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Posted to issues@kylin.apache.org by "Wang, Gang (JIRA)" <ji...@apache.org> on 2017/12/29 06:25:00 UTC

[jira] [Commented] (KYLIN-2903) Support cardinality calculation for Hive view

    [ https://issues.apache.org/jira/browse/KYLIN-2903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16306028#comment-16306028 ] 

Wang, Gang commented on KYLIN-2903:
-----------------------------------

Sorry for the late response. Since the calculation depends on a MR job, compared with HyperLogLog, it is quite slow. While, the calculation happens on Hive table loading(or manually trigger), usually there is some time before cube building, the duration may be acceptable. Also the the cardinality is pretty valuable for cube builder who has little knowledge of data in the Hive tables.   I think this may be one way.

> Support cardinality calculation for Hive view
> ---------------------------------------------
>
>                 Key: KYLIN-2903
>                 URL: https://issues.apache.org/jira/browse/KYLIN-2903
>             Project: Kylin
>          Issue Type: Improvement
>          Components: Job Engine
>            Reporter: Wang, Gang
>            Assignee: Wang, Gang
>            Priority: Minor
>         Attachments: 0001-KYLIN-2903-support-cardinality-calculation-for-Hive-.patch
>
>
> Currently, Kylin leverage HCatlog to calculate column cardinality for Hive tables. While, HCatlog does not support Hive view actually. 



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