I think this is an expected behaviour. The created by column only gets populated if the task is created by a specific user. For all the tasks, which are created by the engine this will be empty.
May I know the reason, why you want to update this?
Thanks for replying.
Yes, this is an expected behavior as you have said. The real issue was Hibernate. I was using Hibernate 3.6.5, which generated a different query compared to the previous versions. After changing the TasksOwned query like below, it started working.
left join t.taskData.createdBy as createdBy...
Sorry for not updating this here.