Github user bomeng commented on a diff in the pull request:
https://github.com/apache/spark/pull/12373#discussion_r59659273
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/nullExpressions.scala
---
@@ -128,6 +128,58 @@ case class IsNaN(child: Expression) extends
UnaryExpression
}
/**
+ * An Expression accepts two parameters and returns null if both
parameters are equal.
+ * If they are not equal, the first parameter value is returned.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(a,b) - Returns null if a equals to b, or a otherwise.")
+case class NullIf(left: Expression, right: Expression) extends
BinaryExpression {
+ override def nullable: Boolean = true
+ override def dataType: DataType = left.dataType
+
+ override def eval(input: InternalRow): Any = {
+ val valueLeft = left.eval(input)
+ val valueRight = right.eval(input)
+ if (valueLeft.equals(valueRight)) {
+ null
+ } else {
+ valueLeft
+ }
+ }
+
+ override def genCode(ctx: CodegenContext, ev: ExprCode): String = {
+ val leftGen = left.gen(ctx)
+ val rightGen = right.gen(ctx)
+ dataType match {
--- End diff --
Thanks, @viirya ! That simplifies the logic!
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