[GitHub] spark pull request #15693: [SPARK-18125][SQL] Fix a compilation error in cod...

[hvanhovell <gi...@git.apache.org>]

Github user hvanhovell commented on a diff in the pull request:

    https://github.com/apache/spark/pull/15693#discussion_r86601596
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ReferenceToExpressions.scala ---
    @@ -63,15 +63,33 @@ case class ReferenceToExpressions(result: Expression, children: Seq[Expression])
     
       override protected def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
         val childrenGen = children.map(_.genCode(ctx))
    -    val childrenVars = childrenGen.zip(children).map {
    -      case (childGen, child) => LambdaVariable(childGen.value, childGen.isNull, child.dataType)
    -    }
    +    val (childrenVars, classChildrenVars) = childrenGen.zip(children).map {
    +      case (childGen, child) =>
    +        val childVar = LambdaVariable(childGen.value, childGen.isNull, child.dataType)
    +
    +        // SPARK-18125: The children vars are local variables. If the result expression uses
    +        // splitExpression, those variables cannot be accessed so compilation fails.
    +        // To fix it, we use class variables to hold those local variables.
    +        val classChildVarName = ctx.freshName("classChildVar")
    +        val classChildVarIsNull = ctx.freshName("classChildVarIsNull")
    +        ctx.addMutableState(ctx.javaType(childVar.dataType), classChildVarName, "")
    +        ctx.addMutableState("boolean", classChildVarIsNull, "")
    +        val classChildVar =
    +          LambdaVariable(classChildVarName, classChildVarIsNull, childVar.dataType)
    +
    +        (childVar, classChildVar)
    +    }.unzip
    +
    +    val initClassChildrenVars = classChildrenVars.zipWithIndex.map { case (classChildrenVar, i) =>
    --- End diff --
    
    Why not generate this code in the previous block?


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