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https://issues.apache.org/jira/browse/HIVE-17037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095819#comment-16095819
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Lefty Leverenz commented on HIVE-17037:
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Doc note: This adds *hive.optimize.joinreducededuplication* to HiveConf.java,
so it will need to be documented in the wiki.
* [Configuration Properties -- Query and DDL Execution |
https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-QueryandDDLExecution]
Added a TODOC3.0 label.
> Use 1-to-1 Tez edge to avoid unnecessary input data shuffle
> -----------------------------------------------------------
>
> Key: HIVE-17037
> URL: https://issues.apache.org/jira/browse/HIVE-17037
> Project: Hive
> Issue Type: Improvement
> Components: Physical Optimizer
> Affects Versions: 3.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Labels: TODOC3.0
> Fix For: 3.0.0
>
> Attachments: HIVE-17037.01.patch, HIVE-17037.02.patch,
> HIVE-17037.03.patch, HIVE-17037.patch
>
>
> As an example, consider the following query:
> {code:sql}
> SELECT *
> FROM (
> SELECT a.value
> FROM src1 a
> JOIN src1 b
> ON (a.value = b.value)
> GROUP BY a.value
> ) a
> JOIN src
> ON (a.value = src.value);
> {code}
> Currently, the plan generated for Tez will contain an unnecessary shuffle
> operation between the subquery and the join, since the records produced by
> the subquery are already sorted by the value.
> This issue is to extend join algorithm selection to be able to shuffle only
> some of the inputs for a given join and avoid unnecessary shuffle operations.
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