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Date: Wed, 5 Jul 2017 10:01:00 +0000 (UTC)
From: "Jesus Camacho Rodriguez (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
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Subject: [jira] [Updated] (HIVE-17037) Extend join algorithm selection to
 avoid unnecessary input data shuffle
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archived-at: Wed, 05 Jul 2017 10:01:04 -0000


     [ https://issues.apache.org/jira/browse/HIVE-17037?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jesus Camacho Rodriguez updated HIVE-17037:
-------------------------------------------
    Status: Patch Available  (was: In Progress)

> Extend join algorithm selection 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
>
> 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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