### 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)

if "start_date" in default_args:
                    self.start_date = default_args.get("start_date")
            if not self.start_date:
                if hasattr(request.module, "DEFAULT_DATE"):
                    self.start_date = getattr(request.module, "DEFAULT_DATE")
                else:
                    DEFAULT_DATE = timezone.datetime(2016, 1, 1)
                    self.start_date = DEFAULT_DATE
            self.kwargs["start_date"] = self.start_date
            self.dag = DAG(dag_id, **self.kwargs)
            self.dag.fileloc = fileloc or request.module.__file__
            self.want_serialized = serialized
            self.processor_subdir = processor_subdir
            return self
        def cleanup(self):
            from airflow.models import DagModel, DagRun, TaskInstance, XCom
            from airflow.models.dataset import DatasetEvent
            from airflow.models.serialized_dag import SerializedDagModel
            from airflow.models.taskmap import TaskMap
            from airflow.utils.retries import run_with_db_retries
            for attempt in run_with_db_retries(logger=self.log):
                with attempt:
                    dag_ids = list(self.dagbag.dag_ids)
                    if not dag_ids:
                        return
                    
                    self.session.rollback()
                    self.session.query(SerializedDagModel).filter(
                        SerializedDagModel.dag_id.in_(dag_ids)
                    ).delete(synchronize_session=False)