Github user yjshen commented on a diff in the pull request:
https://github.com/apache/spark/pull/7365#discussion_r35615752
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
---
@@ -418,51 +418,508 @@ case class Cast(child: Expression, dataType:
DataType)
protected override def nullSafeEval(input: Any): Any = cast(input)
override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode):
String = {
- // TODO: Add support for more data types.
- (child.dataType, dataType) match {
+ val nullSafeCast = nullSafeCastFunction(child.dataType, dataType, ctx)
+ if (nullSafeCast != null) {
+ val eval = child.gen(ctx)
+ eval.code +
+ castCode(ctx, eval.primitive, eval.isNull, ev.primitive,
ev.isNull, dataType, nullSafeCast)
+ } else {
+ super.genCode(ctx, ev)
+ }
+ }
+
+ // three function arguments are: child.primitive, result.primitive and
result.isNull
+ // it returns the code snippets to be put in null safe evaluation region
+ private[this] type CastFunction = (String, String, String) => String
+
+ private[this] def nullSafeCastFunction(
+ from: DataType,
+ to: DataType,
+ ctx: CodeGenContext): CastFunction = to match {
+
+ case _ if from == NullType => (c, evPrim, evNull) => s"$evNull = true;"
+ case _ if to == from => (c, evPrim, evNull) => s"$evPrim = $c;"
--- End diff --
cast expression will be inserted during physical operator
transformation,for example `Average`, in which case its possible we add a `cast
to self` expression.
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