering`

 .. change::
    :tags: feature, sql
    :tickets: 4144

    Added :class:`.Sequence` to the "string SQL" system that will render a
    meaningful string expression (``"<next sequence value: my_sequence>"``)
    when stringifying without a dialect a statement that includes a "sequence
    nextvalue" expression, rather than raising a compilation error.



 .. change::
     :tags: bug, orm
     :tickets: 4232

     An informative exception is re-raised when a primary key value is not
     sortable in Python during an ORM flush under Python 3, such as an ``Enum``
     that has no ``__lt__()`` method; normally Python 3 raises a ``TypeError``
     in this case.   The flush process sorts persistent objects by primary key
     in Python so the values must be sortable.


 .. change::
    :tags: orm, bug
    :tickets: 3604

    Removed the collection converter used by the :class:`.MappedCollection`
    class. This converter was used only to assert that the incoming dictionary
    keys matched that of their corresponding objects, and only during a bulk set
    operation.  The converter can interfere with a custom validator or
    :meth:`.AttributeEvents.bulk_replace` listener that wants to convert
    incoming values further.  The ``TypeError`` which would be raised by this
    converter when an incoming key didn't match the value is removed; incoming
    values during a bulk assignment will be keyed to their value-generated key,
    and not the key that's explicitly present in the dictionary.

    Overall, converter is superseded by the
    :meth:`.AttributeEvents.bulk_replace` event handler added as part of
    :ticket:`3896`.

 .. change::
    :tags: feature, sql
    :tickets: 3989

    Added new naming convention tokens ``column_0N_name``, ``column_0_N_name``,
    etc., which will render the names / keys / labels for all columns referenced
    by a particular constraint in a sequence.  In order to accommodate for the
    length of such a naming convention, the SQL compiler's auto-truncation
    feature now applies itself to constraint names as well, which creates a
    shortened, deterministically generated name for the constraint that will
    apply to a target backend without going over the character limit of that
    backend.

    The change also repairs two other issues.  One is that the  ``column_0_key``
    token wasn't available even though this token was documented, the other was
    that the ``referred_column_0_name`` token would  inadvertently render the
    ``.key`` and not the ``.name`` of the column if these two values were
    different.

    .. seealso::

       :ref:`change_3989`


 .. change::
     :tags: feature, ext
     :tickets: 4196

     Added support for bulk :meth:`.Query.update` and :meth:`.Query.delete`
     to the :class:`.ShardedQuery` class within the horizontal sharding
     extension.  This also adds an additional expansion hook to the
     bulk update/delete methods :meth:`.Query._execute_crud`.

     .. seealso::

         :ref:`change_4196`

 .. change::
     :tags: feature, sql
     :tickets: 4271

     Added new logic to the "expanding IN" bound parameter feature whereby if
     the given list is empty, a special "empty set" expression that is specific
     to different backends is generated, thus allowing IN expressions to be
     fully dynamic including empty IN expressions.

     .. seealso::

         :ref:`change_4271`



 .. change::
     :tags: feature, mysql

     The "pre-ping" feature of the connection pool now uses
     the ``ping()`` method of the DBAPI connection in the case of
     mysqlclient, PyMySQL and mysql-connector-python.  Pull request
     courtesy Maxim Bublis.

     .. seealso::

         :ref:`change_mysql_ping`

 .. change::
     :tags: feature, orm
     :tickets: 4340

     The "selectin" loader strategy now omits the JOIN in the case of a simple
     one-to-many load, where it instead relies loads only from the related
     table, relying upon the foreign key columns of the related table in order
     to match up to primary keys in the parent table.   This optimization can be
     disabled by setting the :paramref:`.relationship.omit_join` flag to False.
     Many thanks to Jayson Reis for the efforts on this.

     .. seealso::

         :ref:`change_4340`

 .. change::
    :tags: bug, orm
    :tickets: 4353

    Added new behavior to the lazy load that takes place when the "old" value of
    a many-to-one is retrieved, such that exceptions which would be raised due
    to either ``lazy="raise"`` or a detached session error are skipped.

    .. seealso::

     :ref:`change_4353`

 .. change::
     :tags: feature, sql

     The Python builtin ``dir()`` is now supported for a SQLAlchemy "properties"
     object, such as that of a Core columns collection (e.g. ``.c``),
     ``mapper.attrs``, etc.  Allows iPython autocompletion to work as well.
     Pull request courtesy Uwe Korn.

