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Fix DAG processor OOM || Avoid loading all TaskInstances when checking DagVersion in write_dag #60937

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Merged
vatsrahul1001 merged 5 commits into from
Jan 23, 2026
Merged

Fix DAG processor OOM || Avoid loading all TaskInstances when checking DagVersion in write_dag #60937

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7b46446
Optimize write_dag to use EXISTS query instead of joinedload
vatsrahul1001 Jan 22, 2026
27222bb
Merge branch 'main' into optimize/write-dag-exists-query
vatsrahul1001 Jan 22, 2026
b82284d
Update airflow-core/src/airflow/models/serialized_dag.py
jedcunningham Jan 22, 2026
1aacb02
Merge branch 'main' of github.com:astronomer/airflow into optimize/wr…
vatsrahul1001 Jan 23, 2026
8d27fde
Revert "Update airflow-core/src/airflow/models/serialized_dag.py"
vatsrahul1001 Jan 23, 2026
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14 changes: 10 additions & 4 deletions airflow-core/src/airflow/models/serialized_dag.py
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Original file line number Diff line number Diff line change
Expand Up @@ -27,9 +27,9 @@

import sqlalchemy_jsonfield
import uuid6
from sqlalchemy import ForeignKey, LargeBinary, String, select, tuple_, update
from sqlalchemy import ForeignKey, LargeBinary, String, exists, select, tuple_, update
from sqlalchemy.dialects.postgresql import JSONB
from sqlalchemy.orm import Mapped, backref, foreign, joinedload, relationship
from sqlalchemy.orm import Mapped, backref, foreign, relationship
from sqlalchemy.sql.expression import func, literal
from sqlalchemy_utils import UUIDType

Expand All @@ -45,6 +45,7 @@
from airflow.models.dagcode import DagCode
from airflow.models.dagrun import DagRun
from airflow.models.deadline_alert import DeadlineAlert as DeadlineAlertModel
from airflow.models.taskinstance import TaskInstance
from airflow.serialization.dag_dependency import DagDependency
from airflow.serialization.definitions.assets import SerializedAssetUniqueKey as UKey
from airflow.serialization.definitions.deadline import DeadlineAlertFields
Expand Down Expand Up @@ -486,7 +487,6 @@ def write_dag(
dag_version = session.scalar(
select(DagVersion)
.where(DagVersion.dag_id == dag.dag_id)
.options(joinedload(DagVersion.task_instances))
.order_by(DagVersion.created_at.desc())
.limit(1)
)
Expand Down Expand Up @@ -520,7 +520,13 @@ def write_dag(
log.debug("Serialized DAG (%s) is unchanged. Skipping writing to DB", dag.dag_id)
return False

if dag_version and not dag_version.task_instances:
has_task_instances: bool = False
if dag_version:
has_task_instances = bool(
session.scalar(select(exists().where(TaskInstance.dag_version_id == dag_version.id)))
)

if dag_version and not has_task_instances:
# This is for dynamic DAGs that the hashes changes often. We should update
# the serialized dag, the dag_version and the dag_code instead of a new version
# if the dag_version is not associated with any task instances
Expand Down