Pin sqlalchemy to latest version 1.2.5

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I'm pinning it to the latest version 1.2.5 for now.

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Changelog

1.2.5

:released: March 6, 2018

.. change::
:tags: bug, sql
🎟️ 4210
:versions: 1.3.0b1

   Fixed bug in :class:.`CTE` construct along the same lines as that of
   :ticket:`4204` where a :class:`.CTE` that was aliased would not copy itself
   correctly during a "clone" operation as is frequent within the ORM as well
   as when using the :meth:`.ClauseElement.params` method.

.. change::
:tags: bug, orm
🎟️ 4199

   Fixed bug in new "polymorphic selectin" loading when a selection of
   polymorphic objects were to be partially loaded from a relationship
   lazy loader, leading to an "empty IN" condition within the load that
   raises an error for the "inline" form of "IN".

.. change::
:tags: bug, sql
🎟️ 4204

   Fixed bug in CTE rendering where a :class:`.CTE` that was also turned into
   an :class:`.Alias` would not render its "ctename AS aliasname" clause
   appropriately if there were more than one reference to the CTE in a FROM
   clause.

.. change::
:tags: bug, orm
🎟️ 4209
:versions: 1.3.0b1

   Fixed 1.2 regression where a mapper option that contains an
   :class:`.AliasedClass` object, as is typical when using the
   :meth:`.QueryableAttribute.of_type` method, could not be pickled.   1.1's
   behavior was to omit the aliased class objects from the path, so this
   behavior is restored.

.. change::
:tags: feature, orm
:versions: 1.3.0b1

   Added new feature :meth:`.Query.only_return_tuples`.  Causes the
   :class:`.Query` object to return keyed tuple objects unconditionally even
   if the query is against a single entity.   Pull request courtesy Eric
   Atkin.

.. change::
:tags: bug, sql
🎟️ 4198

   Fixed bug in new "expanding IN parameter" feature where the bind parameter
   processors for values wasn't working at all, tests failed to cover this
   pretty basic case which includes that ENUM values weren't working.

.. changelog::

1.2.4

:released: February 22, 2018

.. change::
:tags: bug, orm
🎟️ 4193

   Fixed 1.2 regression in ORM versioning feature where a mapping against a
   :func:`.select` or :func:`.alias` that also used a versioning column
   against the underlying table would fail due to the check added as part of
   :ticket:`3673`.

.. change::
:tags: bug, engine
🎟️ 4190

   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::
:tags: bug, sql
🎟️ 4197

   Fixed bug where CTE expressions would not have their name or alias name
   quoted when the given name is case sensitive or otherwise requires quoting.
   Pull request courtesy Eric Atkin.

.. changelog::

1.2.3

:released: February 16, 2018

.. change::
:tags: bug, oracle
🎟️ 4182

   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::
:tags: bug, sqlite

   Fixed the import error raised when a platform
   has neither pysqlite2 nor sqlite3 installed, such
   that the sqlite3-related import error is raised,
   not the pysqlite2 one which is not the actual
   failure mode.  Pull request courtesy Robin.

.. change::
:tags: bug, orm
🎟️ 4175

   Fixed bug where the :class:`.Bundle` object did not
   correctly report upon the primary :class:`.Mapper` object
   represened by the bundle, if any.   An immediate
   side effect of this issue was that the new selectinload
   loader strategy wouldn't work with the horizontal sharding
   extension.

.. change::
:tags: bug, sql
🎟️ 4180

   Fixed bug where the :class:`.Enum` type wouldn't handle
   enum "aliases" correctly, when more than one key refers to the
   same value.  Pull request courtesy Daniel Knell.

.. change::
:tags: bug, engine
🎟️ 4181

   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.

.. change::
:tags: bug, tests
🎟️ 3265

   A test added in 1.2 thought to confirm a Python 2.7 behavior turns out to
   be confirming the behavior only as of Python 2.7.8. Python bug 8743 still
   impacts set comparison in Python 2.7.7 and earlier, so the test in question
   involving AssociationSet no longer runs for these older Python 2.7
   versions.

.. change::
:tags: feature, oracle

   The ON DELETE options for foreign keys are now part of
   Oracle reflection.  Oracle does not support ON UPDATE
   cascades.  Pull request courtesy Miroslav Shubernetskiy.

.. change::
:tags: bug, orm
🎟️ 4188

   Fixed bug in concrete inheritance mapping where user-defined
   attributes such as hybrid properties that mirror the names
   of mapped attributes from sibling classes would be overwritten by
   the mapper as non-accessible at the instance level.   Additionally
   ensured that user-bound descriptors are not implicitly invoked at the class
   level during the mapper configuration stage.

.. change::
:tags: bug, orm
🎟️ 4178

   Fixed bug where the :func:`.orm.reconstructor` event
   helper would not be recognized if it were applied to the
   ``__init__()`` method of the mapped class.

.. change::
:tags: bug, engine
🎟️ 4170

   The :class:`.URL` object now allows query keys to be specified multiple
   times where their values will be joined into a list.  This is to support
   the plugins feature documented at :class:`.CreateEnginePlugin` which
   documents that "plugin" can be passed multiple times. Additionally, the
   plugin names can be passed to :func:`.create_engine` outside of the URL
   using the new :paramref:`.create_engine.plugins` parameter.

.. change::
:tags: feature, sql
🎟️ 3906

   Added support for :class:`.Enum` to persist the values of the enumeration,
   rather than the keys, when using a Python pep-435 style enumerated object.
   The user supplies a callable function that will return the string values to
   be persisted.  This allows enumerations against non-string values to be
   value-persistable as well.  Pull request courtesy Jon Snyder.

.. change::
:tags: feature, orm

   Added new argument :paramref:`.attributes.set_attribute.inititator`
   to the :func:`.attributes.set_attribute` function, allowing an
   event token received from a listener function to be propagated
   to subsequent set events.

.. changelog::

1.2.2

:released: January 24, 2018

.. change::
:tags: bug, mssql
🎟️ 4164

   Added ODBC error code 10054 to the list of error
   codes that count as a disconnect for ODBC / MSSQL server.

.. change::
:tags: bug, orm
🎟️ 4171

   Fixed 1.2 regression regarding new bulk_replace event
   where a backref would fail to remove an object from the
   previous owner when a bulk-assignment assigned the
   object to a new owner.

