Pin sqlalchemy to latest version 1.4.27

[pyup-bot]

This PR pins SQLAlchemy to the latest release 1.4.27.

Changelog

1.4.27

:include_notes_from: unreleased_14

.. changelog::

1.4.26

:released: October 19, 2021

 .. change::
     :tags: orm
     :tickets: 6284

     Passing a :class:`.Query` object to :meth:`_orm.Session.execute` is not
     the intended use of this object, and will now raise a deprecation warning.

 .. change::
     :tags: bug, postgresql
     :tickets: 5387

     Added a "disconnect" condition for the "SSL SYSCALL error: Bad address"
     error message as reported by psycopg2. Pull request courtesy Zeke Brechtel.

 .. change::
     :tags: bug, orm

     Improved the exception message generated when configuring a mapping with
     joined table inheritance where the two tables either have no foreign key
     relationships set up, or where they have multiple foreign key relationships
     set up. The message is now ORM specific and includes context that the
     :paramref:`_orm.Mapper.inherit_condition` parameter may be needed
     particularly for the ambiguous foreign keys case.


 .. change::
     :tags: bug, sql
     :tickets: 6520

     Fixed issue where SQL queries using the
     :meth:`_functions.FunctionElement.within_group` construct could not be
     pickled, typically when using the ``sqlalchemy.ext.serializer`` extension
     but also for general generic pickling.

 .. change::
     :tags: bug, orm
     :tickets: 7189

     Fixed issue with :func:`_orm.with_loader_criteria` feature where ON
     criteria would not be added to a JOIN for a query of the form
     ``select(A).join(B)``, stating a target while making use of an implicit
     ON clause.

 .. change::
     :tags: bug, orm
     :tickets: 7205

     Fixed bug where the ORM "plugin", necessary for features such as
     :func:`_orm.with_loader_criteria` to work correctly, would not be applied
     to a :func:`_sql.select` which queried from an ORM column expression if it
     made use of the :meth:`_sql.ColumnElement.label` modifier.



 .. change::
     :tags: bug, mypy
     :tickets: 6435

     Fixed issue in mypy plugin to improve upon some issues detecting ``Enum()``
     SQL types containing custom Python enumeration classes. Pull request
     courtesy Hiroshi Ogawa.

 .. change::
     :tags: bug, mysql
     :tickets: 7144

     Fixed issue in MySQL :func:`_mysql.match` construct where passing a clause
     expression such as :func:`_sql.bindparam` or other SQL expression for the
     "against" parameter would fail. Pull request courtesy Anton Kovalevich.


 .. change::
     :tags: bug, mssql
     :tickets: 7160

     Fixed issue with :meth:`.Inspector.get_foreign_keys` where foreign
     keys were omitted if they were established against a unique
     index instead of a unique constraint.


 .. change::
     :tags: usecase, mssql

     Added reflection support for SQL Server foreign key options, including
     "ON UPDATE" and "ON DELETE" values of "CASCADE" and "SET NULL".

 .. change::
     :tags: bug, sql
     :tickets: 4123

     Repaired issue in new :paramref:`_sql.HasCTE.cte.nesting` parameter
     introduced with :ticket:`4123` where a recursive :class:`_sql.CTE` using
     :paramref:`_sql.HasCTE.cte.recursive` in typical conjunction with UNION
     would not compile correctly.  Additionally makes some adjustments so that
     the :class:`_sql.CTE` construct creates a correct cache key.
     Pull request courtesy Eric Masseran.

 .. change::
     :tags: bug, engine
     :tickets: 7130

     Fixed issue where the deprecation warning for the :class:`.URL` constructor
     which indicates that the :meth:`.URL.create` method should be used would
     not emit if a full positional argument list of seven arguments were passed;
     additionally, validation of URL arguments will now occur if the constructor
     is called in this way, which was being skipped previously.

 .. change::
     :tags: bug, orm
     :tickets: 7103

     Add missing methods added in :ticket:`6991` to
     :class:`_scoping.scoped_session` and :func:`_asyncio.async_scoped_session`.

 .. change::
     :tags: bug, examples
     :tickets: 7169

     Repaired the examples in examples/versioned_rows to use SQLAlchemy 1.4 APIs
     correctly; these examples had been missed when API changes like removing
     "passive" from :meth:`_orm.Session.is_modified` were made as well as the
     :meth:`_ormevents.SessionEvents.do_orm_execute()` event hook were added.

 .. change::
     :tags: bug, orm
     :tickets: 6974, 6972

     An extra layer of warning messages has been added to the functionality
     of :meth:`_orm.Query.join` and the ORM version of
     :meth:`_sql.Select.join`, where a few places where "automatic aliasing"
     continues to occur will now be called out as a pattern to avoid, mostly
     specific to the area of joined table inheritance where classes that share
     common base tables are being joined together without using explicit aliases.
     One case emits a legacy warning for a pattern that's not recommended,
     the other case is fully deprecated.

     The automatic aliasing within ORM join() which occurs for overlapping
     mapped tables does not work consistently with all APIs such as
     :func:`_orm.contains_eager()`, and rather than continue to try to make
     these use cases work everywhere, replacing with a more user-explicit
     pattern is clearer, less prone to bugs and simplifies SQLAlchemy's
     internals further.

     The warnings include links to the errors.rst page where each pattern is
     demonstrated along with the recommended pattern to fix.

     .. seealso::

         :ref:`error_xaj1`

         :ref:`error_xaj2`

 .. change::
     :tags: bug, sql
     :tickets: 7061

     Account for the :paramref:`_sql.table.schema` parameter passed to
     the :func:`_sql.table` construct, such that it is taken into account
     when accessing the :attr:`_sql.TableClause.fullname` attribute.

 .. change::
     :tags: bug, sql
     :tickets: 7140

     Fixed an inconsistency in the :meth:`_sql.ColumnOperators.any_` /
     :meth:`_sql.ColumnOperators.all_` functions / methods where the special
     behavior these functions have of "flipping" the expression such that the
     "ANY" / "ALL" expression is always on the right side would not function if
     the comparison were against the None value, that is, "column.any_() ==
     None" should produce the same SQL expression as "null() == column.any_()".
     Added more docs to clarify this as well, plus mentions that any_() / all_()
     generally supersede the ARRAY version "any()" / "all()".

 .. change::
     :tags: engine, bug, postgresql
     :tickets: 3247

     The :meth:`_reflection.Inspector.reflect_table` method now supports
     reflecting tables that do not have user defined columns. This allows
     :meth:`_schema.MetaData.reflect` to properly complete reflection on
     databases that contain such tables. Currently, only PostgreSQL is known to
     support such a construct among the common database backends.

