[jira] [Assigned] (SPARK-40862) Unexpected operators when rewriting scalar subqueries with non-deterministic expressions

["Apache Spark (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-40862?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-40862:
------------------------------------

    Assignee:     (was: Apache Spark)

> Unexpected operators when rewriting scalar subqueries with non-deterministic expressions
> ----------------------------------------------------------------------------------------
>
>                 Key: SPARK-40862
>                 URL: https://issues.apache.org/jira/browse/SPARK-40862
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 3.4.0
>            Reporter: Allison Wang
>            Priority: Major
>
> Since SPARK-28379, Spark has supported non-aggregated single-row correlated subqueries. SPARK-40800 handles the majority of the cases where projects can be collapsed. But Spark can throw exceptions for single-row subqueries with non-deterministic expressions. For example:
> {code:java}
> CREATE TEMP VIEW t1 AS SELECT ARRAY('a', 'b') a 
> SELECT (
>   SELECT array_sort(a, (i, j) -> rank[i] - rank[j])[0] + r + r AS sorted
>   FROM (SELECT MAP('a', 1, 'b', 2) rank, rand() as r)
> ) FROM t1{code}
> This throws an exception:
> {code:java}
> Unexpected operator Join Inner
> :- Aggregate [[a,b]], [[a,b] AS a#253]
> :  +- OneRowRelation
> +- Project [map(keys: [a,b], values: [1,2]) AS rank#241, rand(86882494013664043) AS r#242]
>    +- OneRowRelation
>  in correlated subquery{code}
> This is because when Spark rewrites correlated subqueries, it checks whether a scalar subquery is subject to the COUNT bug. It splits the query into parts above the aggregate, the aggregate, and the parts below the aggregate (see `splitSubquery` in the `RewriteCorrelatedScalarSubquery` rule). 
> This pattern is very restrictive and does not work well with non-aggregated single-row subqueries. We should fix this issue.



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