.. change::
:tags: bug, oracle
🎟️ 4163

   The cx_Oracle dialect now calls setinputsizes() with cx_Oracle.NCHAR
   unconditionally when the NVARCHAR2 datatype, in SQLAlchemy corresponding
   to sqltypes.Unicode(), is in use.  Per cx_Oracle's author this allows
   the correct conversions to occur within the Oracle client regardless
   of the setting for NLS_NCHAR_CHARACTERSET.

.. change::
:tags: bug, mysql

   Added more MySQL 8.0 reserved words to the MySQL dialect
   for quoting purposes.  Pull request courtesy
   Riccardo Magliocchetti.

.. changelog::

1.2.1

:released: January 15, 2018

.. change::
:tags: bug, orm
🎟️ 4159

   Fixed regression where pickle format of a Load / _UnboundLoad object (e.g.
   loader options) changed and ``__setstate__()`` was raising an
   UnboundLocalError for an object received from the legacy format, even
   though an attempt was made to do so.  tests are now added to ensure this
   works.

.. change::
:tags: bug, ext
🎟️ 4150

   Fixed regression in association proxy due to :ticket:`3769`
   (allow for chained any() / has()) where contains() against
   an association proxy chained in the form
   (o2m relationship, associationproxy(m2o relationship, m2o relationship))
   would raise an error regarding the re-application of contains()
   on the final link of the chain.

.. change::
:tags: bug, orm
🎟️ 4153

   Fixed regression caused by new lazyload caching scheme in :ticket:`3954`
   where a query that makes use of loader options with of_type would cause
   lazy loads of unrelated paths to fail with a TypeError.

.. change::
:tags: bug, oracle
🎟️ 4157

   Fixed regression where the removal of most setinputsizes
   rules from cx_Oracle dialect impacted the TIMESTAMP
   datatype's ability to retrieve fractional seconds.

.. change::
:tags: bug, tests

   Removed an oracle-specific requirements rule from the public
   test suite that was interfering with third party dialect
   suites.

.. change::
:tags: bug, mssql
🎟️ 4154

   Fixed regression in 1.2 where newly repaired quoting
   of collation names in :ticket:`3785` breaks SQL Server,
   which explicitly does not understand a quoted collation
   name.   Whether or not mixed-case collation names are
   quoted or not is now deferred down to a dialect-level
   decision so that each dialect can prepare these identifiers
   directly.

.. change::
:tags: bug, orm
🎟️ 4156

   Fixed bug in new "selectin" relationship loader where the loader could try
   to load a non-existent relationship when loading a collection of
   polymorphic objects, where only some of the mappers include that
   relationship, typically when :meth:`.PropComparator.of_type` is being used.

.. change::
:tags: bug, tests

   Added a new exclusion rule group_by_complex_expression
   which disables tests that use "GROUP BY <expr>", which seems
   to be not viable for at least two third party dialects.

.. change::
:tags: bug, oracle

   Fixed regression in Oracle imports where a missing comma caused
   an undefined symbol to be present.  Pull request courtesy
   Miroslav Shubernetskiy.

.. changelog::

1.2.0

:released: December 27, 2017

.. change::
:tags: orm, feature
🎟️ 4137

   Added a new data member to the identity key tuple
   used by the ORM's identity map, known as the
   "identity_token".  This token defaults to None but
   may be used by database sharding schemes to differentiate
   objects in memory with the same primary key that come
   from different databases.   The horizontal sharding
   extension integrates this token applying the shard
   identifier to it, thus allowing primary keys to be
   duplicated across horizontally sharded backends.

   .. seealso::

       :ref:`change_4137`

.. change::
:tags: bug, mysql
🎟️ 4115

   Fixed regression from issue 1.2.0b3 where "MariaDB" version comparison can
   fail for some particular MariaDB version strings under Python 3.

.. change::
:tags: enhancement, sql
🎟️ 959

   Implemented "DELETE..FROM" syntax for Postgresql, MySQL, MS SQL Server
   (as well as within the unsupported Sybase dialect) in a manner similar
   to how "UPDATE..FROM" works.  A DELETE statement that refers to more than
   one table will switch into "multi-table" mode and render the appropriate
   "USING" or multi-table "FROM" clause as understood by the database.
   Pull request courtesy Pieter Mulder.

   .. seealso::

       :ref:`change_959`

.. change::
:tags: bug, sql
🎟️ 2694

  Reworked the new "autoescape" feature introduced in
  :ref:`change_2694` in 1.2.0b2 to be fully automatic; the escape
  character now defaults to a forwards slash ``"/"`` and
  is applied to percent, underscore, as well as the escape
  character itself, for fully automatic escaping.  The
  character can also be changed using the "escape" parameter.

  .. seealso::

       :ref:`change_2694`

.. change::
:tags: bug, sql
🎟️ 4147

   Fixed bug where the :meth:`.Table.tometadata` method would not properly
   accommodate :class:`.Index` objects that didn't consist of simple
   column expressions, such as indexes against a :func:`.text` construct,
   indexes that used SQL expressions or :attr:`.func`, etc.   The routine
   now copies expressions fully to a new :class:`.Index` object while
   substituting all table-bound :class:`.Column` objects for those
   of the target table.

.. change::
:tags: bug, sql
🎟️ 4142

   Changed the "visit name" of :class:`.ColumnElement` from "column" to
   "column_element", so that when this element is used as the basis for a
   user-defined SQL element, it is not assumed to behave like a table-bound
   :class:`.ColumnClause` when processed by various SQL traversal utilities,
   as are commonly used by the ORM.

.. change::
:tags: bug, sql, ext
🎟️ 4141

   Fixed issue in :class:`.ARRAY` datatype which is essentially the same
   issue as that of :ticket:`3832`, except not a regression, where
   column attachment events on top of :class:`.ARRAY` would not fire
   correctly, thus interfering with systems which rely upon this.   A key
   use case that was broken by this is the use of mixins to declare
   columns that make use of :meth:`.MutableList.as_mutable`.

.. change::
:tags: feature, engine
🎟️ 4089

   The "password" attribute of the :class:`.url.URL` object can now be
   any user-defined or user-subclassed string object that responds to the
   Python ``str()`` builtin.   The object passed will be maintained as the
   datamember :attr:`.url.URL.password_original` and will be consulted
   when the :attr:`.url.URL.password` attribute is read to produce the
   string value.

