Github user maropu commented on a diff in the pull request:
https://github.com/apache/spark/pull/20135#discussion_r159243470
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -271,33 +271,45 @@ case class ConcatWs(children: Seq[Expression])
}
}
+/**
+ * An expression that returns the `n`-th input in given inputs.
+ * If all inputs are binary, `elt` returns an output as binary. Otherwise,
it returns as string.
+ * If any input is null, `elt` returns null.
+ */
// scalastyle:off line.size.limit
@ExpressionDescription(
- usage = "_FUNC_(n, str1, str2, ...) - Returns the `n`-th string, e.g.,
returns `str2` when `n` is 2.",
+ usage = "_FUNC_(n, input1, input2, ...) - Returns the `n`-th input,
e.g., returns `input2` when `n` is 2.",
examples = """
Examples:
> SELECT _FUNC_(1, 'scala', 'java');
scala
""")
// scalastyle:on line.size.limit
-case class Elt(children: Seq[Expression])
- extends Expression with ImplicitCastInputTypes {
+case class Elt(children: Seq[Expression]) extends Expression {
private lazy val indexExpr = children.head
- private lazy val stringExprs = children.tail.toArray
+ private lazy val inputExprs = children.tail.toArray
/** This expression is always nullable because it returns null if index
is out of range. */
override def nullable: Boolean = true
- override def dataType: DataType = StringType
-
- override def inputTypes: Seq[DataType] = IntegerType +:
Seq.fill(children.size - 1)(StringType)
+ override def dataType: DataType =
inputExprs.map(_.dataType).headOption.getOrElse(StringType)
--- End diff --
sorry, but I miss your point. What's the type of the only 1 parameter?
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