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Posted to issues@spark.apache.org by "Nattavut Sutyanyong (JIRA)" <ji...@apache.org> on 2016/08/06 16:24:20 UTC
[jira] [Commented] (SPARK-16804) Correlated subqueries containing
non-deterministic operators return incorrect results
[ https://issues.apache.org/jira/browse/SPARK-16804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15410651#comment-15410651 ]
Nattavut Sutyanyong commented on SPARK-16804:
---------------------------------------------
The PR also extends the fix to block the {{TABLESAMPLE}} operation in any correlated subquery.
> Correlated subqueries containing non-deterministic operators return incorrect results
> -------------------------------------------------------------------------------------
>
> Key: SPARK-16804
> URL: https://issues.apache.org/jira/browse/SPARK-16804
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Nattavut Sutyanyong
> Original Estimate: 72h
> Remaining Estimate: 72h
>
> Correlated subqueries with LIMIT could return incorrect results. The rule ResolveSubquery in the Analysis phase moves correlated predicates to a join predicates and neglect the semantic of the LIMIT.
> Example:
> {noformat}
> Seq(1, 2).toDF("c1").createOrReplaceTempView("t1")
> Seq(1, 2).toDF("c2").createOrReplaceTempView("t2")
> sql("select c1 from t1 where exists (select 1 from t2 where t1.c1=t2.c2 LIMIT 1)").show
> +---+
> | c1|
> +---+
> | 1|
> +---+
> {noformat}
> The correct result contains both rows from T1.
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