Example:
DAG structure:
```
default_args = {
    'owner': 'dimon',
    'depends_on_past': False,
    'start_date': datetime(2021, 1, 10)
}

dag = DAG(
    'dummy-dag',
    schedule_interval='21 2 * * *',
    catchup=False,
    default_args=default_args
)

DagContext.push_context_managed_dag(dag)
task1 = BashOperator(task_id='task1', bash_command='echo 1')
task2 = BashOperator(task_id='task2', bash_command='echo 2')
task2 << task1
task3 = BashOperator(task_id='task3', bash_command='echo 3')
```

Let’s say you’ve missed the button and typed `--task-regex task4`.
When the backfill starts, firstly it will create a new empty DagRun and puts it in DB. Then the backfill job will go and try to find tasks that match the regex you’ve entered, will not find any obviously and will be stuck in the “running” state together with newly created DagRun forever.

airflow/cli/commands/dag_command.py
"""
    Returns the next execution datetime of a DAG at the command line.
    >>> airflow dags next-execution tutorial
    2018-08-31 10:38:00
    """
    dag = get_dag(args.subdir, args.dag_id)
    if dag.get_is_paused():
        print("[INFO] Please be reminded this DAG is PAUSED now.", file=sys.stderr)
    latest_execution_date = dag.get_latest_execution_date()
    if latest_execution_date:
        next_execution_dttm = dag.following_schedule(latest_execution_date)
        if next_execution_dttm is None:
            print(
                "[WARN] No following schedule can be found. "
                + "This DAG may have schedule interval '@once' or `None`.",
                file=sys.stderr,
            )
            print(None)
        else:
            print(next_execution_dttm)
            for _ in range(1, args.num_executions):
                next_execution_dttm = dag.following_schedule(next_execution_dttm)
                print(next_execution_dttm)
    else:
        print("[WARN] Only applicable when there is execution record found for the DAG.", file=sys.stderr)
        print(None)
@cli_utils.action_logging
@suppress_logs_and_warning
def dag_list_dags(args):
    """Displays dags with or without stats at the command line"""