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From "Raymond Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8001) Avoid unnecessary lazy seek
Date Mon, 11 Mar 2013 01:11:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13598461#comment-13598461
] 

Raymond Liu commented on HBASE-8001:
------------------------------------

[~lhofhansl] I do the test with sequential scans. And without short circuit read, with 1000
client scan caching. 4 node, on each node, 24 map task scan on 24 local region for the single
CF, 18 columns table. other than these, seems no other special thing need to mention.
                
> Avoid unnecessary lazy seek
> ---------------------------
>
>                 Key: HBASE-8001
>                 URL: https://issues.apache.org/jira/browse/HBASE-8001
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>    Affects Versions: 0.94.5
>            Reporter: Raymond Liu
>            Assignee: Raymond Liu
>             Fix For: 0.98.0
>
>         Attachments: HBASE-8001_onescanner.patch, HBASE-8001_onescanner_v2.patch
>
>
> Lazy seek helps to reduce the real seek needed for multi hfile, when the kv from newer
hfile is enough to satisfy the query.
> While in many case, it just push the real seek later, and do not reduce the number of
real seek. e.g. there are only one hfile, or storefilescanner is closed and only one left,
or the scan need to go through all the versions, or there are only one version of row and
a sequence scan is performed. In these case, lazy seek just bring extra overhead.

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