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Revert #59691: it broke per-index trigger rules in mapped task groups #68418

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Merged
uranusjr merged 1 commit into from
Jun 12, 2026
+1 −164
Merged

Revert #59691: it broke per-index trigger rules in mapped task groups #68418

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56 changes: 1 addition & 55 deletions airflow-core/src/airflow/models/taskinstance.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2421,19 +2421,7 @@ def tg2(inp):
# and "ti_count == ancestor_ti_count" does not work, since the further
# expansion may be of length 1.
if not _is_further_mapped_inside(relative, common_ancestor):
# During mapped task group expansion, upstream placeholder task instances
# (map_index = -1) may already have been replaced by their first expanded
# successor (map_index = 0) while downstream task instances are still
# unexpanded and continue resolving dependencies against the placeholder index.
resolved_map_index = (
0
if _should_use_post_expansion_placeholder(
task=task, relative=relative, map_index=ancestor_map_index, run_id=run_id, session=session
)
else ancestor_map_index
)

return resolved_map_index
return ancestor_map_index

# Otherwise we need a partial aggregation for values from selected task
# instances in the ancestor's expansion context.
Expand Down Expand Up @@ -2507,48 +2495,6 @@ def _visit_relevant_relatives_for_mapped(mapped_tasks: Iterable[tuple[str, int]]
return visited


def _should_use_post_expansion_placeholder(
*,
task: Operator,
relative: Operator,
map_index: int,
run_id: str,
session: Session,
) -> bool:
"""
Determine whether upstream dependency resolution should use map_index = 0.

Returns True when the upstream placeholder task instance
(map_index = -1) has already been replaced by its post-expansion
successor (map_index = 0).
"""
if map_index != -1:
return False

rows = session.execute(
select(TaskInstance.task_id, TaskInstance.map_index).where(
TaskInstance.dag_id == relative.dag_id,
TaskInstance.run_id == run_id,
TaskInstance.task_id.in_([task.task_id, relative.task_id]),
TaskInstance.map_index.in_([-1, 0]),
)
).all()

task_to_map_indexes: dict[str, set[int]] = defaultdict(set)
for task_id, mi in rows:
task_to_map_indexes[task_id].add(mi)

# We only rewrite when:
# 1) the current task is still using the placeholder (-1)
# 2) the upstream placeholder (-1) no longer exists
# 3) the post-expansion placeholder (0) does exist
return (
-1 in task_to_map_indexes[task.task_id]
and -1 not in task_to_map_indexes[relative.task_id]
and 0 in task_to_map_indexes[relative.task_id]
)


class TaskInstanceNote(Base):
"""For storage of arbitrary notes concerning the task instance."""

Expand Down
109 changes: 0 additions & 109 deletions airflow-core/tests/unit/models/test_taskinstance.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3523,115 +3523,6 @@ def g(v):
assert result == expected


def test_downstream_placeholder_handles_upstream_post_expansion(dag_maker, session):
"""
Test dynamic task mapping behavior when an upstream placeholder task
(map_index = -1) has been replaced by the first expanded task
(map_index = 0).

This verifies that downstream mapped dependency resolution:
- preserves placeholder behavior before upstream expansion
- correctly resolves the post-expansion transition
- preserves normal expanded task behavior afterwards
"""

with dag_maker(session=session) as dag:

@task
def get_mapping_source():
return ["one", "two", "three"]

@task
def mapped_task(x):
output = f"{x}"
return output

@task_group(prefix_group_id=False)
def the_task_group(x):
start = MockOperator(task_id="start")
upstream = mapped_task(x)

# Downstream task inside the task group that does not directly
# consume the expand input, but is still mapped via the mapped
# task group context.
downstream = MockOperator(task_id="downstream")

start >> upstream >> downstream

mapping_source = get_mapping_source()
mapped_tg = the_task_group.expand(x=mapping_source)

mapping_source >> mapped_tg

# Create DAG run and execute prerequisites.
dr = dag_maker.create_dagrun()

dag_maker.run_ti("get_mapping_source", map_index=-1, dag_run=dr, session=session)

upstream_task = dag.get_task("mapped_task")
downstream_task = dag.get_task("downstream")

# Before upstream expansion occurs, mapped dependency resolution
# should retain the existing placeholder semantics since no concrete
# upstream/downstream map index pairing exists yet.
downstream_ti = dr.get_task_instance(task_id="downstream", map_index=-1, session=session)
downstream_ti.refresh_from_task(downstream_task)

result = downstream_ti.get_relevant_upstream_map_indexes(
upstream=upstream_task,
ti_count=1,
session=session,
)

assert result == -3

# Force expansion of the upstream mapped task.
upstream_task = dag.get_task("mapped_task")
_, max_index = TaskMap.expand_mapped_task(
upstream_task,
dr.run_id,
session=session,
)
upstream_expanded_ti_count = max_index + 1

downstream_task = dag.get_task("downstream")

# Grab the downstream placeholder TI.
downstream_ti = dr.get_task_instance(task_id="downstream", map_index=-1, session=session)
downstream_ti.refresh_from_task(downstream_task)

result = downstream_ti.get_relevant_upstream_map_indexes(
upstream=upstream_task,
ti_count=upstream_expanded_ti_count,
session=session,
)

assert result == 0

# Now do the same for downstream expanded (map_index = 0) to ensure existing behavior is not broken.
# Force expansion of the downstream mapped task.
_, max_index = TaskMap.expand_mapped_task(
downstream_task,
dr.run_id,
session=session,
)
downstream_expanded_ti_count = max_index + 1

# Grab the first expanded downstream task instance (map_index = 0).
downstream_ti = dr.get_task_instance(task_id="downstream", map_index=0, session=session)
downstream_ti.refresh_from_task(downstream_task)

result = downstream_ti.get_relevant_upstream_map_indexes(
upstream=upstream_task,
ti_count=downstream_expanded_ti_count,
session=session,
)

# Verify behavior remains unchanged once the downstream task
# itself has expanded.
assert result == 0


def test_find_relevant_relatives_with_non_mapped_task_as_tuple(dag_maker, session):
"""Test that specifying a non-mapped task as a tuple doesn't raise NotMapped exception."""
# t1 -> t2 (non-mapped) -> t3
Expand Down
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