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Posted to issues@spark.apache.org by "Reynold Xin (JIRA)" <ji...@apache.org> on 2016/11/04 08:51:00 UTC
[jira] [Updated] (SPARK-18000) Aggregation function for computing
endpoints for histograms
[ https://issues.apache.org/jira/browse/SPARK-18000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Reynold Xin updated SPARK-18000:
--------------------------------
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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