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From "ramkrishna.s.vasudevan (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-3855) Performance degradation of memstore because reseek is linear
Date Thu, 26 Jan 2012 07:37:40 GMT

     [ https://issues.apache.org/jira/browse/HBASE-3855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

ramkrishna.s.vasudevan updated HBASE-3855:
------------------------------------------

    Fix Version/s:     (was: 0.90.6)
                   0.90.7

Not fixed in this 0.90.6.  Hence moving it to 0.90.7.
                
> 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: 0.90.7
>
>         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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