2.0.45

Released: December 9, 2025

orm

• [orm] [bug] Fixed issue where calling Mapper.add_property() within mapper event
  hooks such as MapperEvents.instrument_class(),
  MapperEvents.after_mapper_constructed(), or
  MapperEvents.before_mapper_configured() would raise an
  AttributeError because the mapper's internal property collections were
  not yet initialized. The Mapper.add_property() method now handles
  early-stage property additions correctly, allowing properties including
  column properties, deferred columns, and relationships to be added during
  mapper initialization events. Pull request courtesy G Allajmi.

  References: #12858

• [orm] [bug] Fixed issue in Python 3.14 where dataclass transformation would fail when
  a mapped class using MappedAsDataclass included a
  relationship() referencing a class that was not available at
  runtime (e.g., within a TYPE_CHECKING block). This occurred when using
  Python 3.14's PEP 649 deferred annotations feature, which is the
  default behavior without a from __future__ import annotations
  directive.

  References: #12952

examples

• [examples] [bug] Fixed the "short_selects" performance example where the cache was being
  used in all the examples, making it impossible to compare performance with
  and without the cache. Less important comparisons like "lambdas" and
  "baked queries" have been removed.

sql

• [sql] [bug] Some improvements to the _sql.ClauseElement.params() method to
  replace bound parameters in a query were made, however the ultimate issue
  in #12915 involving ORM _orm.aliased() cannot be fixed fully
  until 2.1, where the method is being rewritten to work without relying on
  Core cloned traversal.

  References: #12915

• [sql] [bug] Fixed issue where using the ColumnOperators.in_() operator with a
  nested CompoundSelect statement (e.g. an INTERSECT of
  UNION queries) would raise a NotImplementedError when the
  nested compound select was the first argument to the outer compound select.
  The _scalar_type() internal method now properly handles nested compound
  selects.

  References: #12987

typing

• [typing] [bug] Fixed typing issue where Select.with_for_update() would not support
  lists of ORM entities or other FROM clauses in the
  Select.with_for_update.of parameter. Pull request courtesy
  Shamil.

  References: #12730

• [typing] [bug] Fixed typing issue where coalesce would not return the correct
  return type when a nullable form of that argument were passed, even though
  this function is meant to select the non-null entry among possibly null
  arguments. Pull request courtesy Yannick PÉROUX.

postgresql

• [postgresql] [usecase] Added support for reflection of collation in types for PostgreSQL.
  The collation will be set only if different from the default
  one for the type.
  Pull request courtesy Denis Laxalde.

  References: #6511

• [postgresql] [bug] Fixed issue where PostgreSQL dialect options such as postgresql_include
  on PrimaryKeyConstraint and UniqueConstraint were
  rendered in the wrong position when combined with constraint deferrability
  options like deferrable=True. Pull request courtesy G Allajmi.

  References: #12867

• [postgresql] [bug] Fixed the structure of the SQL string used for the
  engine_insertmanyvalues feature when an explicit sequence with
  nextval() is used. The SQL function invocation for the sequence has
  been moved from being rendered inline within each tuple inside of VALUES to
  being rendered once in the SELECT that reads from VALUES. This change
  ensures the function is invoked in the correct order as rows are processed,
  rather than assuming PostgreSQL will execute inline function calls within
  VALUES in a particular order. While current PostgreSQL versions appear to
  handle the previous approach correctly, the database does not guarantee
  this behavior for future versions.

  References: #13015

mysql

• [mysql] [usecase] Added support for MySQL 8.0.1 + FOR SHARE to be emitted for the
  Select.with_for_update() method, which offers compatibility with
  NOWAIT and SKIP LOCKED. The new syntax is used only for MySQL when
  version 8.0.1 or higher is detected. Pull request courtesy JetDrag.

  References: #12964

sqlite

• [sqlite] [bug] [reflection] A series of improvements have been made for reflection of CHECK constraints
  on SQLite. The reflection logic now correctly handles table names
  containing the strings "CHECK" or "CONSTRAINT", properly supports all four
  SQLite identifier quoting styles (double quotes, single quotes, brackets,
  and backticks) for constraint names, and accurately parses CHECK constraint
  expressions containing parentheses within string literals using balanced
  parenthesis matching with string context tracking. Big thanks to
  GruzdevAV for new test cases and implementation ideas.

  References: #12924

• [sqlite] [bug] Fixed issue where SQLite dialect would fail to reflect constraint names
  that contained uppercase letters or other characters requiring quoting. The
  regular expressions used to parse primary key, foreign key, and unique
  constraint names from the CREATE TABLE statement have been updated to
  properly handle both quoted and unquoted constraint names.

  References: #12954

tests

• [tests] [change] A noxfile.py has been added to allow testing with nox. This is a direct
  port of 2.1's move to nox, however leaves the tox.ini file in place and
  retains all test documentation in terms of tox. Version 2.1 will move to
  nox fully, including deprecation warnings for tox and new testing
  documentation.

