Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/16476#discussion_r95080769
--- 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 {
--- End diff --
`toList` probably causes performance overhead, I don't think we have to
sacrifice the performance for using the pattern match. In the meantime, I still
believe we don't have to check the data type during the runtime. It's supposed
to be done during the `compile` time or only done once for the first time in
`eval`.
The `Field` evaluation is quite confusing, as @gatorsmile suggested, we
need to describe how to evaluate the value when sub expressions' data type are
different.
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