 .. change::
    :tags: feature, orm
    :tickets: 4257

    Added ``.info`` dictionary to the :class:`.InstanceState` class, the object
    that comes from calling :func:`.inspect` on a mapped object.

    .. seealso::

         :ref:`change_4257`

 .. change::
     :tags: feature, sql
     :tickets: 3831

     Added new feature :meth:`.FunctionElement.as_comparison` which allows a SQL
     function to act as a binary comparison operation that can work within the
     ORM.

     .. seealso::

         :ref:`change_3831`

 .. change::
    :tags: bug, orm
    :tickets: 4354

    A long-standing oversight in the ORM, the ``__delete__`` method for a many-
    to-one relationship was non-functional, e.g. for an operation such as ``del
    a.b``.  This is now implemented and is equivalent to setting the attribute
    to ``None``.

    .. seealso::

         :ref:`change_4354`

1.2.19

:released: April 15, 2019

 .. change::
    :tags: bug, orm
    :tickets: 4507

    Fixed a regression in 1.2 due to the introduction of baked queries for
    relationship lazy loaders, where a race condition is created during the
    generation of the "lazy clause" which occurs within a memoized attribute. If
    two threads initialize the memoized attribute concurrently, the baked query
    could be generated with bind parameter keys that are then replaced with new
    keys by the next run, leading to a lazy load query that specifies the
    related criteria as ``None``. The fix establishes that the parameter names
    are fixed before the new clause and parameter objects are generated, so that
    the names are the same every time.

 .. change::
    :tags: bug, oracle
    :tickets: 4506

    Added support for reflection of the :class:`.NCHAR` datatype to the Oracle
    dialect, and added :class:`.NCHAR` to the list of types exported by the
    Oracle dialect.


 .. change::
    :tags: bug, examples
    :tickets: 4528

    Fixed bug in large_resultsets example case where a re-named "id" variable
    due to code reformatting caused the test to fail.  Pull request courtesy
    Matt Schuchhardt.

 .. change::
    :tags: bug, mssql
    :tickets: 4536
    :versions: 1.3.1

    A commit() is emitted after an isolation level change to SNAPSHOT, as both
    pyodbc and pymssql open an implicit transaction which blocks subsequent SQL
    from being emitted in the current transaction.

 .. change::
    :tags: bug, engine
    :tickets: 4406

    Comparing two objects of :class:`.URL` using ``__eq__()`` did not take port
    number into consideration, two objects differing only by port number were
    considered equal. Port comparison is now added in ``__eq__()`` method of
    :class:`.URL`, objects differing by port number are now not equal.
    Additionally, ``__ne__()`` was not implemented for :class:`.URL` which
    caused unexpected result when ``!=`` was used in Python2, since there are no
    implied relationships among the comparison operators in Python2.

.. changelog::

1.2.18

:released: February 15, 2019

 .. change::
    :tags: bug, orm
    :tickets: 4468

    Fixed a regression in 1.2 where a wildcard/load_only loader option would
    not work correctly against a loader path where of_type() were used to limit
    to a particular subclass.  The fix only works for of_type() of a simple
    subclass so far, not a with_polymorphic entity which will be addressed in a
    separate issue; it is unlikely this latter case was working previously.


 .. change::
    :tags: bug, orm
    :tickets: 4489

    Fixed fairly simple but critical issue where the
    :meth:`.SessionEvents.pending_to_persistent` event would be invoked for
    objects not just when they move from pending to persistent, but when they
    were also already persistent and just being updated, thus causing the event
    to be invoked for all objects on every update.

 .. change::
    :tags: bug, sql
    :tickets: 4485

    Fixed issue where the :class:`.JSON` type had a read-only
    :attr:`.JSON.should_evaluate_none` attribute, which would cause failures
    when making use of the :meth:`.TypeEngine.evaluates_none` method in
    conjunction with this type.  Pull request courtesy Sanjana S.

 .. change::
    :tags: bug, mssql
    :tickets: 4499

    Fixed bug where the SQL Server "IDENTITY_INSERT" logic that allows an INSERT
    to proceed with an explicit value on an IDENTITY column was not detecting
    the case where :meth:`.Insert.values` were used with a dictionary that
    contained a :class:`.Column` as key and a SQL expression as a value.

