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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12751) Allow RowLock to be reader writer
Date Tue, 24 Mar 2015 16:47:53 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14378131#comment-14378131

stack commented on HBASE-12751:

Excellent, excellent stuff (this whole issue and this finding)

So, first response is same as yours: Add to memstore after WAL; the edits can't be 'seen'
yet anyways because they are beyond the read point.... But our current ordering of memstore
first was about perf so would need to look at this.

Other things are going on here though FYI, our [~busbey] is looking at WAL perf in the layer
below DFS client and is having some radical thoughts... so this is right time to raise reorder
on the append pipeline; longer time between syncs means more grouping... higher throughput.

You looking at the rerdering then [~eclark]?

> 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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