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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-9751) Excessive readpoints checks in MemStoreScanner and StoreFileScanner
Date Sat, 12 Oct 2013 05:02:43 GMT

     [ https://issues.apache.org/jira/browse/HBASE-9751?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Lars Hofhansl updated HBASE-9751:

    Attachment: 9751-0.94.txt

Here's a sample patch against 0.94.
If a HFileReader can prove that the file does not have any KV with a none-0 memstoreTS, the
scanner does not have even for skippedKV due to the threads readpoint.

> 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
> 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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