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https://issues.apache.org/jira/browse/SPARK-38531?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-38531:
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Assignee: Apache Spark
> "Prune unrequired child index" branch of ColumnPruning has wrong condition
> --------------------------------------------------------------------------
>
> Key: SPARK-38531
> URL: https://issues.apache.org/jira/browse/SPARK-38531
> Project: Spark
> Issue Type: Bug
> Components: Optimizer
> Affects Versions: 3.2.1
> Reporter: Min Yang
> Assignee: Apache Spark
> Priority: Minor
>
> The "prune unrequired references" branch has the condition:
> {code:java}
> case p @ Project(_, g: Generate) if p.references != g.outputSet => {code}
> This is wrong as generators like Inline will always enter this branch as long
> as it does not use all the generator output.
>
> Example:
>
> input: <col1: array<struct<a: struct<a: int, b: int>, b: int>>>
>
> Project(a.a as x)
> - Generate(Inline(col1), ..., a, b)
>
> p.references is [a]
> g.outputSet is [a, b]
>
> This bug makes us never enter the GeneratorNestedColumnAliasing branch below
> thus miss some optimization opportunities. The condition should be
> {code:java}
> g.requiredChildOutput.contains(!p.references.contains(_)) {code}
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