Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/6851#discussion_r35832525
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionals.scala
---
@@ -312,3 +313,103 @@ case class CaseKeyWhen(key: Expression, branches:
Seq[Expression]) extends CaseW
}.mkString
}
}
+
+case class Least(children: Seq[Expression]) extends Expression {
+ require(children.length > 1, "LEAST requires at least 2 arguments, got "
+ children.length)
+
+ override def nullable: Boolean = children.forall(_.nullable)
+ override def foldable: Boolean = children.forall(_.foldable)
+
+ private lazy val ordering = TypeUtils.getOrdering(dataType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ if (children.map(_.dataType).distinct.count(_ != NullType) > 1) {
+ TypeCheckResult.TypeCheckFailure(
+ s"The expressions should all have the same type," +
+ s" got LEAST (${children.map(_.dataType)}).")
+ } else {
+ TypeUtils.checkForOrderingExpr(dataType, "function " + prettyName)
+ }
+ }
+
+ override def dataType: DataType = children.head.dataType
+
+ override def eval(input: InternalRow): Any = {
+ children.foldLeft[Any](null)((r, c) => {
+ val evalc = c.eval(input)
+ if (evalc != null) {
+ if (r == null || ordering.lt(evalc, r)) evalc else r
+ } else {
+ r
+ }
+ })
+ }
+
+ override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode):
String = {
+ val evalChildren = children.map(_.gen(ctx))
+ def updateEval(i: Int): String =
+ s"""
+ if (!${evalChildren(i).isNull} && (${ev.isNull} ||
+ ${ctx.genComp(dataType, evalChildren(i).primitive,
ev.primitive)} < 0)) {
+ ${ev.isNull} = false;
+ ${ev.primitive} = ${evalChildren(i).primitive};
+ }
+ """
+ s"""
+ ${evalChildren.map(_.code).mkString("\n")}
+ boolean ${ev.isNull} = true;
+ ${ctx.javaType(dataType)} ${ev.primitive} =
${ctx.defaultValue(dataType)};
+ ${(0 until children.length).map(updateEval).mkString("\n")}
+ """
+ }
+}
+
+case class Greatest(children: Seq[Expression]) extends Expression {
+ require(children.length > 1, "GREATEST requires at least 2 arguments,
got " + children.length)
+
+ override def nullable: Boolean = children.forall(_.nullable)
+ override def foldable: Boolean = children.forall(_.foldable)
+
+ private lazy val ordering = TypeUtils.getOrdering(dataType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ if (children.map(_.dataType).distinct.count(_ != NullType) > 1) {
--- End diff --
i think the problem is that null literals are not converted into any
non-null type when it happens in greatest.
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