 .. change::
     :tags: sql, bug, regression
     :tickets: 7177

     Fixed issue where "expanding IN" would fail to function correctly with
     datatypes that use the :meth:`_types.TypeEngine.bind_expression` method,
     where the method would need to be applied to each element of the
     IN expression rather than the overall IN expression itself.

 .. change::
     :tags: postgresql, bug, regression
     :tickets: 7177

     Fixed issue where IN expressions against a series of array elements, as can
     be done with PostgreSQL, would fail to function correctly due to multiple
     issues within the "expanding IN" feature of SQLAlchemy Core that was
     standardized in version 1.4.  The psycopg2 dialect now makes use of the
     :meth:`_types.TypeEngine.bind_expression` method with :class:`_types.ARRAY`
     to portably apply the correct casts to elements.  The asyncpg dialect was
     not affected by this issue as it applies bind-level casts at the driver
     level rather than at the compiler level.


 .. change::
     :tags: bug, mysql
     :tickets: 7204

     Fixed installation issue where the ``sqlalchemy.dialects.mysql`` module
     would not be importable if "greenlet" were not installed.

 .. change::
     :tags: bug, mssql
     :tickets: 7168

     Fixed issue with :meth:`.Inspector.has_table` where it would return False
     if a local temp table with the same name from a different session happened
     to be returned first when querying tempdb.  This is a continuation of
     :ticket:`6910` which accounted for the temp table existing only in the
     alternate session and not the current one.

 .. change::
     :tags: bug, orm
     :tickets: 7128

     Fixed bug where iterating a :class:`.Result` from a :class:`_orm.Session`
     after that :class:`_orm.Session` were closed would partially attach objects
     to that session in an essentially invalid state. It now raises an exception
     with a link to new documentation if an **un-buffered** result is iterated
     from a :class:`_orm.Session` that was closed or otherwise had the
     :meth:`_orm.Session.expunge_all` method called after that :class:`.Result`
     was generated. The ``prebuffer_rows`` execution option, as is used
     automatically by the asyncio extension for client-side result sets, may be
     used to produce a :class:`.Result` where the ORM objects are prebuffered,
     and in this case iterating the result will produce a series of detached
     objects.

     .. seealso::

         :ref:`error_lkrp`

 .. change::
     :tags: bug, mssql, regression
     :tickets: 7129

     Fixed bug in SQL Server :class:`_mssql.DATETIMEOFFSET` datatype where the
     ODBC implementation would not generate the correct DDL, for cases where the
     type were converted using the ``dialect.type_descriptor()`` method, the
     usage of which is illustrated in some documented examples for
     :class:`.TypeDecorator`, though not necessary for most datatypes.
     Regression was introduced by :ticket:`6366`. As part of this change, the
     full list of SQL Server date types have been amended to return a "dialect
     impl" that generates the same DDL name as the supertype.

 .. change::
     :tags: bug, sql
     :tickets: 7153

     Adjusted the "column disambiguation" logic that's new in 1.4, where the
     same expression repeated gets an "extra anonymous" label, so that the logic
     more aggressively deduplicates those labels when the repeated element
     is the same Python expression object each time, as occurs in cases like
     when using "singleton" values like :func:`_sql.null`.  This is based on
     the observation that at least some databases (e.g. MySQL, but not SQLite)
     will raise an error if the same label is repeated inside of a subquery.

 .. change::
     :tags: bug, orm
     :tickets: 7154

     Related to :ticket:`7153`, fixed an issue where result column lookups would
     fail for "adapted" SELECT statements that selected for "constant" value
     expressions most typically the NULL expression, as would occur in such
     places as joined eager loading in conjunction with limit/offset. This was
     overall a regression due to issue :ticket:`6259` which removed all
     "adaption" for constants like NULL, "true", and "false" when rewriting
     expressions in a SQL statement, but this broke the case where the same
     adaption logic were used to resolve the constant to a labeled expression
     for the purposes of result set targeting.

 .. change::
     :tags: bug, orm, regression
     :tickets: 7134

     Fixed regression where ORM loaded objects could not be pickled in cases
     where loader options making use of ``"*"`` were used in certain
     combinations, such as combining the :func:`_orm.joinedload` loader strategy
     with ``raiseload('*')`` of sub-elements.


 .. change::
     :tags: bug, engine
     :tickets: 7077

     Implemented proper ``__reduce__()`` methods for all SQLAlchemy exception
     objects to ensure they all support clean round trips when pickling, as
     exception objects are often serialized for the purposes of various
     debugging tools.

 .. change::
     :tags: bug, orm, regression
     :tickets: 7209

     Fixed regression where the use of a :class:`_hybrid.hybrid_property`
     attribute or a mapped :func:`_orm.composite` attribute as a key passed to
     the :meth:`_dml.Update.values` method for an ORM-enabled
     :class:`_dml.Update` statement, as well as when using it via the legacy
     :meth:`_orm.Query.update` method, would be processed for incoming
     ORM/hybrid/composite values within the compilation stage of the UPDATE
     statement, which meant that in those cases where caching occurred,
     subsequent invocations of the same statement would no longer receive the
     correct values. This would include not only hybrids that use the
     :meth:`_hybrid.hybrid_property.update_expression` method, but any use of a
     plain hybrid attribute as well. For composites, the issue instead caused a
     non-repeatable cache key to be generated, which would break caching and
     could fill up the statement cache with repeated statements.

     The :class:`_dml.Update` construct now handles the processing of key/value
     pairs passed to :meth:`_dml.Update.values` and
     :meth:`_dml.Update.ordered_values` up front when the construct is first
     generated, before the cache key has been generated so that the key/value
     pairs are processed each time, and so that the cache key is generated
     against the individual column/value pairs that will ultimately be
     used in the statement.


.. changelog::

1.4.25

:released: September 22, 2021

 .. change::
     :tags: bug, platform, regression
     :tickets: 7024

     Fixed regression due to :ticket:`7024` where the reorganization of the
     "platform machine" names used by the ``greenlet`` dependency mis-spelled
     "aarch64" and additionally omitted uppercase "AMD64" as is needed for
     Windows machines. Pull request courtesy James Dow.

.. changelog::

1.4.24

:released: September 22, 2021

 .. change::
     :tags: bug, asyncio
     :tickets: 6943

     Fixed a bug in :meth:`_asyncio.AsyncSession.execute` and
     :meth:`_asyncio.AsyncSession.stream` that required ``execution_options``
     to be an instance of ``immutabledict`` when defined. It now
     correctly accepts any mapping.

 .. change::
     :tags: engine, asyncio, usecase
     :tickets: 6832

     Improve the interface used by adapted drivers, like the asyncio ones,
     to access the actual connection object returned by the driver.

