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From "Jesus Camacho Rodriguez (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-17037) Extend join algorithm selection to avoid unnecessary input data shuffle
Date Wed, 05 Jul 2017 10:02:00 GMT

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

Jesus Camacho Rodriguez updated HIVE-17037:
-------------------------------------------
    Attachment: HIVE-17037.patch

> 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
>         Attachments: 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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