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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12751) Allow RowLock to be reader writer
Date Mon, 20 Jul 2015 21:01:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14634072#comment-14634072

Elliott Clark commented on HBASE-12751:

Attaching the rebased patch.

bq.How is order in memstore for sure matching the append order to WAL now?
All edits are queued in the wal before they are put in the memstore. After they are queued
the first thing that's done is to assign a sequence number. The insert to memstore waits on
that number to be added to the wal edit.
Once that number is found it's used by the memstore for ordering. Our comparitor on the map
does that.

> 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: Elliott Clark
>         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-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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