.. change::
:tags: bug, orm
🎟️ 4130

   Fixed bug in :func:`.contains_eager` query option where making use of a
   path that used :meth:`.PropComparator.of_type` to refer to a subclass
   across more than one level of joins would also require that the "alias"
   argument were provided with the same subtype in order to avoid adding
   unwanted FROM clauses to the query; additionally,  using
   :func:`.contains_eager` across subclasses that use :func:`.aliased` objects
   of subclasses as the :meth:`.PropComparator.of_type` argument will also
   render correctly.

.. change::
:tags: feature, postgresql

   Added new :class:`.postgresql.MONEY` datatype.  Pull request courtesy
   Cleber J Santos.

.. change::
:tags: bug, sql
🎟️ 4140

   Fixed bug in new "expanding bind parameter" feature whereby if multiple
   params were used in one statement, the regular expression would not
   match the parameter name correctly.

.. change::
:tags: enhancement, ext
🎟️ 4135

   Added new method :meth:`.baked.Result.with_post_criteria` to baked
   query system, allowing non-SQL-modifying transformations to take place
   after the query has been pulled from the cache.  Among other things,
   this method can be used with :class:`.horizontal_shard.ShardedQuery`
   to set the shard identifier.   :class:`.horizontal_shard.ShardedQuery`
   has also been modified such that its :meth:`.ShardedQuery.get` method
   interacts correctly with that of :class:`.baked.Result`.

.. change::
:tags: bug, oracle
🎟️ 4064

   Added some additional rules to fully handle ``Decimal('Infinity')``,
   ``Decimal('-Infinity')`` values with cx_Oracle numerics when using
   ``asdecimal=True``.

.. change::
:tags: bug, mssql
🎟️ 4121

   Fixed bug where sqltypes.BINARY and sqltypes.VARBINARY datatypes
   would not include correct bound-value handlers for pyodbc,
   which allows the pyodbc.NullParam value to be passed that
   helps with FreeTDS.

.. change::
:tags: feature, misc

   Added a new errors section to the documentation with background
   about common error messages.   Selected exceptions within SQLAlchemy
   will include a link in their string output to the relevant section
   within this page.

.. change::
:tags: bug, orm
🎟️ 4032

   The :meth:`.Query.exists` method will now disable eager loaders for when
   the query is rendered.  Previously, joined-eager load joins would be rendered
   unnecessarily as well as subquery eager load queries would be needlessly
   generated.   The new behavior matches that of the :meth:`.Query.subquery`
   method.

.. changelog::

1.2.0b3

:released: December 27, 2017
:released: October 13, 2017

.. change::
:tags: feature, postgresql
🎟️ 4109

   Added a new flag ``use_batch_mode`` to the psycopg2 dialect.  This flag
   enables the use of psycopg2's ``psycopg2.extras.execute_batch``
   extension when the :class:`.Engine` calls upon
   ``cursor.executemany()``. This extension provides a critical
   performance increase by over an order of magnitude when running INSERT
   statements in batch.  The flag is False by default as it is considered
   to be experimental for now.

   .. seealso::

       :ref:`change_4109`

.. change::
:tags: bug, mssql
🎟️ 4061

   SQL Server supports what SQLAlchemy calls "native boolean"
   with its BIT type, as this type only accepts 0 or 1 and the
   DBAPIs return its value as True/False.   So the SQL Server
   dialects now enable "native boolean" support, in that a
   CHECK constraint is not generated for a :class:`.Boolean`
   datatype.  The only difference vs. other native boolean
   is that there are no "true" / "false" constants so "1" and
   "0" are still rendered here.

.. change::
:tags: bug, oracle
🎟️ 4064

   Partial support for persisting and retrieving the Oracle value
   "infinity" is implemented with cx_Oracle, using Python float values
   only, e.g. ``float("inf")``.  Decimal support is not yet fulfilled by
   the cx_Oracle DBAPI driver.

.. change::
:tags: bug, oracle

   The cx_Oracle dialect has been reworked and modernized to take advantage of
   new patterns that weren't present in the old 4.x series of cx_Oracle. This
   includes that the minimum cx_Oracle version is the 5.x series and that
   cx_Oracle 6.x is now fully tested. The most significant change involves
   type conversions, primarily regarding the numeric / floating point and LOB
   datatypes, making more effective use of cx_Oracle type handling hooks to
   simplify how bind parameter and result data is processed.

   .. seealso::

       :ref:`change_cxoracle_12`

.. change::
:tags: bug, oracle
🎟️ 3997

   two phase support for cx_Oracle has been completely removed for all
   versions of cx_Oracle, whereas in 1.2.0b1 this change only took effect for
   the 6.x series of cx_Oracle.  This feature never worked correctly
   in any version of cx_Oracle and in cx_Oracle 6.x, the API which SQLAlchemy
   relied upon was removed.

   .. seealso::

       :ref:`change_cxoracle_12`

.. change::
:tags: bug, oracle

   The column keys present in a result set when using :meth:`.Insert.returning`
   with the cx_Oracle backend now use the correct column / label names
   like that of all other dialects.  Previously, these came out as
   ``ret_nnn``.

   .. seealso::

       :ref:`change_cxoracle_12`

.. change::
:tags: bug, oracle

   Several parameters to the cx_Oracle dialect are now deprecated and will
   have no effect: ``auto_setinputsizes``, ``exclude_setinputsizes``,
   ``allow_twophase``.

   .. seealso::

       :ref:`change_cxoracle_12`

.. change::
:tags: bug, sql
🎟️ 4075

   Added a new method :meth:`.DefaultExecutionContext.get_current_parameters`
   which is used within a function-based default value generator in
   order to retrieve the current parameters being passed to the statement.
   The new function differs from the
   :attr:`.DefaultExecutionContext.current_parameters` attribute in
   that it also provides for optional grouping of parameters that
   correspond to a multi-valued "insert" construct.  Previously it was not
   possible to identify the subset of parameters that were relevant to
   the function call.

   .. seealso::

       :ref:`change_4075`

       :ref:`context_default_functions`

.. change::
:tags: bug, orm
🎟️ 4050

   Fixed regression introduced in 1.2.0b1 due to :ticket:`3934` where the
   :class:`.Session` would fail to "deactivate" the transaction, if a
   rollback failed (the target issue is when MySQL loses track of a SAVEPOINT).
   This would cause a subsequent call to :meth:`.Session.rollback` to raise
   an error a second time, rather than completing and bringing the
   :class:`.Session` back to ACTIVE.

