Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/6938#discussion_r34648756
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala
---
@@ -520,3 +522,204 @@ case class Logarithm(left: Expression, right:
Expression)
"""
}
}
+
+/**
+ * Round the `child`'s result to `scale` decimal place when `scale` >= 0
+ * or round at integral part when `scale` < 0.
+ * For example, round(31.415, 2) would eval to 31.42 and round(31.415, -1)
would eval to 30.
+ *
+ * Child of IntegralType would eval to itself when `scale` >= 0.
+ * Child of FractionalType whose value is NaN or Infinite would always
eval to itself.
+ *
+ * Round's dataType would always equal to `child`'s dataType except for
[[DecimalType.Fixed]],
+ * which leads to scale update in DecimalType's [[PrecisionInfo]]
+ *
+ * @param child expr to be round, all [[NumericType]] is allowed as Input
+ * @param scale new scale to be round to, this should be a constant int at
runtime
+ */
+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)
--- End diff --
i don't think you need this
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