Github user ueshin commented on a diff in the pull request:
https://github.com/apache/spark/pull/22419#discussion_r218531021
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala
---
@@ -1245,3 +1245,65 @@ case class BRound(child: Expression, scale:
Expression)
with Serializable with ImplicitCastInputTypes {
def this(child: Expression) = this(child, Literal(0))
}
+
+/**
+ * The number truncated to scale decimal places.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "_FUNC_(number, scale) - Returns number truncated to scale
decimal places. " +
+ "If scale is omitted, then number is truncated to 0 places. " +
+ "scale can be negative to truncate (make zero) scale digits left of
the decimal point.",
+ examples = """
+ Examples:
+ > SELECT _FUNC_(1234567891.1234567891, 4);
+ 1234567891.1234
+ > SELECT _FUNC_(1234567891.1234567891, -4);
+ 1234560000
+ > SELECT _FUNC_(1234567891.1234567891);
+ 1234567891
+ """)
+// scalastyle:on line.size.limit
+case class Truncate(number: Expression, scale: Expression)
+ extends BinaryExpression with ImplicitCastInputTypes {
+
+ override def left: Expression = number
+ override def right: Expression = scale
+
+ override def inputTypes: Seq[AbstractDataType] =
+ Seq(TypeCollection(DoubleType, DecimalType), IntegerType)
+
+ override def dataType: DataType = left.dataType
+
+ private lazy val foldableTruncScale: Int = scale.eval().asInstanceOf[Int]
+
+ protected override def nullSafeEval(input1: Any, input2: Any): Any = {
+ val truncScale = if (scale.foldable) {
+ foldableTruncScale
+ } else {
+ scale.eval().asInstanceOf[Int]
+ }
+ number.dataType match {
+ case DoubleType => MathUtils.trunc(input1.asInstanceOf[Double],
truncScale)
+ case DecimalType.Fixed(_, _) =>
+ MathUtils.trunc(input1.asInstanceOf[Decimal].toJavaBigDecimal,
truncScale)
--- End diff --
I guess we have to return `Decimal` instead of `java.math.BigDecimal`?
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