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From "ryan rawson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1563) incrementColumnValue does not write to WAL
Date Wed, 24 Jun 2009 02:05:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1563?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723397#action_12723397
] 

ryan rawson commented on HBASE-1563:
------------------------------------

a row lock is only for writing.  The race happens when someone is reading the value you are
incrementing.  They could copy a partially updated view into the RPC buffer, and the user
could see something odd and unexpected (values going down for example).

If we used a ConcurrentSkipListSet, we can't put a duplicate, which requires us to temporarily
remove the KeyValue, then put it back, opens a hole whereby we can look for a value and it
not be there.  

So to support not-in-place modification we need to also move to a ConcurrentSkipListMap in
memcache.

> incrementColumnValue does not write to WAL
> ------------------------------------------
>
>                 Key: HBASE-1563
>                 URL: https://issues.apache.org/jira/browse/HBASE-1563
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.0
>            Reporter: Jonathan Gray
>            Assignee: Jonathan Gray
>             Fix For: 0.20.0
>
>         Attachments: HBASE-1563-v1.patch, HBASE-1563-v2.patch, HBASE-1563-v3.patch
>
>
> Incrementing never writes to the WAL.  Under failure scenarios, you will lose all increments
since the last flush.
> Do we want to expose the option to the client as to whether to write to WAL or not?

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