.. change::
:tags: bug, postgresql
🎟️ 4041

   Fixed bug where the pg8000 driver would fail if using
   :meth:`.MetaData.reflect` with a schema name, since the schema name would
   be sent as a "quoted_name" object that's a string subclass, which pg8000
   doesn't recognize.   The quoted_name type is added to pg8000's
   py_types collection on connect.

.. change::
:tags: bug, postgresql
🎟️ 4016

   Enabled UUID support for the pg8000 driver, which supports native Python
   uuid round trips for this datatype.  Arrays of UUID are still not supported,
   however.

.. change::
:tags: mssql, bug
🎟️ 4057

   Fixed the pymssql dialect so that percent signs in SQL text, such
   as used in modulus expressions or literal textual values, are
   **not** doubled up, as seems to be what pymssql expects.  This is
   despite the fact that the pymssql DBAPI uses the "pyformat" parameter
   style which itself considers the percent sign to be significant.

.. change::
:tags: bug, orm, declarative
🎟️ 4091

   A warning is emitted if a subclass attempts to override an attribute
   that was declared on a superclass using ``declared_attr.cascading``
   that the overridden attribute will be ignored. This use
   case cannot be fully supported down to further subclasses without more
   complex development efforts, so for consistency the "cascading" is
   honored all the way down regardless of overriding attributes.

.. change::
:tags: bug, orm, declarative
🎟️ 4092

   A warning is emitted if the ``declared_attr.cascading`` attribute is
   used with a special declarative name such as ``__tablename__``, as this
   has no effect.

.. change::
:tags: feature, engine
🎟️ 4077

   Added ``__next__()`` and ``next()`` methods to :class:`.ResultProxy`,
   so that the ``next()`` builtin function works on the object directly.
   :class:`.ResultProxy` has long had an ``__iter__()`` method which already
   allows it to respond to the ``iter()`` builtin.   The implementation
   for ``__iter__()`` is unchanged, as performance testing has indicated
   that iteration using a ``__next__()`` method with ``StopIteration``
   is about 20% slower in both Python 2.7 and 3.6.

.. change::
:tags: feature, mssql
🎟️ 4086

   Added a new :class:`.mssql.TIMESTAMP` datatype, that
   correctly acts like a binary datatype for SQL Server
   rather than a datetime type, as SQL Server breaks the
   SQL standard here.  Also added :class:`.mssql.ROWVERSION`,
   as the "TIMESTAMP" type in SQL Server is deprecated in
   favor of ROWVERSION.

.. change::
:tags: bug, orm
🎟️ 4084

   Fixed issue where the :func:`.make_transient_to_detached` function
   would expire all attributes on the target object, including "deferred"
   attributes, which has the effect of the attribute being undeferred
   for the next refesh, causing an unexpected load of the attribute.

.. change::
:tags: bug, orm
🎟️ 4026

   Fixed bug in :ref:`change_3948` which prevented "selectin" and
   "inline" settings in a multi-level class hierarchy from interacting
   together as expected.    A new example is added to the documentation.

   .. seealso::

       :ref:`polymorphic_selectin_and_withpoly`

.. change::
:tags: bug, oracle
🎟️ 4042

   Fixed bug where an index reflected under Oracle with an expression like
   "column DESC" would not be returned, if the table also had no primary
   key, as a result of logic that attempts to filter out the
   index implicitly added by Oracle onto the primary key columns.

.. change::
:tags: bug, orm
🎟️ 4071

  Removed the warnings that are emitted when the LRU caches employed
  by the mapper as well as loader strategies reach their threshold; the
  purpose of this warning was at first a guard against excess cache keys
  being generated but became basically a check on the "creating many
  engines" antipattern.   While this is still an antipattern, the presense
  of test suites which both create an engine per test as well as raise
  on all warnings will be an inconvenience; it should not be critical
  that such test suites change their architecture just for this warning
  (though engine-per-test suite is always better).

.. change::
:tags: bug, orm
🎟️ 4049

   Fixed regression where the use of a :func:`.undefer_group` option
   in conjunction with a lazy loaded relationship option would cause
   an attribute error, due to a bug in the SQL cache key generation
   added in 1.2 as part of :ticket:`3954`.

.. change::
:tags: bug, oracle
🎟️ 4045

   Fixed more regressions caused by cx_Oracle 6.0; at the moment, the only
   behavioral change for users is disconnect detection now detects for
   cx_Oracle.DatabaseError in addition to cx_Oracle.InterfaceError, as
   this behavior seems to have changed.   Other issues regarding numeric
   precision and uncloseable connections are pending with the upstream
   cx_Oracle issue tracker.

.. change::
:tags: bug, mssql
🎟️ 4060

   Fixed bug where the SQL Server dialect could pull columns from multiple
   schemas when reflecting a self-referential foreign key constraint, if
   multiple schemas contained a constraint of the same name against a
   table of the same name.

.. change::
:tags: feature, mssql
🎟️ 4058

   Added support for "AUTOCOMMIT" isolation level, as established
   via :meth:`.Connection.execution_options`, to the
   PyODBC and pymssql dialects.   This isolation level sets the
   appropriate DBAPI-specific flags on the underlying
   connection object.

.. change::
:tags: bug, orm
🎟️ 4073

   Modified the change made to the ORM update/delete evaluator in
   :ticket:`3366` such that if an unmapped column expression is present
   in the update or delete, if the evaluator can match its name to the
   mapped columns of the target class, a warning is emitted, rather than
   raising UnevaluatableError.  This is essentially the pre-1.2 behavior,
   and is to allow migration for applications that are currently relying
   upon this pattern.  However, if the given attribute name cannot be
   matched to the columns of the mapper, the UnevaluatableError is
   still raised, which is what was fixed in :ticket:`3366`.

.. change::
:tags: bug, sql
🎟️ 4087

   Fixed bug in new SQL comments feature where table and column comment
   would not be copied when using :meth:`.Table.tometadata`.

.. change::
:tags: bug, sql
🎟️ 4102

   In release 1.1, the :class:`.Boolean` type was broken in that
   boolean coercion via ``bool()`` would occur for backends that did not
   feature "native boolean", but would not occur for native boolean backends,
   meaning the string ``"0"`` now behaved inconsistently. After a poll, a
   consensus was reached that non-boolean values should be raising an error,
   especially in the ambiguous case of string ``"0"``; so the :class:`.Boolean`
   datatype will now raise ``ValueError`` if an incoming value is not
   within the range ``None, True, False, 1, 0``.

