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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-439) merge small files whenever possible
Date Wed, 17 Jun 2009 23:12:07 GMT

    [ https://issues.apache.org/jira/browse/HIVE-439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720977#action_12720977
] 

Zheng Shao commented on HIVE-439:
---------------------------------

@hive.439.1.patch
We don't need anything in sort key in the reduceSinkOperator. Can you remove the "rand()"
for sort key?
That will make the process faster because all rows are equal (for sorting purpose).


> merge small files whenever possible
> -----------------------------------
>
>                 Key: HIVE-439
>                 URL: https://issues.apache.org/jira/browse/HIVE-439
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: hive.439.1.patch
>
>
> There are cases when the input to a Hive job are thousands of small files. In this case,
there is a mapper for each file. Most of the overhead for spawning all these mappers can be
avoided if these small files are combined into fewer larger files.
> The problem can also be addressed by having a mapper span multiple blocks as in:
> https://issues.apache.org/jira/browse/HIVE-74
> Bit, it also makes sense in HIVE to merge files whenever possible.

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