Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/21193#discussion_r187033550
--- 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}
+ ${castCode(ctx, eval.value, eval.isNull, ev.value, ev.isNull,
dataType, nullSafeCast)}
--- End diff --
We can use `ExprValue` and `Block` around everywhere in `Cast` here (I did
in a local branch), just it increases some code diff, so I'm not sure if we
want it be here or as a follow-up if it's easier for review.
Inputs to `Cast` should be only `eval.value` and `eval.isNull` as it's only
child expression to `Cast`. We add generated codes here but they are not
actually input expressions to `Cast`. So for now I manually let `eval.value`
and `eval.isNull` be tracked.
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