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Date: Wed, 6 Mar 2013 06:54:16 +0000 (UTC)
From: "Raymond Liu (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12635294.1362472204149.389963.1362552856203@arcas>
In-Reply-To: <JIRA.12635294.1362472204149@arcas>
References: <JIRA.12635294.1362472204149@arcas>
Subject: [jira] [Updated] (HBASE-8001) Avoid unnecessary lazy seek
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     [ https://issues.apache.org/jira/browse/HBASE-8001?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Raymond Liu updated HBASE-8001:
-------------------------------

    Description: 
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.


  was:
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, all there are only one version of row and a sequence scan is performed. In these case, lazy seek just bring extra overhead.


> 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
>
>
> 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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