cloud-fan commented on code in PR #45612:
URL: https://github.com/apache/spark/pull/45612#discussion_r1533184546
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/AnsiTypeCoercion.scala:
##########
@@ -180,56 +180,27 @@ object AnsiTypeCoercion extends TypeCoercionBase {
// cast the input to decimal.
case (n: NumericType, DecimalType) => Some(DecimalType.forType(n))
- // Cast null type (usually from null literals) into target types
- // By default, the result type is `target.defaultConcreteType`. When the
target type is
- // `TypeCollection`, there is another branch to find the "closet
convertible data type" below.
- case (NullType, target) if !target.isInstanceOf[TypeCollection] =>
- Some(target.defaultConcreteType)
-
// If a function expects a StringType, no StringType instance should be
implicitly cast to
// StringType with a collation that's not accepted (aka. lockdown
unsupported collations).
case (_: StringType, StringType) => None
case (_: StringType, _: StringTypeCollated) => None
- // This type coercion system will allow implicit converting String type
as other
- // primitive types, in case of breaking too many existing Spark SQL
queries.
- case (StringType, a: AtomicType) =>
- Some(a)
-
- // If the target type is any Numeric type, convert the String type as
Double type.
- case (StringType, NumericType) =>
- Some(DoubleType)
-
- // If the target type is any Decimal type, convert the String type as
the default
- // Decimal type.
- case (StringType, DecimalType) =>
- Some(DecimalType.SYSTEM_DEFAULT)
-
- // If the target type is any timestamp type, convert the String type as
the default
- // Timestamp type.
- case (StringType, AnyTimestampType) =>
- Some(AnyTimestampType.defaultConcreteType)
-
- case (DateType, AnyTimestampType) =>
- Some(AnyTimestampType.defaultConcreteType)
-
- case (_, target: DataType) =>
- if (Cast.canANSIStoreAssign(inType, target)) {
- Some(target)
+ // Ideally the implicit cast rule should be the same as
`Cast.canANSIStoreAssign` so that it's
+ // consistent with table insertion. To avoid breaking too many existing
Spark SQL queries,
+ // we make the system to allow implicitly converting String type as
other primitive types.
+ case (StringType, a @ (_: AtomicType | NumericType | DecimalType |
AnyTimestampType)) =>
+ Some(a.defaultConcreteType)
+
+ // When the target type is `TypeCollection`, there is another branch to
find the
+ // "closet convertible data type" below.
+ case (_, target) if !target.isInstanceOf[TypeCollection] =>
+ val concreteType = target.defaultConcreteType
Review Comment:
It's the default implementation in `DataType`:
```
override private[sql] def defaultConcreteType: DataType = this
```
maybe I just make it as `final`?
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