select userid,count(*) from u_data group by userid order by userid will product MRR.
I think when the result of userid,count(*) is small(one reduce can process the result) . This query plan can optimize to MR ? r7raul1...@163.com
select userid,count(*) from u_data group by userid order by userid will product MRR.
I think when the result of userid,count(*) is small(one reduce can process the result) . This query plan can optimize to MR ? r7raul1...@163.com