[GitHub] [airflow] uranusjr commented on a diff in pull request #25757: Fail task if mapping upstream fails

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

uranusjr commented on code in PR #25757:
URL: https://github.com/apache/airflow/pull/25757#discussion_r947523883


##########
airflow/models/mappedoperator.py:
##########
@@ -682,17 +701,21 @@ def expand_mapped_task(self, run_id: str, *, session: Session) -> Tuple[Sequence
             ti.refresh_from_task(self)  # session.merge() loses task information.
             all_expanded_tis.append(ti)
 
+        # Coerce the None case to 0 -- these two are almost treated identically,
+        # except the unmapped ti (if exists) is marked to different states.
+        total_expanded_ti_count = total_length or 0
+
         # Set to "REMOVED" any (old) TaskInstances with map indices greater
         # than the current map value
         session.query(TaskInstance).filter(
             TaskInstance.dag_id == self.dag_id,
             TaskInstance.task_id == self.task_id,
             TaskInstance.run_id == run_id,
-            TaskInstance.map_index >= total_length,
+            TaskInstance.map_index >= total_expanded_ti_count,
         ).update({TaskInstance.state: TaskInstanceState.REMOVED})
 
         session.flush()
-        return all_expanded_tis, total_length
+        return all_expanded_tis, total_expanded_ti_count - 1

Review Comment:
   I think the old code introduces an off-by-one error? The return value is described as “the maximum map_index” (and is used as such in BackfillJob), which should be one less than the total expand length, right?



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