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From "John Carrino (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4811) Support reverse Scan
Date Wed, 23 Nov 2011 05:30:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13155692#comment-13155692
] 

John Carrino commented on HBASE-4811:
-------------------------------------

So looking at the region splitting code it looks like any scans that
are open on ranges that are split get a special exception type and
then just open a new scanner.  So we don't have to worry about reverse
iteration any more than forward with respect to splitting.

I think this might boil down to writing a reverse iterator
(HFileScanner) for HFile.

-jc


On Tue, Nov 22, 2011 at 3:48 PM, stack (Commented) (JIRA)

                
> 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
>
> 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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