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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-4811) Support reverse Scan
Date Tue, 02 Apr 2013 11:55:15 GMT

     [ https://issues.apache.org/jira/browse/HBASE-4811?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Liang Xie updated HBASE-4811:

    Attachment: HBase-4811-0.94.3modified.txt

Attached HBase-4811-0.94.3modified.txt is an our internal draft implementation for reverse
scan. I thought it may be not suitable to merge into trunk or any branch, so i didn't make
a patch against trunk or 0.94 branch, drop here just in case some guys are interesting on
it, for reference only:) We didn't impletement it like leveldb&cassandra's way, which
done in block layer, our policy is more focused on upper logic layer(scanner & Kv heap),
though we still use seekBefore api.

Performance: i ran PerformanceEvaluation, observed about 20%-40% degraded on scanRange10/100/1000,
and approximately 50% degraded on randomSeekScan.
> Support reverse Scan
> --------------------
>                 Key: HBASE-4811
>                 URL: https://issues.apache.org/jira/browse/HBASE-4811
>             Project: HBase
>          Issue Type: Improvement
>          Components: Client
>    Affects Versions: 0.20.6
>            Reporter: John Carrino
>         Attachments: HBase-4811-0.94.3modified.txt
> All the documentation I find about HBase says that if you want forward and reverse scans
you should just build 2 tables and one be ascending and one descending.  Is there a fundamental
reason that HBase only supports forward Scan?  It seems like a lot of extra space overhead
and coding overhead (to keep them in sync) to support 2 tables.  
> I am assuming this has been discussed before, but I can't find the discussions anywhere
about it or why it would be infeasible.

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