[jira] [Commented] (HIVE-707) add group_concat

["Jian Wang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14052301#comment-14052301 ] 

Jian Wang commented on HIVE-707:
--------------------------------

[~ph4t]
I use this concat_ws(' ', map_keys(UNION_MAP(MAP(your_column, 'dummy')))) method instead of group_concat,but I got a error like this
{code}
FAILED: SemanticException [Error 10011]: Line 172:30 Invalid function 'UNION_MAP'
{/code}
should I add some jars ?


> add group_concat
> ----------------
>
>                 Key: HIVE-707
>                 URL: https://issues.apache.org/jira/browse/HIVE-707
>             Project: 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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