Github user wangyum commented on a diff in the pull request:
https://github.com/apache/spark/pull/22419#discussion_r218749189
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala
---
@@ -1245,3 +1245,80 @@ 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 {
+
+ def this(number: Expression) = this(number, Literal(0))
+
+ override def left: Expression = number
+ override def right: Expression = scale
+
+ override def inputTypes: Seq[AbstractDataType] =
+ Seq(TypeCollection(DoubleType, FloatType, DecimalType), IntegerType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ super.checkInputDataTypes() match {
+ case TypeCheckSuccess =>
+ if (scale.foldable) {
--- End diff --
Same to `RoundBase`. only support foldable:
https://github.com/apache/spark/blob/c7156943a2a32ba57e67aa6d8fa7035a09847e07/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala#L1076
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