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https://issues.apache.org/jira/browse/HIVE-3086?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13457939#comment-13457939
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Yin Huai commented on HIVE-3086:
--------------------------------
@Nadeem: Thanks! Just found another question. It seems that the large table
(which has the skewed keys) will be scanned twice. Is my understanding correct?
> Skewed Join Optimization
> ------------------------
>
> Key: HIVE-3086
> URL: https://issues.apache.org/jira/browse/HIVE-3086
> Project: Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Nadeem Moidu
> Assignee: Namit Jain
> Fix For: 0.10.0
>
> Attachments: hive.3086.1.patch, hive.3086.2.patch, hive.3086.3.patch,
> hive.3086.4.patch, hive.3086.5.patch, hive.3086.6.patch
>
>
> During a join operation, if one of the columns has a skewed key, it can cause
> that particular reducer to become the bottleneck. The following feature will
> address it:
> https://cwiki.apache.org/confluence/display/Hive/Skewed+Join+Optimization
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