[SPARK-12549][SQL] Take Option[Seq[DataType]] in UDF input type specification.

In Spark we allow UDFs to declare its expected input types in order to apply type coercion. The expected input type parameter takes a Seq[DataType] and uses Nil when no type coercion is applied. It makes more sense to take Option[Seq[DataType]] instead, so we can differentiate a no-arg function vs function with no expected input type specified.

Author: Reynold Xin <rxin@databricks.com>

Closes #10504 from rxin/SPARK-12549.

1 files changed, 8 insertions, 4 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala
index 85faa19bbf..64d397bf84 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala
@@ -30,7 +30,10 @@ import org.apache.spark.sql.types.DataType
  *                  null. Use boxed type or [[Option]] if you wanna do the null-handling yourself.
  * @param dataType  Return type of function.
  * @param children  The input expressions of this UDF.
- * @param inputTypes  The expected input types of this UDF.
+ * @param inputTypes  The expected input types of this UDF, used to perform type coercion. If we do
+ *                    not want to perform coercion, simply use "Nil". Note that it would've been
+ *                    better to use Option of Seq[DataType] so we can use "None" as the case for no
+ *                    type coercion. However, that would require more refactoring of the codebase.
  */
 case class ScalaUDF(
     function: AnyRef,
@@ -43,7 +46,7 @@ case class ScalaUDF(
 
   override def toString: String = s"UDF(${children.mkString(",")})"
 
-  // scalastyle:off
+  // scalastyle:off line.size.limit
 
   /** This method has been generated by this script
 
@@ -969,7 +972,7 @@ case class ScalaUDF(
       }
   }
 
-  // scalastyle:on
+  // scalastyle:on line.size.limit
 
   // Generate codes used to convert the arguments to Scala type for user-defined funtions
   private[this] def genCodeForConverter(ctx: CodeGenContext, index: Int): String = {
@@ -1010,7 +1013,7 @@ case class ScalaUDF(
 
     // This must be called before children expressions' codegen
     // because ctx.references is used in genCodeForConverter
-    val converterTerms = (0 until children.size).map(genCodeForConverter(ctx, _))
+    val converterTerms = children.indices.map(genCodeForConverter(ctx, _))
 
     // Initialize user-defined function
     val funcClassName = s"scala.Function${children.size}"
@@ -1054,5 +1057,6 @@ case class ScalaUDF(
   }
 
   private[this] val converter = CatalystTypeConverters.createToCatalystConverter(dataType)
+
   override def eval(input: InternalRow): Any = converter(f(input))
 }