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https://issues.apache.org/jira/browse/HADOOP-372?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chris Smith updated HADOOP-372:
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Attachment: hadoop-372.patch
Attached is a modified version of Tom's patch.
Changes:
* Updated to work against the trunk
* Moved methods from ExtendedJobConf to static methods in FileInputFormat
* Fixed issue described by Johan above (multiple paths with the same
InputFormat and Mappers are now grouped and split together, rather than
separately, so you don't get excessive numbers of map jobs)
* Generally tidied up and documented the code
* Added a few unit tests
> should allow to specify different inputformat classes for different input
> dirs for Map/Reduce jobs
> --------------------------------------------------------------------------------------------------
>
> Key: HADOOP-372
> URL: https://issues.apache.org/jira/browse/HADOOP-372
> Project: Hadoop Core
> Issue Type: New Feature
> Components: mapred
> Affects Versions: 0.4.0
> Environment: all
> Reporter: Runping Qi
> Assignee: Owen O'Malley
> Attachments: hadoop-372.patch, hadoop-372.patch
>
>
> Right now, the user can specify multiple input directories for a map reduce
> job.
> However, the files under all the directories are assumed to be in the same
> format,
> with the same key/value classes. This proves to be a serious limit in many
> situations.
> Here is an example. Suppose I have three simple tables:
> one has URLs and their rank values (page ranks),
> another has URLs and their classification values,
> and the third one has the URL meta data such as crawl status, last crawl
> time, etc.
> Suppose now I need a job to generate a list of URLs to be crawled next.
> The decision depends on the info in all the three tables.
> Right now, there is no easy way to accomplish this.
> However, this job can be done if the framework allows to specify different
> inputformats for different input dirs.
> Suppose my three tables are in the following directory respectively:
> rankTable, classificationTable. and metaDataTable.
> If we extend JobConf class with the following method (as Owen suggested to
> me):
> addInputPath(aPath, anInputFormatClass, anInputKeyClass,
> anInputValueClass)
> Then I can specify my job as follows:
> addInputPath(rankTable, SequenceFileInputFormat.class, UTF8.class,
> DoubleWritable.class)
> addInputPath(classificationTable, TextInputFormat.class, UTF8,class,
> UTF8.class)
> addInputPath(metaDataTable, SequenceFileInputFormat.class, UTF8.class,
> MyRecord.class)
> If an input directory is added through the current API, it will have the same
> meaning as it is now.
> Thus this extension will not affect any applications that do not need this
> new feature.
> It is relatively easy for the M/R framework to create an appropriate record
> reader for a map task based on the above information.
> And that is the only change needed for supporting this extension.
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