Github user gczsjdy commented on a diff in the pull request:
https://github.com/apache/spark/pull/16476#discussion_r106334083
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
---
@@ -340,3 +343,105 @@ object CaseKeyWhen {
CaseWhen(cases, elseValue)
}
}
+
+/**
+ * A function that returns the index of expr in (expr1, expr2, ...) list
or 0 if not found.
+ * It takes at least 2 parameters, and all parameters should be subtype of
AtomicType or NullType.
+ * It's also acceptable to give parameters of different types. When the
parameters have different
+ * types, comparing will be done based on type firstly. For example,
''999'' 's type is StringType,
+ * while 999's type is IntegerType, so that no further comparison need to
be done since they have
+ * different types.
+ * If the search expression is NULL, the return value is 0 because NULL
fails equality comparison
+ * with any value.
+ * To also point out, no implicit cast will be done in this expression.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "_FUNC_(expr, expr1, expr2, ...) - Returns the index of expr in
the expr1, expr2, ... or 0 if not found.",
+ extended = """
+ Examples:
+ > SELECT _FUNC_(10, 9, 3, 10, 4);
+ 3
+ > SELECT _FUNC_('a', 'b', 'c', 'd', 'a');
+ 4
+ > SELECT _FUNC_('999', 'a', 999, 9.99, '999');
+ 4
+ """)
+// scalastyle:on line.size.limit
+case class Field(children: Seq[Expression]) extends Expression {
+
+ /** Even if expr is not found in (expr1, expr2, ...) list, the value
will be 0, not null */
+ override def nullable: Boolean = false
+ override def foldable: Boolean = children.forall(_.foldable)
+
+ private lazy val ordering =
TypeUtils.getInterpretedOrdering(children(0).dataType)
+
+ private val dataTypeMatchIndex: Array[Int] =
children.zipWithIndex.tail.filter(
+ _._1.dataType.sameType(children.head.dataType)).map(_._2).toArray
+
+ override def checkInputDataTypes(): TypeCheckResult = {
--- End diff --
I met a problem, if I first try to cast all parameters to DoubleType in
`TypeCoercion`(as described in 2nd paragraph last comment). I should really
cast in order to know it can success or not, but that will 'execute' in
analysis stage, that seems not right.
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