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https://issues.apache.org/jira/browse/MAPREDUCE-4827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13511046#comment-13511046
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Hadoop QA commented on MAPREDUCE-4827:
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{color:red}-1 overall{color}. Here are the results of testing the latest
attachment
http://issues.apache.org/jira/secure/attachment/12556183/betterhash2.txt
against trunk revision .
{color:green}+1 @author{color}. The patch does not contain any @author
tags.
{color:red}-1 tests included{color}. The patch doesn't appear to include
any new or modified tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
{color:green}+1 javac{color}. The applied patch does not increase the
total number of javac compiler warnings.
{color:green}+1 javadoc{color}. The javadoc tool did not generate any
warning messages.
{color:green}+1 eclipse:eclipse{color}. The patch built with
eclipse:eclipse.
{color:green}+1 findbugs{color}. The patch does not introduce any new
Findbugs (version 1.3.9) warnings.
{color:green}+1 release audit{color}. The applied patch does not increase
the total number of release audit warnings.
{color:green}+1 core tests{color}. The patch passed unit tests in
hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core.
{color:green}+1 contrib tests{color}. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3100//testReport/
Console output:
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/3100//console
This message is automatically generated.
> Increase hash quality of HashPartitioner
> ----------------------------------------
>
> Key: MAPREDUCE-4827
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4827
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Reporter: Radim Kolar
> Attachments: betterhash1.txt, betterhash2.txt
>
>
> hash partitioner is using object.hashCode() for splitting keys into
> partitions. This results in bad distributions because hashCode() quality is
> poor.
> These hashCode() functions are sometimes written by hand (very poor quality)
> and sometimes generated from by commons lang code (poor quality). Applying
> some transformation on top of hashCode() provides better distribution.
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