[jira] [Commented] (HBASE-3996) Support multiple tables and scanners as input to the mapper in map/reduce jobs

["Eran Kutner (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13050368#comment-13050368 ] 

Eran Kutner commented on HBASE-3996:
------------------------------------

I've added three new classes:
MultiTableInputCollection is a collection of table+scanner pairs that should be used as input to the mapper.
MultiTableInputFormatBase and MultiTableInputFormat are closely based on the "non-multi" version with required adaptations.
I've also updated TableMapReduceUtil and TableSplit to support these new classes.

Usage example:
	Scan scan1 = new Scan();
	scan1.setStartRow(start1);
	scan1.setStopRow(end1);

	Scan scan2 = new Scan();
	scan2.setStartRow(start2);
	scan2.setStopRow(end2);
	
	MultiTableInputCollection mtic = new MultiTableInputCollection();
	mtic.Add(tableName1, scan1);
	mtic.Add(tableName2, scan2);

	TableMapReduceUtil.initTableMapperJob(mtic, TestTableMapper.class, Text.class, IntWritable.class, job1);



> Support multiple tables and scanners as input to the mapper in map/reduce jobs
> ------------------------------------------------------------------------------
>
>                 Key: HBASE-3996
>                 URL: https://issues.apache.org/jira/browse/HBASE-3996
>             Project: HBase
>          Issue Type: Improvement
>          Components: mapreduce
>            Reporter: Eran Kutner
>             Fix For: 0.90.4
>
>         Attachments: MultiTableInputCollection.java, MultiTableInputFormat.java, MultiTableInputFormatBase.java, TableMapReduceUtil.java, TableSplit.java
>
>
> It seems that in many cases feeding data from multiple tables or multiple scanners on a single table can save a lot of time when running map/reduce jobs.
> I propose a new MultiTableInputFormat class that would allow doing this.

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