[jira] [Comment Edited] (HIVE-18722) Vectorization: Adding SUM(HASH(..)) to full query seems to produce flakey results -- need to investiage

["Gopal V (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-18722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16366166#comment-16366166 ] 

Gopal V edited comment on HIVE-18722 at 2/15/18 7:44 PM:
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SUM(hash()) out of a Group-by query is not expected to be consistent (since JDK8), because it uses an iterator from a a HashMap

If you're seeing different results with {{set hive.map.aggr=false}}, then it might be worth investigating.

Integer operations are commutative, if they are of the same type - except it can be (long)(int)(a+b) & (long(a) + long(b)) within the partial result.

The GC canary in the group-by operator is the usual problem.


was (Author: gopalv):
SUM(hash()) out of a Group-by query is not expected to be consistent (since JDK8), because it uses an iterator from a a HashMap

If you're seeing different results with {{set hive.map.aggr=false}}, then it might be worth investigating.

> Vectorization: Adding SUM(HASH(..)) to full query seems to produce flakey results -- need to investiage
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-18722
>                 URL: https://issues.apache.org/jira/browse/HIVE-18722
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>    Affects Versions: 3.0.0
>            Reporter: Matt McCline
>            Assignee: Matt McCline
>            Priority: Critical
>
> When added to HIVE-18622 changes, the query results vary from laptop results when run on Hive QA cluster.  Need to investigate after HIVE-18622 commits.



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