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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9815) Add Histogram representative of row key distribution inside a region.
Date Tue, 22 Oct 2013 01:45:43 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801394#comment-13801394

Lars Hofhansl commented on HBASE-9815:

[~jesse_yates], FYI.

> Add Histogram representative of row key distribution inside a region.
> ---------------------------------------------------------------------
>                 Key: HBASE-9815
>                 URL: https://issues.apache.org/jira/browse/HBASE-9815
>             Project: HBase
>          Issue Type: New Feature
>          Components: HFile
>    Affects Versions: 0.89-fb
>            Reporter: Manukranth Kolloju
>            Assignee: Manukranth Kolloju
>             Fix For: 0.89-fb
> Using histogram information, users can parallelize the scan workload into equal sized
scans based on the estimated size from the Histogram information. This will help in enabling
systems which are trying to perform queries on top of HBase to do cost based optimization
while scanning. The Idea is to keep this histogram information into the HFile in the trailer
and populate this on compaction and/or flush. 
> The HRegionInterface can expose an API to return the Histogram information of a region,
which can be generated by merging histograms of all the hfiles.
> Implementing the histogram on the basis of 
> http://jmlr.org/papers/volume11/ben-haim10a/ben-haim10a.pdf
> http://dl.acm.org/citation.cfm?id=1951376
> and NumericHistogram from hive.

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