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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12751) Allow RowLock to be reader writer
Date Thu, 23 Jul 2015 17:44:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14639243#comment-14639243
] 

Elliott Clark commented on HBASE-12751:
---------------------------------------

bq.Let me look at the patch again. The above description sounds like how it mostly worked
previous. Let me see.... Thanks E.
Yeah it's pretty similar. The patch is just adding to the wal append/sync queue earlier. That
allows a creating the sequence id/mvcc number for real. Because the edits are already in the
queue for the wal we know for sure that their ordering is the same as the sequence number.

The bonus nice thing from this re-ordering is that adding to the memstore and the append are
running in parallel.

> 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
>    Affects Versions: 2.0.0, 1.3.0
>            Reporter: Elliott Clark
>            Assignee: Elliott Clark
>             Fix For: 2.0.0, 1.3.0
>
>         Attachments: HBASE-12751-v1.patch, HBASE-12751-v10.patch, HBASE-12751-v10.patch,
HBASE-12751-v11.patch, HBASE-12751-v12.patch, HBASE-12751-v13.patch, HBASE-12751-v14.patch,
HBASE-12751-v15.patch, HBASE-12751-v16.patch, HBASE-12751-v2.patch, HBASE-12751-v3.patch,
HBASE-12751-v4.patch, HBASE-12751-v5.patch, HBASE-12751-v6.patch, HBASE-12751-v7.patch, HBASE-12751-v8.patch,
HBASE-12751-v9.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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