Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/8200#discussion_r48183738
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -464,6 +465,27 @@ object OptimizeIn extends Rule[LogicalPlan] {
}
/**
+ * Convert an expression into its conjunctive normal form (CNF), i.e. AND
of ORs.
+ * For example, a && b || c is normalized to (a || c) && (b || c) by this
method.
+ *
+ * Refer to https://en.wikipedia.org/wiki/Conjunctive_normal_form for
more information
+ */
+object CNFNormalization extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case q: LogicalPlan => q transformExpressionsUp {
+ case or @ Or(left, right) => (left, right) match {
--- End diff --
I would not make this a nested match as I think it makes it unnecessarily
hard to read (and if you just use transform directly you won't have to manually
handle the default case)
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