cloud-fan commented on a change in pull request #30790:
URL: https://github.com/apache/spark/pull/30790#discussion_r545573491
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -528,6 +528,40 @@ object SimplifyConditionals extends Rule[LogicalPlan] with
PredicateHelper {
}
+/**
+ * Push the foldable expression into (if / case) branches.
+ */
+object PushFoldableIntoBranches extends Rule[LogicalPlan] with PredicateHelper
{
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case q: LogicalPlan => q transformExpressionsUp {
+ case b @ BinaryExpression(i @ If(_, trueValue, falseValue), right) if
i.deterministic &&
+ right.foldable && (trueValue.foldable || falseValue.foldable) =>
+ i.copy(
+ trueValue = b.makeCopy(Array(trueValue, right)),
+ falseValue = b.makeCopy(Array(falseValue, right)))
+
+ case b @ BinaryExpression(left, i @ If(_, trueValue, falseValue)) if
i.deterministic &&
+ left.foldable && (trueValue.foldable || falseValue.foldable) =>
Review comment:
let's create a method to count foldables, with comments to explain why
```
// be conservative here: it's only a guaranteed win if all but at most only
one branch
// end up being not foldable.
private def atMostOneUnfoldable(exprs: Seq[Expression]): Boolean = ...
```
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