Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/21193#discussion_r186627099
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
---
@@ -623,8 +624,14 @@ case class Cast(child: Expression, dataType: DataType,
timeZoneId: Option[String
override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
val eval = child.genCode(ctx)
val nullSafeCast = nullSafeCastFunction(child.dataType, dataType, ctx)
+
+ // Below the code comment including `eval.value` and `eval.isNull` is
a trick. It makes the two
+ // expr values are referred by this code block.
ev.copy(code = eval.code +
- castCode(ctx, eval.value, eval.isNull, ev.value, ev.isNull,
dataType, nullSafeCast))
+ code"""
+ // Cast from ${eval.value}, ${eval.isNull}
--- End diff --
I feel it's a little fragile to depend on the `StringContext` to collect
references. 2 proposal:
1. ask the code builder to explicitly specify the references, like
`JavaCode.block(code = xxx, ref1, ref2, ...)`
2. ban `String` in the code block string context, and create a special
class to insert `String` literal to code block, so that we won't mistakently
pass code as string and lose references.
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