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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7051) Read/Updates (increment,checkAndPut) should properly read MVCC
Date Wed, 31 Oct 2012 06:29:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13487581#comment-13487581
] 

Hadoop QA commented on HBASE-7051:
----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12551489/7051.txt
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified
tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:green}+1 hadoop2.0{color}.  The patch compiles against the hadoop 2.0 profile.

    {color:red}-1 javadoc{color}.  The javadoc tool appears to have generated 85 warning messages.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:red}-1 findbugs{color}.  The patch appears to introduce 3 new Findbugs (version
1.3.9) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

     {color:red}-1 core tests{color}.  The patch failed these unit tests:
                       org.apache.hadoop.hbase.regionserver.wal.TestHLogSplit

Test results: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop2-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop1-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-common.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Findbugs warnings: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-server.html
Console output: https://builds.apache.org/job/PreCommit-HBASE-Build/3197//console

This message is automatically generated.
                
> Read/Updates (increment,checkAndPut) should properly read MVCC
> --------------------------------------------------------------
>
>                 Key: HBASE-7051
>                 URL: https://issues.apache.org/jira/browse/HBASE-7051
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.96.0
>            Reporter: Gregory Chanan
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.3, 0.96.0
>
>         Attachments: 7051.txt
>
>
> See, for example:
> {code}
> // TODO: Use MVCC to make this set of increments atomic to reads
> {code}
> Here's an example of what I can happen (would probably be good to write up a test case
for each read/update):
> Concurrent update via increment and put.
> The put grabs the row lock first and updates the memstore, but releases the row lock
before the MVCC is advanced.  Then, the increment grabs the row lock and reads right away,
reading the old value and incrementing based on that.
> There are a few options here:
> 1) Waiting for the MVCC to advance for read/updates: the downside is that you have to
wait for updates on other rows.
> 2) Have an MVCC per-row (table configuration): this avoids the unnecessary contention
of 1)
> 3) Transform the read/updates to write-only with rollup on read..  E.g. an increment
 would just have the number of values to increment.

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