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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-12411) Avoid seek + read completely?
Date Sun, 16 Nov 2014 06:58:34 GMT

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

Lars Hofhansl updated HBASE-12411:
----------------------------------
    Attachment: 12411.txt

Here's a simple patch that allows compactions to have their own private readers. That should
isolate them from normal scan operation.

The idea is to simply clone the StoreFiles objects involved and operate on the cloned objects,
including private readers/inputstream opened by the these StoreFiles.

It's hard to quantify the benefit of this, though.

> 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.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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