2.0.44

Released: October 10, 2025

platform

• [platform] [bug] Unblocked automatic greenlet installation for Python 3.14 now that
  there are greenlet wheels on pypi for python 3.14.

orm

• [orm] [usecase] The way ORM Annotated Declarative interprets Python PEP 695 type aliases
  in Mapped[] annotations has been refined to expand the lookup scheme. A
  PEP 695 type can now be resolved based on either its direct presence in
  _orm.registry.type_annotation_map or its immediate resolved
  value, as long as a recursive lookup across multiple PEP 695 types is
  not required for it to resolve. This change reverses part of the
  restrictions introduced in 2.0.37 as part of #11955, which
  deprecated (and disallowed in 2.1) the ability to resolve any PEP 695
  type that was not explicitly present in
  _orm.registry.type_annotation_map. Recursive lookups of
  PEP 695 types remains deprecated in 2.0 and disallowed in version 2.1,
  as do implicit lookups of NewType types without an entry in
  _orm.registry.type_annotation_map.

  Additionally, new support has been added for generic PEP 695 aliases that
  refer to PEP 593 Annotated constructs containing
  _orm.mapped_column() configurations. See the sections below for
  examples.

  References: #12829

• [orm] [bug] Fixed a caching issue where _orm.with_loader_criteria() would
  incorrectly reuse cached bound parameter values when used with
  _sql.CompoundSelect constructs such as _sql.union(). The
  issue was caused by the cache key for compound selects not including the
  execution options that are part of the _sql.Executable base class,
  which _orm.with_loader_criteria() uses to apply its criteria
  dynamically. The fix ensures that compound selects and other executable
  constructs properly include execution options in their cache key traversal.

  References: #12905

engine

• [engine] [bug] Implemented initial support for free-threaded Python by adding new tests
  and reworking the test harness to include Python 3.13t and Python 3.14t in
  test runs. Two concurrency issues have been identified and fixed: the first
  involves initialization of the .c collection on a FromClause, a
  continuation of #12302, where an optional mutex under
  free-threading is added; the second involves synchronization of the pool
  "first_connect" event, which first received thread synchronization in
  #2964, however under free-threading the creation of the mutex
  itself runs under the same free-threading mutex. Support for free-threaded
  wheels on Pypi is implemented as well within the 2.1 series only. Initial
  pull request and test suite courtesy Lysandros Nikolaou.

  References: #12881

sql

• [sql] [bug] Improved the implementation of UpdateBase.returning() to use more
  robust logic in setting up the .c collection of a derived statement
  such as a CTE. This fixes issues related to RETURNING clauses that feature
  expressions based on returned columns with or without qualifying labels.

  References: #12271

schema

• [schema] [bug] Fixed issue where _schema.MetaData.reflect() did not forward
  dialect-specific keyword arguments to the _engine.Inspector
  methods, causing options like oracle_resolve_synonyms to be ignored
  during reflection. The method now ensures that all extra kwargs passed to
  _schema.MetaData.reflect() are forwarded to
  _engine.Inspector.get_table_names() and related reflection methods.
  Pull request courtesy Lukáš Kožušník.

  References: #12884

typing

• [typing] [bug] Fixed typing bug where the Session.execute() method advertised that
  it would return a CursorResult if given an insert/update/delete
  statement. This is not the general case as several flavors of ORM
  insert/update do not actually yield a CursorResult which cannot
  be differentiated at the typing overload level, so the method now yields
  Result in all cases. For those cases where
  CursorResult is known to be returned and the .rowcount
  attribute is required, please use typing.cast().

  References: #12813

• [typing] [bug] Added new decorator _orm.mapped_as_dataclass(), which is a function
  based form of _orm.registry.mapped_as_dataclass(); the method form
  _orm.registry.mapped_as_dataclass() does not seem to be correctly
  recognized within the scope of PEP 681 in recent mypy versions.

  References: #12855

asyncio

• [asyncio] [usecase] Generalize the terminate logic employed by the asyncpg dialect to reuse
  it in the aiomysql and asyncmy dialect implementation.

  References: #12273

postgresql

• [postgresql] [bug] Fixed issue where selecting an enum array column containing NULL values
  would fail to parse properly in the PostgreSQL dialect. The
  _split_enum_values() function now correctly handles NULL entries by
  converting them to Python None values.

  References: #12847

• [postgresql] [bug] Fixed issue where the _sql.any_() and _sql.all_() aggregation
  operators would not correctly coerce the datatype of the compared value, in
  those cases where the compared value were not a simple int/str etc., such
  as a Python Enum or other custom value. This would lead to execution
  time errors for these values. This issue is essentially the same as
  #6515 which was for the now-legacy ARRAY.any() and
  ARRAY.all() methods.

  References: #12874

sqlite

• [sqlite] [bug] Fixed issue where SQLite table reflection would fail for tables using
  WITHOUT ROWID and/or STRICT table options when the table contained
  generated columns. The regular expression used to parse CREATE TABLE
  statements for generated column detection has been updated to properly
  handle these SQLite table options that appear after the column definitions.
  Pull request courtesy Tip ten Brink.

