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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12751) Allow RowLock to be reader writer
Date Tue, 24 Mar 2015 02:33:53 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14377157#comment-14377157

Elliott Clark commented on HBASE-12751:

So [~nkedel] and I have been debugging this today. The test that's failing is a real test
failure. However it's do to the late binding sequence id work that went in a while ago.

The issue is that if we allow two WALEdits for the same row to be outstanding then it's possible
that the pre-created sequence number (1M + a incrementing long) will not sort in the same
way as the sequence id inside of the waledit. This late binding is currently pretty intwined
with the FSHLog.

[~stack] or [~busbey] or [~jeffreyz] any thoughts on how to fix this cleanly? My only thought
was to move memstore insertion after hlog.append.

> Allow RowLock to be reader writer
> ---------------------------------
>                 Key: HBASE-12751
>                 URL: https://issues.apache.org/jira/browse/HBASE-12751
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: Elliott Clark
>            Assignee: Nate Edel
>         Attachments: HBASE-12751-v1.patch, HBASE-12751.patch
> Right now every write operation grabs a row lock. This is to prevent values from changing
during a read modify write operation (increment or check and put). However it limits parallelism
in several different scenarios.
> If there are several puts to the same row but different columns or stores then this is
very limiting.
> If there are puts to the same column then mvcc number should ensure a consistent ordering.
So locking is not needed.
> However locking for check and put or increment is still needed.

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