Yongzhi Chen created HIVE-11502: ----------------------------------- Summary: Map side aggregation is extremely slow Key: HIVE-11502 URL: https://issues.apache.org/jira/browse/HIVE-11502 Project: Hive Issue Type: Bug Components: Logical Optimizer, Physical Optimizer Affects Versions: 1.2.0 Reporter: Yongzhi Chen Assignee: Yongzhi Chen
For the query as following: {noformat} create table tbl2 as select col1, max(col2) as col2 from tbl1 group by col1; {noformat} If the column for group by has many different values (for example 400000), the map side aggregation is very slow. I ran the query which took more than 3 hours , after 3 hours, I have to kill the query. The same query can finish in 7 seconds, if I turn off map side aggregation by: {noformat} set hive.map.aggr = false; {noformat} -- This message was sent by Atlassian JIRA (v6.3.4#6332)