database transactions check and restore support
backup/restore module is broken right now, test of backup/restore data is needed.
please remove the try-catch from the database module comments upgrade code, the exceptions are handled automatically, you should never call print_error() this way in upgrade code, thanks
hmm, I think it is not necessary to use the table_exists too, the version number test should prevent it
1. remove try-catch code
2. call get_coursemodule_from_instance only when dataid or courseid changed
3. delete record if comment->add run successfully
4. use upgrade_set_timeout
I kept table_exists there to prevent an upgrade error.
feel free to reopen if you find any problem