Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/3150#discussion_r19997693
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
---
@@ -37,8 +42,62 @@ case class Cast(child: Expression, dataType: DataType)
extends UnaryExpression w
case (BooleanType, DateType) => true
case (DateType, _: NumericType) => true
case (DateType, BooleanType) => true
- case (_, DecimalType.Fixed(_, _)) => true // TODO: not all upcasts
here can really give null
- case _ => child.nullable
+ case (_, DecimalType.Fixed(_, _)) => true // TODO: not all upcasts
here can really give null
+ case _ => false
+ }
+
+ private[this] def resolvableNullability(from: Boolean, to: Boolean) =
!from || to
+
+ private[this] def resolve(from: DataType, to: DataType): Boolean = {
+ (from, to) match {
+ case (from, to) if from == to => true
+
+ case (NullType, _) => true
+
+ case (_, StringType) => true
+
+ case (StringType, BinaryType) => true
+
+ case (StringType, BooleanType) => true
+ case (DateType, BooleanType) => true
+ case (TimestampType, BooleanType) => true
+ case (_: NumericType, BooleanType) => true
+
+ case (StringType, TimestampType) => true
+ case (BooleanType, TimestampType) => true
+ case (DateType, TimestampType) => true
+ case (_: NumericType, TimestampType) => true
+
+ case (_, DateType) => true
+
+ case (StringType, _: NumericType) => true
+ case (BooleanType, _: NumericType) => true
+ case (DateType, _: NumericType) => true
+ case (TimestampType, _: NumericType) => true
+ case (_: NumericType, _: NumericType) => true
+
+ case (ArrayType(from, fn), ArrayType(to, tn)) =>
+ resolve(from, to) &&
+ resolvableNullability(fn || forceNullable(from, to), tn)
+
+ case (MapType(fromKey, fromValue, fn), MapType(toKey, toValue, tn))
=>
+ resolve(fromKey, toKey) &&
+ (!forceNullable(fromKey, toKey)) &&
+ resolve(fromValue, toValue) &&
+ resolvableNullability(fn || forceNullable(fromValue, toValue),
tn)
+
+ case (StructType(fromFields), StructType(toFields)) =>
+ fromFields.size == toFields.size &&
+ fromFields.zip(toFields).forall {
+ case (fromField, toField) =>
+ resolve(fromField.dataType, toField.dataType) &&
+ resolvableNullability(
+ fromField.nullable || forceNullable(fromField.dataType,
toField.dataType),
+ toField.nullable)
+ }
+
+ case _ => false
--- End diff --
I am wondering if throwing exception will be more informative, than plain
`UnresolvedException` thrown in logical plan analyzing.
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