0-args Java UDF should not be called only once

Author: HyukjinKwon

sql/core/src/main/scala/org/apache/spark/sql/UDFRegistration.scala

@@ -142,16 +142,16 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
       val anyCast = s".asInstanceOf[UDF$i[$anyTypeArgs]]"
       val anyParams = (1 to i).map(_ => "_: Any").mkString(", ")
       val version = if (i == 0) "2.3.0" else "1.3.0"
-      val funcCall = if (i == 0) "() => func" else "func"
+      val funcCall = if (i == 0) s"() => f$anyCast.call($anyParams)" else s"f$anyCast.call($anyParams)"
       println(s"""
         |/**
         | * Register a deterministic Java UDF$i instance as user-defined function (UDF).
         | * @since $version
         | */
         |def register(name: String, f: UDF$i[$extTypeArgs], returnType: DataType): Unit = {
-        |  val func = f$anyCast.call($anyParams)
+        |  val func = $funcCall
         |  def builder(e: Seq[Expression]) = if (e.length == $i) {
-        |    ScalaUDF($funcCall, returnType, e, e.map(_ => false), udfName = Some(name))
+        |    ScalaUDF(func, returnType, e, e.map(_ => false), udfName = Some(name))
         |  } else {
         |    throw new AnalysisException("Invalid number of arguments for function " + name +
         |      ". Expected: $i; Found: " + e.length)
@@ -717,9 +717,9 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
    * @since 2.3.0
    */
   def register(name: String, f: UDF0[_], returnType: DataType): Unit = {
-    val func = f.asInstanceOf[UDF0[Any]].call()
+    val func = () => f.asInstanceOf[UDF0[Any]].call()
     def builder(e: Seq[Expression]) = if (e.length == 0) {
-      ScalaUDF(() => func, returnType, e, e.map(_ => false), udfName = Some(name))
+      ScalaUDF(func, returnType, e, e.map(_ => false), udfName = Some(name))
     } else {
       throw new AnalysisException("Invalid number of arguments for function " + name +
         ". Expected: 0; Found: " + e.length)

sql/core/src/main/scala/org/apache/spark/sql/functions.scala

@@ -3932,7 +3932,7 @@ object functions {
     val anyTypeArgs = (0 to i).map(_ => "Any").mkString(", ")
     val anyCast = s".asInstanceOf[UDF$i[$anyTypeArgs]]"
     val anyParams = (1 to i).map(_ => "_: Any").mkString(", ")
-    val funcCall = if (i == 0) "() => func" else "func"
+    val funcCall = if (i == 0) s"() => f$anyCast.call($anyParams)" else s"f$anyCast.call($anyParams)"
     println(s"""
       |/**
       | * Defines a Java UDF$i instance as user-defined function (UDF).
@@ -3944,8 +3944,8 @@ object functions {
       | * @since 2.3.0
       | */
       |def udf(f: UDF$i[$extTypeArgs], returnType: DataType): UserDefinedFunction = {
-      |  val func = f$anyCast.call($anyParams)
-      |  SparkUserDefinedFunction($funcCall, returnType, inputSchemas = Seq.fill($i)(None))
+      |  val func = $funcCall
+      |  SparkUserDefinedFunction(func, returnType, inputSchemas = Seq.fill($i)(None))
       |}""".stripMargin)
   }
 
@@ -4145,8 +4145,8 @@ object functions {
    * @since 2.3.0
    */
   def udf(f: UDF0[_], returnType: DataType): UserDefinedFunction = {
-    val func = f.asInstanceOf[UDF0[Any]].call()
-    SparkUserDefinedFunction(() => func, returnType, inputSchemas = Seq.fill(0)(None))
+    val func = () => f.asInstanceOf[UDF0[Any]].call()
+    SparkUserDefinedFunction(func, returnType, inputSchemas = Seq.fill(0)(None))
   }
 
   /**

sql/core/src/test/scala/org/apache/spark/sql/UDFSuite.scala

@@ -514,4 +514,13 @@ class UDFSuite extends QueryTest with SharedSQLContext {
       assert(df.collect().toSeq === Seq(Row(expected)))
     }
   }
+
+  test("SPARK-28321 0-args Java UDF should not be called only once") {
+    val nonDeterministicJavaUDF = udf(
+      new UDF0[Int] {
+        override def call(): Int = scala.util.Random.nextInt()
+      }, IntegerType).asNondeterministic()
+
+    assert(spark.range(2).select(nonDeterministicJavaUDF()).distinct().count() == 2)
+  }
 }