     The :class:`._ConnectionFairy` object has two new attributes:

     * :attr:`._ConnectionFairy.dbapi_connection` always represents a DBAPI
       compatible object. For pep-249 drivers, this is the DBAPI connection as
       it always has been, previously accessed under the ``.connection``
       attribute. For asyncio drivers that SQLAlchemy adapts into a pep-249
       interface, the returned object will normally be a SQLAlchemy adaption
       object called :class:`_engine.AdaptedConnection`.
     * :attr:`._ConnectionFairy.driver_connection` always represents the actual
       connection object maintained by the third party pep-249 DBAPI or async
       driver in use. For standard pep-249 DBAPIs, this will always be the same
       object as that of the ``dbapi_connection``. For an asyncio driver, it
       will be the underlying asyncio-only connection object.

     The ``.connection`` attribute remains available and is now a legacy alias
     of ``.dbapi_connection``.

     .. seealso::

         :ref:`faq_dbapi_connection`


 .. change::
     :tags: bug, sql
     :tickets: 7052

     Implemented missing methods in :class:`_functions.FunctionElement` which,
     while unused, would lead pylint to report them as unimplemented abstract
     methods.

 .. change::
     :tags: bug, mssql, reflection
     :tickets: 6910

     Fixed an issue where :meth:`_reflection.has_table` returned
     ``True`` for local temporary tables that actually belonged to a
     different SQL Server session (connection). An extra check is now
     performed to ensure that the temp table detected is in fact owned
     by the current session.

 .. change::
     :tags: bug, engine, regression
     :tickets: 6913

     Fixed issue where the ability of the
     :meth:`_events.ConnectionEvents.before_execute` method to alter the SQL
     statement object passed, returning the new object to be invoked, was
     inadvertently removed. This behavior has been restored.


 .. change::
     :tags: bug, engine
     :tickets: 6958

     Ensure that ``str()`` is called on the an
     :paramref:`_url.URL.create.password` argument, allowing usage of objects
     that implement the ``__str__()`` method as password attributes. Also
     clarified that one such object is not appropriate to dynamically change the
     password for each database connection; the approaches at
     :ref:`engines_dynamic_tokens` should be used instead.

 .. change::
     :tags: bug, orm, regression
     :tickets: 6979

     Fixed ORM issue where column expressions passed to ``query()`` or
     ORM-enabled ``select()`` would be deduplicated on the identity of the
     object, such as a phrase like ``select(A.id, null(), null())`` would
     produce only one "NULL" expression, which previously was not the case in
     1.3. However, the change also allows for ORM expressions to render as given
     as well, such as ``select(A.data, A.data)`` will produce a result row with
     two columns.

 .. change::
     :tags: bug, engine
     :tickets: 6983

     Fixed issue in :class:`_engine.URL` where validation of "drivername" would
     not appropriately respond to the ``None`` value where a string were
     expected.

 .. change::
     :tags: bug, mypy
     :tickets: 6950

     Fixed issue where mypy plugin would crash when interpreting a
     ``query_expression()`` construct.

 .. change::
     :tags: usecase, sql
     :tickets: 4123

     Added new parameter :paramref:`_sql.HasCTE.cte.nesting` to the
     :class:`_sql.CTE` constructor and :meth:`_sql.HasCTE.cte` method, which
     flags the CTE as one which should remain nested within an enclosing CTE,
     rather than being moved to the top level of the outermost SELECT. While in
     the vast majority of cases there is no difference in SQL functionality,
     users have identified various edge-cases where true nesting of CTE
     constructs is desirable. Much thanks to Eric Masseran for lots of work on
     this intricate feature.

 .. change::
     :tags: usecase, engine, orm
     :tickets: 6990

     Added new methods :meth:`_orm.Session.scalars`,
     :meth:`_engine.Connection.scalars`, :meth:`_asyncio.AsyncSession.scalars`
     and :meth:`_asyncio.AsyncSession.stream_scalars`, which provide a short cut
     to the use case of receiving a row-oriented :class:`_result.Result` object
     and converting it to a :class:`_result.ScalarResult` object via the
     :meth:`_engine.Result.scalars` method, to return a list of values rather
     than a list of rows. The new methods are analogous to the long existing
     :meth:`_orm.Session.scalar` and :meth:`_engine.Connection.scalar` methods
     used to return a single value from the first row only. Pull request
     courtesy Miguel Grinberg.

 .. change::
     :tags: usecase, orm
     :tickets: 6955

     Added loader options to :meth:`_orm.Session.merge` and
     :meth:`_asyncio.AsyncSession.merge` via a new
     :paramref:`_orm.Session.merge.options` parameter, which will apply the
     given loader options to the ``get()`` used internally by merge, allowing
     eager loading of relationships etc. to be applied when the merge process
     loads a new object. Pull request courtesy Daniel Stone.

 .. change::
     :tags: feature, asyncio, mysql
     :tickets: 6993

     Added initial support for the ``asyncmy`` asyncio database driver for MySQL
     and MariaDB. This driver is very new, however appears to be the only
     current alternative to the ``aiomysql`` driver which currently appears to
     be unmaintained and is not working with current Python versions. Much
     thanks to long2ice for the pull request for this dialect.

     .. seealso::

         :ref:`asyncmy`

 .. change::
     :tags: bug, asyncio

     Added missing ``**kw`` arguments to the
     :meth:`_asyncio.AsyncSession.connection` method.

 .. change::
     :tags: bug, sql
     :tickets: 7055

     Fixed a two issues where combinations of ``select()`` and ``join()`` when
     adapted to form a copy of the element would not completely copy the state
     of all column objects associated with subqueries. A key problem this caused
     is that usage of the :meth:`_sql.ClauseElement.params` method (which should
     probably be moved into a legacy category as it is inefficient and error
     prone) would leave copies of the old :class:`_sql.BindParameter` objects
     around, leading to issues in correctly setting the parameters at execution
     time.



 .. change::
     :tags: bug, orm, regression
     :tickets: 6924

     Fixed issue in recently repaired ``Query.with_entities()`` method where the
     flag that determines automatic uniquing for legacy ORM ``Query`` objects
     only would be set to ``True`` inappropriately in cases where the
     ``with_entities()`` call would be setting the ``Query`` to return
     column-only rows, which are not uniqued.

 .. change::
     :tags: bug, postgresql
     :tickets: 6912

     Qualify ``version()`` call to avoid shadowing issues if a different
     search path is configured by the user.

 .. change::
     :tags: bug, engine, postgresql
     :tickets: 6963

     Fixed issue where an engine that had
     :paramref:`_sa.create_engine.implicit_returning` set to False would fail to
     function when PostgreSQL's "fast insertmany" feature were used in
     conjunction with a ``Sequence``, as well as if any kind of "executemany"
     with "return_defaults()" were used in conjunction with a ``Sequence``. Note
     that PostgreSQL "fast insertmany" uses "RETURNING" by definition, when the
     SQL statement is passed to the driver; overall, the
     :paramref:`_sa.create_engine.implicit_returning` flag is legacy and has no
     real use in modern SQLAlchemy, and will be deprecated in a separate change.

