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From "Wang, Gang (JIRA)" <>
Subject [jira] [Updated] (KYLIN-2903) support cardinality calculation for Hive view
Date Tue, 19 Dec 2017 11:35:00 GMT


Wang, Gang updated KYLIN-2903:
    Attachment: 0001-KYLIN-2903-support-cardinality-calculation-for-Hive-.patch

Attached it a patch.
One way is to leverage HQL 'COUNT DISTINCT' statement to calculate column cardinality, and
use 'INSERT OVERWRITE DIRECTORY' to put the result in the output path. To make it recognizable
for the following step HiveColumnCardinalityUpdateJob, the output need following the specified
format as following:
column1 cardinality
column2 cardinality
column3 cardinality

And this can be reached as well by setting 'ROW FORMAT DELIMITED' and adding line break in

> support cardinality calculation for Hive view
> ---------------------------------------------
>                 Key: KYLIN-2903
>                 URL:
>             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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