[jira] [Created] (SPARK-38531) "Prune unrequired child index" branch of ColumnPruning has wrong condition

["Min Yang (Jira)" <ji...@apache.org>]

Min Yang created SPARK-38531:
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             Summary: "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


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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