Fix sqlalchemy primary key black-out error on DDRQ (#27538)

closes #27509

airflow/models/dataset.py

@@ -116,6 +116,7 @@ class DagScheduleDatasetReference(Base):
             DagScheduleDatasetReference.dataset_id == foreign(DatasetDagRunQueue.dataset_id),
             DagScheduleDatasetReference.dag_id == foreign(DatasetDagRunQueue.target_dag_id),
         )""",
+        cascade="all, delete, delete-orphan",
     )
 
     __tablename__ = "dag_schedule_dataset_reference"

tests/models/test_taskinstance.py

@@ -1914,6 +1914,43 @@ def test_outlet_datasets_skipped(self, create_task_instance):
         # check that no dataset events were generated
         assert session.query(DatasetEvent).count() == 0
 
+    def test_changing_of_dataset_when_ddrq_is_already_populated(self, dag_maker, session):
+        """
+        Test that when a task that produces dataset has ran, that changing the consumer
+        dag dataset will not cause primary key blank-out
+        """
+        from airflow import Dataset
+
+        with dag_maker(schedule=None, serialized=True) as dag1:
+
+            @task(outlets=Dataset("test/1"))
+            def test_task1():
+                print(1)
+
+            test_task1()
+
+        dr1 = dag_maker.create_dagrun()
+        test_task1 = dag1.get_task("test_task1")
+
+        with dag_maker(dag_id="testdag", schedule=[Dataset("test/1")], serialized=True):
+
+            @task
+            def test_task2():
+                print(1)
+
+            test_task2()
+
+        ti = dr1.get_task_instance(task_id="test_task1")
+        ti.run()
+        # Change the dataset.
+        with dag_maker(dag_id="testdag", schedule=[Dataset("test2/1")], serialized=True):
+
+            @task
+            def test_task2():
+                print(1)
+
+            test_task2()
+
     @staticmethod
     def _test_previous_dates_setup(
         schedule_interval: str | datetime.timedelta | None,