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https://issues.apache.org/jira/browse/HBASE-1823?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Gray updated HBASE-1823:
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Attachment: HBASE-1823-v2.patch
Had partial comment in first patch. Cleans up the line in Scan class comment,
notes as Expert.
> Ability for Scanners to bypass the block cache
> ----------------------------------------------
>
> Key: HBASE-1823
> URL: https://issues.apache.org/jira/browse/HBASE-1823
> Project: Hadoop HBase
> Issue Type: New Feature
> Components: client, regionserver
> Affects Versions: 0.20.0
> Reporter: Jonathan Gray
> Assignee: Jonathan Gray
> Fix For: 0.20.1, 0.21.0
>
> Attachments: HBASE-1823-v1.patch, HBASE-1823-v2.patch
>
>
> There are a number of use cases where exposing the ability to not cache
> blocks during a scan would be valuable. For example, running row counts.
> The LRU is scan-resistant, so it does provide some protection already, but
> even in that case all you prevent is the eviction of hot blocks. The LRU
> still runs many evictions and the blocks are referenced for much longer
> periods of time, so this adds enormous stress to the GC.
> Compactions already do this. This issue is about exposing that as a switch
> to the client-side Scan object (will also enable it for MR jobs then).
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