 .. change::
     :tags: bug, mypy
     :tickets: 6937

     Fixed issue in mypy plugin where columns on a mixin would not be correctly
     interpreted if the mapped class relied upon a ``__tablename__`` routine
     that came from a superclass.

 .. change::
     :tags: bug, postgresql
     :tickets: 6106

     The :class:`_postgresql.ENUM` datatype is PostgreSQL-native and therefore
     should not be used with the ``native_enum=False`` flag. This flag is now
     ignored if passed to the :class:`_postgresql.ENUM` datatype and a warning
     is emitted; previously the flag would cause the type object to fail to
     function correctly.


 .. change::
     :tags: bug, sql
     :tickets: 7036

     Fixed issue related to new :meth:`_sql.HasCTE.add_cte` feature where
     pairing two "INSERT..FROM SELECT" statements simultaneously would lose
     track of the two independent SELECT statements, leading to the wrong SQL.

 .. change::
     :tags: asyncio, bug
     :tickets: 6746

     Deprecate usage of :class:`_orm.scoped_session` with asyncio drivers. When
     using Asyncio the :class:`_asyncio.async_scoped_session` should be used
     instead.

 .. change::
     :tags: bug, platform
     :tickets: 7024

     Further adjusted the "greenlet" package specifier in setup.cfg to use a
     long chain of "or" expressions, so that the comparison of
     ``platform_machine`` to a specific identifier matches only the complete
     string.

 .. change::
     :tags: bug, sqlite

     Fixed bug where the error message for SQLite invalid isolation level on the
     pysqlite driver would fail to indicate that "AUTOCOMMIT" is one of the
     valid isolation levels.

 .. change::
     :tags: bug, sql
     :tickets: 7060

     Fixed issue where using ORM column expressions as keys in the list of
     dictionaries passed to :meth:`_sql.Insert.values` for "multi-valued insert"
     would not be processed correctly into the correct column expressions.

 .. change::
     :tags: asyncio, usecase
     :tickets: 6746

     The :class:`_asyncio.AsyncSession` now supports overriding which
     :class:`_orm.Session` it uses as the proxied instance. A custom ``Session``
     class can be passed using the :paramref:`.AsyncSession.sync_session_class`
     parameter or by subclassing the ``AsyncSession`` and specifying a custom
     :attr:`.AsyncSession.sync_session_class`.

 .. change::
     :tags: bug, oracle, performance
     :tickets: 4486

     Added a CAST(VARCHAR2(128)) to the "table name", "owner", and other
     DDL-name parameters as used in reflection queries against Oracle system
     views such as ALL_TABLES, ALL_TAB_CONSTRAINTS, etc to better enable
     indexing to take place against these columns, as they previously would be
     implicitly handled as NVARCHAR2 due to Python's use of Unicode for strings;
     these columns are documented in all Oracle versions as being VARCHAR2 with
     lengths varying from 30 to 128 characters depending on server version.
     Additionally, test support has been enabled for Unicode-named DDL
     structures against Oracle databases.

.. changelog::

1.4.23

:released: August 18, 2021

 .. change::
     :tags: bug, sql
     :tickets: 6752

     Fix issue in :class:`_sql.CTE` where new :meth:`_sql.HasCTE.add_cte` method
     added in version 1.4.21 / :ticket:`6752` failed to function correctly for
     "compound select" structures such as :func:`_sql.union`,
     :func:`_sql.union_all`, :func:`_sql.except`, etc. Pull request courtesy
     Eric Masseran.

 .. change::
     :tags: orm, usecase
     :tickets: 6808

     Added new attribute :attr:`_sql.Select.columns_clause_froms` that will
     retrieve the FROM list implied by the columns clause of the
     :class:`_sql.Select` statement. This differs from the old
     :attr:`_sql.Select.froms` collection in that it does not perform any ORM
     compilation steps, which necessarily deannotate the FROM elements and do
     things like compute joinedloads etc., which makes it not an appropriate
     candidate for the :meth:`_sql.Select.select_from` method. Additionally adds
     a new parameter
     :paramref:`_sql.Select.with_only_columns.maintain_column_froms` that
     transfers this collection to :meth:`_sql.Select.select_from` before
     replacing the columns collection.

     In addition, the :attr:`_sql.Select.froms` is renamed to
     :meth:`_sql.Select.get_final_froms`, to stress that this collection is not
     a simple accessor and is instead calculated given the full state of the
     object, which can be an expensive call when used in an ORM context.

     Additionally fixes a regression involving the
     :func:`_orm.with_only_columns` function to support applying criteria to
     column elements that were replaced with either
     :meth:`_sql.Select.with_only_columns` or :meth:`_orm.Query.with_entities` ,
     which had broken as part of :ticket:`6503` released in 1.4.19.

 .. change::
     :tags: bug, orm, sql
     :tickets: 6824

     Fixed issue where a bound parameter object that was "cloned" would cause a
     name conflict in the compiler, if more than one clone of this parameter
     were used at the same time in a single statement. This could occur in
     particular with things like ORM single table inheritance queries that
     indicated the same "discriminator" value multiple times in one query.


 .. change::
     :tags: bug, mssql, sql
     :tickets: 6863

     Fixed issue where the ``literal_binds`` compiler flag, as used externally
     to render bound parameters inline, would fail to work when used with a
     certain class of parameters known as "literal_execute", which covers things
     like LIMIT and OFFSET values for dialects where the drivers don't allow a
     bound parameter, such as SQL Server's "TOP" clause.  The issue locally
     seemed to affect only the MSSQL dialect.

 .. change::
     :tags: bug, orm
     :tickets: 6869

     Fixed issue in loader strategies where the use of the
     :meth:`_orm.Load.options` method, particularly when nesting multiple calls,
     would generate an overly long and more importantly non-deterministic cache
     key, leading to very large cache keys which were also not allowing
     efficient cache usage, both in terms of total memory used as well as number
     of entries used in the cache itself.

 .. change::
     :tags: bug, sql
     :tickets: 6858

     Fixed an issue in the ``CacheKey.to_offline_string()`` method used by the
     dogpile.caching example where attempting to create a proper cache key from
     the special "lambda" query generated by the lazy loader would fail to
     include the parameter values, leading to an incorrect cache key.


 .. change::
     :tags: bug, orm
     :tickets: 6887

     Revised the means by which the
     :attr:`_orm.ORMExecuteState.user_defined_options` accessor receives
     :class:`_orm.UserDefinedOption` and related option objects from the
     context, with particular emphasis on the "selectinload" on the loader
     strategy where this previously was not working; other strategies did not
     have this problem. The objects that are associated with the current query
     being executed, and not that of a query being cached, are now propagated
     unconditionally. This essentially separates them out from the "loader
     strategy" options which are explicitly associated with the compiled state
     of a query and need to be used in relation to the cached query.

