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Posted to issues-all@impala.apache.org by "Gabor Kaszab (Jira)" <ji...@apache.org> on 2020/07/07 14:13:00 UTC
[jira] [Closed] (IMPALA-9632) Implement ds_hll_sketch() and
ds_hll_estimate() functions
[ https://issues.apache.org/jira/browse/IMPALA-9632?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Gabor Kaszab closed IMPALA-9632.
--------------------------------
Resolution: Fixed
https://gerrit.cloudera.org/#/c/16000/
> Implement ds_hll_sketch() and ds_hll_estimate() functions
> ---------------------------------------------------------
>
> Key: IMPALA-9632
> URL: https://issues.apache.org/jira/browse/IMPALA-9632
> Project: IMPALA
> Issue Type: New Feature
> Components: Backend, Frontend
> Reporter: Gabor Kaszab
> Assignee: Gabor Kaszab
> Priority: Major
>
> These should be built-in functions that use DataSketches functionality that was integrated by IMPALA-9631.
> ds_hll_sketch() should receive a primitive expression and return a sketch.
> ds_hll_estimate() should receive a sketch and return a primitive that is the cardinality estimate for that set of data provided to the sketch.
> Usage:
> select ds_hll_estimate(ds_hll_sketch(col_name)) from table_name;
> Returns a cardinality estimate (similarly to ndv() ) for that particular column.
> Hive change that introduced the same: https://issues.apache.org/jira/browse/HIVE-22940
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