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From "Chao Shi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9000) Linear reseek in Memstore
Date Thu, 31 Oct 2013 02:52:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13809870#comment-13809870
] 

Chao Shi commented on HBASE-9000:
---------------------------------

bq. 'reseek to next row' gets slower with patch. If "linear.search.limit" is lowered, would
the slow down be less ?

Yes, the optimal value should vary case by case. I think a default value of 5 should not add
much observable overhead.

I think a long-term solution would be implementing our own version of lock-free skip-list,
where we can access its higher-level of next pointers (i.e. to skip) from the current position.
This patch could be a temporary solution for now, as it is very simple.

> Linear reseek in Memstore
> -------------------------
>
>                 Key: HBASE-9000
>                 URL: https://issues.apache.org/jira/browse/HBASE-9000
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.89-fb
>            Reporter: Shane Hogan
>            Priority: Minor
>             Fix For: 0.89-fb
>
>         Attachments: hbase-9000-benchmark-program.patch, hbase-9000-port-fb.patch
>
>
> This is to address the linear reseek in MemStoreScanner. Currently reseek iterates over
the kvset and the snapshot linearly by just calling next repeatedly. The new solution is to
do this linear seek up to a configurable maximum amount of times then if the seek is not yet
complete fall back to logarithmic seek.



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