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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Created] (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 Fri, 15 Jul 2011 00:18:02 GMT
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
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                 Key: HBASE-4102
                 URL: https://issues.apache.org/jira/browse/HBASE-4102
             Project: HBase
          Issue Type: New Feature
            Reporter: stack


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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