when i read patchs from http://bazaar.launchpad.net/~knielsen/maria/dingqi-parallel-replication/changes, i found a problem (maybe would cause bug) :main SQL thread read a event from relay log, it make the log_event->thd point to the thd of main SQL thread. But when a log_event is disaptched to a sub SQL thread, the log_event->thd still point to the old value instead of the thd of sub SQL thread.

this problem will lead check_stack_overrun() fails, then lead open_table() fails...