Github user viirya commented on a diff in the pull request: https://github.com/apache/spark/pull/16476#discussion_r101515786 --- 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 -- Oh, yeah, right, if use `foldLeft`, there is still a floating `else`. We can only use `foldRight` to remove it.
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