[SPARK-31594][SQL] Do not display the seed of rand/randn with no argument in output schema

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/randomExpressions.scala

@@ -83,9 +83,12 @@ trait ExpressionWithRandomSeed {
   """,
   since = "1.5.0")
 // scalastyle:on line.size.limit
-case class Rand(child: Expression) extends RDG with ExpressionWithRandomSeed {
+case class Rand(child: Expression, hideSeed: Boolean = false)
+  extends RDG with ExpressionWithRandomSeed {
 
-  def this() = this(Literal(Utils.random.nextLong(), LongType))
+  def this() = this(Literal(Utils.random.nextLong(), LongType), true)
+
+  def this(child: Expression) = this(child, false)
 
   override def withNewSeed(seed: Long): Rand = Rand(Literal(seed, LongType))
 
@@ -101,7 +104,12 @@ case class Rand(child: Expression) extends RDG with ExpressionWithRandomSeed {
       isNull = FalseLiteral)
   }
 
-  override def freshCopy(): Rand = Rand(child)
+  override def freshCopy(): Rand = Rand(child, hideSeed)
+
+  override def flatArguments: Iterator[Any] = Iterator(child)
+  override def sql: String = {
+    s"rand(${if (hideSeed) "" else child.sql})"
+  }
 }
 
 object Rand {
@@ -126,9 +134,12 @@ object Rand {
   """,
   since = "1.5.0")
 // scalastyle:on line.size.limit
-case class Randn(child: Expression) extends RDG with ExpressionWithRandomSeed {
+case class Randn(child: Expression, hideSeed: Boolean = false)
+  extends RDG with ExpressionWithRandomSeed {
 
-  def this() = this(Literal(Utils.random.nextLong(), LongType))
+  def this() = this(Literal(Utils.random.nextLong(), LongType), true)
+
+  def this(child: Expression) = this(child, false)
 
   override def withNewSeed(seed: Long): Randn = Randn(Literal(seed, LongType))
 
@@ -144,7 +155,12 @@ case class Randn(child: Expression) extends RDG with ExpressionWithRandomSeed {
       isNull = FalseLiteral)
   }
 
-  override def freshCopy(): Randn = Randn(child)
+  override def freshCopy(): Randn = Randn(child, hideSeed)
+
+  override def flatArguments: Iterator[Any] = Iterator(child)
+  override def sql: String = {
+    s"randn(${if (hideSeed) "" else child.sql})"
+  }
 }
 
 object Randn {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/RandomSuite.scala

@@ -34,4 +34,11 @@ class RandomSuite extends SparkFunSuite with ExpressionEvalHelper {
     checkEvaluation(Rand(5419823303878592871L), 0.7145363364564755)
     checkEvaluation(Randn(5419823303878592871L), 0.7816815274533012)
   }
+
+  test("SPARK-31594: Do not display the seed of rand/randn with no argument in output schema") {
+    assert(Rand(Literal(1L), true).sql === "rand()")
+    assert(Randn(Literal(1L), true).sql === "randn()")
+    assert(Rand(Literal(1L), false).sql === "rand(1L)")
+    assert(Randn(Literal(1L), false).sql === "randn(1L)")
+  }
 }

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

@@ -3425,6 +3425,29 @@ class SQLQuerySuite extends QueryTest with SharedSparkSession with AdaptiveSpark
       assert(SQLConf.get.getConf(SQLConf.CODEGEN_FALLBACK) === true)
     }
   }
+
+  test("SPARK-31594: Do not display the seed of rand/randn with no argument in output schema") {
+    def checkIfSeedExistsInExplain(df: DataFrame): Unit = {
+      val output = new java.io.ByteArrayOutputStream()
+      Console.withOut(output) {
+        df.explain()
+      }
+      val projectExplainOutput = output.toString.split("\n").find(_.contains("Project")).get
+      assert(projectExplainOutput.matches(""".*randn?\(-?[0-9]+\).*"""))
+    }
+    val df1 = sql("SELECT rand()")
+    assert(df1.schema.head.name === "rand()")
+    checkIfSeedExistsInExplain(df1)
+    val df2 = sql("SELECT rand(1L)")
+    assert(df2.schema.head.name === "rand(1)")
+    checkIfSeedExistsInExplain(df2)
+    val df3 = sql("SELECT randn()")
+    assert(df3.schema.head.name === "randn()")
+    checkIfSeedExistsInExplain(df1)
+    val df4 = sql("SELECT randn(1L)")
+    assert(df4.schema.head.name === "randn(1)")
+    checkIfSeedExistsInExplain(df2)
+  }
 }
 
 case class Foo(bar: Option[String])