Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/19901#discussion_r155403171
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
---
@@ -180,13 +180,18 @@ case class CaseWhen(
}
override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
- // This variable represents whether the first successful condition is
met or not.
- // It is initialized to `false` and it is set to `true` when the first
condition which
- // evaluates to `true` is met and therefore is not needed to go on
anymore on the computation
- // of the following conditions.
- val conditionMet = ctx.freshName("caseWhenConditionMet")
- ctx.addMutableState(ctx.JAVA_BOOLEAN, ev.isNull)
- ctx.addMutableState(ctx.javaType(dataType), ev.value)
+ // This variable holds the state of the result:
+ // -1 means the condition is not met yet and the result is unknown.
+ val NOT_MATCHED = -1
+ // 0 means the condition is met and result is not null.
+ val HAS_NONNULL = 0
+ // 1 means the condition is met and result is null.
+ val HAS_NULL = 1
+ // It is initialized to `-1`, and if it's set to `1` or `0`, We won't
go on anymore on the
--- End diff --
nit: since you define the constants above, why not use them in this comment?
```It is initialized to `NOT_MATCHED`, and if it's set to `HAS_NULL` or
`HAS_NONNULL`...```
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