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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-69) genMapRedTasks does not use the tree walker and uses implicit state which makes it difficult to enhance
Date Mon, 01 Dec 2008 22:11:44 GMT

    [ https://issues.apache.org/jira/browse/HIVE-69?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12652181#action_12652181
] 

Namit Jain commented on HIVE-69:
--------------------------------


The following query will not work:

select count(1) FROM ( select a.x as x from x  UNION  ALL  select b.x as x from b ) out;

Union followed by reduce sink will not work  - since we have already made the child of reduce
sink null.

It can be easily fixed in the new framework since tree walking/splitting etc. are independent






> genMapRedTasks does not use the tree walker and uses implicit state which makes it difficult
to enhance
> -------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-69
>                 URL: https://issues.apache.org/jira/browse/HIVE-69
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>
> In SemanticAnalyzer, genmapredtasks() does not use a tree walker. For map-side joins,
the taskplan needs to be enhanced to be possibly
> broken at MapSink also. Basically, the code is very difficult to enhance since there
are implicit assumptions that reduce sink is the only
> operator where the plan breaks.
> This should be enhanced so that the user can implement their own task generation logic
which is independent of the tree walking.

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