Github user yhuai commented on a diff in the pull request:
https://github.com/apache/spark/pull/7175#discussion_r33748126
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
---
@@ -704,19 +704,46 @@ object HiveTypeCoercion {
/**
* Casts types according to the expected input types for Expressions
that have the trait
- * [[AutoCastInputTypes]].
+ * [[ExpectsInputTypes]].
*/
object ImplicitTypeCasts extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan
transformAllExpressions {
// Skip nodes who's children have not been resolved yet.
case e if !e.childrenResolved => e
- case e: AutoCastInputTypes if e.children.map(_.dataType) !=
e.inputTypes =>
- val newC = (e.children, e.children.map(_.dataType),
e.inputTypes).zipped.map {
- case (child, actual, expected) =>
- if (actual == expected) child else Cast(child, expected)
+ case e: ExpectsInputTypes =>
+ val children: Seq[Expression] = e.children.zip(e.inputTypes).map {
case (in, expected) =>
+ implicitCast(in, expected)
}
- e.withNewChildren(newC)
+ e.withNewChildren(children)
+ }
+
+ /**
+ * If needed, cast the expression into the expected type.
+ * If the implicit cast is not allowed, return the expression itself.
+ */
+ def implicitCast(e: Expression, expectedType: AbstractDataType):
Expression = {
+ (e, expectedType) match {
+ // Cast null type (usually from null literals) into target types
+ case (in @ NullType(), target: DataType) => Cast(in,
target.defaultConcreteType)
+
+ // Implicit cast among numeric types
+ case (in @ NumericType(), target: NumericType) if in.dataType !=
target =>
+ Cast(in, target)
+
+ // Implicit cast between date time types
+ case (in @ DateType(), TimestampType) => Cast(in, TimestampType)
+ case (in @ TimestampType(), DateType) => Cast(in, DateType)
+
+ // Implicit from string to atomic types, and vice versa
--- End diff --
Seems this comment is not very consistent with the code below? For `case
(in, StringType) if in.dataType != StringType`, we also cast complex types to
string?
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