hadoop-common-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Runping Qi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1440) JobClient should not sort input-splits
Date Mon, 11 Jun 2007 20:58:27 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12503622
] 

Runping Qi commented on HADOOP-1440:
------------------------------------


That does not really address the problem this Jira tries to address:

In the reduce=None case, the user wants to control two things:

1. Whether the input files are splittable.
2. If it is set that the input files are not splitable, the number of the output files must
be the same as 
that of input files, and the relative order of the input files is the same as that of the
corresponding 
output files.

That is why I proposed to use the input filenames as the prefix for the output filenames.

 

> JobClient should not sort input-splits
> --------------------------------------
>
>                 Key: HADOOP-1440
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1440
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.12.3
>         Environment: All
>            Reporter: Milind Bhandarkar
>            Assignee: Milind Bhandarkar
>             Fix For: 0.14.0
>
>
> Currently, the JobClient sorts the InputSplits returned by InputFormat in descending
order, so that the map tasks corresponding to larger input-splits are scheduled first for
execution than smaller ones. However, this causes problems in applications that produce data-sets
partitioned similarly to the input partition with -reducer NONE.
> With -reducer NONE, map task i produces part-i. Howver, in the typical applications that
use -reducer NONE it should produce a partition that has the same index as the input parrtition.
> (Of course, this requires that each partition should be fed in its entirety to a map,
rather than splitting it into blocks, but that is a separate issue.)
> Thus, sorting input splits should be either controllable via a configuration variable,
or the FileInputFormat should sort the splits and JobClient should honor the order of splits.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message