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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-707) add group_concat
Date Thu, 30 Jul 2009 23:49:14 GMT

    [ https://issues.apache.org/jira/browse/HIVE-707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12737360#action_12737360
] 

Zheng Shao commented on HIVE-707:
---------------------------------

Shall we do the follow-up jira to provide the capability before we do this?
Without the follow-up jira, the group_concat is non-deterministic, so it's harder to write
a test.


> add group_concat
> ----------------
>
>                 Key: HIVE-707
>                 URL: https://issues.apache.org/jira/browse/HIVE-707
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Min Zhou
>
> Moving the discussion to a new jira:
> I've implemented group_cat() in a rush, and found something difficult to slove:
> 1. function group_cat() has a internal order by clause, currently, we can't implement
such an aggregation in hive.
> 2. when the strings will be group concated are too large, in another words, if data skew
appears, there is often not enough memory to store such a big result.

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