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From "Yongzhi Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11502) Map side aggregation is extremely slow
Date Wed, 19 Aug 2015 04:03:45 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14702409#comment-14702409
] 

Yongzhi Chen commented on HIVE-11502:
-------------------------------------

The vectorized_parquet_types failure is not related.
It is just random failure caused by data precision. 

< 1	121	1	8	1.1749999970197678	2.062159062730128	90.33
---
> 1	121	1	8	1.1749999970197678	2.0621590627301285	90.33
378c378
< 3	120	1	7	1.171428578240531	1.8	90.21
---
> 3	120	1	7	1.171428578240531	1.7999999999999996	90.21

Same test passed on my local machine.




> 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
>         Attachments: HIVE-11502.1.patch, HIVE-11502.2.patch, HIVE-11502.3.patch
>
>
> 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) and it is in
type double, 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}



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