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Date: Tue, 30 Oct 2012 22:42:14 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-4583) Integrate RWCC with Append and
 Increment operations
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    [ https://issues.apache.org/jira/browse/HBASE-4583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13487326#comment-13487326 ] 

Lars Hofhansl commented on HBASE-4583:
--------------------------------------

I was checking out why readpoint - 1 is needed. Turns out the patch is not entirely correct.

The new KV is newer than the current readpoint (by definition, because it is written from a new transaction). A scanner running at the current readpoint, thus, will not see the new KV, but rather the older one. That means that we can only remove older KVs if there is a newer one that is still older than the current readpoint (which means all new scanner will see that one).
readpoint - 1 fixed it for my test case, but it is not generally correct.
                
> Integrate RWCC with Append and Increment operations
> ---------------------------------------------------
>
>                 Key: HBASE-4583
>                 URL: https://issues.apache.org/jira/browse/HBASE-4583
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.3, 0.96.0
>
>         Attachments: 4583-trunk-less-radical.txt, 4583-trunk-less-radical-v2.txt, 4583-trunk-radical.txt, 4583-trunk-radical_v2.txt, 4583-trunk-v3.txt, 4583.txt, 4583-v2.txt, 4583-v3.txt, 4583-v4.txt
>
>
> Currently Increment and Append operations do not work with RWCC and hence a client could see the results of multiple such operation mixed in the same Get/Scan.
> The semantics might be a bit more interesting here as upsert adds and removes to and from the memstore.

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