 .. change::
    :tags: bug, sqlite
    :tickets: 4474

    Fixed bug in SQLite DDL where using an expression as a server side default
    required that it be contained within parenthesis to be accepted by the
    sqlite parser.  Pull request courtesy Bartlomiej Biernacki.

 .. change::
    :tags: bug, mysql
    :tickets: 4492

    Fixed a second regression caused by :ticket:`4344` (the first was
    :ticket:`4361`), which works around MySQL issue 88718, where the lower
    casing function used was not correct for Python 2 with OSX/Windows casing
    conventions, which would then raise ``TypeError``.  Full coverage has been
    added to this logic so that every codepath is exercised in a mock style for
    all three casing conventions on all versions of Python. MySQL 8.0 has
    meanwhile fixed issue 88718 so the workaround is only applies to a
    particular span of MySQL 8.0 versions.

.. changelog::

1.2.17

:released: January 25, 2019

 .. change::
    :tags: feature, orm
    :tickets: 4461

    Added new event hooks :meth:`.QueryEvents.before_compile_update` and
    :meth:`.QueryEvents.before_compile_delete` which complement
    :meth:`.QueryEvents.before_compile` in the case of the :meth:`.Query.update`
    and :meth:`.Query.delete` methods.


 .. change::
    :tags: bug, postgresql
    :tickets: 4463

    Revised the query used when reflecting CHECK constraints to make use of the
    ``pg_get_constraintdef`` function, as the ``consrc`` column is being
    deprecated in PG 12.  Thanks to John A Stevenson for the tip.


 .. change::
    :tags: bug, orm
    :tickets: 4454

    Fixed issue where when using single-table inheritance in conjunction with a
    joined inheritance hierarchy that uses "with polymorphic" loading, the
    "single table criteria" for that single-table entity could get confused for
    that of other entities from the same hierarchy used in the same query.The
    adaption of the "single table criteria" is made more specific to the target
    entity to avoid it accidentally getting adapted to other tables in the
    query.


 .. change::
    :tags: bug, oracle
    :tickets: 4457

    Fixed regression in integer precision logic due to the refactor of the
    cx_Oracle dialect in 1.2.  We now no longer apply the cx_Oracle.NATIVE_INT
    type to result columns sending integer values (detected as positive
    precision with scale ==0) which encounters integer overflow issues with
    values that go beyond the 32 bit boundary.  Instead, the output variable
    is left untyped so that cx_Oracle can choose the best option.

.. changelog::

1.2.16

:released: January 11, 2019

 .. change::
    :tag: bug, sql
    :tickets: 4394

    Fixed issue in "expanding IN" feature where using the same bound parameter
    name more than once in a query would lead to a KeyError within the process
    of rewriting the parameters in the query.

 .. change::
    :tags: bug, postgresql
    :tickets: 4416

    Fixed issue where a :class:`.postgresql.ENUM` or a custom domain present
    in a remote schema would not be recognized within column reflection if
    the name of the enum/domain or the name of the schema required quoting.
    A new parsing scheme now fully parses out quoted or non-quoted tokens
    including support for SQL-escaped quotes.

 .. change::
    :tags: bug, postgresql

    Fixed issue where multiple :class:`.postgresql.ENUM` objects referred to
    by the same :class:`.MetaData` object would fail to be created if
    multiple objects had the same name under different schema names.  The
    internal memoization the PostgreSQL dialect uses to track if it has
    created a particular :class:`.postgresql.ENUM` in the database during
    a DDL creation sequence now takes schema name into account.

 .. change::
    :tags: bug, engine
    :tickets: 4429

    Fixed a regression introduced in version 1.2 where a refactor
    of the :class:`.SQLAlchemyError` base exception class introduced an
    inappropriate coercion of a plain string message into Unicode under
    python 2k, which is not handled by the Python interpreter for characters
    outside of the platform's encoding (typically ascii).  The
    :class:`.SQLAlchemyError` class now passes a bytestring through under
    Py2K for ``__str__()`` as is the behavior of exception objects in general
    under Py2K, does a safe coercion to unicode utf-8 with
    backslash fallback for ``__unicode__()``.  For Py3K the message is
    typically unicode already, but if not is again safe-coerced with utf-8
    with backslash fall