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Date: Wed, 31 Jul 2013 22:11:50 +0000 (UTC)
From: "Bryan Keller (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12643055.1366237708847.147713.1375308710578@arcas>
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Subject: [jira] [Commented] (HBASE-8369) MapReduce over snapshot files
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    [ https://issues.apache.org/jira/browse/HBASE-8369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13725769#comment-13725769 ] 

Bryan Keller commented on HBASE-8369:
-------------------------------------

FWIW, I am using this (slightly tweaked) in our production system now, and it has been a huge improvement to scan performance, up to 2.5x. The bottleneck is now in HRegion rather than region server. Setting up permissions in HDFS to allow these scans is the tricky part.
                
> 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-8369-0.94.patch, HBASE-8369-0.94_v2.patch, HBASE-8369-0.94_v3.patch, HBASE-8369-0.94_v4.patch, HBASE-8369-0.94_v5.patch, HBASE-8369-trunk_v1.patch, HBASE-8369-trunk_v2.patch, HBASE-8369-trunk_v3.patch, 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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