Ability for Scanners to bypass the block cache
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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
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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