report “Window query not supported” when using state_window in TDengine

Question

I'm using state_window syntax in TDengine database.

My SQL statement is:

select t.*
  from (
        select ts,
               tbname as app_id,
               tenant_name,
               queue_code,
               task_name,
               sum(allocated) as allocated
          from yarn
         where ts > now - 6m
     partition by ts,tbname,tenant_name,queue_code,task_name
       ) t
partition by ts, app_id, tenant_name, queue_code, task_name
state_window((CASE WHEN allocated > 100 THEN 1 ELSE 0 END));

Then I encountered an error report:

DB error: Window query not supported, since the result of subquery not include valid timestamp column

I don't particularly understand its meaning, and how to fix the problem.