2.0.53

Released: September 14, 2026

orm

• [orm] [bug] Fixed issue where an expression passed to _orm.with_expression() that embedded a _sql.select(), such as a correlated _sql.exists(), would fail to populate the attribute correctly on the second and subsequent executions of an otherwise identical statement, when the _orm.query_expression() attribute was loaded by a relationship loader that emits a second query, i.e. _orm.selectinload(), _orm.lazyload() or _orm.immediateload().

  References: #13560

• [orm] [bug] Fixed memory issue where mapped classes, along with their Table and _orm.Mapper objects, would not be garbage collected after the _orm.registry in which they were mapped had been disposed and dereferenced. The issue would occur for mappings that made use of _orm.relationship() together with constructs such as an Index established against an ORM-annotated expression.

  References: #13566

• [orm] [bug] Fixed issue where pickling an ORM object that had an instance level lazy loader established, such as when the _orm.raiseload() option is used, would emit a spurious warning regarding the loader containing additional criteria, if the object had itself been unpickled from a previous serialization. This would occur for objects that cross more than one serialization boundary, such as when using multiprocessing.

  References: #13574

• [orm] [bug] Fixed issue where calling _orm.aliased() against an existing _orm.aliased() construct, without passing an explicit selectable, would disregard the selectable of the existing construct and produce an alias of the mapped table instead, if that selectable were anything other than a table or a plain subquery, leading to incorrect results and/or non-working queries.

  This includes _orm.aliased() against a _orm.with_polymorphic() construct, which would previously produce an alias of the base mapped class only, discarding the polymorphic selectable and additional mappers. The new construct now retains these, so that criteria against subclass attributes and the innerjoin and selectable parameters of _orm.with_polymorphic() take effect, and subclass columns are loaded up front. The SQL rendered for these constructs now includes the polymorphic selectable.

  References: #13583, #13584

• [orm] [bug] Fixed issue where using _orm.aliased() with both the _orm.aliased.name and _orm.aliased.flat parameters, against an entity that is mapped to a join which includes anonymously named aliases, would embed the anonymous name symbol within the names generated for each element of the join, producing unusable SQL. An anonymously named element of the join is now aliased anonymously.

  References: #13583

engine

• [engine] [bug] [asyncio] [pool] Fixed issue where a DBAPI connection would be left open and unreachable if an exception were raised within the _events.PoolEvents.connect() or _events.PoolEvents.first_connect() event handlers, which is where Dialect.initialize() runs. The connection had been created but not yet associated with anything that could close it, so it was neither returned to the pool nor closed. For an asyncio driver in particular this could leak a server-side session for the life of the process, as the garbage collector is not able to close a connection that requires the event loop.

  References: #13548

sql

• [sql] [bug] Fixed issue where calling _sql.CTE.alias() on a _sql.CTE that was itself produced by _sql.CTE.alias() would render SQL that referred to the name of the intermediate alias, which is not present in the WITH clause, rather than to the name of the original CTE, producing invalid SQL.

  References: #13583

schema

• [schema] [bug] Fixed issue where reflecting a table with a foreign key constraint that names the same source column more than once, such as FOREIGN KEY (a, a) REFERENCES r (b, c) which is accepted by backends such as PostgreSQL, would raise ArgumentError and fail the reflection of the entire table. As ForeignKeyConstraint has no representation for this form, the constraint is now skipped with a warning, in the same way as one that names columns which are not present in the table, so that the remainder of the table is still reflected.

  Note that in the SQLAlchemy 2.1 series, full support for reflecting and constructing foreign key constraints with duplicated source columns has been added, with no warnings or skips.

  References: #13525

postgresql

• [postgresql] [bug] Fixed bug in _reflection.Inspector.get_schema_names() for PostgreSQL where the query used to exclude system schemas relied on NOT LIKE 'pg_%', which treats the underscore as a SQL LIKE wildcard rather than a literal character. This caused user-created schemas that happen to start with "pg" followed by any other character, such as pgsql or pgstats, to be silently excluded along with actual system schemas like pg_catalog. Pull request courtesy Evan Rusackas.

  References: #13472

mysql

• [mysql] [bug] Ensure that CREATE TABLE DDL statements for MySQL and MariaDB dialects render the table options in a deterministic order. Previously the order could change depending on the Python seed.

  References: #13523

sqlite

• [sqlite] [usecase] [reflection] Implemented _engine.Inspector.get_table_options() for the SQLite dialect, which previously raised NotImplementedError. The method returns the sqlite_with_rowid and sqlite_strict dialect options for a table that was created using the WITHOUT ROWID and / or STRICT keywords. As a result, these keywords are now also present in _schema.Table.kwargs for a _schema.Table that is reflected using autoload, so that a table which is recreated from its reflected form, such as by Alembic's batch migration mode, renders the keywords again rather than silently dropping them.

  References: #13543

• [sqlite] [bug] [reflection] Fixed issue in SQLite reflection where the name of a PRIMARY KEY, UNIQUE or FOREIGN KEY constraint would be reflected as None if the CONSTRAINT <name> clause were separated from the keyword that follows it by a newline rather than by spaces. As SQLite stores the CREATE TABLE statement as it was originally typed, this affected tables created from hand-written DDL that spans multiple lines. The regular expressions used to recover constraint names, as well as the ON UPDATE / ON DELETE, DEFERRABLE and INITIALLY options of a foreign key constraint, now accept any whitespace between tokens.

  References: #13528

• [sqlite] [bug] [reflection] Reworked the regular expression that parses FOREIGN KEY constraints during SQLite CREATE TABLE reflection so that the referred column list is matched unambiguously avoiding potential exponential backtracking. Pull request courtesy of Javid Khan.

  References: #13530

mssql

• [mssql] [bug] [reflection] Fixed issue in SQL Server reflection where TEXT and NTEXT columns would be reflected with a spurious length of 16 and 8, respectively. These are unlengthed LOB datatypes; the value originates from the sys.columns.max_length column, which reports the size of the in-row LOB pointer rather than a character length for these types. The reflected _mssql.TEXT and _mssql.NTEXT types now have a length of None, so that a reflected table emits valid DDL when re-created, which previously failed with "Cannot specify a column width on data type text". Pull request courtesy Sam Debruyn.

  References: #13451

oracle

• [oracle] [usecase] Added support for oracledb's new terminate() feature, which allows for clean termination of an Oracle database connection in an asyncio context where the connection's state has fallen out of the event loop, and needs to be garbage collected. The feature is enabled automatically when using oracledb 26.0.0 or greater.

  References: #13578

tests

• [tests] [bug] Altered the dialect reflection test test_check_constraint_parenthesized_expressions() so that it does not convert the reflected constraint to lowercase, which interferes with some third party dialect's representation of reflected check constraints.

  References: #13521

misc

• [bug] [installation] Added the AUTHORS file to the set of license files included in the built wheel, where previously only the LICENSE file was present. As the text of LICENSE refers to AUTHORS for the list of copyright holders, the reference would not resolve for tools that inspect an installed distribution.

  References: #13518