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Posted to issues@kylin.apache.org by "Prashant Prakash (JIRA)" <ji...@apache.org> on 2016/01/12 04:36:39 UTC

[jira] [Updated] (KYLIN-1304) Incorrect count estimate upon HyperLogLogPlusCounter.merge operation.

     [ https://issues.apache.org/jira/browse/KYLIN-1304?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Prashant Prakash updated KYLIN-1304:
------------------------------------
    Attachment: registers.txt

Attaching HyperLogLogPlusCounter.registers as test input.

> Incorrect count estimate upon HyperLogLogPlusCounter.merge operation.
> ---------------------------------------------------------------------
>
>                 Key: KYLIN-1304
>                 URL: https://issues.apache.org/jira/browse/KYLIN-1304
>             Project: Kylin
>          Issue Type: Bug
>    Affects Versions: v1.1.1
>            Reporter: Prashant Prakash
>         Attachments: registers.txt
>
>
> We are using hllc12 for evaluating uniques for a measure in a table partitioned over date.
> The uniques estimate for individual dates 2016-01-07, 2016-01-08, 2016-01-09 are 93,728,324, 90,982,364, 45,485,278 respectively. 
> But the uniques across days, which is calculated through HyperLogLogPlusCounter.merge operation gives a incorrect value 67,980,576. 



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