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From "santosh kumar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14128) Fix inability to run Multiple MR over the same Snapshot
Date Mon, 27 Jul 2015 20:10:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14643306#comment-14643306
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santosh kumar commented on HBASE-14128:
---------------------------------------

Noob here - so could you look at my questions:

1. What version is this targeted for?
2. I looked at the code and find that this method is being used by MultiTableSnapshotInputFormat
and TableSnapshotInputFormat and for those 2 I can understand the usage. However, ScanPerformanceEvaluation
uses this as well, but it is a Test class(being found in src/test), for which I don't understand
the usage.
3. What would the target table name be based off ?  A timestamp to prevent duplicate?
4. Is the underlying assumption that the underlying Hbase table doesn't exist when TableMapReduceUtil.initTableSnapshotMapperJob
makes an attempt to run this restore? Would it be better if the 'target' table is passed as
a parameter instead?

> Fix inability to run Multiple MR over the same Snapshot
> -------------------------------------------------------
>
>                 Key: HBASE-14128
>                 URL: https://issues.apache.org/jira/browse/HBASE-14128
>             Project: HBase
>          Issue Type: Bug
>          Components: mapreduce, snapshots
>            Reporter: Matteo Bertozzi
>            Assignee: santosh kumar
>            Priority: Minor
>              Labels: beginner, noob
>
> from the list, running multiple MR over the same snapshot does not work
> {code}
> public static void copySnapshotForScanner(Configuration conf, FileSystem ..
>     RestoreSnapshotHelper helper = new RestoreSnapshotHelper(conf, fs,
>       manifest, manifest.getTableDescriptor(), restoreDir, monitor, status);
> {code}
> the problem is that manifest.getTableDescriptor() will try to clone the snapshot with
the same target name. ending up in "file already exist" exceptions.
> we just need to clone that descriptor and generate a new target table name



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