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From "Raghotham Murthy (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 Tue, 18 Nov 2008 23:11:44 GMT

    [ https://issues.apache.org/jira/browse/HIVE-69?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648800#action_12648800
] 

Raghotham Murthy commented on HIVE-69:
--------------------------------------

ql/src/java/org/apache/hadoop/hive/ql/parse/GenMapRedTaskProcessor.java:128	As we discussed,
this switch statement can be replaced with a more scalable framework for rules. You would
then have a tree pattern matcher (actually just a path matcher initially) and a lookup for
the associated transformer. With this switch statement code structure, adding a new rule would
either mean writing a new visitor (duplicated code) or adding more cases to this switch statement
(resulting in huge functions).

> 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
>            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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