Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/8200#discussion_r48331134
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -464,6 +465,24 @@ 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 {
+ // reverse Or with its And child to eliminate (And under Or)
occurrence
+ case Or(And(innerLhs, innerRhs), rhs) =>
+ And(Or(innerLhs, rhs), Or(innerRhs, rhs))
+ case Or(lhs, And(innerLhs, innerRhs)) =>
+ And(Or(lhs, innerLhs), Or(lhs, innerRhs))
+ }
+ }
+}
--- End diff --
We should probably include/move those `Not` push-down rules added in PR
#5700 defined in `BooleanSimplification` here, since they are essential for CNF
normalization.
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