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https://issues.apache.org/jira/browse/HIVE-7402?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gopal V resolved HIVE-7402.
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Resolution: Duplicate
> add `approx_distinct` & composable nDV UDAFs
> --------------------------------------------
>
> Key: HIVE-7402
> URL: https://issues.apache.org/jira/browse/HIVE-7402
> Project: Hive
> Issue Type: New Feature
> Reporter: Gopal V
> Priority: Major
>
> Build composable approximate distinct UDAFs into hive.
> This is useful for approximate queries, particularly for collapsing partial
> nDV values whenever a partition is added.
> {code}
> hive> select approx_distinct(ss_item_sk), approx_distinct(ss_quantity) from
> tpcds_orc_10000.store_sales;
> OK
> 403760 100
> Time taken: 238.258 seconds, Fetched: 1 row(s)
> {code}
> Prototype hive UDAF/UDFs at https://github.com/t3rmin4t0r/hive-hll-udf/
> Uses [~prasanth_j]'s fast HLL++ impl for the horsepower.
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