kazuyukitanimura commented on a change in pull request #33930:
URL: https://github.com/apache/spark/pull/33930#discussion_r719870007
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
##########
@@ -441,6 +457,27 @@ 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(a) && canSimplifyNot(b) =>
EqualTo(a, Not(b))
Review comment:
I addressed this by using `q.transformExpressionsDownWithPruning()` that
optimizes from top to bottom. That is helpful for the case like in the test `'e
=!= ('f === ('g === Not('h)))` It will be optimized as
```
'e =!= ('f === ('g === Not('h))) => 'e === ('f =!= ('g === Not('h))) => 'e
=== ('f === ('g =!= Not('h))) => 'e === ('f === ('g === Not(Not('h)))) => 'e
=== ('f === ('g === 'h))
```
Only the last `Not(Not('h))` will need to re-visit `BooleanSimplification`
one more time. Otherwise it will stay the fist `Not` propagation is done within
`NotPropagation`
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