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https://issues.apache.org/jira/browse/HBASE-9751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13793269#comment-13793269
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Lars Hofhansl commented on HBASE-9751:
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And note that in a large system most KVs are in HFiles that have been compacted
and the probability is high that they were older than the oldest scanner at
compaction time; hence their memstoreTS is set to 0 in the HFile, and hence
this optimization works.
[~vrodionov], if you have any ideas about the areas you mention, as well as how
avoid getting the readpoint on each call to next in MemstoreScanner, I'd love
to hear them.
> 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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