   .. seealso::

       :ref:`change_4102`

.. change::
:tags: bug, sql
🎟️ 4063

   Refined the behavior of :meth:`.Operators.op` such that in all cases,
   if the :paramref:`.Operators.op.is_comparison` flag is set to True,
   the return type of the resulting expression will be
   :class:`.Boolean`, and if the flag is False, the return type of the
   resulting expression will be the same type as that of the left-hand
   expression, which is the typical default behavior of other operators.
   Also added a new parameter :paramref:`.Operators.op.return_type` as well
   as a helper method :meth:`.Operators.bool_op`.

   .. seealso::

       :ref:`change_4063`

.. change::
:tags: bug, mysql
🎟️ 4072

   Changed the name of the ``.values`` attribute of the new MySQL
   INSERT..ON DUPLICATE KEY UPDATE construct to ``.inserted``, as
   :class:`.Insert` already has a method called :meth:`.Insert.values`.
   The ``.inserted`` attribute ultimately renders the MySQL ``VALUES()``
   function.

.. change::
:tags: bug, mssql, orm
🎟️ 4062

   Added a new class of "rowcount support" for dialects that is specific to
   when "RETURNING", which on SQL Server looks like "OUTPUT inserted", is in
   use, as the PyODBC backend isn't able to give us rowcount on an UPDATE or
   DELETE statement when OUTPUT is in effect.  This primarily affects the ORM
   when a flush is updating a row that contains server-calcluated values,
   raising an error if the backend does not return the expected row count.
   PyODBC now states that it supports rowcount except if OUTPUT.inserted is
   present, which is taken into account by the ORM during a flush as to
   whether it will look for a rowcount.

.. change::
:tags: bug, sql
🎟️ 4088

   Internal refinements to the :class:`.Enum`, :class:`.Interval`, and
   :class:`.Boolean` types, which now extend a common mixin
   :class:`.Emulated` that indicates a type that provides Python-side
   emulation of a DB native type, switching out to the DB native type when a
   supporting backend is in use.   The Postgresql :class:`.INTERVAL` type
   when used directly will now include the correct type coercion rules for
   SQL expressions that also take effect for :class:`.sqltypes.Interval`
   (such as adding a date to an interval yields a datetime).

.. change::
:tags: bug, mssql, orm

   Enabled the "sane_rowcount" flag for the pymssql dialect, indicating
   that the DBAPI now reports the correct number of rows affected from
   an UPDATE or DELETE statement.  This impacts mostly the ORM versioning
   feature in that it now can verify the number of rows affected on a
   target version.

.. change:: 4028
:tags: bug, engine
🎟️ 4028

   Made some adjustments to :class:`.Pool` and :class:`.Connection` such
   that recovery logic is not run underneath exception catches for
   ``pool.Empty``, ``AttributeError``, since when the recovery operation
   itself fails, Python 3 creates a misleading stack trace referring to the
   ``Empty`` / ``AttributeError`` as the cause, when in fact these exception
   catches are part of control flow.

.. change::
:tags: bug, oracle
🎟️ 4076

   Fixed bug where Oracle 8 "non ansi" join mode would not add the
   ``(+)`` operator to expressions that used an operator other than the
   ``=`` operator.  The ``(+)`` needs to be on all columns that are part
   of the right-hand side.

.. change::
:tags: bug, mssql
🎟️ 4059

   Added a rule to SQL Server index reflection to ignore the so-called
   "heap" index that is implicitly present on a table that does not
   specify a clustered index.

.. changelog::

1.2.0b2

:released: December 27, 2017
:released: July 24, 2017

.. change:: 4033
:tags: bug, orm
🎟️ 4033

   Fixed regression from 1.1.11 where adding additional non-entity
   columns to a query that includes an entity with subqueryload
   relationships would fail, due to an inspection added in 1.1.11 as a
   result of :ticket:`4011`.

.. changelog::

1.2.0b1

:released: December 27, 2017
:released: July 10, 2017

.. change:: scoped_autocommit
:tags: feature, orm

   Added ``.autocommit`` attribute to :class:`.scoped_session`, proxying
   the ``.autocommit`` attribute of the underling :class:`.Session`
   currently assigned to the thread.  Pull request courtesy
   Ben Fagin.

.. change:: 4009
:tags: feature, mysql
🎟️ 4009

   Added support for MySQL's ON DUPLICATE KEY UPDATE
   MySQL-specific :class:`.mysql.dml.Insert` object.
   Pull request courtesy Michael Doronin.

   .. seealso::

       :ref:`change_4009`

.. change:: 4018
:tags: bug, sql
🎟️ 4018

   The rules for type coercion between :class:`.Numeric`, :class:`.Integer`,
   and date-related types now include additional logic that will attempt
   to preserve the settings of the incoming type on the "resolved" type.
   Currently the target for this is the ``asdecimal`` flag, so that
   a math operation between :class:`.Numeric` or :class:`.Float` and
   :class:`.Integer` will preserve the "asdecimal" flag as well as
   if the type should be the :class:`.Float` subclass.

   .. seealso::

       :ref:`change_floats_12`

.. change:: 4020
:tags: bug, sql, mysql
🎟️ 4020

   The result processor for the :class:`.Float` type now unconditionally
   runs values through the ``float()`` processor if the dialect
   specifies that it also supports "native decimal" mode.  While most
   backends will deliver Python ``float`` objects for a floating point
   datatype, the MySQL backends in some cases lack the typing information
   in order to provide this and return ``Decimal`` unless the float
   conversion is done.

   .. seealso::

       :ref:`change_floats_12`

.. change:: 4017
:tags: bug, sql
🎟️ 4017

   Added some extra strictness to the handling of Python "float" values
   passed to SQL statements.  A "float" value will be associated with the
   :class:`.Float` datatype and not the Decimal-coercing :class:`.Numeric`
   datatype as was the case before, eliminating a confusing warning
   emitted on SQLite as well as unecessary coercion to Decimal.

   .. seealso::

       :ref:`change_floats_12`

.. change:: 3058
:tags: feature, orm
🎟️ 3058

   Added a new feature :func:`.orm.with_expression` that allows an ad-hoc
   SQL expression to be added to a specific entity in a query at result
   time.  This is an alternative to the SQL expression being delivered as
   a separate element in the result tuple.

   .. seealso::

       :ref:`change_3058`

.. change:: 3496
:tags: bug, orm
🎟️ 3496

   An UPDATE emitted as a result of the
   :paramref:`.relationship.post_update` feature will now integrate with
   the versioning feature to both bump the version id of the row as well
   as assert that the existing version number was matched.

