[GitHub] [spark] kazuyukitanimura commented on a change in pull request #33930: [SPARK-36665][SQL] Add more Not operator simplifications

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kazuyukitanimura commented on a change in pull request #33930:
URL: https://github.com/apache/spark/pull/33930#discussion_r704639466



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -441,6 +456,24 @@ object BooleanSimplification extends Rule[LogicalPlan] with PredicateHelper {
 
       case Not(IsNull(e)) => IsNotNull(e)
       case Not(IsNotNull(e)) => IsNull(e)
+
+      // Using Not(null) == null rules
+      case IsNull(Not(e)) => IsNull(e)
+      case IsNotNull(Not(e)) => IsNotNull(e)
+
+      // Using (Not(a) === b) == (a === Not(b)), (Not(a) <=> b) == (a <=> Not(b)) rules
+      case EqualTo(Not(a), b) if canSimplifyNot(b) => EqualTo(a, Not(b))

Review comment:
       For example of the `EqualTo(Not(a), b)` where `b = Not(c)`, it will become `EqualTo(a, Not(b))` => `EqualTo(a, Not(Not(c)))` => `EqualTo(a, c)`
   In addition, `if canSimplifyNot(b)` checks if the optimization can converge that avoids the situation two conditions are returning to each other.
   I plan to add those explanations to the comment.




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