  References: #12864

mssql

• [mssql] [bug] Improved the base implementation of the asyncio cursor such that it
  includes the option for the underlying driver's cursor to be actively
  closed in those cases where it requires await in order to complete the
  close sequence, rather than relying on garbage collection to "close" it,
  when a plain Result is returned that does not use await for
  any of its methods. The previous approach of relying on gc was fine for
  MySQL and SQLite dialects but has caused problems with the aioodbc
  implementation on top of SQL Server. The new option is enabled
  for those dialects which have an "awaitable" cursor.close(), which
  includes the aioodbc, aiomysql, and asyncmy dialects (aiosqlite is also
  modified for 2.1 only).

  References: #12798

• [mssql] [bug] Fixed issue where the index reflection for SQL Server would
  not correctly return the order of the column inside an index
  when the order of the columns in the index did not match the
  order of the columns in the table.
  Pull request courtesy of Allen Chen.

  References: #12894

• [mssql] [bug] [reflection] Fixed issue in the MSSQL dialect's foreign key reflection query where
  duplicate rows could be returned when a foreign key column and its
  referenced primary key column have the same name, and both the referencing
  and referenced tables have indexes with the same name. This resulted in an
  "ForeignKeyConstraint with duplicate source column references are not
  supported" error when attempting to reflect such tables. The query has been
  corrected to exclude indexes on the child table when looking for unique
  indexes referenced by foreign keys.

  References: #12907

misc

• [bug] [ext] Fixed issue caused by an unwanted functional change while typing
  the MutableList class.
  This change also reverts all other functional changes done in
  the same change.

  References: #12802

2.0.43

Released: August 11, 2025

orm

• [orm] [bug] Fixed issue where using the post_update feature would apply incorrect
  "pre-fetched" values to the ORM objects after a multi-row UPDATE process
  completed. These "pre-fetched" values would come from any column that had
  an Column.onupdate callable or a version id generator used by
  orm.Mapper.version_id_generator; for a version id generator
  that delivered random identifiers like timestamps or UUIDs, this incorrect
  data would lead to a DELETE statement against those same rows to fail in
  the next step.

  References: #12748

• [orm] [bug] Fixed issue where _orm.mapped_column.use_existing_column
  parameter in _orm.mapped_column() would not work when the
  _orm.mapped_column() is used inside of an Annotated type alias in
  polymorphic inheritance scenarios. The parameter is now properly recognized
  and processed during declarative mapping configuration.

  References: #12787

• [orm] [bug] Improved the implementation of the _orm.selectin_polymorphic()
  inheritance loader strategy to properly render the IN expressions using
  chunks of 500 records each, in the same manner as that of the
  _orm.selectinload() relationship loader strategy. Previously, the IN
  expression would be arbitrarily large, leading to failures on databases
  that have limits on the size of IN expressions including Oracle Database.

  References: #12790

engine

• [engine] [usecase] Added new parameter create_engine.skip_autocommit_rollback
  which provides for a per-dialect feature of preventing the DBAPI
  .rollback() from being called under any circumstances, if the
  connection is detected as being in "autocommit" mode. This improves upon
  a critical performance issue identified in MySQL dialects where the network
  overhead of the .rollback() call remains prohibitive even if autocommit
  mode is set.

  References: #12784

postgresql

• [postgresql] [bug] Fixed regression in PostgreSQL dialect where JSONB subscription syntax
  would generate incorrect SQL for JSONB-returning functions, causing syntax
  errors. The dialect now properly wraps function calls and expressions in
  parentheses when using the [] subscription syntax, generating
  (function_call)[index] instead of function_call[index] to comply
  with PostgreSQL syntax requirements.

  References: #12778

oracle

• [oracle] [usecase] Extended _oracle.VECTOR to support sparse vectors. This update
  introduces _oracle.VectorStorageType to specify sparse or dense
  storage and added _oracle.SparseVector. Pull request courtesy
  Suraj Shaw.

  References: #12711

2.0.42

Released: July 29, 2025

orm

• [orm] [usecase] Added dataclass_metadata argument to all ORM attribute constructors
  that accept dataclasses parameters, e.g. mapped_column.dataclass_metadata,
  relationship.dataclass_metadata, etc.
  It's passed to the underlying dataclass metadata attribute
  of the dataclass field. Pull request courtesy Sigmund Lahn.

  References: #10674

• [orm] [bug] Implemented the _orm.defer(), _orm.undefer() and
  _orm.load_only() loader options to work for composite attributes, a
  use case that had never been supported previously.

  References: #12593

• [orm] [bug] Fixed bug where the ORM would pull in the wrong column into an UPDATE when
  a key name inside of the ValuesBase.values() method could be located
  from an ORM entity mentioned in the statement, but where that ORM entity
  was not the actual table that the statement was inserting or updating. An
  extra check for this edge case is added to avoid this problem.

