Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/10737#discussion_r49679817
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
---
@@ -137,45 +137,50 @@ case class CaseWhen(branches: Seq[(Expression,
Expression)], elseValue: Option[E
}
override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode):
String = {
- val got = ctx.freshName("got")
+ val len = branches.length
- val cases = branches.map { case (condition, value) =>
- val cond = condition.gen(ctx)
- val res = value.gen(ctx)
- s"""
- if (!$got) {
+ def genBranch(branchIndex: Int): String =
+ if (branchIndex >= len) {
+ if (elseValue.isDefined) {
+ val res = elseValue.get.gen(ctx)
+ s"""
+ ${res.code}
+ ${ev.isNull} = ${res.isNull};
+ ${ev.value} = ${res.value};
+ """
+ } else {
+ ""
+ }
+ } else {
+ val cond = branches(branchIndex)._1.gen(ctx)
+ val res = branches(branchIndex)._2.gen(ctx)
+
+ val currentBranch = s"""
${cond.code}
if (!${cond.isNull} && ${cond.value}) {
- $got = true;
${res.code}
${ev.isNull} = ${res.isNull};
${ev.value} = ${res.value};
}
- }
- """
- }.mkString("\n")
-
- val elseCase = {
- if (elseValue.isDefined) {
- val res = elseValue.get.gen(ctx)
- s"""
- if (!$got) {
- ${res.code}
- ${ev.isNull} = ${res.isNull};
- ${ev.value} = ${res.value};
- }
"""
- } else {
- ""
+
+ val moreBranch = genBranch(branchIndex + 1)
+ if (moreBranch != "") {
+ s"""
+ $currentBranch
+ else {
+ $moreBranch
--- End diff --
It will be slightly more efficient when we succeeds in front conditions and
can skip checking of `got` variable for late branches. Before that we still
need to check `got` content many times even first condition is already
satisfied.
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