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https://issues.apache.org/jira/browse/KYLIN-2620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16743356#comment-16743356
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KANG-SEN LU commented on KYLIN-2620:
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I am having doubt in this sentence:
"Kylin should check if "ORDER BY col_id LIMIT topncapacity" is present in the
query to determine whether to rewrite."
this sentence should be corrected into:
Kylin should check if "ORDER BY measure LIMIT topncapacity" is present in the
query to determine whether to rewrite.
Am I right?
> 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
> Priority: Major
>
> 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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