[GitHub] [spark] JoshRosen commented on a change in pull request #24636: [SPARK-27684][SQL] Avoid conversion overhead for primitive types

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JoshRosen commented on a change in pull request #24636: [SPARK-27684][SQL] Avoid conversion overhead for primitive types
URL: https://github.com/apache/spark/pull/24636#discussion_r285347516
 
 

 ##########
 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala
 ##########
 @@ -1003,22 +1003,38 @@ case class ScalaUDF(
     // such as IntegerType, its javaType is `int` and the returned type of user-defined
     // function is Object. Trying to convert an Object to `int` will cause casting exception.
     val evalCode = evals.map(_.code).mkString("\n")
-    val (funcArgs, initArgs) = evals.zipWithIndex.map { case (eval, i) =>
-      val argTerm = ctx.freshName("arg")
-      val convert = s"$convertersTerm[$i].apply(${eval.value})"
-      val initArg = s"Object $argTerm = ${eval.isNull} ? null : $convert;"
-      (argTerm, initArg)
+    val (funcArgs, initArgs) = evals.zipWithIndex.zip(children.map(_.dataType)).map {
+      case ((eval, i), dt) =>
+        val argTerm = ctx.freshName("arg")
+        val initArg = if (CatalystTypeConverters.isPrimitive(dt)) {
+          val convertedTerm = ctx.freshName("conv")
+          s"""
+             |${CodeGenerator.boxedType(dt)} $convertedTerm = ${eval.value};
 
 Review comment:
   Out of curiosity, why do we need this extra `convertedTerm` for the boxing? Could you instead do
   
   ```
   Object $argTerm = ${eval.isNull} ? null : ${eval.value};
   ```
   
   and avoid the use of an extra variable name? Or if you want more typechecking, do
   
   ```
   ${CodeGenerator.boxedType(dt)} $argTerm = ${eval.isNull} ? null : ${eval.value};
   ```
   
   and used the boxed type as `$argTerm`'s type?
   
   To avoid repetition and more tightly scope the conditional part of the argument convert logic, we even might consider something like this
   
   ```scala
   val boxedType = CodeGenerator.boxedType(dt)
   val maybeConverted = if (CatalystTypeConverters.isPrimitive(dt)) {
     eval.value
   } else {
     "$convertersTerm[$i].apply(${eval.value})"
   }
   s"$boxedType $argTerm = ${eval.isNull} ? null : $maybeConverted;"
   ```
   
   

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