rajat315315 opened a new pull request, #70051:
URL: https://github.com/apache/airflow/pull/70051
### Description
### Motivation
Addresses issue #70050 .
Eliminates the N+1 database queries storm when checking if DAGs are paused
(`DagUnpausedDep`) in the scheduling loop. By utilizing SQLAlchemy `joinedload`
for `TI.dag_model` when fetching task instances for a DAG run, the pause check
can be resolved entirely in memory.
### Proposed Changes
1. **Query Optimization**: Modified `DagRun.fetch_task_instances` in
`airflow/models/dagrun.py` to add `joinedload(TI.dag_model)` to the
`select(TI)` statement.
2. **Dependency Check Update**: Modified `DagUnpausedDep._get_dep_statuses`
in `airflow/ti_deps/deps/dag_unpaused_dep.py` to use `ti.dag_model.is_paused`
instead of running `_is_dag_paused()` database selects.
### Verification
Ran benchmark tests on SQLite simulating a scheduler batch evaluation of
1,000 task instances:
* **Before**: 101 queries executed, taking 610.05 ms.
* **After**: 1 query executed, taking 320.95 ms (99% query count reduction,
**1.90x speedup**).
* **Unit Tests**: Passed successfully on
`airflow-core/tests/unit/models/test_dagrun.py`.
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