SQLAlchemy rel_2_0_52

2.0.52

Released: August 11, 2026

platform

• [platform] [bug] Python 3.15 support has been added and tested, including minimal changes for full compatibility.

  References: #13477

orm

• [orm] [bug] Fixed a result-column misalignment bug in ORM-enabled UPDATE statements where synchronize_session="fetch" is in use, either explicitly or because the statement uses constructs such as CTEs that implicitly select for it. Columns in rows returned by .returning() could be returned under incorrect keys (e.g. row[SomeClass.a] returning the value of a different column), a problem most likely to manifest under concurrent workloads. ORM DELETE statements were not affected.

  References: #13439

• [orm] [bug] Fixed bug where a failed _orm.Session.bulk_insert_mappings(), _orm.Session.bulk_update_mappings() or _orm.Session.bulk_save_objects() call could leave the _orm.Session permanently in a "flushing" state, such as when the transaction could not be begun because a previous flush had left it needing a rollback. Unlike _orm.Session.flush(), the bulk methods set the internal flushing flag and began the transaction outside of the try/finally block that resets it, so that neither _orm.Session.rollback() nor _orm.Session.close() would clear it, and every subsequent flush would raise InvalidRequestError: Session is already flushing. Pull request courtesy Hamody We.

  References: #13485

• [orm] [bug] Fixed issue where unpickling an ORM object that were loaded using loader options making use of wildcard tokens, such as _orm.load_only() or _orm.raiseload() with "*", would fail with KeyError or IndexError if the process doing the unpickling had not yet constructed a loader path making use of that same token. This would typically be observed when the object were unpickled in a separate process, such as with the spawn or forkserver multiprocessing start methods, the latter of which became the default on POSIX platforms as of Python 3.14. The internal collection of these tokens is now established up front, so that it is identical in every process.

  References: #13493

• [orm] [bug] Fixed issue where a string ending in "*" passed to a _orm.Load strategy method, such as Load(A).joinedload("bs.*"), would bypass the check which rejects string attribute names in loader options, silently producing a loader path that matched nothing. Such a string now raises ArgumentError with the same message given for any other string attribute name. The bare wildcard "*", as in Load(A).lazyload("*"), continues to be accepted.

  References: #13493

• [orm] [bug] Calling _orm.aliased() against a _sql.select() or _sql.union() / _sql.CompoundSelect construct, which previously failed with an obscure AttributeError regarding a missing .mapper attribute, now raises when using SQLAlchemy 2.1, and emits a deprecation warning under SQLAlchemy 2.0 as it coerces the construct into a subquery instead. This matches the behavior of other similar implicit SELECT-to-FROM coercions. Pull request courtesy Rens Groothuijsen.

  References: #6274

orm declarative

• [bug] [orm declarative] Fixed issue where using PEP 593 Annotated wrapping a PEP 695 type alias, such as Annotated[SomeTypeAlias, mapped_column()], would crash with AttributeError: __value__. The internal is_pep695() check incorrectly identified the Annotated type as a PEP 695 type alias due to a quirk in Annotated.__origin__ returning the first type argument rather than Annotated itself.

  References: #13386

sql

• [sql] [bug] Fixed issue where _sql.Select.get_final_froms() would emit a deprecation warning when the statement made use of the PostgreSQL-specific expression argument to _sql.Select.distinct(); the same spurious warning would be emitted when stringifying such a statement without explicitly using a PostgreSQL dialect. The fix ensures that this 1.4-era warning is suppressed under both 2.0 and 2.1.

  Note that under SQLAlchemy 2.1, passing an expression to _sql.Select.distinct() is deprecated overall, and is replaced by a new PostgreSQL-specific construct (see #12342).

  References: #13396

• [sql] [bug] Fixed an issue in Numeric where the Numeric.decimal_return_scale parameter was ignored when the DBAPI does not support native decimal objects (i.e. dialect.supports_native_decimal is False). In this path the result processor was computing the conversion scale from Numeric.scale directly, bypassing Numeric.decimal_return_scale entirely. The behavior now matches Float, which already used the correct _effective_decimal_return_scale property. Pull request courtesy Kadir Can Ozden.

  References: #13424

• [sql] [bug] Added auditing to the test suite which exercises the literal execute processors across all datatypes and dialects to ensure that string input is either appropriately rejected or correctly escaped. Literal execute processors are invoked when the bindparam.literal_execute parameter is used with an explicit bindparam() object, which overrides DBAPI-native bind handling to render the value inline with the statement instead. Datatypes that were updated include the originally reported SQL Server Uuid / UNIQUEIDENTIFIER rendering which now escapes properly, the JSONPATH type that's currently PostgreSQL-only, and a full family of numeric types stemming from the _types.Float and _types.Numeric bases which now coerce the value to a number, rejecting non-numeric input. Thanks to Javid Khan for helping to identify the issue.

  References: #13448

schema

• [schema] [bug] Fixed an issue where _schema.Table.to_metadata() reused column default and on-update objects, causing the defaults on the original columns to refer to the copied columns. Default generators, including sequences, and server-side defaults are now copied and remain associated with their respective columns and metadata collections. Applications that inspected these objects will now see distinct defaults on the copied table instead of the objects owned by the original table. Pull request courtesy Goutam Adwant.

  References: #13481

postgresql

• [postgresql] [bug] [reflection] Fixed reflection of PostgreSQL CHECK constraints where an expression made up of multiple parenthesized sub-expressions, such as (x IS NULL OR y IS NULL) AND (x IS NULL OR y IS NULL), would have its leading and trailing parentheses incorrectly stripped, producing an unbalanced and syntactically invalid reflected expression. Pull request courtesy Shaurya Singh.

  References: #13157

• [postgresql] [bug] Fixed bug in the PostgreSQL dialect where a single quote in a sequence, table, or schema name, such as one supplied via a schema_translate_map or an explicit Sequence, could result in a malformed nextval() statement. The quote is now properly escaped. Pull request courtesy dxbjavid.

  References: #13429

sqlite

• [sqlite] [bug] Reworked the regular expression that detects inline UNIQUE column constraints during SQLite CREATE TABLE reflection so that the whitespace separating a column's type from a following clause is matched unambiguously. The previous pattern had three overlapping quantifiers that could each consume a space character, so a column definition carrying a long run of whitespace in the stored schema made _reflection.Inspector.get_unique_constraints() spend cubic time backtracking before returning. Fix courtesy of Javid Khan.

  References: #13419

mssql

• [mssql] [bug] Tightened the construction of the ODBC connection string in the pyodbc connector (as well as the mssql-python connector in 2.1) so that the driver name, the names of pass-through connection parameters, and values containing } are brace-quoted. Previously a } in the driver name or in a pass-through value, or a ; in the name of a pass-through parameter, could close the surrounding token early and allow the remainder of the string to be interpreted as additional connection attributes. Pull request courtesy dxbjavid.

  References: #13380

tests

• [tests] [bug] Fixed class-scoped pytest fixtures that were defined as instance methods using self, which is deprecated as of pytest 9.1 and will be removed in pytest 10. Fixtures are now decorated with a compatibility @classmethod decorator and use cls as the first parameter.

  References: #13392