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https://issues.apache.org/jira/browse/HIVE-17114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16094381#comment-16094381
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Rui Li commented on HIVE-17114:
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[~gopalv], thanks for your input. Since HIVE-7074 is superseded by HIVE-7121,
the murmur hash is sufficient to solve my problem here.
[~kellyzly], I don't think it's related to how many times the join is
performed. It happens when the data has the particular keys and we choose the
particular number of reducers.
> HoS: Possible skew in shuffling when data is not really skewed
> --------------------------------------------------------------
>
> Key: HIVE-17114
> URL: https://issues.apache.org/jira/browse/HIVE-17114
> Project: Hive
> Issue Type: Bug
> Reporter: Rui Li
> Assignee: Rui Li
> Priority: Minor
> Attachments: HIVE-17114.1.patch, HIVE-17114.2.patch
>
>
> Observed in HoS and may apply to other engines as well.
> When we join 2 tables on a single int key, we use the key itself as hash code
> in {{ObjectInspectorUtils.hashCode}}:
> {code}
> case INT:
> return ((IntObjectInspector) poi).get(o);
> {code}
> Suppose the keys are different but are all some multiples of 10. And if we
> choose 10 as #reducers, the shuffle will be skewed.
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