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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8369) MapReduce over snapshot files
Date Thu, 18 Apr 2013 08:07:19 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13634972#comment-13634972
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Matteo Bertozzi commented on HBASE-8369:
----------------------------------------

in general I'm against having another way to direct access the data, since it means that you're
giving up on optimizing the main one.

but if the final implementation will be like this one using the HRegion object, I'll be +1.

                
> MapReduce over snapshot files
> -----------------------------
>
>                 Key: HBASE-8369
>                 URL: https://issues.apache.org/jira/browse/HBASE-8369
>             Project: HBase
>          Issue Type: New Feature
>          Components: mapreduce, snapshots
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.0, 0.95.2
>
>         Attachments: hbase-8369_v0.patch
>
>
> The idea is to add an InputFormat, which can run the mapreduce job over snapshot files
directly bypassing hbase server layer. The IF is similar in usage to TableInputFormat, taking
a Scan object from the user, but instead of running from an online table, it runs from a table
snapshot. We do one split per region in the snapshot, and open an HRegion inside the RecordReader.
A RegionScanner is used internally for doing the scan without any HRegionServer bits. 
> Users have been asking and searching for ways to run MR jobs by reading directly from
hfiles, so this allows new use cases if reading from stale data is ok:
>  - Take snapshots periodically, and run MR jobs only on snapshots.
>  - Export snapshots to remote hdfs cluster, run the MR jobs at that cluster without HBase
cluster.
>  - (Future use case) Combine snapshot data with online hbase data: Scan from yesterday's
snapshot, but read today's data from online hbase cluster. 

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