     The effect of this fix is that a user-defined option, such as those used
     by the dogpile.caching example as well as for other recipes such as
     defining a "shard id" for the horizontal sharing extension, will be
     correctly propagated to eager and lazy loaders regardless of whether
     a cached query was ultimately invoked.


 .. change::
     :tags: bug, sql
     :tickets: 6886

     Adjusted the "from linter" warning feature to accommodate for a chain of
     joins more than one level deep where the ON clauses don't explicitly match
     up the targets, such as an expression such as "ON TRUE". This mode of use
     is intended to cancel the cartesian product warning simply by the fact that
     there's a JOIN from "a to b", which was not working for the case where the
     chain of joins had more than one element.

 .. change::
     :tags: bug, postgresql
     :tickets: 6886

     Added the "is_comparison" flag to the PostgreSQL "overlaps",
     "contained_by", "contains" operators, so that they work in relevant ORM
     contexts as well as in conjunction with the "from linter" feature.

 .. change::
     :tags: bug, orm
     :tickets: 6812

     Fixed issue where the unit of work would internally use a 2.0-deprecated
     SQL expression form, emitting a deprecation warning when SQLALCHEMY_WARN_20
     were enabled.


 .. change::
     :tags: bug, orm
     :tickets: 6881

     Fixed issue in :func:`_orm.selectinload` where use of the new
     :meth:`_orm.PropComparator.and_` feature within options that were nested
     more than one level deep would fail to update bound parameter values that
     were in the nested criteria, as a side effect of SQL statement caching.


 .. change::
     :tags: bug, general
     :tickets: 6136

     The setup requirements have been modified such ``greenlet`` is a default
     requirement only for those platforms that are well known for ``greenlet``
     to be installable and for which there is already a pre-built binary on
     pypi; the current list is ``x86_64 aarch64 ppc64le amd64 win32``. For other
     platforms, greenlet will not install by default, which should enable
     installation and test suite running of SQLAlchemy 1.4 on platforms that
     don't support ``greenlet``, excluding any asyncio features. In order to
     install with the ``greenlet`` dependency included on a machine architecture
     outside of the above list, the ``[asyncio]`` extra may be included by
     running ``pip install sqlalchemy[asyncio]`` which will then attempt to
     install ``greenlet``.

     Additionally, the test suite has been repaired so that tests can complete
     fully when greenlet is not installed, with appropriate skips for
     asyncio-related tests.

 .. change::
     :tags: enum, schema
     :tickets: 6146

     Unify behaviour :class:`_schema.Enum` in native and non-native
     implementations regarding the accepted values for an enum with
     aliased elements.
     When :paramref:`_schema.Enum.omit_aliases` is ``False`` all values,
     alias included, are accepted as valid values.
     When :paramref:`_schema.Enum.omit_aliases` is ``True`` only non aliased values
     are accepted as valid values.

 .. change::
     :tags: bug, ext
     :tickets: 6816

     Fixed issue where the horizontal sharding extension would not correctly
     accommodate for a plain textual SQL statement passed to
     :meth:`_orm.Session.execute`.

 .. change::
     :tags: bug, orm
     :tickets: 6889, 6079

     Adjusted ORM loader internals to no longer use the "lambda caching" system
     that was added in 1.4, as well as repaired one location that was still
     using the previous "baked query" system for a query. The lambda caching
     system remains an effective way to reduce the overhead of building up
     queries that have relatively fixed usage patterns. In the case of loader
     strategies, the queries used are responsible for moving through lots of
     arbitrary options and criteria, which is both generated and sometimes
     consumed by end-user code, that make the lambda cache concept not any more
     efficient than not using it, at the cost of more complexity. In particular
     the problems noted by :ticket:`6881` and :ticket:`6887` are made are made
     considerably less complicated by removing this feature internally.



 .. change::
     :tags: bug, orm
     :tickets: 6889

     Fixed an issue where the :class:`_orm.Bundle` construct would not create
     proper cache keys, leading to inefficient use of the query cache.  This
     had some impact on the "selectinload" strategy and was identified as
     part of :ticket:`6889`.

 .. change::
     :tags: usecase, mypy
     :tickets: 6804, 6759

     Added support for SQLAlchemy classes to be defined in user code using
     "generic class" syntax as defined by ``sqlalchemy2-stubs``, e.g.
     ``Column[String]``, without the need for qualifying these constructs within
     a ``TYPE_CHECKING`` block by implementing the Python special method
     ``__class_getitem__()``, which allows this syntax to pass without error at
     runtime.

 .. change::
     :tags: bug, sql

     Fixed issue in lambda caching system where an element of a query that
     produces no cache key, like a custom option or clause element, would still
     populate the expression in the "lambda cache" inappropriately.

.. changelog::

1.4.22

:released: July 21, 2021

 .. change::
     :tags: bug, sql
     :tickets: 6786

     Fixed issue where use of the :paramref:`_sql.case.whens` parameter passing
     a dictionary positionally and not as a keyword argument would emit a 2.0
     deprecation warning, referring to the deprecation of passing a list
     positionally. The dictionary format of "whens", passed positionally, is
     still supported and was accidentally marked as deprecated.


 .. change::
     :tags: bug, orm
     :tickets: 6775

     Fixed issue in new :meth:`_schema.Table.table_valued` method where the
     resulting :class:`_sql.TableValuedColumn` construct would not respond
     correctly to alias adaptation as is used throughout the ORM, such as for
     eager loading, polymorphic loading, etc.


 .. change::
     :tags: bug, orm
     :tickets: 6769

     Fixed issue where usage of the :meth:`_result.Result.unique` method with an
     ORM result that included column expressions with unhashable types, such as
     ``JSON`` or ``ARRAY`` using non-tuples would silently fall back to using
     the ``id()`` function, rather than raising an error. This now raises an
     error when the :meth:`_result.Result.unique` method is used in a 2.0 style
     ORM query. Additionally, hashability is assumed to be True for result
     values of unknown type, such as often happens when using SQL functions of
     unknown return type; if values are truly not hashable then the ``hash()``
     itself will raise.

     For legacy ORM queries, since the legacy :class:`_orm.Query` object
     uniquifies in all cases, the old rules remain in place, which is to use
     ``id()`` for result values of unknown type as this legacy uniquing is
     mostly for the purpose of uniquing ORM entities and not column values.

 .. change::
     :tags: orm, bug
     :tickets: 6771

     Fixed an issue where clearing of mappers during things like test suite
     teardowns could cause a "dictionary changed size" warning during garbage
     collection, due to iteration of a weak-referencing dictionary. A ``list()``
     has been applied to prevent concurrent GC from affecting this operation.

