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

[Lin Tingmao (JIRA)]

Lin Tingmao created KYLIN-2620:
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             Summary: 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
            Reporter: Lin Tingmao


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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