viirya commented on a change in pull request #33142:
URL: https://github.com/apache/spark/pull/33142#discussion_r661597406
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -135,33 +125,47 @@ class EquivalentExpressions {
// For some special expressions we cannot just recurse into all of its
children, but we can
// recursively add the common expressions shared between all of its children.
private def commonChildrenToRecurse(expr: Expression): Seq[Seq[Expression]]
= expr match {
+ case _: CodegenFallback => Nil
case i: If => Seq(Seq(i.trueValue, i.falseValue))
case c: CaseWhen =>
// We look at subexpressions in conditions and values of `CaseWhen`
separately. It is
// because a subexpression in conditions will be run no matter which
condition is matched
// if it is shared among conditions, but it doesn't need to be shared in
values. Similarly,
// a subexpression among values doesn't need to be in conditions because
no matter which
// condition is true, it will be evaluated.
- val conditions = c.branches.tail.map(_._1)
+ val conditions = if (c.branches.length > 1) {
Review comment:
This fixed
https://github.com/apache/spark/pull/30245#discussion_r660870034.
> The only drawback is, if there are common subexpressions among the
conditions, they will always be counted as "appear twice" and gets codegened
into methods.
I just don't get this. You mean for `If(a + b > 1, 1, a + b + c > 1, 2, a +
b + c > 2, 3)`, `a + b + c` will be counted twice and considered as common
subexpression?
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