fix DagPriorityParsingRequest unique constraint error when dataset aliases are resolved into new datasets

airflow/datasets/manager.py

@@ -140,10 +140,8 @@ def register_dataset_change(
 
         dags_to_reparse = dags_to_queue_from_dataset_alias - dags_to_queue_from_dataset
         if dags_to_reparse:
-            session.add_all(
-                DagPriorityParsingRequest(fileloc=fileloc)
-                for fileloc in {dag.fileloc for dag in dags_to_reparse}
-            )
+            file_locs = {dag.fileloc for dag in dags_to_reparse}
+            cls._send_dag_priority_parsing_request(file_locs, session)
         session.flush()
 
         cls.notify_dataset_changed(dataset=dataset)
@@ -208,6 +206,35 @@ def _postgres_queue_dagruns(cls, dataset_id: int, dags_to_queue: set[DagModel],
         stmt = insert(DatasetDagRunQueue).values(dataset_id=dataset_id).on_conflict_do_nothing()
         session.execute(stmt, values)
 
+    @classmethod
+    def _send_dag_priority_parsing_request(cls, file_locs: Iterable[str], session: Session) -> None:
+        if session.bind.dialect.name == "postgresql":
+            return cls._postgres_send_dag_priority_parsing_request(file_locs, session)
+        return cls._slow_path_send_dag_priority_parsing_request(file_locs, session)
+
+    @classmethod
+    def _slow_path_send_dag_priority_parsing_request(cls, file_locs: Iterable[str], session: Session) -> None:
+        def _send_dag_priority_parsing_request_if_needed(fileloc: str) -> str | None:
+            # Don't error whole transaction when a single DagPriorityParsingRequest item conflicts.
+            # https://docs.sqlalchemy.org/en/14/orm/session_transaction.html#using-savepoint
+            req = DagPriorityParsingRequest(fileloc=fileloc)
+            try:
+                with session.begin_nested():
+                    session.merge(req)
+            except exc.IntegrityError:
+                cls.logger().debug("Skipping request %s, already present", req, exc_info=True)
+                return None
+            return req.fileloc
+
+        (_send_dag_priority_parsing_request_if_needed(fileloc) for fileloc in file_locs)
+
+    @classmethod
+    def _postgres_send_dag_priority_parsing_request(cls, file_locs: Iterable[str], session: Session) -> None:
+        from sqlalchemy.dialects.postgresql import insert
+
+        stmt = insert(DagPriorityParsingRequest).on_conflict_do_nothing()
+        session.execute(stmt, {"fileloc": fileloc for fileloc in file_locs})
+
 
 def resolve_dataset_manager() -> DatasetManager:
     """Retrieve the dataset manager."""