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From "Andrei Dragomir (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HBASE-493) Write-If-Not-Modified-Since support
Date Fri, 08 Jan 2010 13:32:54 GMT

     [ https://issues.apache.org/jira/browse/HBASE-493?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrei Dragomir updated HBASE-493:
----------------------------------

    Affects Version/s: 0.21.0
               Status: Patch Available  (was: Reopened)

I have a patch related to this. 

Basically, it's working just like HTable.checkAndPut, except that it checks timestamp, not
value. There is still a lock on the row, but it's done in the HRegion object, close to the
data. We could make it without, but I don't see how we could guarantee that it works ok. 


> Write-If-Not-Modified-Since support
> -----------------------------------
>
>                 Key: HBASE-493
>                 URL: https://issues.apache.org/jira/browse/HBASE-493
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: client, io, regionserver
>    Affects Versions: 0.21.0
>            Reporter: Chris Richard
>            Priority: Minor
>             Fix For: 0.21.0
>
>
> Write-If-Not-Modified-Since for optimistic concurrency control:
> Client retrieves cell (or row) and stores timestamp.
> Client writes to same cell (or row) and passes timestamp.
> If the cell's (or row's) latest timestamp matches the passed timestamp, the write succeeds.
If the timestamps do not match, the write fails and the client is notified. The client must
re-retrieve the cell/row to get the latest timestamp before attempting to write back.
> This behavior would be optional, if the client doesn't pass a timestamp to the write
method, no modified check would be enforced.
> Note: blocked behind HBASE-489 due to requirement that client be able to access timestamp
values.

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