 .. change::
     :tags: bug, sql
     :tickets: 6770

     Fixed issue where type-specific bound parameter handlers would not be
     called upon in the case of using the :meth:`_sql.Insert.values` method with
     the Python ``None`` value; in particular, this would be noticed when using
     the :class:`_types.JSON` datatype as well as related PostgreSQL specific
     types such as :class:`_postgresql.JSONB` which would fail to encode the
     Python ``None`` value into JSON null, however the issue was generalized to
     any bound parameter handler in conjunction with this specific method of
     :class:`_sql.Insert`.


 .. change::
     :tags: bug, engine
     :tickets: 6740

     Added some guards against ``KeyError`` in the event system to accommodate
     the case that the interpreter is shutting down at the same time
     :meth:`_engine.Engine.dispose` is being called, which would cause stack
     trace warnings.


 .. change::
     :tags: bug, orm, regression
     :tickets: 6793

     Fixed critical caching issue where the ORM's persistence feature using
     INSERT..RETURNING would cache an incorrect query when mixing the "bulk
     save" and standard "flush" forms of INSERT.

.. changelog::

1.4.21

:released: July 14, 2021

 .. change::
     :tags: usecase, orm
     :tickets: 6708

     Modified the approach used for history tracking of scalar object
     relationships that are not many-to-one, i.e. one-to-one relationships that
     would otherwise be one-to-many. When replacing a one-to-one value, the
     "old" value that would be replaced is no longer loaded immediately, and is
     instead handled during the flush process. This eliminates an historically
     troublesome lazy load that otherwise often occurs when assigning to a
     one-to-one attribute, and is particularly troublesome when using
     "lazy='raise'" as well as asyncio use cases.

     This change does cause a behavioral change within the
     :meth:`_orm.AttributeEvents.set` event, which is nonetheless currently
     documented, which is that the event applied to such a one-to-one attribute
     will no longer receive the "old" parameter if it is unloaded and the
     :paramref:`_orm.relationship.active_history` flag is not set. As is
     documented in :meth:`_orm.AttributeEvents.set`, if the event handler needs
     to receive the "old" value when the event fires off, the active_history
     flag must be established either with the event listener or with the
     relationship. This is already the behavior with other kinds of attributes
     such as many-to-one and column value references.

     The change additionally will defer updating a backref on the "old" value
     in the less common case that the "old" value is locally present in the
     session, but isn't loaded on the relationship in question, until the
     next flush occurs.  If this causes an issue, again the normal
     :paramref:`_orm.relationship.active_history` flag can be set to ``True``
     on the relationship.

 .. change::
     :tags: usecase, sql
     :tickets: 6752

     Added new method :meth:`_sql.HasCTE.add_cte` to each of the
     :func:`_sql.select`, :func:`_sql.insert`, :func:`_sql.update` and
     :func:`_sql.delete` constructs. This method will add the given
     :class:`_sql.CTE` as an "independent" CTE of the statement, meaning it
     renders in the WITH clause above the statement unconditionally even if it
     is not otherwise referenced in the primary statement. This is a popular use
     case on the PostgreSQL database where a CTE is used for a DML statement
     that runs against database rows independently of the primary statement.

 .. change::
     :tags: bug, postgresql
     :tickets: 6755

     Fixed issue in :meth:`_postgresql.Insert.on_conflict_do_nothing` and
     :meth:`_postgresql.Insert.on_conflict_do_update` where the name of a unique
     constraint passed as the ``constraint`` parameter would not be properly
     truncated for length if it were based on a naming convention that generated
     a too-long name for the PostgreSQL max identifier length of 63 characters,
     in the same way which occurs within a CREATE TABLE statement.

 .. change::
     :tags: bug, sql
     :tickets: 6710

     Fixed issue in CTE constructs where a recursive CTE that referred to a
     SELECT that has duplicate column names, which are typically deduplicated
     using labeling logic in 1.4, would fail to refer to the deduplicated label
     name correctly within the WITH clause.

 .. change::
     :tags: bug, regression, mssql
     :tickets: 6697

     Fixed regression where the special dotted-schema name handling for the SQL
     Server dialect would not function correctly if the dotted schema name were
     used within the ``schema_translate_map`` feature.

 .. change::
     :tags: orm, regression
     :tickets: 6718

     Fixed ORM regression where ad-hoc label names generated for hybrid
     properties and potentially other similar types of ORM-enabled expressions
     would usually be propagated outwards through subqueries, allowing the name
     to be retained in the final keys of the result set even when selecting from
     subqueries. Additional state is now tracked in this case that isn't lost
     when a hybrid is selected out of a Core select / subquery.


 .. change::
     :tags: bug, postgresql
     :tickets: 6739

     Fixed issue where the PostgreSQL ``ENUM`` datatype as embedded in the
     ``ARRAY`` datatype would fail to emit correctly in create/drop when the
     ``schema_translate_map`` feature were also in use. Additionally repairs a
     related issue where the same ``schema_translate_map`` feature would not
     work for the ``ENUM`` datatype in combination with a ``CAST``, that's also
     intrinsic to how the ``ARRAY(ENUM)`` combination works on the PostgreSQL
     dialect.


 .. change::
     :tags: bug, sql, regression
     :tickets: 6735

     Fixed regression where the :func:`_sql.tablesample` construct would fail to
     be executable when constructed given a floating-point sampling value not
     embedded within a SQL function.

 .. change::
     :tags: bug, postgresql
     :tickets: 6696

     Fixed issue in :meth:`_postgresql.Insert.on_conflict_do_nothing` and
     :meth:`_postgresql.Insert.on_conflict_do_update` where the name of a unique
     constraint passed as the ``constraint`` parameter would not be properly
     quoted if it contained characters which required quoting.


 .. change::
     :tags: bug, regression, orm
     :tickets: 6698

     Fixed regression caused in 1.4.19 due to :ticket:`6503` and related
     involving :meth:`_orm.Query.with_entities` where the new structure used
     would be inappropriately transferred to an enclosing :class:`_orm.Query`
     when making use of set operations such as :meth:`_orm.Query.union`, causing
     the JOIN instructions within to be applied to the outside query as well.

 .. change::
     :tags: bug, orm, regression
     :tickets: 6762

     Fixed regression which appeared in version 1.4.3 due to :ticket:`6060`
     where rules that limit ORM adaptation of derived selectables interfered
     with other ORM-adaptation based cases, in this case when applying
     adaptations for a :func:`_orm.with_polymorphic` against a mapping which
     uses a :func:`_orm.column_property` which in turn makes use of a scalar
     select that includes a :func:`_orm.aliased` object of the mapped table.

