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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-284) Column pruning after join+group-by query
Date Mon, 09 Feb 2009 23:39:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12672053#action_12672053
] 

Namit Jain commented on HIVE-284:
---------------------------------

Thats right - currently, column pruning is only on top of the base table i.e if a column is
not being used at all, it is removed right away

> Column pruning after join+group-by query
> ----------------------------------------
>
>                 Key: HIVE-284
>                 URL: https://issues.apache.org/jira/browse/HIVE-284
>             Project: Hadoop Hive
>          Issue Type: Improvement
>    Affects Versions: 0.2.0, 0.3.0
>            Reporter: Zheng Shao
>
> The query is:
> explain INSERT OVERWRITE TABLE t
>     SELECT t1.r, t2.c, sum(t1.v * t2.v)
>     FROM t1 join t2 on t1.c = t2.r
> GROUP BY t1.r, t2.c;
> The FileSinkOperator after the join is serializing all 6 columns from the 2 tables (both
have 3 columns: r, c, v) instead of the 4 that is needed later.

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