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https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14642106#comment-14642106
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Elliott Clark commented on HBASE-12751:
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bq.So mvcc has its own running sequenceid-like thing now and it runs
independent of sequenceid
All sequence id numbers are the mvcc number of the edit. Anything that doesn't
apply a wal edit get's a sequence id by creating a mvcc write number and
waiting for it to be completed.
> 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-v17.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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