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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4102) atomicAppend: A put that appends to the latest version of a cell; i.e. reads current value then adds the bytes offered by the client to the tail and writes out a new entry
Date Sat, 08 Oct 2011 22:11:29 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13123572#comment-13123572
] 

Lars Hofhansl commented on HBASE-4102:
--------------------------------------

I have this working now.

But now I realized two things:
1. I modeled it after the old ICV. I assume we want something like the new Increment API.
2. Is this something that even want to build into HBase? Or should a user implement this with
a coprocessor endpoint? (It would be possible to do with a coprocessor, albeit not quite as
efficient as an endpoint would have no access to the Stores.

                
> atomicAppend: A put that appends to the latest version of a cell; i.e. reads current
value then adds the bytes offered by the client to the tail and writes out a new entry
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-4102
>                 URL: https://issues.apache.org/jira/browse/HBASE-4102
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: stack
>            Assignee: Lars Hofhansl
>
> Its come up a few times that clients want to add to an existing cell rather than make
a new cell each time.  At our place, the frontend keeps a list of urls a user has visited
-- their md5s -- and updates it as user progresses.  Rather than read, modify client-side,
then write new value back to hbase, it would be sweet if could do it all in one operation
in hbase server.  TSDB aims to be space efficient.  Rather than pay the cost of the KV wrapper
per metric, it would rather have a KV for an interval an in this KV have a value that is all
the metrics for the period.
> It could be done as a coprocessor but this feels more like a fundamental feature.
> BenoƮt suggests that atomicAppend take a flag to indicate whether or not the client
wants to see the resulting cell; often a client won't want to see the result and in this case,
why pay the price formulating and delivering a response that client just drops.

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