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Date: Thu, 1 Jan 2009 12:27:44 -0800 (PST)
From: "Michael Gottesman (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Updated: (HBASE-1106) Expose getClosestRowBefore in HTable
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     [ https://issues.apache.org/jira/browse/HBASE-1106?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Gottesman updated HBASE-1106:
-------------------------------------

    Attachment: hbase-1106.patch

> Expose getClosestRowBefore in HTable
> ------------------------------------
>
>                 Key: HBASE-1106
>                 URL: https://issues.apache.org/jira/browse/HBASE-1106
>             Project: Hadoop HBase
>          Issue Type: New Feature
>            Reporter: Michael Gottesman
>            Priority: Minor
>         Attachments: hbase-1106.patch
>
>
> Exposes the functionality of getClosestRowBefore in HTable. It can be useful in combination with atomic check and save in the following manner to create a global auto-id creation scheme:
> Presteps:
> 1. In your application, have a reserved value.
> 2. Create a reverse index table of your main table (best algorithm in my opinion is bitwise-not of key and append max-utf8 character)
> 3. Have an offset row in said reverse index table that your application does not allow to be set (usually this will be a bitwise inverse of some prefix + maximum UTF-8 character)
> Algorithm:
> 1. Use getClosestRowBefore to find the last created row before the offset (which will be the last row created)
> 2. Deinverse key and then increment the row key of the row returned by getClosestRowBefore
> 3. Attempt to reserve the row key with checkAndSave checking if reserved has been set.
> 4. If it fails try again.
> Attached is a patch to expose getClosestRowBefore. Comments are of course always welcome =).

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