  References: #12692

engine

• [engine] Improved validation of execution parameters passed to the
  _engine.Connection.execute() and similar methods to
  provided a better error when tuples are passed in.
  Previously the execution would fail with a difficult to
  understand error message.

sql

• [sql] [usecase] The _sql.values() construct gains a new method _sql.Values.cte(),
  which allows creation of a named, explicit-columns CTE against an
  unnamed VALUES expression, producing a syntax that allows column-oriented
  selection from a VALUES construct on modern versions of PostgreSQL, SQLite,
  and MariaDB.

  References: #12734

• [sql] [bug] Fixed issue where select() of a free-standing scalar expression that
  has a unary operator applied, such as negation, would not apply result
  processors to the selected column even though the correct type remains in
  place for the unary expression.

  References: #12681

• [sql] [bug] Hardening of the compiler's actions for UPDATE statements that access
  multiple tables to report more specifically when tables or aliases are
  referenced in the SET clause; on cases where the backend does not support
  secondary tables in the SET clause, an explicit error is raised, and on the
  MySQL or similar backends that support such a SET clause, more specific
  checking for not-properly-included tables is performed. Overall the change
  is preventing these erroneous forms of UPDATE statements from being
  compiled, whereas previously it was relied on the database to raise an
  error, which was not always guaranteed to happen, or to be non-ambiguous,
  due to cases where the parent table included the same column name as the
  secondary table column being updated.

  References: #12692

postgresql

• [postgresql] [usecase] Added support for PostgreSQL 14+ JSONB subscripting syntax. When connected
  to PostgreSQL 14 or later, JSONB columns now automatically use the native
  subscript notation jsonb_col['key'] instead of the arrow operator
  jsonb_col -> 'key' for both read and write operations. This provides
  better compatibility with PostgreSQL's native JSONB subscripting feature
  while maintaining backward compatibility with older PostgreSQL versions.
  JSON columns continue to use the traditional arrow syntax regardless of
  PostgreSQL version.

  References: #10927

• [postgresql] [usecase] Added postgresql_ops key to the dialect_options entry in reflected
  dictionary. This maps names of columns used in the index to respective
  operator class, if distinct from the default one for column's data type.
  Pull request courtesy Denis Laxalde.

  References: #8664

• [postgresql] [bug] [reflection] Fixed regression caused by #10665 where the newly modified
  constraint reflection query would fail on older versions of PostgreSQL
  such as version 9.6. Pull request courtesy Denis Laxalde.

  References: #12600

• [postgresql] [bug] Re-raise catched CancelledError in the terminate method of the
  asyncpg dialect to avoid possible hangs of the code execution.

  References: #12728

• [postgresql] [bug] [reflection] Fixes bug that would mistakenly interpret a domain or enum type
  with name starting in interval as an INTERVAL type while
  reflecting a table.

  References: #12744

mysql

• [mysql] [bug] Fixed yet another regression caused by by the DEFAULT rendering changes in
  2.0.40 #12425, similar to #12488, this time where using a
  CURRENT_TIMESTAMP function with a fractional seconds portion inside a
  textual default value would also fail to be recognized as a
  non-parenthesized server default.

  References: #12648

mssql

• [mssql] [bug] Reworked SQL Server column reflection to be based on the sys.columns
  table rather than information_schema.columns view. By correctly using
  the SQL Server object_id() function as a lead and joining to related
  tables on object_id rather than names, this repairs a variety of issues in
  SQL Server reflection, including:

  -   Issue where reflected column comments would not correctly line up
      with the columns themselves in the case that the table had been ALTERed
  
  -   Correctly targets tables with awkward names such as names with brackets,
      when reflecting not just the basic table / columns but also extended
      information including IDENTITY, computed columns, comments which
      did not work previously
  
  -   Correctly targets IDENTITY, computed status from temporary tables
      which did not work previously
  

  References: #12654

2.0.41

Released: May 14, 2025

platform

• [platform] [bug] Adjusted the test suite as well as the ORM's method of scanning classes for
  annotations to work under current beta releases of Python 3.14 (currently
  3.14.0b1) as part of an ongoing effort to support the production release of
  this Python release. Further changes to Python's means of working with
  annotations is expected in subsequent beta releases for which SQLAlchemy's
  test suite will need further adjustments.

  References: #12405

engine

• [engine] [bug] The error message that is emitted when a URL cannot be parsed no longer
  includes the URL itself within the error message.

  References: #12579

typing

• [typing] [bug] Removed __getattr__() rule from sqlalchemy/__init__.py that
  appeared to be trying to correct for a previous typographical error in the
  imports. This rule interferes with type checking and is removed.

  References: #12588

postgresql

• [postgresql] [usecase] Added support for postgresql_include keyword argument to
  _schema.UniqueConstraint and _schema.PrimaryKeyConstraint.
  Pull request courtesy Denis Laxalde.

