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https://issues.apache.org/jira/browse/HIVE-3421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14161455#comment-14161455
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Lefty Leverenz commented on HIVE-3421:
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It's already documented in the wiki, with a link from the Statistics doc:
* [Column Level Top K Statistics |
https://cwiki.apache.org/confluence/display/Hive/Top+K+Stats]
* [Statistics in Hive -- Scope |
https://cwiki.apache.org/confluence/display/Hive/StatsDev#StatsDev-Scope]
It was hidden under "How to Contribute" so I've just moved it into DesignDocs
(In Progress).
> Column Level Top K Values Statistics
> ------------------------------------
>
> Key: HIVE-3421
> URL: https://issues.apache.org/jira/browse/HIVE-3421
> Project: Hive
> Issue Type: New Feature
> Reporter: Feng Lu
> Assignee: Feng Lu
> Attachments: HIVE-3421.patch.1.txt, HIVE-3421.patch.2.txt,
> HIVE-3421.patch.3.txt, HIVE-3421.patch.4.txt, HIVE-3421.patch.5.txt,
> HIVE-3421.patch.6.txt, HIVE-3421.patch.7.txt, HIVE-3421.patch.8.txt,
> HIVE-3421.patch.9.txt, HIVE-3421.patch.txt
>
>
> Compute (estimate) top k values statistics for each column, and put the most
> skewed column into skewed info, if user hasn't specified skew.
> This feature depends on ListBucketing (create table skewed on)
> https://cwiki.apache.org/Hive/listbucketing.html.
> All column topk can be added to skewed info, if in the future skewed info
> supports multiple independent columns.
> The TopK algorithm is based on this paper:
> http://www.cs.ucsb.edu/research/tech_reports/reports/2005-23.pdf
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