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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14867) SimpleRegionNormalizer needs to have better heuristics to trigger merge operation
Date Tue, 22 Dec 2015 21:44:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15068772#comment-15068772
] 

Ted Yu commented on HBASE-14867:
--------------------------------

I wonder if RegionNormalizer should have knowledge of the history of each region.

This would allow the normalizer to distinguish whether region R has been empty since inception
or, was populated with data but became empty due to data cleaned up (due to TTL) later on.

> SimpleRegionNormalizer needs to have better heuristics to trigger merge operation
> ---------------------------------------------------------------------------------
>
>                 Key: HBASE-14867
>                 URL: https://issues.apache.org/jira/browse/HBASE-14867
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 1.2.0
>            Reporter: Romil Choksi
>
> SimpleRegionNormalizer needs to have better heuristics to trigger merge operation. SimpleRegionNormalizer
is not able to trigger a merge action if the table's smallest region has neighboring regions
that are larger than table's average region size, whereas there are other smaller regions
whose combined size is less than the average region size. 
> For example, 
> - Consider a table with six region, say r1 to r6. 
> - Keep r1 as empty and create some data say, 100K rows of data for each of the regions
r2, r3 and r4. Create smaller amount of data for regions r5 and r6, say about 27K rows of
data.
> - Run the normalizer. Verify the number the regions for that table and also check the
master log to see if any merge action was triggered as a result of normalization. 
> In such scenario, it would be better to have a merge action triggered for those two smaller
regions r5 and r6 even though either of them is not the smallest one



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