TJaniF opened a new issue, #48852:
URL: https://github.com/apache/airflow/issues/48852
### Apache Airflow version
3.0.0
### If "Other Airflow 2 version" selected, which one?
current main
### What happened?
I encountered this passing an embedding vector (list of lists) as XCom using
a dag that works in 2.10. The below dag reproduces the issue:
```
from airflow.sdk import dag
from airflow.decorators import task
@dag()
def lazy_list_xcom():
@task
def create_long_list():
big_list = [[i for i in range(100)] for _ in range(1000)]
return big_list
@task
def print_list(x):
print(x)
print_list(create_long_list())
lazy_list_xcom()
```
When running this dag the `create_long_list` task finishes successfully and
the `print_list` task gets stuck in running state (without any error that I can
see in the components).
Once I clear the `print_list` task I get the following error in the logs:
```
Log message source details:
sources=["/root/airflow/logs/dag_id=lazy_list_xcom/run_id=manual__2025-04-06T18:45:31.764375+00:00/task_id=print_list/attempt=1.log"]
[[2](http://localhost:28080/dags/lazy_list_xcom/runs/manual__2025-04-06T18:45:31.764375+00:00/tasks/print_list?try_number=1#2)025-04-06,
18:45:33] INFO - DAG bundles loaded: dags-folder:
source="airflow.dag_processing.bundles.manager.DagBundlesManager"
[2025-04-06,
18:45:[3](http://localhost:28080/dags/lazy_list_xcom/runs/manual__2025-04-06T18:45:31.764375+00:00/tasks/print_list?try_number=1#3)3]
INFO - Filling up the DagBag from /files/dags/lazy_list_xcom.py:
source="airflow.models.dagbag.DagBag"
[2025-04-06,
18:[4](http://localhost:28080/dags/lazy_list_xcom/runs/manual__2025-04-06T18:45:31.764375+00:00/tasks/print_list?try_number=1#4)6:53]
ERROR - Exception rendering Jinja template for task 'print_list', field
'op_args'. Template: (XComArg(<Task(_PythonDecoratedOperator):
create_long_list>),):
source="airflow.sdk.definitions._internal.abstractoperator"
RuntimeError: Direct database access via the ORM is not allowed in Airflow
3.0
File
"/opt/airflow/task-sdk/src/airflow/sdk/definitions/_internal/abstractoperator.py",
line 379 in _do_render_template_fields
File
"/opt/airflow/task-sdk/src/airflow/sdk/definitions/_internal/templater.py",
line 193 in render_template
File
"/opt/airflow/task-sdk/src/airflow/sdk/definitions/_internal/templater.py",
line 193 in <genexpr>
File
"/opt/airflow/task-sdk/src/airflow/sdk/definitions/_internal/templater.py",
line 189 in render_template
File "/opt/airflow/task-sdk/src/airflow/sdk/definitions/xcom_arg.py", line
345 in resolve
File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/task_runner.py",
line 348 in xcom_pull
File "/opt/airflow/task-sdk/src/airflow/sdk/bases/xcom.py", line 256 in
get_one
File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/task_runner.py",
line 564 in get_message
File "/opt/airflow/airflow-core/src/airflow/jobs/scheduler_job_runner.py",
line 227 in _exit_gracefully
File "/opt/airflow/airflow-core/src/airflow/utils/session.py", line 101 in
wrapper
File "/usr/local/lib/python3.9/contextlib.py", line 119 in __enter__
File "/opt/airflow/airflow-core/src/airflow/utils/session.py", line 41 in
create_session
File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/supervisor.py",
line 218 in __init__
```
The movie:
https://github.com/user-attachments/assets/a320951f-b3ac-4d76-99d3-deb6949479cb
### What you think should happen instead?
The task should run successfully and print the list of lists.
### How to reproduce
Run the dag above. See the second task get stuck. Then clear the task to see
the database access error.
### Operating System
MacOs
### Versions of Apache Airflow Providers
latest main
### Deployment
Other
### Deployment details
breeze
### Anything else?
I think this might be an issue that occurs dependent on lazy xcom access...
small XComs work fine.
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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