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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3387) Custom Splitter for handling many small files
Date Thu, 15 May 2008 17:21:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3387?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12597202#action_12597202

Owen O'Malley commented on HADOOP-3387:

If there are deficiencies, please work to fix the current implementation. Having N instances
of each input format isn't very useful.

1. If you ask for 10 maps and there are 5 files and it generates 5 maps, I don't understand
how the planner was supposed to know that you really wanted one.

2.If you ask for 3 maps, I don't understand why you are upset that it allocated 3 maps.

Your goals don't seem to be well defined.

> Custom Splitter for handling many small files
> ---------------------------------------------
>                 Key: HADOOP-3387
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3387
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Subramaniam Krishnan
>            Assignee: Subramaniam Krishnan
>             Fix For: 0.18.0
> Hadoop by default allocates a Map to a file irrespective of size. This is not optimal
if you have a large number of small files, for e.g:- If you 2000 100KB files, 2000 Maps will
be allocated for the job.
> The Custom Multi File Splitter collapses all the small files to a single split till the
DFS Block Size is hit. 
> It also take care of handling big files by splitting them on Block Size and adding up
all the reminders(if any) to a further splits of Block Size. 

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