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From "xiaodongzhang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (KYLIN-3883) Kylin supports column count aggregation
Date Mon, 18 Mar 2019 05:55:00 GMT
xiaodongzhang created KYLIN-3883:
------------------------------------

             Summary: Kylin supports column count aggregation
                 Key: KYLIN-3883
                 URL: https://issues.apache.org/jira/browse/KYLIN-3883
             Project: Kylin
          Issue Type: New Feature
          Components: Job Engine
    Affects Versions: all
            Reporter: xiaodongzhang
            Assignee: xiaodongzhang
             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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