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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12394) Support multiple regions as input to each mapper in map/reduce jobs
Date Sat, 01 Nov 2014 17:49:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14193306#comment-14193306
] 

Ted Yu commented on HBASE-12394:
--------------------------------

Mind putting patch on reviewboard ?
hbase.mapreduce.scan.regionspermapper controls how many mappers would be used.
Have you considered specifying number of mappers for this feature ?

Thanks

> Support multiple regions as input to each mapper in map/reduce jobs
> -------------------------------------------------------------------
>
>                 Key: HBASE-12394
>                 URL: https://issues.apache.org/jira/browse/HBASE-12394
>             Project: HBase
>          Issue Type: Improvement
>          Components: mapreduce
>    Affects Versions: 2.0.0, 0.98.6.1
>            Reporter: Weichen Ye
>         Attachments: HBASE-12394.patch
>
>
> For Hadoop cluster, a job with large HBase table as input always consumes a large amount
of computing resources. For example, we need to create a job with 1000 mappers to scan a table
with 1000 regions. This patch is to support one mapper using multiple regions as input.
>  
> The following new files are included in this patch:
> TableMultiRegionInputFormat.java
> TableMultiRegionInputFormatBase.java
> TableMultiRegionMapReduceUtil.java
> *TestTableMultiRegionInputFormatScan1.java
> *TestTableMultiRegionInputFormatScan2.java
> *TestTableMultiRegionInputFormatScanBase.java
> *TestTableMultiRegionMapReduceUtil.java
>  
> The files start with * are tests.
> In order to support multiple regions for one mapper, we need a new property in configuration--"hbase.mapreduce.scan.regionspermapper"
> This is an example,which means each mapper has 3 regions as input.
> <property>
>      <name>hbase.mapreduce.scan.regionspermapper</name>
>      <value>3</value>
> </property>
> This is an example for Java code:
> TableMultiRegionMapReduceUtil.initTableMapperJob(tablename, scan, Map.class, Text.class,
Text.class, job);
>  
>       



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