Fix DetachedInstanceError when accessing DagRun.created_dag_version

[kaxil]

The error occurred when trying to access dag_run.created_dag_version on a DagRun object that was detached from its SQLAlchemy session.

Stacktrace:

[2025-08-08T19:03:28.761+0000] {scheduler_job_runner.py:935} ERROR - Marking task instance <TaskInstance: sell_oms_shipconfirm_mao_to_ecom_load_delta_quarterly.shipconfirm_delta_to_kafka_notebook_task scheduled__2025-08-08T07:30:00+00:00 [running]> as failed Traceback (most recent call last): File "/usr/local/lib/python3.12/site-packages/airflow/jobs/scheduler_job_runner.py", line 925, in process_executor_events dag = scheduler_dag_bag.get_dag(dag_run=ti.dag_run, session=session) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/airflow/jobs/scheduler_job_runner.py", line 141, in get_dag version = self._version_from_dag_run(dag_run=dag_run, session=session) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/airflow/jobs/scheduler_job_runner.py", line 135, in _version_from_dag_run dag_version = dag_run.created_dag_version ^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 487, in __get__ return self.impl.get(state, dict_) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 959, in get value = self._fire_loader_callables(state, key, passive) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/sqlalchemy/orm/attributes.py", line 995, in _fire_loader_callables return self.callable_(state, passive) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/local/lib/python3.12/site-packages/sqlalchemy/orm/strategies.py", line 863, in _load_for_state raise orm_exc.DetachedInstanceError( sqlalchemy.orm.exc.DetachedInstanceError: Parent instance <DagRun at 0x7f46d309a5d0> is not bound to a Session; lazy load operation of attribute 'created_dag_version' cannot proceed (Background on this error at: https://sqlalche.me/e/14/bhk3) 

Two-layer fix:

1. Proactive loading: Add selectinload for created_dag_version in process_executor_events query to ensure optimal performance for this critical path
2. Defensive code: Add relationship loading check in DBDagBag._version_from_dag_run to handle all call sites safely using SQLAlchemy inspect pattern

---

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[kaxil]

cc @karenbraganz

[github-actions]

Backport failed to create: v3-0-test. View the failure log Run details

Status	Branch	Result
❌	v3-0-test

You can attempt to backport this manually by running:

cherry_picker 05d2229 v3-0-test

This should apply the commit to the v3-0-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

[kaxil]

Manually cherry-picked 364d246