Github user yijieshen commented on a diff in the pull request: https://github.com/apache/spark/pull/6938#discussion_r34000276 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala --- @@ -600,3 +604,146 @@ case class Logarithm(left: Expression, right: Expression) """ } } + +case class Round(child: Expression, scale: Expression) extends Expression with ExpectsInputTypes { + + def this(child: Expression) = { + this(child, Literal(0)) + } + + override def children: Seq[Expression] = Seq(child, scale) + + 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( + // rely on precedence to implicit cast String into Double + TypeCollection(DecimalType, DoubleType, FloatType, LongType, IntegerType, ShortType, ByteType), + TypeCollection(LongType, IntegerType, ShortType, ByteType)) + + override def checkInputDataTypes(): TypeCheckResult = { + child.dataType match { + case _: NumericType => // satisfy requirement + case dt => + return TypeCheckFailure(s"Only numeric type is allowed for ROUND function, got $dt") + } + scale match { + case Literal(value, LongType) => + if (value.asInstanceOf[Long] < Int.MinValue || value.asInstanceOf[Long] > Int.MaxValue) { + return TypeCheckFailure("ROUND scale argument out of allowed range") + } + case _ => + if (scale.dataType.isInstanceOf[IntegralType] && scale.foldable) { + // TODO: How to check out of range for foldable LongType Expression + // satisfy requirement + } else { + return TypeCheckFailure("Only foldable Integral Expression " + + s"is allowed for ROUND scale arguments, got ${child.dataType}") --- End diff -- Yes, you are right, I was hesitate to do `eval` in checkInputDataTypes, therefore, find it hard to check out of range for LongType foldable expressions, and leave it in comment for some guidance. :)
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