Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/6982#discussion_r33461668
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
---
@@ -245,13 +254,26 @@ abstract class UnaryExpression extends Expression
with trees.UnaryNode[Expressio
ctx: CodeGenContext,
ev: GeneratedExpressionCode,
f: String => String): String = {
+ nullSafeCodeGen(ctx, ev, (result, eval) => {
+ s"$result = ${f(eval)};"
+ })
+ }
+
+ /**
+ * Called by unary expressions to generate a code block that returns
null if its parent returns
+ * null, and if not not null, use `f` to generate the expression.
+ */
+ protected def nullSafeCodeGen(
+ ctx: CodeGenContext,
+ ev: GeneratedExpressionCode,
+ f: (String, String) => String): String = {
val eval = child.gen(ctx)
- // reuse the previous isNull
- ev.isNull = eval.isNull
--- End diff --
I removed this because if `child` is `Literal`, then `eval.isNull` is
literal boolean, and we can't change `ev.isNull` afterwards. It's not a problem
before as we won't change `ev.isNull` in `defineCodeGen`, but now we will and
need to do it in `nullSafeCodeGen`.
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