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Posted to issues@kylin.apache.org by "xiaodongzhang (JIRA)" <ji...@apache.org> on 2019/03/18 05:55:00 UTC

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

xiaodongzhang created KYLIN-3883:
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             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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