Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/7202#discussion_r33886072
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
---
@@ -713,39 +715,68 @@ object HiveTypeCoercion {
case e: ExpectsInputTypes =>
val children: Seq[Expression] = e.children.zip(e.inputTypes).map {
case (in, expected) =>
- implicitCast(in, expected)
+ // If we cannot do the implicit cast, just use the original
input.
+ implicitCast(in, expected).getOrElse(in)
}
e.withNewChildren(children)
}
/**
- * If needed, cast the expression into the expected type.
- * If the implicit cast is not allowed, return the expression itself.
+ * Given an expected data type, try to cast the expression and return
the cast expression.
+ *
+ * If the expression already fits the input type, we simply return the
expression itself.
+ * If the expression has an incompatible type that cannot be
implicitly cast, return None.
*/
- def implicitCast(e: Expression, expectedType: AbstractDataType):
Expression = {
+ def implicitCast(e: Expression, expectedType: AbstractDataType):
Option[Expression] = {
val inType = e.dataType
- (inType, expectedType) match {
+
+ // Note that ret is nullable to avoid typing a lot of Some(...) in
this local scope.
+ // We wrap immediately an Option after this.
+ @Nullable val ret: Expression = (inType, expectedType) match {
+
+ // If the expected type is already a parent of the input type, no
need to cast.
+ case _ if expectedType.isParentOf(inType) => e
+
// Cast null type (usually from null literals) into target types
- case (NullType, target: DataType) => Cast(e,
target.defaultConcreteType)
+ case (NullType, target) => Cast(e, target.defaultConcreteType)
// Implicit cast among numeric types
+ // If input is decimal, and we expect a decimal type, just use the
input.
+ case (_: DecimalType, DecimalType) => e
+ // If input is a numeric type but not decimal, and we expect a
decimal type,
+ // cast the input to unlimited precision decimal.
+ case (_: NumericType, DecimalType) if
!inType.isInstanceOf[DecimalType] =>
+ Cast(e, DecimalType.Unlimited)
+ // For any other numeric types, implicitly cast to each other,
e.g. long -> int, int -> long
case (_: NumericType, target: NumericType) if e.dataType != target
=> Cast(e, target)
+ case (_: NumericType, target: NumericType) => e
// Implicit cast between date time types
case (DateType, TimestampType) => Cast(e, TimestampType)
case (TimestampType, DateType) => Cast(e, DateType)
// Implicit cast from/to string
- case (StringType, NumericType) => Cast(e, DoubleType)
--- End diff --
there isn't a numeric adt anymore.
we can consider adding it back for expressions like round
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