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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-12411) Avoid seek + read completely?
Date Tue, 18 Nov 2014 18:03:36 GMT

     [ https://issues.apache.org/jira/browse/HBASE-12411?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lars Hofhansl updated HBASE-12411:
----------------------------------
    Release Note: 
This introduces two new configuration options:
# hbase.storescanner.user.pread enables postional reads for all scanners (except compactions).
Default off (i.e. try to use seek+read as before)
# hbase.regionserver.compaction.private.readers has compaction run with their own readers.
Default off (i.e. share readers with all other scanners as before)

> Avoid seek + read completely?
> -----------------------------
>
>                 Key: HBASE-12411
>                 URL: https://issues.apache.org/jira/browse/HBASE-12411
>             Project: HBase
>          Issue Type: Brainstorming
>          Components: Performance
>            Reporter: Lars Hofhansl
>         Attachments: 12411-v2.txt, 12411-v3.txt, 12411.txt
>
>
> In the light of HDFS-6735 we might want to consider refraining from seek + read completely
and only perform preads.
> For example currently a compaction can lock out every other scanner over the file which
the compaction is currently reading for compaction.
> At the very least we can introduce an option to avoid seek + read, so we can allow testing
this in various scenarios.
> This will definitely be of great importance for projects like Phoenix which parallelize
queries intra region (and hence readers will used concurrently by multiple scanner with high
likelihood.)



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