   .. seealso::

       :ref:`change_3496`

.. change:: 3769
:tags: bug, ext
🎟️ 3769

   The :meth:`.AssociationProxy.any`, :meth:`.AssociationProxy.has`
   and :meth:`.AssociationProxy.contains` comparison methods now support
   linkage to an attribute that is itself also an
   :class:`.AssociationProxy`, recursively.

   .. seealso::

       :ref:`change_3769`

.. change:: 3853
:tags: bug, ext
🎟️ 3853

   Implemented in-place mutation operators ``__ior__``, ``__iand__``,
   ``__ixor__`` and ``__isub__`` for :class:`.mutable.MutableSet`
   and ``__iadd__`` for :class:`.mutable.MutableList` so that change
   events are fired off when these mutator methods are used to alter the
   collection.

   .. seealso::

       :ref:`change_3853`

.. change:: 3847
:tags: bug, declarative
🎟️ 3847

   A warning is emitted if the :attr:`.declared_attr.cascading` modifier
   is used with a declarative attribute that is itself declared on
   a class that is to be mapped, as opposed to a declarative mixin
   class or ``__abstract__`` class.  The :attr:`.declared_attr.cascading`
   modifier currently only applies to mixin/abstract classes.

.. change:: 4003
:tags: feature, oracle
🎟️ 4003

   The Oracle dialect now inspects unique and check constraints when using
   :meth:`.Inspector.get_unique_constraints`,
   :meth:`.Inspector.get_check_constraints`.
   As Oracle does not have unique constraints that are separate from a unique
   :class:`.Index`, a :class:`.Table` that's reflected will still continue
   to not have :class:`.UniqueConstraint` objects associated with it.
   Pull requests courtesy Eloy Felix.

   .. seealso::

       :ref:`change_4003`

.. change:: 3948
:tags: feature, orm
🎟️ 3948

   Added a new style of mapper-level inheritance loading
   "polymorphic selectin".  This style of loading
   emits queries for each subclass in an inheritance
   hierarchy subsequent to the load of the base
   object type, using IN to specify the desired
   primary key values.

   .. seealso::

       :ref:`change_3948`

.. change:: 3472
:tags: bug, orm
🎟️ 3471, 3472

   Repaired several use cases involving the
   :paramref:`.relationship.post_update` feature when used in conjunction
   with a column that has an "onupdate" value.   When the UPDATE emits,
   the corresponding object attribute is now expired or refreshed so that
   the newly generated "onupdate" value can populate on the object;
   previously the stale value would remain.  Additionally, if the target
   attribute is set in Python for the INSERT of the object, the value is
   now re-sent during the UPDATE so that the "onupdate" does not overwrite
   it (note this works just as well for server-generated onupdates).
   Finally, the :meth:`.SessionEvents.refresh_flush` event is now emitted
   for these attributes when refreshed within the flush.

   .. seealso::

       :ref:`change_3471`

.. change:: 3996
:tags: bug, orm
🎟️ 3996

   Fixed bug where programmatic version_id counter in conjunction with
   joined table inheritance would fail if the version_id counter
   were not actually incremented and no other values on the base table
   were modified, as the UPDATE would have an empty SET clause.  Since
   programmatic version_id where version counter is not incremented
   is a documented use case, this specific condition is now detected
   and the UPDATE now sets the version_id value to itself, so that
   concurrency checks still take place.

.. change:: 3848
:tags: bug, orm, declarative
🎟️ 3848

   Fixed bug where using :class:`.declared_attr` on an
   :class:`.AbstractConcreteBase` where a particular return value were some
   non-mapped symbol, including ``None``, would cause the attribute
   to hard-evaluate just once and store the value to the object
   dictionary, not allowing it to invoke for subclasses.   This behavior
   is normal when :class:`.declared_attr` is on a mapped class, and
   does not occur on a mixin or abstract class.  Since
   :class:`.AbstractConcreteBase` is both "abstract" and actually
   "mapped", a special exception case is made here so that the
   "abstract" behavior takes precedence for :class:`.declared_attr`.

.. change:: 3673
:tags: bug, orm
🎟️ 3673

   The versioning feature does not support NULL for the version counter.
   An exception is now raised if the version id is programmatic and
   was set to NULL for an UPDATE.  Pull request courtesy Diana Clarke.

.. change:: 3999
:tags: bug, sql
🎟️ 3999

   The operator precedence for all comparison operators such as LIKE, IS,
   IN, MATCH, equals, greater than, less than, etc. has all been merged
   into one level, so that expressions which make use of these against
   each other will produce parentheses between them.   This suits the
   stated operator precedence of databases like Oracle, MySQL and others
   which place all of these operators as equal precedence, as well as
   Postgresql as of 9.5 which has also flattened its operator precendence.

   .. seealso::

       :ref:`change_3999`

.. change:: 3796
:tags: bug, orm
🎟️ 3796

   Removed a very old keyword argument from :class:`.scoped_session`
   called ``scope``.  This keyword was never documented and was an
   early attempt at allowing for variable scopes.

   .. seealso::

       :ref:`change_3796`

.. change:: 3871
:tags: bug, mysql
🎟️ 3871

   Added support for views that are unreflectable due to stale
   table definitions, when calling :meth:`.MetaData.reflect`; a warning
   is emitted for the table that cannot respond to ``DESCRIBE``,
   but the operation succeeds.

.. change:: baked_opts
:tags: feature, ext

   Added new flag :paramref:`.Session.enable_baked_queries` to the
   :class:`.Session` to allow baked queries to be disabled
   session-wide, reducing memory use.   Also added new :class:`.Bakery`
   wrapper so that the bakery returned by :paramref:`.BakedQuery.bakery`
   can be inspected.

.. change:: 3988
:tags: bug, orm
🎟️ 3988

   Fixed bug where combining a "with_polymorphic" load in conjunction
   with subclass-linked relationships that specify joinedload with
   innerjoin=True, would fail to demote those "innerjoins" to
   "outerjoins" to suit the other polymorphic classes that don't
   support that relationship.   This applies to both a single and a
   joined inheritance polymorphic load.

.. change:: 3991
:tags: bug, orm
🎟️ 3991

   Added new argument :paramref:`.with_for_update` to the
   :meth:`.Session.refresh` method.  When the :meth:`.Query.with_lockmode`
   method were deprecated in favor of :meth:`.Query.with_for_update`,
   the :meth:`.Session.refresh` method was never updated to reflect
   the new option.

