Sourced from sqlalchemy's releases.

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

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