Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/12267#discussion_r59154875
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -787,6 +788,28 @@ object BooleanSimplification extends Rule[LogicalPlan]
with PredicateHelper {
}
/**
+ * Simplifies semantically-equal non-nullable expressions:
+ * 1) Replace '=', '<=', and '>=' with 'true' literal
+ * 2) Replace '<' and '>' with 'false' literal
+ */
+object NonNullableBinaryComparisonSimplification extends Rule[LogicalPlan]
with PredicateHelper {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case q: LogicalPlan => q transformExpressionsUp {
+ // True with equality
+ case a EqualTo b if !a.nullable && !b.nullable &&
a.semanticEquals(b) => TrueLiteral
+ case a EqualNullSafe b if !a.nullable && !b.nullable &&
a.semanticEquals(b) => TrueLiteral
--- End diff --
Oh. @cloud-fan . When I looked at the `EqualNullSafe` one more time, I
realized that that `a EqualNullSafe b` is null-safe but both `a` and `b` are
not. The following is the code snippet of `EqualNullSafe`.
```
case class EqualNullSafe(left: Expression, right: Expression) extends
BinaryComparison {
...
override def nullable: Boolean = false
...
override def eval(input: InternalRow): Any = {
val input1 = left.eval(input)
val input2 = right.eval(input)
if (input1 == null && input2 == null) {
true
```
In this case, I think we should keep `!a.nullable && !b.nullable` because
we need to evaluate `a` and `b` indeed. How do you think about that?
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