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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7805) Scan of same region processed serially if table has region observer coprocessor
Date Sun, 10 Feb 2013 19:27:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7805?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575501#comment-13575501
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Ted Yu commented on HBASE-7805:
-------------------------------

If 0.94 tests output both serial and parallel runtime statistics upon failure, that would
help us gauge performance characteristics in various scenarios.
By raising amplifier to 7/4 I could get the test to fail:
{code}
Failed tests:   testParallelScanAgainstSameRegionWithCoProc(org.apache.hadoop.hbase.client.TestParallelScan):
serial 305, parallel 186
  testParallelScanAgainstSameRegion(org.apache.hadoop.hbase.client.TestParallelScan): serial
223, parallel 133
{code}
Good news is that parallel scanning is faster than serial.
But as James found out, the presence of region observer does slow down the overall performance.
                
> Scan of same region processed serially if table has region observer coprocessor
> -------------------------------------------------------------------------------
>
>                 Key: HBASE-7805
>                 URL: https://issues.apache.org/jira/browse/HBASE-7805
>             Project: HBase
>          Issue Type: Bug
>          Components: Coprocessors, Scanners
>    Affects Versions: 0.94.4
>            Reporter: James Taylor
>             Fix For: 0.96.0, 0.94.6
>
>         Attachments: 7805-0.94.patch, 7805-trunk.txt, 7805-trunk-v2.txt, ParallelScanTestCoProc.java,
ParallelScanTest.java
>
>
> If multiple scans to different parts of the same region are executed in parallel, they
are processed serially if the table has a region observer coprocessor.

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