dbtsai commented on a change in pull request #33930:
URL: https://github.com/apache/spark/pull/33930#discussion_r706562712
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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 +456,25 @@ object BooleanSimplification extends Rule[LogicalPlan]
with PredicateHelper {
case Not(IsNull(e)) => IsNotNull(e)
case Not(IsNotNull(e)) => IsNull(e)
+
+ // Move `Not` from one side of `EqualTo`/`EqualNullSafe` to the other
side if it's beneficial.
+ // E.g. `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.
+ case EqualTo(Not(a), b) if canSimplifyNot(b) => EqualTo(a, Not(b))
+ case EqualTo(a, Not(b)) if canSimplifyNot(a) => EqualTo(Not(a), b)
+ case EqualNullSafe(Not(a), b) if canSimplifyNot(b) => EqualNullSafe(a,
Not(b))
+ case EqualNullSafe(a, Not(b)) if canSimplifyNot(a) =>
EqualNullSafe(Not(a), b)
+
+ // Push `Not` to one side of `EqualTo`/`EqualNullSafe` if it's
beneficial.
+ // E.g. Not(EqualTo(x, false)) => EqualTo(x, true)
+ case Not(EqualTo(a, b)) if canSimplifyNot(b) => EqualTo(a, Not(b))
+ case Not(EqualTo(a, b)) if canSimplifyNot(a) => EqualTo(Not(a), b)
Review comment:
Let's say if both `a` and `b` can be simplified, does it mean we always
try to simplify `Not(b)` first? It becomes ordering dependent, and how do we
know which one to simplify first is better?
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