Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/14033#discussion_r69425803
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
---
@@ -94,6 +94,62 @@ 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)
--- End diff --
Can you check what's the type coercion rule for hive? It looks to me that
the values for same column should be same type, but not all values should be
same type.
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