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https://issues.apache.org/jira/browse/HBASE-7051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13488176#comment-13488176
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Gregory Chanan commented on HBASE-7051:
---------------------------------------

I'm +1 on this.  I haven't looked at HBASE-7071 enough to +1 it.  Want me to?
                
> Read/Updates (increment,checkAndPut) should properly read MVCC
> --------------------------------------------------------------
>
>                 Key: HBASE-7051
>                 URL: https://issues.apache.org/jira/browse/HBASE-7051
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.96.0
>            Reporter: Gregory Chanan
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.3, 0.96.0
>
>         Attachments: 7051.txt
>
>
> See, for example:
> {code}
> // TODO: Use MVCC to make this set of increments atomic to reads
> {code}
> Here's an example of what I can happen (would probably be good to write up a 
> test case for each read/update):
> Concurrent update via increment and put.
> The put grabs the row lock first and updates the memstore, but releases the 
> row lock before the MVCC is advanced.  Then, the increment grabs the row lock 
> and reads right away, reading the old value and incrementing based on that.
> There are a few options here:
> 1) Waiting for the MVCC to advance for read/updates: the downside is that you 
> have to wait for updates on other rows.
> 2) Have an MVCC per-row (table configuration): this avoids the unnecessary 
> contention of 1)
> 3) Transform the read/updates to write-only with rollup on read..  E.g. an 
> increment  would just have the number of values to increment.

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