hadoop-mapreduce-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Scott Chen (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-2212) MapTask and ReduceTask should only compress/decompress the final map output file
Date Tue, 07 Dec 2010 19:50:13 GMT
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 cause 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 do the compression only for the final map output file that is been transmit 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