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Posted to issues@kylin.apache.org by "nichunen (JIRA)" <ji...@apache.org> on 2019/07/05 14:06:01 UTC

[jira] [Closed] (KYLIN-2620) Check for "ORDER BY LIMIT" clause when rewrite SUM query as TOPN

     [ https://issues.apache.org/jira/browse/KYLIN-2620?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

nichunen closed KYLIN-2620.
---------------------------

Resolved in release 2.6.3

> Check for "ORDER BY LIMIT" clause when rewrite SUM query as TOPN
> ----------------------------------------------------------------
>
>                 Key: KYLIN-2620
>                 URL: https://issues.apache.org/jira/browse/KYLIN-2620
>             Project: Kylin
>          Issue Type: Bug
>          Components: Measure - TopN
>            Reporter: Lin Tingmao
>            Assignee: Chao Long
>            Priority: Major
>             Fix For: v3.0.0, v2.6.3
>
>         Attachments: cube_desc.png, sql.png
>
>
> When running the following query
> select sum(measure) from table group by col_id
> if there exists TOPN(measure, group by col_id)  measure, TopNMeasureType.isTopNCompatibleSum()    will pass, so the SUM is rewritten to TOPN. This confuses the user since they may expect a accurate result for every distinct value of group by column(s). 
> Kylin should check if "ORDER BY col_id LIMIT topncapacity" is present in the query to determine whether to rewrite.



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