### 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)

import logging.config
    from airflow import settings
    from airflow.utils.module_loading import import_string
    logging_config = import_string(settings.LOGGING_CLASS_PATH)
    logging.config.dictConfig(logging_config)
@pytest.fixture(scope="module", autouse=True)
def _clear_db(request):
    """Clear DB before each test module run."""
    if not request.config.option.db_cleanup:
        return
    dist_option = getattr(request.config.option, "dist", "no")
    if dist_option != "no" or hasattr(request.config, "workerinput"):
        
        return
    try:
        clear_all()
    except Exception as ex:
        exc_name_parts = [type(ex).__name__]
        exc_module = type(ex).__module__
        if exc_module != "builtins":
            exc_name_parts.insert(0, exc_module)
        extra_msg = "" if request.config.option.db_init else ", try to run with flag --with-db-init"
        pytest.exit(f"Unable clear test DB{extra_msg}, got error {'.'.join(exc_name_parts)}: {ex}")
@pytest.fixture(autouse=True)
def clear_lru_cache():
    from airflow.executors.executor_loader import ExecutorLoader
    from airflow.utils.entry_points import _get_grouped_entry_points
    ExecutorLoader.validate_database_executor_compatibility.cache_clear()
    _get_grouped_entry_points.cache_clear()