  References: #10665

mysql

• [mysql] [bug] Fixed regression caused by the DEFAULT rendering changes in version 2.0.40
  via #12425 where using lowercase on update in a MySQL server
  default would incorrectly apply parenthesis, leading to errors when MySQL
  interpreted the rendered DDL. Pull request courtesy Alexander Ruehe.

  References: #12488

sqlite

• [sqlite] [bug] Fixed and added test support for some SQLite SQL functions hardcoded into
  the compiler, most notably the localtimestamp function which rendered
  with incorrect internal quoting.

  References: #12566

oracle

• [oracle] [usecase] Added new datatype _oracle.VECTOR and accompanying DDL and DQL
  support to fully support this type for Oracle Database. This change
  includes the base _oracle.VECTOR type that adds new type-specific
  methods l2_distance, cosine_distance, inner_product as well as
  new parameters oracle_vector for the Index construct,
  allowing vector indexes to be configured, and oracle_fetch_approximate
  for the Select.fetch() clause. Pull request courtesy Suraj Shaw.

  References: #12317, #12341

misc

• [bug] [installation] Removed the "license classifier" from setup.cfg for SQLAlchemy 2.0, which
  eliminates loud deprecation warnings when building the package. SQLAlchemy
  2.1 will use a full PEP 639 configuration in pyproject.toml while
  SQLAlchemy 2.0 remains using setup.cfg for setup.

2.0.40

Released: March 27, 2025

orm

• [orm] [bug] Fixed regression which occurred as of 2.0.37 where the checked
  ArgumentError that's raised when an inappropriate type or object
  is used inside of a Mapped annotation would raise TypeError
  with "boolean value of this clause is not defined" if the object resolved
  into a SQL expression in a boolean context, for programs where future
  annotations mode was not enabled. This case is now handled explicitly and
  a new error message has also been tailored for this case. In addition, as
  there are at least half a dozen distinct error scenarios for intepretation
  of the Mapped construct, these scenarios have all been unified
  under a new subclass of ArgumentError called
  MappedAnnotationError, to provide some continuity between these
  different scenarios, even though specific messaging remains distinct.

  References: #12329

• [orm] [bug] Fixed regression in ORM Annotated Declarative class interpretation caused
  by typing_extension==4.13.0 that introduced a different implementation
  for TypeAliasType while SQLAlchemy assumed that it would be equivalent
  to the typing version, leading to pep-695 type annotations not
  resolving to SQL types as expected.

  References: #12473

sql

• [sql] [usecase] Implemented support for the GROUPS frame specification in window functions
  by adding _sql.over.groups option to _sql.over()
  and FunctionElement.over(). Pull request courtesy Kaan Dikmen.

  References: #12450

• [sql] [bug] Fixed issue in CTE constructs involving multiple DDL
  _sql.Insert statements with multiple VALUES parameter sets where the
  bound parameter names generated for these parameter sets would conflict,
  generating a compile time error.

  References: #12363

• [sql] [bug] Fixed regression caused by #7471 leading to a SQL compilation
  issue where name disambiguation for two same-named FROM clauses with table
  aliasing in use at the same time would produce invalid SQL in the FROM
  clause with two "AS" clauses for the aliased table, due to double aliasing.

  References: #12451

asyncio

• [asyncio] [bug] Fixed issue where AsyncSession.get_transaction() and
  AsyncSession.get_nested_transaction() would fail with
  NotImplementedError if the "proxy transaction" used by
  AsyncSession were garbage collected and needed regeneration.

  References: #12471

postgresql

• [postgresql] [usecase] Added support for specifying a list of columns for SET NULL and SET DEFAULT actions of ON DELETE clause of foreign key definition on
  PostgreSQL. Pull request courtesy Denis Laxalde.

  References: #11595

• [postgresql] [usecase] When building a PostgreSQL ARRAY literal using
  _postgresql.array with an empty clauses argument, the
  _postgresql.array.type_ parameter is now significant in that it
  will be used to render the resulting ARRAY[] SQL expression with a
  cast, such as ARRAY[]::INTEGER. Pull request courtesy Denis Laxalde.

  References: #12432

mysql

• [mysql] [bug] Support has been re-added for the MySQL-Connector/Python DBAPI using the
  mysql+mysqlconnector:// URL scheme. The DBAPI now works against
  modern MySQL versions as well as MariaDB versions (in the latter case it's
  required to pass charset/collation explicitly). Note however that
  server side cursor support is disabled due to unresolved issues with this
  driver.

  References: #12332

• [mysql] [bug] Fixed issue in MySQL server default reflection where a default that has
  spaces would not be correctly reflected. Additionally, expanded the rules
  for when to apply parenthesis to a server default in DDL to suit the
  general case of a default string that contains non-word characters such as
  spaces or operators and is not a string literal.

  References: #12425

sqlite

• [sqlite] [bug] Expanded the rules for when to apply parenthesis to a server default in DDL
  to suit the general case of a default string that contains non-word
  characters such as spaces or operators and is not a string literal.

