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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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Zhenhua Wang updated SPARK-18000:
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Summary: Aggregation function for computing endpoints for histograms (was:
Aggregation function for computing endpoints for numeric histograms)
> Aggregation function for computing endpoints for histograms
> -----------------------------------------------------------
>
> Key: SPARK-18000
> URL: https://issues.apache.org/jira/browse/SPARK-18000
> Project: Spark
> Issue Type: New Feature
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Zhenhua Wang
>
> For a column of numeric type (including date and timestamp), 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).
> This agg function computes values and their frequencies using a small
> hashmap, whose size is less than or equal to "numBins", and returns an
> equi-width histogram.
> When the size of hashmap exceeds "numBins", it cleans the hashmap and
> utilizes ApproximatePercentile to return endpoints of equi-height histogram.
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