Gopal V created HIVE-7402:
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Summary: 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
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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