  References: #12425

2.0.39

Released: March 11, 2025

orm

• [orm] [bug] Fixed bug where using DML returning such as Insert.returning() with
  an ORM model that has _orm.column_property() constructs that contain
  subqueries would fail with an internal error.

  References: #12326

• [orm] [bug] Fixed bug in ORM enabled UPDATE (and theoretically DELETE) where using a
  multi-table DML statement would not allow ORM mapped columns from mappers
  other than the primary UPDATE mapper to be named in the RETURNING clause;
  they would be omitted instead and cause a column not found exception.

  References: #12328

• [orm] [bug] Fixed issue where the "is ORM" flag of a select() or other ORM
  statement would not be propagated to the ORM Session based on a
  multi-part operator expression alone, e.g. such as Cls.attr + Cls.attr + Cls.attr or similar, leading to ORM behaviors not taking place for such
  statements.

  References: #12357

• [orm] [bug] Fixed issue where using _orm.aliased() around a CTE
  construct could cause inappropriate "duplicate CTE" errors in cases where
  that aliased construct appeared multiple times in a single statement.

  References: #12364

sql

• [sql] [bug] Added new parameters AddConstraint.isolate_from_table and
  DropConstraint.isolate_from_table, defaulting to True, which
  both document and allow to be controllable the long-standing behavior of
  these two constructs blocking the given constraint from being included
  inline within the "CREATE TABLE" sequence, under the assumption that
  separate add/drop directives were to be used.

  References: #12382

typing

• [typing] [usecase] Support generic types for compound selects (_sql.union(),
  _sql.union_all(), _sql.Select.union(),
  _sql.Select.union_all(), etc) returning the type of the first select.
  Pull request courtesy of Mingyu Park.

  References: #11922

asyncio

• [asyncio] [bug] Fixed bug where _asyncio.AsyncResult.scalar(),
  _asyncio.AsyncResult.scalar_one_or_none(), and
  _asyncio.AsyncResult.scalar_one() would raise an AttributeError
  due to a missing internal attribute. Pull request courtesy Allen Ho.

  References: #12338

postgresql

• [postgresql] [bug] Add SQL typing to reflection query used to retrieve a the structure
  of IDENTITY columns, adding explicit JSON typing to the query to suit
  unusual PostgreSQL driver configurations that don't support JSON natively.

  References: #11751

• [postgresql] [bug] Fixed issue affecting PostgreSQL 17.3 and greater where reflection of
  domains with "NOT NULL" as part of their definition would include an
  invalid constraint entry in the data returned by
  _postgresql.PGInspector.get_domains() corresponding to an additional
  "NOT NULL" constraint that isn't a CHECK constraint; the existing
  "nullable" entry in the dictionary already indicates if the domain
  includes a "not null" constraint. Note that such domains also cannot be
  reflected on PostgreSQL 17.0 through 17.2 due to a bug on the PostgreSQL
  side; if encountering errors in reflection of domains which include NOT
  NULL, upgrade to PostgreSQL server 17.3 or greater.

• [postgresql] [bug] Fixed issue in PostgreSQL network types _postgresql.INET,
  _postgresql.CIDR, _postgresql.MACADDR,
  _postgresql.MACADDR8 where sending string values to compare to
  these types would render an explicit CAST to VARCHAR, causing some SQL /
  driver combinations to fail. Pull request courtesy Denis Laxalde.

  References: #12060

• [postgresql] [bug] Fixed compiler issue in the PostgreSQL dialect where incorrect keywords
  would be passed when using "FOR UPDATE OF" inside of a subquery.

  References: #12417

sqlite

• [sqlite] [bug] Fixed issue that omitted the comma between multiple SQLite table extension
  clauses, currently WITH ROWID and STRICT, when both options
  Table.sqlite_with_rowid and Table.sqlite_strict
  were configured at their non-default settings at the same time. Pull
  request courtesy david-fed.

  References: #12368

2.0.38

Released: February 6, 2025

engine

• [engine] [bug] Fixed event-related issue where invoking Engine.execution_options()
  on a Engine multiple times while making use of event-registering
  parameters such as isolation_level would lead to internal errors
  involving event registration.

  References: #12289

sql

• [sql] [bug] Reorganized the internals by which the .c collection on a
  FromClause gets generated so that it is resilient against the
  collection being accessed in concurrent fashion. An example is creating a
  Alias or Subquery and accessing it as a module level
  variable. This impacts the Oracle dialect which uses such module-level
  global alias objects but is of general use as well.

  References: #12302

• [sql] [bug] Fixed SQL composition bug which impacted caching where using a None
  value inside of an in_() expression would bypass the usual "expanded
  bind parameter" logic used by the IN construct, which allows proper caching
  to take place.

  References: #12314

postgresql

• [postgresql] [usecase] [asyncio] Added an additional asyncio.shield() call within the connection
  terminate process of the asyncpg driver, to mitigate an issue where
  terminate would be prevented from completing under the anyio concurrency
  library.

