Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/1055#discussion_r13683452
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
---
@@ -202,3 +203,139 @@ case class If(predicate: Expression, trueValue:
Expression, falseValue: Expressi
override def toString = s"if ($predicate) $trueValue else $falseValue"
}
+
+// scalastyle:off
+/**
+ * Case statements of the form "CASE WHEN a THEN b [WHEN c THEN d]* [ELSE
e] END".
+ * Refer to this link for the corresponding semantics:
+ *
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-ConditionalFunctions
+ *
+ * Note that branches are considered in consecutive pairs (cond, val), and
the optional last element
+ * is the val for the default catch-all case (if provided). Hence,
`branches` consist of at least
+ * two elements, and can have an odd or even length.
+ */
+// scalastyle:on
+case class CaseWhen(branches: Seq[Expression]) extends Expression {
+ type EvaluatedType = Any
+ def children = branches
+ def references = children.flatMap(_.references).toSet
+ def dataType = {
+ if (!resolved) {
+ throw new UnresolvedException(this, "cannot resolve due to differing
types in some branches")
+ }
+ branches(1).dataType
+ }
+
+ override def nullable = branches.sliding(2, 2).map {
+ case Seq(cond, value) => value.nullable
+ case Seq(elseValue) => elseValue.nullable
+ }.reduce(_ || _)
+
+ override lazy val resolved = {
+ lazy val allCondBooleans = branches.sliding(2, 2).map {
--- End diff --
Is there a reason to make these inner variables lazy?
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