数据库内核月报 － 2017 / 08

SET GTID_NEXT;        # GTID设置为ON时           
BEGIN;  
INSERT row1;
INSERT row2;
COMMIT;

Gtid_log_event::do_apply_event()

  if (thd->owned_gtid.sidno)
  {
    /*
      Slave will execute this code if a previous Gtid_log_event was applied
      but the GTID wasn't consumed yet (the transaction was not committed
      nor rolled back).
      On a client session we cannot do consecutive SET GTID_NEXT without
      a COMMIT or a ROLLBACK in the middle.
      Applying this event without rolling back the current transaction may
      lead to problems, as a "BEGIN" event following this GTID will
      implicitly commit the "partial transaction" and will consume the
      GTID. If this "partial transaction" was left in the relay log by the
      IO thread restarting in the middle of a transaction, you could have
      the partial transaction being logged with the GTID on the slave,
      causing data corruption on replication.
    */
    if (thd->transaction.all.ha_list)
    {
      /* This is not an error (XA is safe), just an information */
      rli->report(INFORMATION_LEVEL, 0,
                  "Rolling back unfinished transaction (no COMMIT "
                  "or ROLLBACK in relay log). A probable cause is partial "
                  "transaction left on relay log because of restarting IO "
                  "thread with auto-positioning protocol.");
      const_cast<Relay_log_info*>(rli)->cleanup_context(thd, 1);
    }
    gtid_rollback(thd);
  }

exec_relay_log_event()
/*
      GTID protocol will put a FORMAT_DESCRIPTION_EVENT from the master with
      log_pos != 0 after each (re)connection if auto positioning is enabled.
      This means that the SQL thread might have already started to apply the
      current group but, as the IO thread had to reconnect, it left this
      group incomplete and will start it again from the beginning.
      So, before applying this FORMAT_DESCRIPTION_EVENT, we must let the
      worker roll back the current group and gracefully finish its work,
      before starting to apply the new (complete) copy of the group.
    */
    if (ev->get_type_code() == FORMAT_DESCRIPTION_EVENT &&
        ev->server_id != ::server_id && ev->log_pos != 0 &&
        rli->is_parallel_exec() && rli->curr_group_seen_gtid)
    {
      if (coord_handle_partial_binlogged_transaction(rli, ev))
        /*
          In the case of an error, coord_handle_partial_binlogged_transaction
          will not try to get the rli->data_lock again.
        */
        DBUG_RETURN(1);
    }