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https://issues.apache.org/jira/browse/HIVE-12325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14995113#comment-14995113
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Lefty Leverenz commented on HIVE-12325:
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Doc note: This changes the default value of *hive.map.groupby.sorted* and
removes *hive.map.groupby.sorted.testmode* from HiveConf.java. Neither is
documented yet in the wiki (except for their inclusion in the 0.13 default for
*hive.security.authorization.sqlstd.confwhitelist*), so both need to be
documented with version information about these changes.
* [Configuration Properties -- Query and DDL Execution |
https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-QueryandDDLExecution]
*hive.map.groupby.sorted* was introduced by HIVE-3432 in 0.10.0 and
*hive.map.groupby.sorted.testmode* was introduced by HIVE-4281 in 0.11.0.
> Turn hive.map.groupby.sorted on by default
> ------------------------------------------
>
> Key: HIVE-12325
> URL: https://issues.apache.org/jira/browse/HIVE-12325
> Project: Hive
> Issue Type: Improvement
> Components: Logical Optimizer
> Reporter: Ashutosh Chauhan
> Assignee: Chetna Chaudhari
> Labels: TODOC2.0
> Fix For: 2.0.0
>
> Attachments: HIVE-12325.1.patch
>
>
> When applicable it can avoid shuffle phase altogether for group by, which
> will be a performance win.
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