[GitHub] [airflow] mik-laj commented on a change in pull request #10956: Officially support running more than one scheduler concurrently.

[GitBox <gi...@apache.org>]

mik-laj commented on a change in pull request #10956:
URL: https://github.com/apache/airflow/pull/10956#discussion_r499494587



##########
File path: airflow/models/dag.py
##########
@@ -1572,6 +1661,21 @@ def bulk_sync_to_db(cls, dags: Collection["DAG"], sync_time=None, session=None):
             session.add(orm_dag)
             orm_dags.append(orm_dag)
 
+        # Get the latest dag run for each existing dag as a single query (avoid n+1 query)
+        most_recent_dag_runs = dict(session.query(DagRun.dag_id, func.max_(DagRun.execution_date)).filter(
+            DagRun.dag_id.in_(existing_dag_ids),
+            or_(
+                DagRun.run_type == DagRunType.BACKFILL_JOB.value,
+                DagRun.run_type == DagRunType.SCHEDULED.value,
+            ),
+        ).group_by(DagRun.dag_id).all())
+
+        num_active_runs = dict(session.query(DagRun.dag_id, func.count('*')).filter(
+            DagRun.dag_id.in_(existing_dag_ids),
+            DagRun.state == State.RUNNING,  # pylint: disable=comparison-with-callable
+            DagRun.external_trigger.is_(False)
+        ).group_by(DagRun.dag_id).all())

Review comment:
       I wonder if it should be done in this method.  This method only talks about data synchronization, not updating other fields.




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