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https://issues.apache.org/jira/browse/TRAFODION-2758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16190494#comment-16190494
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ASF GitHub Bot commented on TRAFODION-2758:
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Github user asfgit closed the pull request at:
https://github.com/apache/incubator-trafodion/pull/1250
> Sort operator that uses TopN sort at runtime is not accurately determined at
> compile time
> -----------------------------------------------------------------------------------------
>
> Key: TRAFODION-2758
> URL: https://issues.apache.org/jira/browse/TRAFODION-2758
> Project: Apache Trafodion
> Issue Type: Bug
> Components: sql-cmp
> Affects Versions: 2.2-incubating
> Reporter: Suresh Subbiah
> Assignee: Suresh Subbiah
> Priority: Minor
>
> When a query has FIRST N clause along with an ORDER BY, the resultannt Sort
> operator is enable to do TopN optimization. The compiler needs to be aware of
> this so that memory can be shared appropriately between all big memory
> operators in the query. There are some flaws in the logic the compiler is
> using to determine if a sort is TopN enabled. Currently the compiler thinks
> all sort operators in the FirstN query are TopN enabled. This is incorrect,
> only the first Sort, when traversing the query tree downwards from FirstN
> will be enabled for this optimization, and that too with certain restrictions.
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