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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-261) union all query hangs
Date Tue, 03 Feb 2009 01:03:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12669827#action_12669827
] 

Zheng Shao commented on HIVE-261:
---------------------------------

I am very surprised at the number of levels that antlr needs to go through to parse this query.
Also it seems msgs.pop() was not executed for some reason.


> union all query hangs
> ---------------------
>
>                 Key: HIVE-261
>                 URL: https://issues.apache.org/jira/browse/HIVE-261
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Hao Liu
>
> we have this query:
> SELECT a.u, b.id FROM (
>  SELECT a1.u, a1.id as id FROM t_1 a1 WHERE a1.date = '2009-01-01' UNION ALL
>  SELECT a2.u, a2.id as id FROM t_2 a2 WHERE a2.date = '2009-01-01' UNION ALL
>  ...
>  SELECT aN.u, aN.id as id FROM t_N an WHERE aN.date = '2009-01-01'
> ) a 
> JOIN t b ON a.id = b.id WHERE b.date='2009-01-01' 
> GROUP BY a.u, b.id
> When we union more than 20 tables, the query will hang. It looks like something wrong
in the compiler.

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