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Posted to issues@impala.apache.org by "Fucun Chu (Jira)" <ji...@apache.org> on 2020/10/24 02:29:00 UTC
[jira] [Created] (IMPALA-10282) Implement ds_cpc_sketch() and
ds_cpc_estimate() functions
Fucun Chu created IMPALA-10282:
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Summary: Implement ds_cpc_sketch() and ds_cpc_estimate() functions
Key: IMPALA-10282
URL: https://issues.apache.org/jira/browse/IMPALA-10282
Project: IMPALA
Issue Type: New Feature
Components: Backend, Frontend
Reporter: Fucun Chu
Assignee: Fucun Chu
These should be built-in functions that use DataSketches functionality that was integrated by [IMPALA-1027|https://issues.apache.org/jira/browse/IMPALA-10279].
ds_cpc_sketch() should receive a primitive expression and return a sketch in string type (or binary once that work is submitted).
ds_cpc_estimate() should receive a sketch and return an estimate of unique count from a given CpcSketch.
Usage:
select ds_cpc_estimate(ds_cpc_sketch(col_name)) from table_name;
Hive change that introduced the same:
https://issues.apache.org/jira/browse/HIVE-22940
Some further examples found here:
[http://datasketches.apache.org/docs/CPC/CpcCppExample.html]
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