### Apache Airflow version

Other Airflow 2 version (please specify below)

### What happened

Airflow 2.3.4 (but actual code seems to have same behaviour).

I have mapped task with xcom value.

I want to get xcom value of particular instance or xcom values of all task instances.

I am using standard REST API method /dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/xcomEntries/{xcom_key}

And it throws an error
`
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/orm/query.py&#34;, line 2850, in one_or_none
    return self._iter().one_or_none()
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 1510, in one_or_none
    return self._only_one_row(
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 614, in _only_one_row
    raise exc.MultipleResultsFound(
sqlalchemy.exc.MultipleResultsFound: Multiple rows were found when one or none was required
`

Is it any way of getting xcom of mapped tasks via API?

### What you think should happen instead

_No response_

### How to reproduce

Make dag with mapped task. Return xcom value in every task. Try to get xcom value via API.

### Operating System

ubuntu 20.04

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

Standard

### Anything else

_No response_

### 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)

from airflow.utils.session import create_session
    with create_session() as session:
        yield session
        session.rollback()
@pytest.fixture()
def get_test_dag():
    def _get(dag_id):
        from airflow.models.dagbag import DagBag
        from airflow.models.serialized_dag import SerializedDagModel
        dag_file = os.path.join(os.path.dirname(os.path.realpath(__file__)), "dags", f"{dag_id}.py")
        dagbag = DagBag(dag_folder=dag_file, include_examples=False)
        dag = dagbag.get_dag(dag_id)
        dag.sync_to_db()
        SerializedDagModel.write_dag(dag)
        return dag
    return _get
@pytest.fixture()
def create_log_template(request):
    session = settings.Session()
    def _create_log_template(filename_template, elasticsearch_id=""):
        log_template = LogTemplate(filename=filename_template, elasticsearch_id=elasticsearch_id)
        session.add(log_template)
        session.commit()
        def _delete_log_template():
            session.delete(log_template)
            session.commit()
        request.addfinalizer(_delete_log_template)
    return _create_log_template
@pytest.fixture()
def reset_logging_config():