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https://issues.apache.org/jira/browse/HIVE-16274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15941458#comment-15941458
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Pengcheng Xiong commented on HIVE-16274:
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[~ashutoshc] or [~jdere], could u review it? Thanks.
> Support tuning of NDV of columns using lower/upper bounds
> ---------------------------------------------------------
>
> Key: HIVE-16274
> URL: https://issues.apache.org/jira/browse/HIVE-16274
> Project: Hive
> Issue Type: Bug
> Reporter: Pengcheng Xiong
> Assignee: Pengcheng Xiong
> Attachments: HIVE-16274.01.patch, HIVE-16274.02.patch
>
>
> For partitioned tables, the distinct value (nDV) estimate for a column is by
> default set to the largest nDV value in any of the partitions being
> considered, which is a lower bound on the nDV estimate.
> This provides a config setting to allow the estimate to a specified fraction
> (0.0 - 1.0) of the higher bound on the nDV estimate (the sum of all the nDVs
> in all partitions).
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