Using rake file to fix existing denpency problem in databse

Should run "rake dbfix: pos_denpendency" on the production server. I've tested on my local, it works.
I think it's should not have side effects. But I'm not sure if the old schema has things like: duplicate_logs. 

Also I don't think this should be put into git, it's no use since the bug is fixed. You close this issue then download the file and  manually do for course 97?