cloud-fan commented on a change in pull request #30504:
URL: https://github.com/apache/spark/pull/30504#discussion_r533540575
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -48,6 +48,9 @@ object ConstantFolding extends Rule[LogicalPlan] {
// object and running eval unnecessarily.
case l: Literal => l
+ case Size(c: CreateArray, _) => Literal(c.children.length)
+ case Size(c: CreateMap, _) => Literal(c.children.length / 2)
Review comment:
Seems we need a way to propagate the no-side-effect property:
```
def hasNoSideEffect(e: Expression): Boolean = e match {
case _: Attribute => true
case _: Literal => true
case _: NoSideEffect => e.children.forall(hasNoSideEffect)
case _ => false
}
...
case Size(c: CreateArray, _) if c.children.forall(hasNoSideEffect) =>
Literal(c.children.length)
case Size(c: CreateMap, _) if c.children.forall(hasNoSideEffect) =>
Literal(c.children.length / 2)
```
`CreateStruct/Array/Map` can extend the trait `NoSideEffect`, and we can add
more in the future.
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