fix over outputting in merge join
fix over outputting in merge join

eric-haibin-lin/peloton,eric-haibin-lin/peloton,eric-haibin-lin/peloton,eric-haibin-lin/peloton,eric-haibin-lin/peloton,eric-haibin-lin/peloton,eric-haibin-lin/peloton