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From "chunhui shen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7495) parallel seek in StoreScanner
Date Wed, 30 Jan 2013 01:55:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13566063#comment-13566063
] 

chunhui shen commented on HBASE-7495:
-------------------------------------

It's better to measure the performance in the normal case with some pressure.

Parallel seeking seems to decrease response time, but in fact we would take resource for context
switch frequently and thread production

                
> parallel seek in StoreScanner
> -----------------------------
>
>                 Key: HBASE-7495
>                 URL: https://issues.apache.org/jira/browse/HBASE-7495
>             Project: HBase
>          Issue Type: Bug
>          Components: Scanners
>    Affects Versions: 0.94.3, 0.96.0
>            Reporter: Liang Xie
>            Assignee: Liang Xie
>         Attachments: HBASE-7495.txt, HBASE-7495.txt, HBASE-7495.txt, HBASE-7495-v2.txt,
HBASE-7495-v3.txt, HBASE-7495-v4.txt, HBASE-7495-v4.txt
>
>
> seems there's a potential improvable space before doing scanner.next:
> {code:title=StoreScanner.java|borderStyle=solid}
>     if (explicitColumnQuery && lazySeekEnabledGlobally) {
>       for (KeyValueScanner scanner : scanners) {
>         scanner.requestSeek(matcher.getStartKey(), false, true);
>       }
>     } else {
>       for (KeyValueScanner scanner : scanners) {
>         scanner.seek(matcher.getStartKey());
>       }
>     }
> {code} 
> we can do scanner.requestSeek or scanner.seek in parallel, instead of current serialization,
to reduce latency for special case.
> Any ideas on it ?  I'll have a try if the comments/suggestions are positive:)

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