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Posted to issues@hbase.apache.org by "stack (JIRA)" <ji...@apache.org> on 2011/09/16 21:32:10 UTC

[jira] [Commented] (HBASE-3855) Performance degradation of memstore because reseek is linear

    [ https://issues.apache.org/jira/browse/HBASE-3855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13106744#comment-13106744 ] 

stack commented on HBASE-3855:
------------------------------

@Andrew I ran tests with this hbase-4195 in place on 0.90.  I ran 20 iterations and I did not see failure (Previous I'd see 1/5th fail).  What you think of applying hbase-4195 to 0.90 and then closing this issue? 

> Performance degradation of memstore because reseek is linear
> ------------------------------------------------------------
>
>                 Key: HBASE-3855
>                 URL: https://issues.apache.org/jira/browse/HBASE-3855
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.92.0
>
>         Attachments: memstoreReseek.txt, memstoreReseek2.txt
>
>
> The scanner use reseek to find the next row (or next column) as part of a scan. The reseek code iterates over a Set to position itself at the right place. If there are many thousands of kvs that need to be skipped over, then the time-cost is very high. In this case, a seek would be far lesser in cost than a reseek.

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