  References: #12077

• [postgresql] [bug] Adjusted the asyncpg connection wrapper so that the
  connection.transaction() call sent to asyncpg sends None for
  isolation_level if not otherwise set in the SQLAlchemy dialect/wrapper,
  thereby allowing asyncpg to make use of the server level setting for
  isolation_level in the absense of a client-level setting. Previously,
  this behavior of asyncpg was blocked by a hardcoded read_committed.

  References: #12159

mariadb

• [mariadb] [bug] [dml] [mysql] Fixed a bug where the MySQL statement compiler would not properly compile
  statements where _mysql.Insert.on_duplicate_key_update() was passed
  values that included ORM-mapped attributes (e.g.
  InstrumentedAttribute objects) as keys. Pull request courtesy of
  mingyu.

  References: #12117

sqlite

• [sqlite] [bug] [aiosqlite] [asyncio] [pool] Changed default connection pool used by the aiosqlite dialect
  from NullPool to AsyncAdaptedQueuePool; this change
  should have been made when 2.0 was first released as the pysqlite
  dialect was similarly changed to use QueuePool as detailed
  in change_7490.

  References: #12285

2.0.37

Released: January 9, 2025

orm

• [orm] [bug] Fixed issue regarding Union types that would be present in the
  _orm.registry.type_annotation_map of a _orm.registry
  or declarative base class, where a Mapped element that included
  one of the subtypes present in that Union would be matched to that
  entry, potentially ignoring other entries that matched exactly. The
  correct behavior now takes place such that an entry should only match in
  _orm.registry.type_annotation_map exactly, as a Union type
  is a self-contained type. For example, an attribute with Mapped[float]
  would previously match to a _orm.registry.type_annotation_map
  entry Union[float, Decimal]; this will no longer match and will now
  only match to an entry that states float. Pull request courtesy Frazer
  McLean.

  References: #11370

• [orm] [bug] Fixed bug in how type unions were handled within
  _orm.registry.type_annotation_map as well as
  _orm.Mapped that made the lookup behavior of a | b different
  from that of Union[a, b].

  References: #11944

• [orm] [bug] Consistently handle TypeAliasType (defined in PEP 695) obtained with
  the type X = int syntax introduced in python 3.12. Now in all cases one
  such alias must be explicitly added to the type map for it to be usable
  inside Mapped. This change also revises the approach added in
  #11305, now requiring the TypeAliasType to be added to the
  type map. Documentation on how unions and type alias types are handled by
  SQLAlchemy has been added in the
  orm_declarative_mapped_column_type_map section of the documentation.

  References: #11955

• [orm] [bug] Fixed regression caused by an internal code change in response to recent
  Mypy releases that caused the very unusual case of a list of ORM-mapped
  attribute expressions passed to ColumnOperators.in_() to no longer
  be accepted.

  References: #12019

• [orm] [bug] Fixed issues in type handling within the
  _orm.registry.type_annotation_map feature which prevented the
  use of unions, using either pep-604 or Union syntaxes under future
  annotations mode, which contained multiple generic types as elements from
  being correctly resolvable.

  References: #12207

• [orm] [bug] Fixed issue in event system which prevented an event listener from being
  attached and detached from multiple class-like objects, namely the
  sessionmaker or scoped_session targets that assign to
  Session subclasses.

  References: #12216

sql

• [sql] [bug] Fixed issue in "lambda SQL" feature where the tracking of bound parameters
  could be corrupted if the same lambda were evaluated across multiple
  compile phases, including when using the same lambda across multiple engine
  instances or with statement caching disabled.

  References: #12084

postgresql

• [postgresql] [usecase] The _postgresql.Range type now supports
  _postgresql.Range.__contains__(). Pull request courtesy of Frazer
  McLean.

  References: #12093

• [postgresql] [bug] Fixes issue in Dialect.get_multi_indexes() in the PostgreSQL
  dialect, where an error would be thrown when attempting to use alembic with
  a vector index from the pgvecto.rs extension.

  References: #11724

• [postgresql] [bug] Fixed issue where creating a table with a primary column of
  _sql.SmallInteger and using the asyncpg driver would result in
  the type being compiled to SERIAL rather than SMALLSERIAL.

  References: #12170

• [postgresql] [bug] Adjusted the asyncpg dialect so that an empty SQL string, which is valid
  for PostgreSQL server, may be successfully processed at the dialect level,
  such as when using Connection.exec_driver_sql(). Pull request
  courtesy Andrew Jackson.

  References: #12220

mysql

• [mysql] [usecase] [mariadb] Added support for the LIMIT clause with DELETE for the MySQL and
  MariaDB dialects, to complement the already present option for
  UPDATE. The Delete.with_dialect_options() method of the
  delete() construct accepts parameters for mysql_limit and
  mariadb_limit, allowing users to specify a limit on the number of rows
  deleted. Pull request courtesy of Pablo Nicolás Estevez.

