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https://issues.apache.org/jira/browse/HBASE-1806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12766384#action_12766384
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stack commented on HBASE-1806:
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Thanks Andrew.  I added a note to javadoc a while back.

> Scanners do not respect row locks; scanner view could return a skewed view on 
> row if ongoing update
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-1806
>                 URL: https://issues.apache.org/jira/browse/HBASE-1806
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>
> What I'm seeing is that BaseScanner misses updates made by an update 
> milliseconds before -- even hundreds of milliseconds before.  See hbase-1784 
> where I'm seeing double-assignment of regions.
> Scanners do not respect row locks.  They should else could return a row with 
> partial updates committed.  What if a .META. region has tens of storefiles 
> and a scan does a get full row which takes a long time.  Say an update comes 
> in during this read.  First it will go in because no row lock is outstanding. 
>  Second, we'll miss the edit given we look at things in order -- memstore, 
> then each storefile down to the oldest.  What if the update is followed by an 
> update of server state; e.g. region is moved out of intransition state?  And 
> inside in same server, say the master, it makes decisions dependent on what 
> it sees when it does a scanner#next; e.g. BaseScanner checking for assignment?

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