hadoop-mapreduce-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Joydeep Sen Sarma (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-2212) MapTask and ReduceTask should only compress/decompress the final map output file
Date Tue, 07 Dec 2010 23:15:02 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12969071#action_12969071
] 

Joydeep Sen Sarma commented on MAPREDUCE-2212:
----------------------------------------------

makes sense - hadn't thought about backwards compatibility. so that would imply an additional
(new) option to turn off intermediate run compression.

> MapTask and ReduceTask should only compress/decompress the final map output file
> --------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2212
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2212
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: task
>    Affects Versions: 0.23.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>             Fix For: 0.23.0
>
>
> Currently if we set mapred.map.output.compression.codec
> 1. MapTask will compress every spill, decompress every spill, merge and compress the
final map output file
> 2. ReduceTask will decompress, merge and compress every map output file. And repeat the
compression/decompression every pass.
> This causes all the data being compressed/decompressed many times.
> The reason we need mapred.map.output.compression.codec is for network traffic.
> We should not compress/decompress the data again and again during merge sort.
> We should only compress the final map output file that will be transmitted over the network.

-- 
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