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https://issues.apache.org/jira/browse/IMPALA-15189?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Quanlong Huang resolved IMPALA-15189.
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Fix Version/s: Impala 5.0.0
Resolution: Fixed
> HBO for computing SortNode cardinality
> --------------------------------------
>
> Key: IMPALA-15189
> URL: https://issues.apache.org/jira/browse/IMPALA-15189
> Project: IMPALA
> Issue Type: New Feature
> Reporter: Quanlong Huang
> Assignee: Quanlong Huang
> Priority: Major
> Fix For: Impala 5.0.0
>
>
> A sort only reorders rows, so its output row count equals its child's
> *unless* it applies a limit: TopN, Partitioned TopN, or a total sort carrying
> a LIMIT.
> For instance, the SortNode created for the following analytic function is a
> Partitioned TopN:
> {code:sql}
> select ..., rank() over (partition by a order by b) rnk ... where rnk <
> 5"{code}
> Its output cardinality depends on the distinct number of column a and the
> per-partition limit 5.
> HBO should track cardinality for SortNodes when they are not
> cardinality-preserving.
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