hi,
 
If character_set in different Query_log_events changed, worker threads may apply them with wrong character_set. the codes leading this problem is in Query_log_event::do_apply_event, that is:
      if (charset_inited)
      {
        if (rli->cached_charset_compare(charset))
        {
          /* Verify that we support the charsets found in the event. */
          if (!(thd->variables.character_set_client=
                get_charset(uint2korr(charset), MYF(MY_WME))) ||
              !(thd->variables.collation_connection=
                get_charset(uint2korr(charset+2), MYF(MY_WME))) ||
              !(thd->variables.collation_server=
                get_charset(uint2korr(charset+4), MYF(MY_WME))))
          {
 
There is a charset[6] in rli, which cached last Query_log_event's charset in serial replication. But in parallel replication it would lead mistake, because every worker thread can read and set rli->charset[6], so rli->charset[6] isn't any worker threads' last Query_log_event charset. but rli->charset[6] can affect every worker threads' thd->variables.character_set_* setting.
2014-04-17
nanyi607rao