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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7495) parallel scanner seek in StoreScanner's constructor
Date Sat, 05 Jan 2013 05:18:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13544583#comment-13544583
] 

Lars Hofhansl commented on HBASE-7495:
--------------------------------------

{{requestSeek(matcher.getStartKey(), false, true)}} is hardly doing anything, I do not think
we'll see any measurable improvement from this.

What generally might help is to scan families in parallel (rather than serially the way we
do that now), but that is very tricky.
                
> parallel scanner seek in StoreScanner's constructor
> ---------------------------------------------------
>
>                 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
>
> 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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