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Date: Tue, 26 Feb 2013 13:54:14 +0000 (UTC)
From: "Jean-Marc Spaggiari (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12630009.1359583572226.342162.1361886854432@arcas>
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Subject: [jira] [Commented] (HBASE-7721) Local Transactions in META
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    [ https://issues.apache.org/jira/browse/HBASE-7721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13587129#comment-13587129 ] 

Jean-Marc Spaggiari commented on HBASE-7721:
--------------------------------------------

bq. I think we should try this for 0.94. It would allow for online schema alter (and with HBASE-7403) online schema merge.
I totally agree with this statement. I'm eager to see online merge in.
                
> Local Transactions in META
> --------------------------
>
>                 Key: HBASE-7721
>                 URL: https://issues.apache.org/jira/browse/HBASE-7721
>             Project: HBase
>          Issue Type: Improvement
>          Components: Coprocessors, regionserver
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.95.0
>
>
> Thanks to Lars' local transactions patch (HBASE-5229), we can entertain the possibility of doing local transactions within META regions.
> We need this mainly for region splits and merges. Clients scan the META concurrent to the split/merge operations, and to prevent the clients from seeing overlapping region boundaries or holes in META, we just through hoops. For more backgroun, see BlockingMetaScannerVisitor, HBASE-5986, and my comments at https://reviews.apache.org/r/8716/. 
> Now, for the actual implementation options: 
>  1. As outlined in http://hadoop-hbase.blogspot.com/2012_02_01_archive.html, 
>    - We have to implement a Custom RegionSplitPolicy for the META regions to ensure that a table's regions are always co-located in the same META region. Then we can add MultiRowMutationEndpoint as a system level coprocessor, and use it for META operations. 
>  2. Do smt like HBASE-7716, and expose local atomic multi-row operations as a native API.
>  3. Move META to zookeeper. Use zookeeper.multi.  
> Then we can change region split / merge logic to make use of atomic META operations. 
> Thoughts, suggestions? 

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