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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2035) Use block-level merge for RCFile if merging intermediate results are needed
Date Wed, 27 Apr 2011 17:32:03 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13025909#comment-13025909
] 

Ning Zhang commented on HIVE-2035:
----------------------------------

Ashutosh, it seems the review request #669 got a wrong HIVE JIRA reference? 

> Use block-level merge for RCFile if merging intermediate results are needed
> ---------------------------------------------------------------------------
>
>                 Key: HIVE-2035
>                 URL: https://issues.apache.org/jira/browse/HIVE-2035
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Ning Zhang
>            Assignee: He Yongqiang
>
> Currently if hive.merge.mapredfiles and/or hive.merge.mapfile is set to true the intermediate
data could be merged using an additional MapReduce job. This could be quite expensive if the
data size is large. With HIVE-1950, merging can be done in the RCFile block level so that
it bypasses the (de-)compression, (de-)serialization phases. This could improve the merge
process significantly. 
> This JIRA should handle the case where the input table is not stored in RCFile, but the
destination table is (which requires the intermediate data should be stored in the same format
as the destination table). 

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