Feng Lu created HIVE-3421:
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             Summary: 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


Compute (estimate) top k values for each column, and put the most skewed column 
into skewed info, if user hasn't specified skew.

This feature depends on ListBucketing (create skewed table) 
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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