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https://issues.apache.org/jira/browse/HBASE-4811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697578#comment-13697578
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chunhui shen commented on HBASE-4811:
-------------------------------------
bq.we need to change one line in HFileReaderV2.seekBefore() in trunk patch(but
not 0.94's):
I have found and changed this one in current patch.
bq.didn't enable *lazy seek" for reverse scan, and we had supported it in our
internal codebase, i can make a new 0.94 patch later.
It's nice, we could import it in a new improvement issue after this feature is
stable.
Recently I have found one bug in ClientScanner if the reversed scan cross two
or more regions(The scan order will be wrong between regions in ClientScanner).
I will upload the new patch with fixing this bug later.
> 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, 0.94.7
> Reporter: John Carrino
> Assignee: Liang Xie
> Attachments: 4811-trunk-v10.txt, 4811-trunk-v5.patch,
> HBase-4811-0.94.3modified.txt, HBase-4811-0.94-v2.txt,
> hbase-4811-trunkv11.patch, hbase-4811-trunkv1.patch,
> hbase-4811-trunkv4.patch, hbase-4811-trunkv6.patch, hbase-4811-trunkv7.patch,
> hbase-4811-trunkv8.patch, hbase-4811-trunkv9.patch
>
>
> 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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