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https://issues.apache.org/jira/browse/HBASE-18090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16159188#comment-16159188
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Mikhail Antonov commented on HBASE-18090:
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Thanks for the patch!
Before I go in reviews..opening regions in read-only mode for snapshots seems
reasonable. That change would only affect MR over snapshots codebase or some
other paths too?
and another question - if we set readonly flag we skip replaying WAL and don't
create those tmp files. Will that work for snapshots created with skipFlush
option? Is it always safe to skip WAL in that case?
> Improve TableSnapshotInputFormat to allow more multiple mappers per region
> --------------------------------------------------------------------------
>
> Key: HBASE-18090
> URL: https://issues.apache.org/jira/browse/HBASE-18090
> Project: HBase
> Issue Type: Improvement
> Components: mapreduce
> Affects Versions: 1.4.0
> Reporter: Mikhail Antonov
> Assignee: xinxin fan
> Attachments: HBASE-18090-branch-1.3-v1.patch,
> HBASE-18090-branch-1.3-v2.patch
>
>
> TableSnapshotInputFormat runs one map task per region in the table snapshot.
> This places unnecessary restriction that the region layout of the original
> table needs to take the processing resources available to MR job into
> consideration. Allowing to run multiple mappers per region (assuming
> reasonably even key distribution) would be useful.
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