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Posted to issues@kylin.apache.org by "nichunen (Jira)" <ji...@apache.org> on 2019/12/20 05:39:00 UTC

[jira] [Commented] (KYLIN-3883) Kylin supports column count aggregation

    [ https://issues.apache.org/jira/browse/KYLIN-3883?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17000631#comment-17000631 ] 

nichunen commented on KYLIN-3883:
---------------------------------

Resolved in release 3.0.0(2019-12-20)

> Kylin supports column count aggregation
> ---------------------------------------
>
>                 Key: KYLIN-3883
>                 URL: https://issues.apache.org/jira/browse/KYLIN-3883
>             Project: Kylin
>          Issue Type: New Feature
>          Components: Query Engine
>    Affects Versions: all
>            Reporter: xiaodongzhang
>            Assignee: xiaodongzhang
>            Priority: Major
>             Fix For: v3.0.0
>
>
> Kylin目前只支持对常量1进行count聚合预计算，即count(1)，count(col_1)的查询内部全部重写到对count(1)的查询，这样会导致一个问题：当col_1列中存在null值时，count(col_1)的查询结果并不准确。这样就导致Kylin的查询结果和Hive、Spark等不一致。该Patch中，提供了对count(col_1)的支持。



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