   .. seealso::

       :ref:`change_3991`

.. change:: 3984
:tags: bug, orm
🎟️ 3984

   Fixed bug where a :func:`.column_property` that is also marked as
   "deferred" would be marked as "expired" during a flush, causing it
   to be loaded along with the unexpiry of regular attributes even
   though this attribute was never accessed.

.. change:: 3873
:tags: bug, sql
🎟️ 3873

   Repaired issue where the type of an expression that used
   :meth:`.ColumnOperators.is_` or similar would not be a "boolean" type,
   instead the type would be "nulltype", as well as when using custom
   comparison operators against an untyped expression.   This typing can
   impact how the expression behaves in larger contexts as well as
   in result-row-handling.

.. change:: 3941
:tags: bug, ext
🎟️ 3941

   Improved the association proxy list collection so that premature
   autoflush against a newly created association object can be prevented
   in the case where ``list.append()`` is being used, and a lazy load
   would be invoked when the association proxy accesses the endpoint
   collection.  The endpoint collection is now accessed first before
   the creator is invoked to produce the association object.

.. change:: 3969
:tags: bug, sql
🎟️ 3969

   Fixed the negation of a :class:`.Label` construct so that the
   inner element is negated correctly, when the :func:`.not_` modifier
   is applied to the labeled expression.

.. change:: 3944
:tags: feature, orm
🎟️ 3944

   Added a new kind of eager loading called "selectin" loading.  This
   style of loading is very similar to "subquery" eager loading,
   except that it uses an IN expression given a list of primary key
   values from the loaded parent objects, rather than re-stating the
   original query.   This produces a more efficient query that is
   "baked" (e.g. the SQL string is cached) and also works in the
   context of :meth:`.Query.yield_per`.

   .. seealso::

       :ref:`change_3944`

.. change::
:tags: bug, orm
🎟️ 3967

   Fixed bug in subquery eager loading where the "join_depth" parameter
   for self-referential relationships would not be correctly honored,
   loading all available levels deep rather than correctly counting
   the specified number of levels for eager loading.

.. change::
:tags: bug, orm

   Added warnings to the LRU "compiled cache" used by the :class:`.Mapper`
   (and ultimately will be for other ORM-based LRU caches) such that
   when the cache starts hitting its size limits, the application will
   emit a warning that this is a performance-degrading situation that
   may require attention.   The LRU caches can reach their size limits
   primarily if an application is making use of an unbounded number
   of :class:`.Engine` objects, which is an antipattern.  Otherwise,
   this may suggest an issue that should be brought to the SQLAlchemy
   developer's attention.

.. change:: 3964
:tags: bug, postgresql
🎟️ 3964

   Fixed bug where the base :class:`.sqltypes.ARRAY` datatype would not
   invoke the bind/result processors of :class:`.postgresql.ARRAY`.

.. change:: 3963
:tags: bug, orm
🎟️ 3963

   Fixed bug to improve upon the specificity of loader options that
   take effect subsequent to the lazy load of a related entity, so
   that the loader options will match to an aliased or non-aliased
   entity more specifically if those options include entity information.

.. change:: 3954
:tags: feature, orm
🎟️ 3954

   The ``lazy="select"`` loader strategy now makes used of the
   :class:`.BakedQuery` query caching system in all cases.  This
   removes most overhead of generating a :class:`.Query` object and
   running it into a :func:`.select` and then string SQL statement from
   the process of lazy-loading related collections and objects.  The
   "baked" lazy loader has also been improved such that it can now
   cache in most cases where query load options are used.

   .. seealso::

       :ref:`change_3954`

.. change:: 3740
:tags: bug, sql
🎟️ 3740

   The system by which percent signs in SQL statements are "doubled"
   for escaping purposes has been refined.   The "doubling" of percent
   signs mostly associated with the :obj:`.literal_column` construct
   as well as operators like :meth:`.ColumnOperators.contains` now
   occurs based on the stated paramstyle of the DBAPI in use; for
   percent-sensitive paramstyles as are common with the Postgresql
   and MySQL drivers the doubling will occur, for others like that
   of SQLite it will not.   This allows more database-agnostic use
   of the :obj:`.literal_column` construct to be possible.

   .. seealso::

       :ref:`change_3740`

.. change:: 3959
:tags: bug, postgresql
🎟️ 3959

   Added support for all possible "fields" identifiers when reflecting the
   Postgresql ``INTERVAL`` datatype, e.g. "YEAR", "MONTH", "DAY TO
   MINUTE", etc..   In addition, the :class:`.postgresql.INTERVAL`
   datatype itself now includes a new parameter
   :paramref:`.postgresql.INTERVAL.fields` where these qualifiers can be
   specified; the qualifier is also reflected back into the resulting
   datatype upon reflection / inspection.

   .. seealso::

       :ref:`change_3959`

.. change:: 3957
:tags: bug, sql
🎟️ 3957

   Fixed bug where a column-level :class:`.CheckConstraint` would fail
   to compile the SQL expression using the underlying dialect compiler
   as well as apply proper flags to generate literal values as
   inline, in the case that the sqltext is a Core expression and
   not just a plain string.   This was long-ago fixed for table-level
   check constraints in 0.9 as part of :ticket:`2742`, which more commonly
   feature Core SQL expressions as opposed to plain string expressions.

.. change:: 2626
:tags: bug, mssql
🎟️ 2626

   The SQL Server dialect now allows for a database and/or owner name
   with a dot inside of it, using brackets explicitly in the string around
   the owner and optionally the database name as well.  In addition,
   sending the :class:`.quoted_name` construct for the schema name will
   not split on the dot and will deliver the full string as the "owner".
   :class:`.quoted_name` is also now available from the ``sqlalchemy.sql``
   import space.

   .. seealso::

       :ref:`change_2626`

.. change:: 3953
:tags: feature, sql
🎟️ 3953

   Added a new kind of :func:`.bindparam` called "expanding".  This is
   for use in ``IN`` expressions where the list of elements is rendered
   into individual bound parameters at statement execution time, rather
   than at statement compilation time.  This allows both a single bound
   parameter name to be linked to an IN expression of multiple elements,
   as well as allows query caching to be used with IN expressions.  The
   new feature allows the related features of "select in" loading and
   "polymorphic in" loading to make use of the baked query extension
   to reduce call overhead.   This feature should be considered to be
   **experimental** for 1.2.

