kaxil commented on code in PR #54103:
URL: https://github.com/apache/airflow/pull/54103#discussion_r2705247082
##########
airflow-core/src/airflow/jobs/scheduler_job_runner.py:
##########
@@ -490,10 +515,60 @@ def _executable_task_instances_to_queued(self, max_tis:
int, session: Session) -
.where(~DM.is_paused)
.where(TI.state == TaskInstanceState.SCHEDULED)
.where(DM.bundle_name.is_not(None))
+ .join(
+ dr_task_concurrency_subquery,
+ and_(
+ TI.dag_id == dr_task_concurrency_subquery.c.dag_id,
Review Comment:
Nice - the outer join with COALESCE handles dag runs with 0 executing tasks
cleanly.
##########
airflow-core/src/airflow/jobs/scheduler_job_runner.py:
##########
@@ -194,6 +207,16 @@ def _is_parent_process() -> bool:
return multiprocessing.current_process().name == "MainProcess"
Review Comment:
This queries the same data as `ConcurrencyMap.load()` which is still called
and used for the check at lines 617-634. With the SQL-level filtering now in
place, that Python check should always pass (barring race conditions). Worth
adding a comment explaining why we keep both - race condition protection
between query time and check time?
##########
airflow-core/src/airflow/jobs/scheduler_job_runner.py:
##########
@@ -490,10 +515,60 @@ def _executable_task_instances_to_queued(self, max_tis:
int, session: Session) -
.where(~DM.is_paused)
.where(TI.state == TaskInstanceState.SCHEDULED)
.where(DM.bundle_name.is_not(None))
+ .join(
+ dr_task_concurrency_subquery,
+ and_(
+ TI.dag_id == dr_task_concurrency_subquery.c.dag_id,
+ TI.run_id == dr_task_concurrency_subquery.c.run_id,
+ ),
+ isouter=True,
+ )
+ .where(
+
func.coalesce(dr_task_concurrency_subquery.c.task_per_dr_count, 0) <
DM.max_active_tasks
+ )
.options(selectinload(TI.dag_model))
.order_by(-TI.priority_weight, DR.logical_date, TI.map_index)
)
+ # Create a subquery with row numbers partitioned by dag_id and
run_id.
+ # Different dags can have the same run_id but
+ # the dag_id combined with the run_id uniquely identify a run.
+ ranked_query = (
+ query.add_columns(
+ func.row_number()
+ .over(
+ partition_by=[TI.dag_id, TI.run_id],
+ order_by=[-TI.priority_weight, DR.logical_date,
TI.map_index],
+ )
+ .label("row_num"),
+ DM.max_active_tasks.label("dr_max_active_tasks"),
+ # Create columns for the order_by checks here for sqlite.
+ TI.priority_weight.label("priority_weight_for_ordering"),
+ DR.logical_date.label("logical_date_for_ordering"),
+ TI.map_index.label("map_index_for_ordering"),
+ )
+ ).subquery()
+
+ # Select only rows where row_number <= max_active_tasks.
+ query = (
+ select(TI)
+ .select_from(ranked_query)
+ .join(
+ TI,
+ (TI.dag_id == ranked_query.c.dag_id)
+ & (TI.task_id == ranked_query.c.task_id)
+ & (TI.run_id == ranked_query.c.run_id)
+ & (TI.map_index == ranked_query.c.map_index),
+ )
+ .where(ranked_query.c.row_num <=
ranked_query.c.dr_max_active_tasks)
+ # Add the order_by columns from the ranked query for sqlite.
+ .order_by(
+ -ranked_query.c.priority_weight_for_ordering,
+ ranked_query.c.logical_date_for_ordering,
+ ranked_query.c.map_index_for_ordering,
+ )
+ )
Review Comment:
This new query is missing `.options(selectinload(TI.dag_model))` which was
on the original query above. When we rebuild the query here, we lose the eager
loading - so every access to `ti.dag_model` later will trigger a separate
query. With 50 TIs that's 50+ extra queries per loop, which partially negates
the perf gains from this PR.
Also missing the `.with_hint(TI, "USE INDEX (ti_state)",
dialect_name="mysql")` - should add both here.
##########
airflow-core/src/airflow/jobs/scheduler_job_runner.py:
##########
@@ -515,7 +590,13 @@ def _executable_task_instances_to_queued(self, max_tis:
int, session: Session) -
try:
locked_query = with_row_locks(query, of=TI, session=session,
skip_locked=True)
- task_instances_to_examine: list[TI] =
list(session.scalars(locked_query).all())
+ task_instances_to_examine = session.scalars(locked_query).all()
+
+ self.log.debug("Length of the tis to examine is %d",
len(task_instances_to_examine))
+ self.log.debug(
+ "TaskInstance selection is: %s",
Review Comment:
nit: The `Counter()` iteration happens even when debug logging is disabled.
Not a big deal but if we're optimizing for perf, might want to guard this:
```python
if self.log.isEnabledFor(logging.DEBUG):
self.log.debug(...)
```
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