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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4583) Integrate RWCC with Append and Increment operations
Date Fri, 04 Nov 2011 03:02:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13143712#comment-13143712
] 

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

(on a computer now)

So to be more specific... The problem is that we cannot remove duplicate KVs unless we can
guarantee that no scanners still operation on these KVs; the only way (currently) to guarantee
this is to set the memstoreTS of the changed (new) KVs to 0 and hence making them available
to all scanners immediately.
That on the other hand means that we cannot delay the visibility of any CFs until after all
CFs are updated.
If we do not remove duplicate KVs the memstore will explode :) (and I also have to investigate
the strange behavior I saw with atomic operations with identical timestamps).

We can still, however, at least update and sync the WAL first and then modify the memstore.

                
> 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: 0.94.0
>
>         Attachments: 4583-v2.txt, 4583-v3.txt, 4583-v4.txt, 4583.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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