   .. seealso::

       :ref:`change_3953`

.. change:: 3923
:tags: bug, sql
🎟️ 3923

   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.

.. change:: 3785
:tags: bug, sql
🎟️ 3785

   The expression used for COLLATE as rendered by the column-level
   :func:`.expression.collate` and :meth:`.ColumnOperators.collate` is now
   quoted as an identifier when the name is case sensitive, e.g. has
   uppercase characters.  Note that this does not impact type-level
   collation, which is already quoted.

   .. seealso::

       :ref:`change_3785`

.. change:: 3229
:tags: feature, orm, ext
🎟️ 3229

   The :meth:`.Query.update` method can now accommodate both
   hybrid attributes as well as composite attributes as a source
   of the key to be placed in the SET clause.   For hybrids, an
   additional decorator :meth:`.hybrid_property.update_expression`
   is supplied for which the user supplies a tuple-returning function.

   .. seealso::

       :ref:`change_3229`

.. change:: 3753
:tags: bug, orm
🎟️ 3753

   The :func:`.attributes.flag_modified` function now raises
   :class:`.InvalidRequestError` if the named attribute key is not
   present within the object, as this is assumed to be present
   in the flush process.  To mark an object "dirty" for a flush
   without referring to any specific attribute, the
   :func:`.attributes.flag_dirty` function may be used.

   .. seealso::

       :ref:`change_3753`

.. change:: 3911_3912
:tags: bug, ext
🎟️ 3911, 3912

   The :class:`sqlalchemy.ext.hybrid.hybrid_property` class now supports
   calling mutators like ``setter``, ``expression`` etc. multiple times
   across subclasses, and now provides a ``getter`` mutator, so that
   a particular hybrid can be repurposed across subclasses or other
   classes.  This now matches the behavior of ``property`` in standard
   Python.

   .. seealso::

       :ref:`change_3911_3912`

.. change:: 1546
:tags: feature, sql, postgresql, mysql, oracle
🎟️ 1546

   Added support for SQL comments on :class:`.Table` and :class:`.Column`
   objects, via the new :paramref:`.Table.comment` and
   :paramref:`.Column.comment` arguments.   The comments are included
   as part of DDL on table creation, either inline or via an appropriate
   ALTER statement, and are also reflected back within table reflection,
   as well as via the :class:`.Inspector`.   Supported backends currently
   include MySQL, Postgresql, and Oracle.  Many thanks to Frazer McLean
   for a large amount of effort on this.

   .. seealso::

       :ref:`change_1546`

.. change:: 3919
:tags: feature, engine
🎟️ 3919

   Added native "pessimistic disconnection" handling to the :class:`.Pool`
   object.  The new parameter :paramref:`.Pool.pre_ping`, available from
   the engine as :paramref:`.create_engine.pool_pre_ping`, applies an
   efficient form of the "pre-ping" recipe featured in the pooling
   documentation, which upon each connection check out, emits a simple
   statement, typically "SELECT 1", to test the connection for liveness.
   If the existing connection is no longer able to respond to commands,
   the connection is transparently recycled, and all other connections
   made prior to the current timestamp are invalidated.

   .. seealso::

       :ref:`pool_disconnects_pessimistic`

       :ref:`change_3919`

.. change:: 3939
:tags: bug, sql
🎟️ 3939

   Fixed bug where the use of an :class:`.Alias` object in a column
   context would raise an argument error when it tried to group itself
   into a parenthesized expression.   Using :class:`.Alias` in this way
   is not yet a fully supported API, however it applies to some end-user
   recipes and may have a more prominent role in support of some
   future Postgresql features.

.. change:: 3366
:tags: bug, orm
🎟️ 3366

   The "evaluate" strategy used by :meth:`.Query.update` and
   :meth:`.Query.delete` can now accommodate a simple
   object comparison from a many-to-one relationship to an instance,
   when the attribute names of the primary key / foreign key columns
   don't match the actual names of the columns.  Previously this would
   do a simple name-based match and fail with an AttributeError.

.. change:: 3896_a
:tags: feature, orm
🎟️ 3896

   Added new attribute event :meth:`.AttributeEvents.bulk_replace`.
   This event is triggered when a collection is assigned to a
   relationship, before the incoming collection is compared with the
   existing one.  This early event allows for conversion of incoming
   non-ORM objects as well.  The event is integrated with the
   ``validates`` decorator.

   .. seealso::

       :ref:`change_3896_event`

.. change:: 3896_b
:tags: bug, orm
🎟️ 3896

   The ``validates`` decorator now allows the decorated method to receive
   objects from a "bulk collection set" operation that have not yet
   been compared to the existing collection.  This allows incoming values
   to be converted to compatible ORM objects as is already allowed
   from an "append" event.   Note that this means that the
   ``validates`` method is called for **all** values during a collection
   assignment, rather than just the ones that are new.

   .. seealso::

       :ref:`change_3896_validates`

.. change:: 3938
:tags: bug, engine
🎟️ 3938

   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:: 3303
:tags: feature, orm
🎟️ 3303

   Added new event handler :meth:`.AttributeEvents.modified` which is
   triggered when the func:`.attributes.flag_modified` function is
   invoked, which is common when using the :mod:`sqlalchemy.ext.mutable`
   extension module.

   .. seealso::

       :ref:`change_3303`

.. change:: 3918
:tags: bug, ext
🎟️ 3918

   Fixed a bug in the ``sqlalchemy.ext.serializer`` extension whereby
   an "annotated" SQL element (as produced by the ORM for many types
   of SQL expressions) could not be reliably serialized.  Also bumped
   the default pickle level for the serializer to "HIGHEST_PROTOCOL".

.. change:: 3891
:tags: bug, orm
🎟️ 3891

   Fixed bug in single-table inheritance where the select_from()
   argument would not be taken into account when limiting rows
   to a subclass.  Previously, only expressions in the
   columns requested would be taken into account.

   .. seealso::

       :ref:`change_3891`

.. change:: 3913
:tags: bug, orm
🎟️ 3913

   When assigning a collection to an attribute mapped by a relationship,
   the previous collection is no longer mutated.  Previously, the old
   collection would be emptied out in conjunction with the "item remove"
   events that fire off; the events now fire off without affecting
   the old collection.

   .. seealso::

       :ref:`change_3913`

.. change:: 3932
:tags: bug, oracle
🎟️ 3932

   The cx_Oracle dialect now supports "sane multi rowcount", that is,
   when a series of parameter sets a