cloud-fan commented on code in PR #36455:
URL: https://github.com/apache/spark/pull/36455#discussion_r866433341
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala:
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@@ -127,56 +127,18 @@ class EquivalentExpressions {
// There are some special expressions that we should not recurse into all of
its children.
// 1. CodegenFallback: it's children will not be used to generate code
(call eval() instead)
- // 2. If: common subexpressions will always be evaluated at the beginning,
but the true and
- // false expressions in `If` may not get accessed, according to the
predicate
- // expression. We should only recurse into the predicate expression.
- // 3. CaseWhen: like `If`, the children of `CaseWhen` only get accessed in
a certain
- // condition. We should only recurse into the first condition
expression as it
- // will always get accessed.
- // 4. Coalesce: it's also a conditional expression, we should only recurse
into the first
- // children, because others may not get accessed.
- // 5. NaNvl: it's a conditional expression, we can only guarantee the left
child can be always
- // accessed. And if we hit the left child, the right will not be
accessed.
+ // 2. ConditionalExpression: use it's specified expression
Review Comment:
```suggestion
// 2. ConditionalExpression: use its children that will always be
evaluated.
```
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