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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9751) Excessive readpoints checks in StoreFileScanner
Date Sat, 12 Oct 2013 23:11:42 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13793524#comment-13793524
] 

Lars Hofhansl commented on HBASE-9751:
--------------------------------------

I see. You're talking about new code. How do you find stopRowReal efficiently?
Also what if a filter seek hint jumps you past stopRowReal?

In any case, I think we can good consensus already. This patch is a good improvement I think;
and I like your idea of passing the readpoint to the MemstoreScanner constructor.


> Excessive  readpoints checks in 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
>             Fix For: 0.98.0, 0.94.13, 0.96.1
>
>         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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