Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/12353#discussion_r60179863
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
---
@@ -142,16 +139,54 @@ case class CaseWhen(branches: Seq[(Expression,
Expression)], elseValue: Option[E
}
}
- def shouldCodegen: Boolean = {
- branches.length < CaseWhen.MAX_NUM_CASES_FOR_CODEGEN
+ override def toString: String = {
+ val cases = branches.map { case (c, v) => s" WHEN $c THEN $v"
}.mkString
+ val elseCase = elseValue.map(" ELSE " + _).getOrElse("")
+ "CASE" + cases + elseCase + " END"
}
+ override def sql: String = {
+ val cases = branches.map { case (c, v) => s" WHEN ${c.sql} THEN
${v.sql}" }.mkString
+ val elseCase = elseValue.map(" ELSE " + _.sql).getOrElse("")
+ "CASE" + cases + elseCase + " END"
+ }
+}
+
+
+/**
+ * Case statements of the form "CASE WHEN a THEN b [WHEN c THEN d]* [ELSE
e] END".
+ * When a = true, returns b; when c = true, returns d; else returns e.
+ *
+ * @param branches seq of (branch condition, branch value)
+ * @param elseValue optional value for the else branch
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "CASE WHEN a THEN b [WHEN c THEN d]* [ELSE e] END - When a =
true, returns b; when c = true, return d; else return e.")
+// scalastyle:on line.size.limit
+case class CaseWhen(
+ val branches: Seq[(Expression, Expression)],
+ val elseValue: Option[Expression] = None)
+ extends CaseWhenBase(branches, elseValue) with CodegenFallback with
Serializable {
--- End diff --
That would be right. `CaseWhenCodegen` is always generated from `CaseWhen`.
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