Github user janplus commented on a diff in the pull request:
https://github.com/apache/spark/pull/13966#discussion_r69098161
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -162,6 +163,46 @@ case class ConcatWs(children: Seq[Expression])
}
}
+@ExpressionDescription(
+ usage = "_FUNC_(n, str1, str2, ...) - returns the n-th string, e.g.
returns str2 when n is 2",
+ extended = "> SELECT _FUNC_(1, 'scala', 'java') FROM src LIMIT 1;\n" +
"'scala'")
+case class Elt(children: Seq[Expression])
+ extends Expression with ImplicitCastInputTypes with CodegenFallback {
+
+ private lazy val indexExpr = children.head
+ private lazy val stringExprs = 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 checkInputDataTypes(): TypeCheckResult = {
+ if (children.size < 2) {
+ TypeCheckResult.TypeCheckFailure("elt function requires at least two
arguments")
+ } else {
+ super[ImplicitCastInputTypes].checkInputDataTypes()
+ }
+ }
+
+ override def eval(input: InternalRow): Any = {
+ val indexObj = indexExpr.eval(input)
+ if (indexObj == null) {
+ null
+ } else {
+ val index = indexObj.asInstanceOf[Int]
+ if (index <= 0 || index > stringExprs.length) {
+ null
+ } else {
+ stringExprs(index - 1).eval(input)
--- End diff --
Why not just use children(index) instead of using an extra stringExprs?
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
