cloud-fan commented on a change in pull request #32987:
URL: https://github.com/apache/spark/pull/32987#discussion_r661476268
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -134,24 +154,18 @@ 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 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)
- // For an expression to be in all branch values of a CaseWhen statement,
it must also be in
- // the elseValue.
- val values = if (c.elseValue.nonEmpty) {
- c.branches.map(_._2) ++ c.elseValue
- } else {
- Nil
- }
- Seq(conditions, values)
- case c: Coalesce => Seq(c.children.tail)
+ private def commonChildrenToRecurse(expr: Expression): Seq[Expression] =
expr match {
+ case i: If => Seq(i.trueValue, i.falseValue)
+ case c: CaseWhen if c.elseValue.nonEmpty => c.branches.map(_._2) ++
c.elseValue
+ case _ => Nil
+ }
+
+ // Finds expressions that are conditionally evaluated, so that if they are
definitely evaluated
+ // elsewhere, we can create a subexpression to optimize the conditional case.
+ private def conditionallyEvaluatedChildren(expr: Expression):
Seq[Expression] = expr match {
Review comment:
I feel it's a bit more overcomplicated: now we have childen,
commonChildren, conditionallyEvaluatedChildren.
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