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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10018) Change the location prefetch
Date Fri, 22 Nov 2013 21:46:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13830341#comment-13830341
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stack commented on HBASE-10018:
-------------------------------

Does the prefetch have to be done inline?  Can it be lazy?  What to do though if 1M regions?
 What do we fetch?  Maybe we don't want prefetch when we now have a bounded size for our cache.
 Could just flip the configuration to turn off prefetch in 0.98?  When the prefetch was added,
i thought there was also added a facility for reading in all of the meta -- reading from HDFS
IIRC? -- but I can't find it so probably a pigment of my emancipation.

> Change the location prefetch
> ----------------------------
>
>                 Key: HBASE-10018
>                 URL: https://issues.apache.org/jira/browse/HBASE-10018
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.98.0, 0.96.0
>            Reporter: Nicolas Liochon
>            Assignee: Nicolas Liochon
>            Priority: Minor
>             Fix For: 0.98.0, 0.96.1
>
>
> Issues with prefetching are:
> - we do two calls to meta: one for the exact row, one for the prefetch 
> - it's done in a lock
> - we take the next 10 regions. Why 10, why the 10 next?
> - is it useful if the table has 100K regions?
> Options are:
> - just remove it
> - replace it with a reverse scan: this would save a call
>  



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