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https://issues.apache.org/jira/browse/HBASE-9751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13793464#comment-13793464
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Ted Yu commented on HBASE-9751:
-------------------------------
I see the following pattern in various classes which are involved in scanning
(HRegion line 3473 e.g.):
{code}
// This could be a new thread from the last time we called next().
MultiVersionConsistencyControl.setThreadReadPoint(this.readPt);
return nextRaw(outResults, limit);
{code}
We could pass the readpoint into nextXX() methods to remove the call to
MultiVersionConsistencyControl.getThreadReadPoint().
This would be a bigger refactoring and can be done in another JIRA.
> Excessive readpoints checks in MemStoreScanner and StoreFileScanner
> --------------------------------------------------------------------
>
> Key: HBASE-9751
> URL: https://issues.apache.org/jira/browse/HBASE-9751
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.98.0, 0.94.12, 0.96.0
> Reporter: Vladimir Rodionov
> Assignee: Lars Hofhansl
> Attachments: 9751-0.94.txt, 9751-trunk.txt
>
>
> It seems that usage of skipKVsNewerThanReadpoint in StoreFileScanner can be
> greatly reduced or even eliminated all together (HFiles are immutable and no
> new KVs can be inserted after scanner instance is created). The same is true
> for MemStoreScanner which checks readpoint on every next() and seek(). Each
> readpoint check is ThreadLocal.get() and it is quite expensive.
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