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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Assigned: (HADOOP-4156) [hive] duplicate expression elimination for group by stage 1
Date Thu, 11 Sep 2008 01:32:44 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-4156?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Namit Jain reassigned HADOOP-4156:

    Assignee: Namit Jain

> [hive] duplicate expression elimination for group by stage 1
> ------------------------------------------------------------
>                 Key: HADOOP-4156
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4156
>             Project: Hadoop Core
>          Issue Type: Bug
>            Reporter: Namit Jain
>            Assignee: Namit Jain
> In the first job we evaluate all the input columns + all group by clause expressions
+ parameters to all the aggregation functions and do not eliminate all the duplicates because
we treat expression resolution and column resolution differently.
> Consider the following:
> src(key, value)
> select src.key, sum(src.value) from src group by src;
> Both src.key and src.value will be added twice - one from src's row resolver and one
each from group expression and parameter. It is needed that way filter looks at (table, column)
in row resolver, whereas group by expression looks
> at (", COLREF table column)

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