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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10018) Change the location prefetch
Date Wed, 26 Feb 2014 22:14:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13913603#comment-13913603
] 

Enis Soztutar commented on HBASE-10018:
---------------------------------------

Before removing the prefetch, I think we should have an idea whether this will bring a regression.
Hopefully not, but would be good if we can have a better idea. 
bq. replace it with a reverse scan: this would save a call
+1 to that. Makes sense to dog food. Should we get rid of HTable.getRowOrBefore() or keep
that as an interface, but implement it via small reverse scan? 
This is good, even though we might still have prefetch. 
{code}
+    @Deprecated
     public void setRegionCachePrefetch(final byte[] tableName,
         final boolean enable) {
{code}

> 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
>             Fix For: 0.98.1, 0.99.0
>
>         Attachments: 10018.v1.patch, 10018.v2.patch
>
>
> 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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