Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/10333#discussion_r48047005
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
---
@@ -548,20 +566,31 @@ abstract class TernaryExpression extends Expression {
f: (String, String, String) => String): String = {
val evals = children.map(_.gen(ctx))
val resultCode = f(evals(0).value, evals(1).value, evals(2).value)
- s"""
- ${evals(0).code}
- boolean ${ev.isNull} = true;
- ${ctx.javaType(dataType)} ${ev.value} =
${ctx.defaultValue(dataType)};
- if (!${evals(0).isNull}) {
- ${evals(1).code}
- if (!${evals(1).isNull}) {
- ${evals(2).code}
- if (!${evals(2).isNull}) {
- ${ev.isNull} = false; // resultCode could change nullability
- $resultCode
+ if (nullable) {
--- End diff --
if a `TernaryExpression` is nullable, currently we will always generate 3
nested `if` branches. But we still have chance to remove some `if` branches if
some children are non-nullable, how about doing this optimization based on
children's nullability?
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