Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/6938#discussion_r34404086
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala
---
@@ -520,3 +522,127 @@ case class Logarithm(left: Expression, right:
Expression)
"""
}
}
+
+case class Round(child: Expression, scale: Expression)
+ extends BinaryExpression with ExpectsInputTypes {
+
+ import BigDecimal.RoundingMode.HALF_UP
+
+ def this(child: Expression) = this(child, Literal(0))
+
+ override def left: Expression = child
+ override def right: Expression = scale
+
+ override def children: Seq[Expression] = Seq(child, scale)
+
+ // round of Decimal would eval to null if it fails to `changePrecision`
+ override def nullable: Boolean = true
+
+ override def foldable: Boolean = child.foldable
+
+ override lazy val dataType: DataType = child.dataType match {
+ case DecimalType.Fixed(p, s) => DecimalType(p, _scale)
+ case t => t
+ }
+
+ override def inputTypes: Seq[AbstractDataType] = Seq(NumericType,
IntegerType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ super.checkInputDataTypes() match {
+ case TypeCheckSuccess =>
+ if (scale.foldable) {
+ TypeCheckSuccess
+ } else {
+ TypeCheckFailure("Only foldable Expression is allowed for scale
arguments")
+ }
+ case f => f
+ }
+ }
+
+ private lazy val scaleV = scale.eval(EmptyRow)
+ private lazy val _scale = if (scaleV != null) scaleV.asInstanceOf[Int]
else 0
+
+ protected override def nullSafeEval(input1: Any, input2: Any): Any = {
+ child.dataType match {
+ case _: DecimalType =>
+ val decimal = input1.asInstanceOf[Decimal]
+ if (decimal.changePrecision(decimal.precision, _scale)) decimal
else null
+ case ByteType =>
+ BigDecimal(input1.asInstanceOf[Byte]).setScale(_scale,
HALF_UP).toByte
+ case ShortType =>
+ BigDecimal(input1.asInstanceOf[Short]).setScale(_scale,
HALF_UP).toShort
+ case IntegerType =>
+ BigDecimal(input1.asInstanceOf[Int]).setScale(_scale,
HALF_UP).toInt
+ case LongType =>
+ BigDecimal(input1.asInstanceOf[Long]).setScale(_scale,
HALF_UP).toLong
+ case FloatType =>
+ val f = input1.asInstanceOf[Float]
+ if (f.isNaN || f.isInfinite) {
+ f
+ } else {
+ BigDecimal(f).setScale(_scale, HALF_UP).toFloat
+ }
+ case DoubleType =>
+ val d = input1.asInstanceOf[Double]
+ if (d.isNaN || d.isInfinite) {
+ d
+ } else {
+ BigDecimal(d).setScale(_scale, HALF_UP).toDouble
+ }
+ }
+ }
+
+ override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode):
String = {
+ val ce = child.gen(ctx)
+
+ val evaluationCode = child.dataType match {
--- End diff --
for integral types, can you special case scale <= 0? in those cases, you
can just return the value.
for round, special case scale == 0, which you can just call java math round?
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