kaxil opened a new pull request, #57460:
URL: https://github.com/apache/airflow/pull/57460
When users have limited DAG access, the DAG list query was inefficiently
grouping all DagRuns in the database before filtering. This caused severe
performance degradation in large deployments where a user might access only a
few DAGs out of hundreds or thousands.
The fix filters both the main DAG query and the DagRun subquery by
accessible dag_ids before performing the expensive GROUP BY operation.
Before (queries all dagruns):
```sql
SELECT ... FROM dag
LEFT OUTER JOIN (
SELECT dag_run.dag_id, max(dag_run.id) AS max_dag_run_id
FROM dag_run
GROUP BY dag_run.dag_id
) AS mrq ON dag.dag_id = mrq.dag_id
```
After (filters to accessible dags):
```sql
SELECT ... FROM dag
LEFT OUTER JOIN (
SELECT dag_run.dag_id, max(dag_run.id) AS max_dag_run_id
FROM dag_run
WHERE dag_run.dag_id IN ('accessible_dag_1', 'accessible_dag_2')
GROUP BY dag_run.dag_id
) AS mrq ON dag.dag_id = mrq.dag_id
WHERE dag.dag_id IN ('accessible_dag_1', 'accessible_dag_2')
```
Performance impact: In a deployment with 100 DAGs (100 runs each) where a
user has access to only 2 DAGs, this reduces the subquery from grouping 10,000
rows down to 200 rows (50x improvement), and eliminates fetching 98 unnecessary
DAG models.
Fixes #57427
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