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Date: Fri, 19 Jun 2009 17:44:07 -0700 (PDT)
From: "Namit Jain (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Subject: [jira] Commented: (HIVE-439) merge small files whenever possible
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    [ https://issues.apache.org/jira/browse/HIVE-439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12722104#action_12722104 ] 

Namit Jain commented on HIVE-439:
---------------------------------

Some follow-up jiras:

https://issues.apache.org/jira/browse/HIVE-569
https://issues.apache.org/jira/browse/HIVE-570

> 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, hive.439.2.patch, hive.439.3.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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