### 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)

with create_session() as session:
            dagrun = DagRun(
                dag_id=self.dag_id,
                run_id=self.run_id,
                execution_date=self.execution_date_parsed,
                start_date=self.execution_date_parsed,
                run_type=DagRunType.MANUAL,
            )
            session.add(dagrun)
            ti = TaskInstance(EmptyOperator(task_id=self.task_id), run_id=self.run_id)
            ti.dag_id = self.dag_id
            session.add(ti)
        with create_session() as session:
            for i in range(1, 11):
                xcom = XCom(
                    dag_run_id=dagrun.id,
                    key=f"TEST_XCOM_KEY{i}",
                    value=b"null",
                    run_id=self.run_id,
                    task_id=self.task_id,
                    dag_id=self.dag_id,
                    timestamp=self.execution_date_parsed,
                )
                session.add(xcom)
        response = self.client.get(url, environ_overrides={"REMOTE_USER": "test"})
        assert response.status_code == 200
        assert response.json["total_entries"] == 10
        conn_ids = [conn["key"] for conn in response.json["xcom_entries"] if conn]
        assert conn_ids == expected_xcom_ids