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https://issues.apache.org/jira/browse/HBASE-2294?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845638#action_12845638
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Henry Robinson commented on HBASE-2294:
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bq. Stated differently: the current row lock feature can be implemented on the
client side through use of an atomic compareAndSet primitive. So, if we provide
CAS within the region server, row lock primitives are redundant and add
complexity for no apparent gain.
The only downside of CAS compared to a lock is that the client has to handle
the retry on failure. Putting CAS in a tight loop on a contended row might be
painful as well. Still preferable to locks, in my opinion!
> Enumerate ACID properties of HBase in a well defined spec
> ---------------------------------------------------------
>
> Key: HBASE-2294
> URL: https://issues.apache.org/jira/browse/HBASE-2294
> Project: Hadoop HBase
> Issue Type: Task
> Components: documentation
> Reporter: Todd Lipcon
> Priority: Blocker
> Fix For: 0.20.4, 0.21.0
>
>
> It's not written down anywhere what the guarantees are for each operation in
> HBase with regard to the various ACID properties. I think the developers know
> the answers to these questions, but we need a clear spec for people building
> systems on top of HBase. Here are a few sample questions we should endeavor
> to answer:
> - For a multicell put within a CF, is the update made durable atomically?
> - For a put across CFs, is the update made durable atomically?
> - Can a read see a row that hasn't been sync()ed to the HLog?
> - What isolation do scanners have? Somewhere between snapshot isolation and
> no isolation?
> - After a client receives a "success" for a write operation, is that
> operation guaranteed to be visible to all other clients?
> etc
> I see this JIRA as having several points of discussion:
> - Evaluation of what the current state of affairs is
> - Evaluate whether we currently provide any guarantees that aren't useful to
> users of the system (perhaps we can drop in exchange for performance)
> - Evaluate whether we are missing any guarantees that would be useful to
> users of the system
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