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https://issues.apache.org/jira/browse/SPARK-19350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15837081#comment-15837081
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Apache Spark commented on SPARK-19350:
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User 'wzhfy' has created a pull request for this issue:
https://github.com/apache/spark/pull/16696
> Cardinality estimation of Limit and Sample
> ------------------------------------------
>
> Key: SPARK-19350
> URL: https://issues.apache.org/jira/browse/SPARK-19350
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Zhenhua Wang
>
> Currently, LocalLimit/GlobalLimit/Sample propagates the same row count and
> column stats from its child, which is incorrect.
> We can get the correct rowCount in Statistics for Limit/Sample whether cbo is
> enabled or not. And column stats should not be propagated because we don't
> know the distribution of columns after Limit or Sample.
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