  References: #11764

• [mysql] [bug] [mariadb] Added logic to ensure that the mysql_limit and mariadb_limit
  parameters of Update.with_dialect_options() and
  Delete.with_dialect_options() when compiled to string will only
  compile if the parameter is passed as an integer; a ValueError is
  raised otherwise.

mariadb

• [mariadb] [usecase] Added sql types INET4 and INET6 in the MariaDB dialect. Pull
  request courtesy Adam Žurek.

  References: #10720

sqlite

• [sqlite] [usecase] Added SQLite table option to enable STRICT tables. Pull request
  courtesy of Guilherme Crocetti.

  References: #7398

oracle

• [oracle] [feature] Added new table option oracle_tablespace to specify the TABLESPACE
  option when creating a table in Oracle. This allows users to define the
  tablespace in which the table should be created. Pull request courtesy of
  Miguel Grillo.

  References: #12016

• [oracle] [usecase] Use the connection attribute max_identifier_length available
  in oracledb since version 2.5 when determining the identifier length
  in the Oracle dialect.

  References: #12032

• [oracle] [bug] Fixed compilation of TABLE function when used in a FROM clause in
  Oracle Database dialect.

  References: #12100

• [oracle] [bug] Fixed issue in oracledb / cx_oracle dialects where output type handlers for
  CLOB were being routed to NVARCHAR rather than VARCHAR, causing
  a double conversion to take place.

  References: #12150

2.0.36

Released: October 15, 2024

orm

• [orm] [usecase] Added new parameter _orm.mapped_column.hash to ORM constructs
  such as _orm.mapped_column(), _orm.relationship(), etc.,
  which is interpreted for ORM Native Dataclasses in the same way as other
  dataclass-specific field parameters.

  References: #11923

• [orm] [bug] Fixed bug in ORM bulk update/delete where using RETURNING with bulk
  update/delete in combination with populate_existing would fail to
  accommodate the populate_existing option.

  References: #11912

• [orm] [bug] Continuing from #11912, columns marked with
  mapped_column.onupdate,
  mapped_column.server_onupdate, or Computed are now
  refreshed in ORM instances when running an ORM enabled UPDATE with WHERE
  criteria, even if the statement does not use RETURNING or
  populate_existing.

  References: #11917

• [orm] [bug] Fixed regression caused by fixes to joined eager loading in #11449
  released in 2.0.31, where a particular joinedload case could not be
  asserted correctly. We now have an example of that case so the assertion
  has been repaired to allow for it.

  References: #11965

• [orm] [bug] Improved the error message emitted when trying to map as dataclass a class
  while also manually providing the __table__ attribute.
  This usage is currently not supported.

  References: #11973

• [orm] [bug] Refined the check which the ORM lazy loader uses to detect "this would be
  loading by primary key and the primary key is NULL, skip loading" to take
  into account the current setting for the
  orm.Mapper.allow_partial_pks parameter. If this parameter is
  False, then a composite PK value that has partial NULL elements should
  also be skipped. This can apply to some composite overlapping foreign key
  configurations.

  References: #11995

• [orm] [bug] Fixed bug in ORM "update with WHERE clause" feature where an explicit
  .returning() would interfere with the "fetch" synchronize strategy due
  to an assumption that the ORM mapped class featured the primary key columns
  in a specific position within the RETURNING. This has been fixed to use
  appropriate ORM column targeting.

  References: #11997

sql

• [sql] [usecase] Datatypes that are binary based such as VARBINARY will resolve to
  LargeBinary when the TypeEngine.as_generic() method is
  called.

  References: #11978

• [sql] [bug] [regression] Fixed regression from 1.4 where some datatypes such as those derived from
  TypeDecorator could not be pickled when they were part of a
  larger SQL expression composition due to internal supporting structures
  themselves not being pickleable.

  References: #12002

schema

• [schema] [bug] Fixed bug where SQL functions passed to
  _schema.Column.server_default would not be rendered with the
  particular form of parenthesization now required by newer versions of MySQL
  and MariaDB. Pull request courtesy of huuya.

  References: #11317

postgresql

• [postgresql] [bug] [reflection] Fixed bug in reflection of table comments where unrelated text would be
  returned if an entry in the pg_description table happened to share the
  same oid (objoid) as the table being reflected.

  References: #11961

• [postgresql] [bug] The postgresql.JSON and postgresql.JSONB datatypes will
  now render a "bind cast" in all cases for all PostgreSQL backends,
  including psycopg2, whereas previously it was only enabled for some
  backends. This allows greater accuracy in allowing the database server to
  recognize when a string value is to be interpreted as JSON.

  References: #11994

mysql

• [mysql] [performance] Improved a query used for the MySQL 8 backend when reflecting foreign keys
  to be better optimized. Previously, for a database that had millions of
  columns across all tables, the query could be prohibitively slow; the query
  has been reworked to take better advantage of existing indexes.

  References: #11975