### 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)

integration_name = marker.args[0]
    environment_variable_name = "INTEGRATION_" + integration_name.upper()
    environment_variable_value = os.environ.get(environment_variable_name)
    if not environment_variable_value or environment_variable_value != "true":
        pytest.skip(
            "The test requires {integration_name} integration started and "
            "{name} environment variable to be set to true (it is '{value}')."
            " It can be set by specifying '--integration {integration_name}' at breeze startup"
            ": {item}".format(
                name=environment_variable_name,
                value=environment_variable_value,
                integration_name=integration_name,
                item=item,
            )
        )
def skip_if_wrong_backend(marker, item):
    valid_backend_names = marker.args
    environment_variable_name = "BACKEND"
    environment_variable_value = os.environ.get(environment_variable_name)
    if not environment_variable_value or environment_variable_value not in valid_backend_names:
        pytest.skip(
            f"The test requires one of {valid_backend_names} backend started and "
            f"{environment_variable_name} environment variable to be set to 'true' (it is "
            f"'{environment_variable_value}'). It can be set by specifying backend at breeze startup: {item}"
        )
def skip_if_credential_file_missing(item):