dstandish commented on code in PR #69565:
URL: https://github.com/apache/airflow/pull/69565#discussion_r3539413349
##########
airflow-core/src/airflow/models/taskinstance.py:
##########
@@ -203,6 +203,33 @@ def _stop_remaining_tasks(*, task_instance: TaskInstance,
task_teardown_map=None
log.info("Not skipping teardown task '%s'", ti.task_id)
+def _add_and_prime_mapped_ti(
+ ti: TaskInstance,
+ task: Operator,
+ dag_run: DagRun,
+ *,
+ session: Session,
+ context_carrier: dict | None = None,
+) -> None:
+ """
+ Attach a newly-created mapped TI to the session and prime its ``dag_run``
cache.
+
+ Used by mapped-task expansion (``TaskMap.expand_mapped_task``,
+ ``DagRun._revise_map_indexes_if_mapped``) to persist a brand-new mapped TI
without
+ the per-row SELECT that ``session.merge()`` would issue, and to prime
``dag_run`` so
+ a later ``ti.get_dagrun()`` during dependency evaluation is a cache hit
rather than
+ another per-TI SELECT.
+
+ :meta private:
+ """
+ task_instance_mutation_hook(ti, dag_run=dag_run)
+ session.add(ti)
+ if context_carrier is not None:
+ ti.context_carrier = context_carrier
+ ti.refresh_from_task(task, dag_run=dag_run)
+ set_committed_value(ti, "dag_run", dag_run)
Review Comment:
ok so in the current call sites, it just happens that there's no difference.
why: because the TIs that are passed to it happen to be transient. if this
helper were to be used for a persisted ti, then set_committed_value would avoid
an unnecessary N+1 because it bypasses the orm event system.
there is precedent for it in TI.get_dagrun
so the reason to use it is it's defensive and consistent with other
instances where we set a cached value
the reason to not use it is because it's not strictly necessary in the
usages *right now* and the other way is more idiomatic.
i lean ever so slightly to keeping the usage of set_committed_value -- but i
do *not* feel strongly about it
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