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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2017/01/25 02:58:27 UTC

[jira] [Commented] (SPARK-19350) Cardinality estimation of Limit and Sample

    [ https://issues.apache.org/jira/browse/SPARK-19350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15837081#comment-15837081 ] 

Apache Spark commented on SPARK-19350:
--------------------------------------

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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