Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/14033#discussion_r69407641
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
---
@@ -94,6 +96,61 @@ case class UserDefinedGenerator(
}
/**
+ * Separate v1, ..., vk into n rows. Each row will have k/n columns. n
must be constant.
+ * {{{
+ * SELECT stack(2, 1, 2, 3)) ->
+ * 1 2
+ * 3 NULL
+ * }}}
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(n, v1, ..., vk) - Separate v1, ..., vk into n rows.",
+ extended = "> SELECT _FUNC_(2, 1, 2, 3);\n [1,2]\n [3,null]")
+case class Stack(children: Seq[Expression])
+ extends Expression with Generator with ImplicitCastInputTypes with
CodegenFallback {
+
+ override def inputTypes: Seq[DataType] =
+ Seq(IntegerType) ++ Seq.fill(children.length -
1)(children.tail.head.dataType)
+
+ override def checkInputDataTypes(): TypeCheckResult = {
--- End diff --
```
scala> sql("select stack(1.0,2,3)");
java.lang.ClassCastException: org.apache.spark.sql.types.Decimal cannot be
cast to java.lang.Integer
```
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