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https://issues.apache.org/jira/browse/SPARK-18000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Reynold Xin updated SPARK-18000:
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Issue Type: Sub-task (was: New Feature)
Parent: SPARK-16026
> Aggregation function for computing endpoints for histograms
> -----------------------------------------------------------
>
> Key: SPARK-18000
> URL: https://issues.apache.org/jira/browse/SPARK-18000
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Zhenhua Wang
>
> For a column, we will generate a equi-width or equi-height histogram,
> depending on if its ndv is large than the maximum number of bins allowed in
> one histogram (denoted as numBins).
> The agg function for a column returns bins - (distinct value, frequency)
> pairs of equi-width histogram when the number of distinct values is less than
> or equal to numBins. Otherwise, 1) for column of string type, it returns an
> empty map; 2) for column of numeric type (including DateType and
> TimestampType), it returns endpoints of equi-height histogram - approximate
> percentiles at percentages 0.0, 1/numBins, 2/numBins, ...,
> (numBins-1)/numBins, 1.0.
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