[GitHub] Fokko commented on a change in pull request #4298: [AIRFLOW-3478] Make sure that the session is closed

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Fokko commented on a change in pull request #4298: [AIRFLOW-3478] Make sure that the session is closed
URL: https://github.com/apache/incubator-airflow/pull/4298#discussion_r240329624
 
 

 ##########
 File path: airflow/api/common/experimental/mark_tasks.py
 ##########
 @@ -180,18 +180,15 @@ def set_state(task, execution_date, upstream=False, downstream=False,
             tis_altered += qry_sub_dag.with_for_update().all()
         for ti in tis_altered:
             ti.state = state
-        session.commit()
     else:
         tis_altered = qry_dag.all()
         if len(sub_dag_ids) > 0:
             tis_altered += qry_sub_dag.all()
 
-    session.expunge_all()
 
 Review comment:
   I had to dig deeper into this. By default, [the objects are cleaned up](https://docs.sqlalchemy.org/en/latest/orm/session_api.html#sqlalchemy.orm.session.Session.commit): By default, the `Session` also expires all database loaded state on all ORM-managed attributes after transaction commit. This so that subsequent operations load the most recent data from the database. This behavior can be disabled using the `expire_on_commit=False` option to sessionmaker or the `Session`constructor. 
   
   But I've noticed that we explicitly set the `expire_on_commit=False`.
   https://github.com/apache/incubator-airflow/blob/ded25e16c1fb912019d3d0e5d47d020dccaa54b7/airflow/settings.py#L198
   
   In this case this change would indeed change behaviour. Maybe remove the `expire_on_commit ` to make it simpeler?

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