.. changelog::

1.4.20

:released: June 28, 2021

 .. change::
     :tags: bug, regression, orm
     :tickets: 6680

     Fixed regression in ORM regarding an internal reconstitution step for the
     :func:`_orm.with_polymorphic` construct, when the user-facing object is
     garbage collected as the query is processed. The reconstitution was not
     ensuring the sub-entities for the "polymorphic" case were handled, leading
     to an ``AttributeError``.

 .. change::
     :tags: usecase, sql
     :tickets: 6646

     Add a impl parameter to :class:`_types.PickleType` constructor, allowing
     any arbitrary type to be used in place of the default implementation of
     :class:`_types.LargeBinary`. Pull request courtesy jason3gb.

 .. change::
     :tags: bug, engine
     :tickets: 5348

     Fixed an issue in the C extension for the :class:`_result.Row` class which
     could lead to a memory leak in the unlikely case of a :class:`_result.Row`
     object which referred to an ORM object that then was mutated to refer back
     to the ``Row`` itself, creating a cycle. The Python C APIs for tracking GC
     cycles has been added to the native :class:`_result.Row` implementation to
     accommodate for this case.


 .. change::
     :tags: bug, engine
     :tickets: 6665

     Fixed old issue where a :func:`_sql.select()` made against the token "*",
     which then yielded exactly one column, would fail to correctly organize the
     ``cursor.description`` column name into the keys of the result object.



 .. change::
     :tags: usecase, mysql
     :tickets: 6659

     Made a small adjustment in the table reflection feature of the MySQL
     dialect to accommodate for alternate MySQL-oriented databases such as TiDB
     which include their own "comment" directives at the end of a constraint
     directive within "CREATE TABLE" where the format doesn't have the
     additional space character after the comment, in this case the TiDB
     "clustered index" feature. Pull request courtesy Daniël van Eeden.

 .. change::
     :tags: bug, schema
     :tickets: 6685

     Fixed issue where passing ``None`` for the value of
     :paramref:`_schema.Table.prefixes` would not store an empty list, but
     rather the constant ``None``, which may be unexpected by third party
     dialects. The issue is revealed by a usage in recent versions of Alembic
     that are passing ``None`` for this value. Pull request courtesy Kai
     Mueller.

 .. change::
     :tags: bug, regression, ext
     :tickets: 6679

     Fixed regression in :mod:`sqlalchemy.ext.automap` extension such that the
     use case of creating an explicit mapped class to a table that is also the
     :paramref:`_orm.relationship.secondary` element of a
     :func:`_orm.relationship` that automap will be generating would emit the
     "overlaps" warnings introduced in 1.4 and discussed at :ref:`error_qzyx`.
     While generating this case from automap is still subject to the same
     caveats that the "overlaps" warning refers towards, as automap is intended
     for more ad-hoc use cases, the condition which produces the warning is
     disabled when a many-to-many relationship with this particular pattern is
     generated.



 .. change::
     :tags: bug, regression, orm
     :tickets: 6678

     Adjusted :meth:`_orm.Query.union` and similar set operations to be
     correctly compatible with the new capabilities just added in
     :ticket:`6661`, with SQLAlchemy 1.4.19, such that the SELECT statements
     rendered as elements of the UNION or other set operation will include
     directly mapped columns that are mapped as deferred; this both fixes a
     regression involving unions with multiple levels of nesting that would
     produce a column mismatch, and also allows the :func:`_orm.undefer` option
     to be used at the top level of such a :class:`_orm.Query` without having to
     apply the option to each of the elements within the UNION.

 .. change::
     :tags: bug, sql, orm
     :tickets: 6668

     Fixed the class hierarchy for the :class:`_schema.Sequence` and the more
     general :class:`_schema.DefaultGenerator` base, as these are "executable"
     as statements they need to include :class:`_sql.Executable` in their
     hierarchy, not just :class:`_roles.StatementRole` as was applied
     arbitrarily to :class:`_schema.Sequence` previously. The fix allows
     :class:`_schema.Sequence` to work in all ``.execute()`` methods including
     with :meth:`_orm.Session.execute` which was not working in the case that a
     :meth:`_orm.SessionEvents.do_orm_execute` handler was also established.


 .. change::
     :tags: bug, orm
     :tickets: 6538

     Adjusted the check in the mapper for a callable object that is used as a
     ``validates`` validator function or a ``reconstructor`` reconstruction
     function, to check for "callable" more liberally such as to accommodate
     objects based on fundamental attributes like ``__func__`` and
     ``__call___``, rather than testing for ``MethodType`` / ``FunctionType``,
     allowing things like cython functions to work properly. Pull request
     courtesy Miłosz Stypiński.

.. changelog::

1.4.19

:released: June 22, 2021

 .. change::
     :tags: bug, mssql
     :tickets: 6658

     Fixed bug where the "schema_translate_map" feature would fail to function
     correctly in conjunction with an INSERT into a table that has an IDENTITY
     column, where the value of the IDENTITY column were specified in the values
     of the INSERT thus triggering SQLAlchemy's feature of setting IDENTITY
     INSERT to "on"; it's in this directive where the schema translate map would
     fail to be honored.


 .. change::
     :tags: bug, sql
     :tickets: 6663

     Fixed issue in CTE constructs mostly relevant to ORM use cases where a
     recursive CTE against "anonymous" labels such as those seen in ORM
     ``column_property()`` mappings would render in the
     ``WITH RECURSIVE xyz(...)`` section as their raw internal label and not a
     cleanly anonymized name.

 .. change::
     :tags: mssql, change
     :tickets: 6503, 6253

     Made improvements to the server version regexp used by the pymssql dialect
     to prevent a regexp overflow in case of an invalid version string.

 .. change::
     :tags: bug, orm, regression
     :tickets: 6503, 6253

     Fixed further regressions in the same area as that of :ticket:`6052` where
     loader options as well as invocations of methods like
     :meth:`_orm.Query.join` would fail if the left side of the statement for
     which the option/join depends upon were replaced by using the
     :meth:`_orm.Query.with_entities` method, or when using 2.0 style queries
     when using the :meth:`_sql.Select.with_only_columns` method. A new set of
     state has been added to the objects which tracks the "left" entities that
     the options / join were made against which is memoized when the lead
     entities are changed.

 .. change::
     :tags: bug, asyncio, postgresql
     :tickets: 6652

     Fixed bug in asyncio implementation where the greenlet adaptation system
     failed to propagate ``BaseException`` subclasses, most notably including
     ``asyncio.CancelledError``, to the exception handling logic used by the
     engine to invalidate and clean up the connection, thus preventing
     connections from being correctly disposed when a task was cancelled.



 .. change::
     :tags: usecase, asyncio
     :tickets: 6583

     Implemented :class:`_asyncio.async_scoped_session` to address some
     asyncio-related incompatibilities between :class:`_orm.scoped_session` and
     :class:`_asyncio.AsyncSession`, in which some methods (notably the
     :meth:`_asyncio.async_scoped_session.remove` method) should be used with
     the ``await`` keyword.

