1fanwang opened a new issue, #66796:
URL: https://github.com/apache/airflow/issues/66796
### Apache Airflow version
main (3.x)
### What happened?
`SerializedDagModel.get_count()` returns
`session.scalar(select(func.count()).select_from(cls)) or 0`. The `or 0`
collapses the legitimately-impossible None case with the "table is empty" case
(which actually returns 0, not None) — and also masks any transient DB error
that surfaces as None from `session.scalar()`.
In practice the only path that reaches `or 0` is a DB-side failure, and
silently emitting `serialized_dag.count = 0` causes false on-call pages ("all
DAGs disappeared!") while hiding the real problem.
### What you think should happen instead?
Drop the `or 0`. `select(func.count())` on an aggregate is guaranteed to
return an int, so a None return is anomalous and should raise (or log warning +
raise). Callers can opt into try/except as needed.
### Anything else?
This is a 1-line change in the model; one caller in
`dag_processing/manager.py` emits the count to a metric path and should wrap in
try/except after the change.
### Are you willing to submit PR?
- [X] Yes I am willing to submit a PR!
### Code of Conduct
- [X] I agree to follow this project's Code of Conduct
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