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https://issues.apache.org/jira/browse/HBASE-5229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201354#comment-13201354
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Lars Hofhansl edited comment on HBASE-5229 at 2/9/12 9:18 PM:
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http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
<https://reviews.apache.org/r/3748/#comment10616>

    Do we need to be sorting rowsToLock?
    
    I'm thinking of multiple concurrent mutateRows operation, trying to lock 
the same set of rows.
    
    Perhaps, throwing IOException is going to prevent us from a situation where 
we end up with a deadlock. But, we still might want to sort it to ensure 
(better) progress (no livelock).


- Amitanand

                
      was (Author: jirapos...@reviews.apache.org):
    
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http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
<https://reviews.apache.org/r/3748/#comment10616>

    Do we need to be sorting rowsToLock?
    
    I'm thinking of multiple concurrent mutateRows operation, trying to lock 
the same set of rows.
    
    Perhaps, throwing IOException is going to prevent us from a situation where 
we end up with a deadlock. But, we still might want to sort it to ensure 
(better) progress (no livelock).


- Amitanand


On 2012-02-03 19:59:55, Lars Hofhansl wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/3748/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2012-02-03 19:59:55)
bq.  
bq.  
bq.  Review request for hbase.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  This builds on HBASE-3584, HBASE-5203, and HBASE-5304.
bq.  
bq.  Multiple Rows can be locked and applied atomically as long as the 
application ensures that all rows reside in the same Region (by presplitting or 
a custom RegionSplitPolicy).
bq.  At SFDC we can use this to colocate subsets of a tenant's data and allow 
atomic operations over these subsets.
bq.  
bq.  Obviously this is an advanced features and this prominently called out in 
the Javadoc.
bq.  
bq.  
bq.  This addresses bug HBASE-5229.
bq.      https://issues.apache.org/jira/browse/HBASE-5229
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/client/HTable.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/client/HTableInterface.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/client/MultiRowMutation.java
 PRE-CREATION 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/coprocessor/CoprocessorHost.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/ipc/HRegionInterface.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/rest/client/RemoteHTable.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide.java
 1239953 
bq.    
http://svn.apache.org/repos/asf/hbase/trunk/src/test/java/org/apache/hadoop/hbase/regionserver/TestAtomicOperation.java
 1239953 
bq.  
bq.  Diff: https://reviews.apache.org/r/3748/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  Tests added to TestFromClientSide and TestAtomicOperation
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Lars
bq.  
bq.


                  
> Provide basic building blocks for "multi-row" local transactions.
> -----------------------------------------------------------------
>
>                 Key: HBASE-5229
>                 URL: https://issues.apache.org/jira/browse/HBASE-5229
>             Project: HBase
>          Issue Type: New Feature
>          Components: client, regionserver
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.0
>
>         Attachments: 5229-endpoint.txt, 5229-final.txt, 5229-multiRow-v2.txt, 
> 5229-multiRow.txt, 5229-seekto-v2.txt, 5229-seekto.txt, 5229.txt
>
>
> In the final iteration, this issue provides a generalized, public 
> mutateRowsWithLocks method on HRegion, that can be used by coprocessors to 
> implement atomic operations efficiently.
> Coprocessors are already region aware, which makes this is a good pairing of 
> APIs. This feature is by design not available to the client via the HTable 
> API.
> It took a long time to arrive at this and I apologize for the public exposure 
> of my (erratic in retrospect) thought processes.
> Was:
> HBase should provide basic building blocks for multi-row local transactions. 
> Local means that we do this by co-locating the data. Global (cross region) 
> transactions are not discussed here.
> After a bit of discussion two solutions have emerged:
> 1. Keep the row-key for determining grouping and location and allow efficient 
> intra-row scanning. A client application would then model tables as 
> HBase-rows.
> 2. Define a prefix-length in HTableDescriptor that defines a grouping of 
> rows. Regions will then never be split inside a grouping prefix.
> #1 is true to the current storage paradigm of HBase.
> #2 is true to the current client side API.
> I will explore these two with sample patches here.
> --------------------
> Was:
> As discussed (at length) on the dev mailing list with the HBASE-3584 and 
> HBASE-5203 committed, supporting atomic cross row transactions within a 
> region becomes simple.
> I am aware of the hesitation about the usefulness of this feature, but we 
> have to start somewhere.
> Let's use this jira for discussion, I'll attach a patch (with tests) 
> momentarily to make this concrete.

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