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https://issues.apache.org/jira/browse/IMPALA-8759?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Armstrong updated IMPALA-8759:
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Fix Version/s: Impala 3.4.0
> Use double precision for HLL
> ----------------------------
>
> Key: IMPALA-8759
> URL: https://issues.apache.org/jira/browse/IMPALA-8759
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Affects Versions: Impala 3.2.0
> Reporter: Peter Ebert
> Assignee: Wenzhe Zhou
> Priority: Major
> Labels: perf, ramp-up
> Fix For: Impala 3.4.0
>
>
> For /be/src/exprs/aggregate-functions-ir.cc the finalize function uses a
> float which is only capable of 6-9 digits of precision. More accurate
> estimates for larger cardinalities (beyond 999,999) should be possible with
> double precision. Another c++ implementation uses double as well
> [https://github.com/dialtr/libcount]
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