[jira] [Commented] (HBASE-4583) Integrate RWCC with Append and Increment operations

["Jonathan Gray (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13126224#comment-13126224 ] 

Jonathan Gray commented on HBASE-4583:
--------------------------------------

We likely won't be able to do in-place modifications or direct KV removal from MemStore.  A simple way would be to also introduce a delete marker that removes the previous value, but the marker will have the rwcc of the new edit, so you'll have the right consistency.

This will lead to a build up of unnecessary KVs in the MemStore.  Periodically cleaning that up would be possible but unnecessarily complex I think.

Another option would be to remove the previous KVs after you roll rwcc forward and release the row lock, before dropping the region-level lock.  Should definitely be possible.  Will obviously require a remangling of upsert but it's kinda dirty anyways.
                
> Integrate RWCC with Append and Increment operations
> ---------------------------------------------------
>
>                 Key: HBASE-4583
>                 URL: https://issues.apache.org/jira/browse/HBASE-4583
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>             Fix For: 0.94.0
>
>
> Currently Increment and Append operations do not work with RWCC and hence a client could see the results of multiple such operation mixed in the same Get/Scan.
> The semantics might be a bit more interesting here as upsert adds and removes to and from the memstore.

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