     .. seealso::

         :ref:`asyncio_scoped_session`

 .. change::
     :tags: usecase, mysql
     :tickets: 6132

     Added new construct :class:`_mysql.match`, which provides for the full
     range of MySQL's MATCH operator including multiple column support and
     modifiers. Pull request courtesy Anton Kovalevich.

     .. seealso::

         :class:`_mysql.match`

 .. change::
     :tags: bug, postgresql, oracle
     :tickets: 6649

     Fixed issue where the ``INTERVAL`` datatype on PostgreSQL and Oracle would
     produce an ``AttributeError`` when used in the context of a comparison
     operation against a ``timedelta()`` object. Pull request courtesy
     MajorDallas.

 .. change::
     :tags: bug, mypy
     :tickets: 6476

     Fixed issue in mypy plugin where class info for a custom declarative base
     would not be handled correctly on a cached mypy pass, leading to an
     AssertionError being raised.

 .. change::
     :tags: bug, orm
     :tickets: 6661

     Refined the behavior of ORM subquery rendering with regards to deferred
     columns and column properties to be more compatible with that of 1.3 while
     also providing for 1.4's newer features. As a subquery in 1.4 does not make
     use of loader options, including :func:`_orm.undefer`, a subquery that is
     against an ORM entity with deferred attributes will now render those
     deferred attributes that refer directly to mapped table columns, as these
     are needed in the outer SELECT if that outer SELECT makes use of these
     columns; however a deferred attribute that refers to a composed SQL
     expression as we normally do with :func:`_orm.column_property` will not be
     part of the subquery, as these can be selected explicitly if needed in the
     subquery. If the entity is being SELECTed from this subquery, the column
     expression can still render on "the outside" in terms of the derived
     subquery columns. This produces essentially the same behavior as when
     working with 1.3. However in this case the fix has to also make sure that
     the ``.selected_columns`` collection of an ORM-enabled :func:`_sql.select`
     also follows these rules, which in particular allows recursive CTEs to
     render correctly in this scenario, which were previously failing to render
     correctly due to this issue.

 .. change::
     :tags: bug, postgresql
     :tickets: 6621

     Fixed issue where the pool "pre ping" feature would implicitly start a
     transaction, which would then interfere with custom transactional flags
     such as PostgreSQL's "read only" mode when used with the psycopg2 driver.


.. changelog::

1.4.18

:released: June 10, 2021

 .. change::
     :tags: bug, orm
     :tickets: 6072, 6487

     Clarified the current purpose of the
     :paramref:`_orm.relationship.bake_queries` flag, which in 1.4 is to enable
     or disable "lambda caching" of statements within the "lazyload" and
     "selectinload" loader strategies; this is separate from the more
     foundational SQL query cache that is used for most statements.
     Additionally, the lazy loader no longer uses its own cache for many-to-one
     SQL queries, which was an implementation quirk that doesn't exist for any
     other loader scenario. Finally, the "lru cache" warning that the lazyloader
     and selectinloader strategies could emit when handling a wide array of
     class/relationship combinations has been removed; based on analysis of some
     end-user cases, this warning doesn't suggest any significant issue. While
     setting ``bake_queries=False`` for such a relationship will remove this
     cache from being used, there's no particular performance gain in this case
     as using no caching vs. using a cache that needs to refresh often likely
     still wins out on the caching being used side.


 .. change::
     :tags: bug, asyncio
     :tickets: 6575

     Fixed an issue that presented itself when using the :class:`_pool.NullPool`
     or the :class:`_pool.StaticPool` with an async engine. This mostly affected
     the aiosqlite dialect.

 .. change::
     :tags: bug, sqlite, regression
     :tickets: 6586

     The fix for pysqlcipher released in version 1.4.3 :ticket:`5848` was
     unfortunately non-working, in that the new ``on_connect_url`` hook was
     erroneously not receiving a ``URL`` object under normal usage of
     :func:`_sa.create_engine` and instead received a string that was unhandled;
     the test suite failed to fully set up the actual conditions under which
     this hook is called. This has been fixed.

 .. change::
     :tags: bug, postgresql, regression
     :tickets: 6581

     Fixed regression where using the PostgreSQL "INSERT..ON CONFLICT" structure
     would fail to work with the psycopg2 driver if it were used in an
     "executemany" context along with bound parameters in the "SET" clause, due
     to the implicit use of the psycopg2 fast execution helpers which are not
     appropriate for this style of INSERT statement; as these helpers are the
     default in 1.4 this is effectively a regression.  Additional checks to
     exclude this kind of statement from that particular extension have been
     added.

 .. change::
     :tags: bug, orm, regression
     :tickets: 6285

     Adjusted the means by which classes such as :class:`_orm.scoped_session`
     and :class:`_asyncio.AsyncSession` are generated from the base
     :class:`_orm.Session` class, such that custom :class:`_orm.Session`
     subclasses such as that used by Flask-SQLAlchemy don't need to implement
     positional arguments when they call into the superclass method, and can
     continue using the same argument styles as in previous releases.

 .. change::
     :tags: bug, orm, regression
     :tickets: 6595

     Fixed issue where query production for joinedload against a complex left
     hand side involving joined-table inheritance could fail to produce a
     correct query, due to a clause adaption issue.

 .. change::
     :tags: bug, orm, regression, performance
     :tickets: 6596

     Fixed regression involving how the ORM would resolve a given mapped column
     to a result row, where under cases such as joined eager loading, a slightly
     more expensive "fallback" could take place to set up this resolution due to
     some logic that was removed since 1.3. The issue could also cause
     deprecation warnings involving column resolution to be emitted when using a
     1.4 style query with joined eager loading.

 .. change::
     :tags: bug, orm
     :tickets: 6591

     Fixed issue in experimental "select ORM objects from INSERT/UPDATE" use
     case where an error was raised if the statement were against a
     single-table-inheritance subclass.

 .. change::
     :tags: bug, asyncio
     :tickets: 6592

     Added ``asyncio.exceptions.TimeoutError``,
     ``asyncio.exceptions.CancelledError`` as so-called "exit exceptions", a
     class of exceptions that include things like ``GreenletExit`` and
     ``KeyboardInterrupt``, which are considered to be events that warrant
     considering a DBAPI connection to be in an unusable state where it should
     be recycled.

 .. change::
     :tags: bug, orm
     :tickets: 6400

     The warning that's emitted for :func:`_orm.relationship` when multiple
     relationships would overlap with each other as far as foreign key
     attributes written towards, now includes the specific "overlaps" argument
     to use for each warning in order to silence the warning without changing
     the mapping.

 .. change::
     :tags: usecase, asyncio
     :tickets: 6319

     Implemented a new registry architecture that allows t