uranusjr commented on code in PR #30641:
URL: https://github.com/apache/airflow/pull/30641#discussion_r1169413547
##########
airflow/models/xcom_arg.py:
##########
@@ -309,11 +310,26 @@ def zip(self, *others: XComArg, fillvalue: Any = NOTSET)
-> ZipXComArg:
return super().zip(*others, fillvalue=fillvalue)
def get_task_map_length(self, run_id: str, *, session: Session) -> int |
None:
+ from airflow.models.taskinstance import TaskInstance
from airflow.models.taskmap import TaskMap
from airflow.models.xcom import XCom
task = self.operator
if isinstance(task, MappedOperator):
+ unfinished_ti_count_query =
session.query(func.count(TaskInstance.map_index)).filter(
Review Comment:
TI is indexed in this query so scanning should not happen, and having
`COUNT` reduces data sent through the wire. IIRC we did a micro benchmark
against a similar query sometime back; the best choice in theory is `EXISTS`
but it’s not universally supported. The second best is `SELECT 1 FROM ...` +
`first()` but that reads pretty weird, and `COUNT` is the next best choice.
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