Github user gczsjdy commented on a diff in the pull request:
https://github.com/apache/spark/pull/16476#discussion_r101673768
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
---
@@ -340,3 +341,91 @@ object CaseKeyWhen {
CaseWhen(cases, elseValue)
}
}
+
+/**
+ * A function that returns the index of str in (str1, str2, ...) list or 0
if not found.
+ * It takes at least 2 parameters, and all parameters' types should be
subtypes of AtomicType.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(str, str1, str2, ...) - Returns the index of str in the
str1,str2,... or 0 if not found.",
+ extended = """
+ Examples:
+ > SELECT _FUNC_(10, 9, 3, 10, 4);
+ 3
+ """)
+case class Field(children: Seq[Expression]) extends Expression {
+
+ override def nullable: Boolean = false
+ override def foldable: Boolean = children.forall(_.foldable)
+
+ private lazy val ordering =
TypeUtils.getInterpretedOrdering(children(0).dataType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ if (children.length <= 1) {
+ TypeCheckResult.TypeCheckFailure(s"FIELD requires at least 2
arguments")
+ } else if (!children.forall(_.dataType.isInstanceOf[AtomicType])) {
+ TypeCheckResult.TypeCheckFailure(s"FIELD requires all arguments to
be of AtomicType")
+ } else
+ TypeCheckResult.TypeCheckSuccess
+ }
+
+ override def dataType: DataType = IntegerType
+
+ override def eval(input: InternalRow): Any = {
+ val target = children.head.eval(input)
+ val targetDataType = children.head.dataType
+ def findEqual(target: Any, params: Seq[Expression], index: Int): Int =
{
+ params.toList match {
+ case Nil => 0
+ case head::tail if targetDataType == head.dataType
+ && head.eval(input) != null && ordering.equiv(target,
head.eval(input)) => index
+ case _ => findEqual(target, params.tail, index + 1)
+ }
+ }
+ if(target == null)
+ 0
+ else
+ findEqual(target, children.tail, 1)
+ }
+
+ protected def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ val evalChildren = children.map(_.genCode(ctx))
+ val target = evalChildren(0)
+ val targetDataType = children(0).dataType
+ val rest = evalChildren.drop(1)
+ val restDataType = children.drop(1).map(_.dataType)
+
+ def updateEval(evalWithIndex: ((ExprCode, DataType), Int)): String = {
+ val ((eval, dataType), index) = evalWithIndex
+ s"""
+ ${eval.code}
+ if (${dataType.equals(targetDataType)}
+ && ${ctx.genEqual(targetDataType, eval.value, target.value)}) {
+ ${ev.value} = ${index};
+ }
+ """
+ }
+
+ def genIfElseStructure(code1: String, code2: String): String = {
--- End diff --
For now, I use `reduceRight`, which I think is a 'special case' function of
`foldRight`.
If I understand your meaning of floating `else` right(could you please
explain it a little bit?), these 2 functions both can't avoid floating `else`,
because we need nested `else` in `else` block, like this:
`if (xxx)
else {
if (xxx)
else {
...
}
}
`, so if we avoid floating `else` in `genIfElseStructure`, `else` should be
in `updateEval`, which will make the code unclear and complicated.
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