Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/16057#discussion_r90012747
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -714,6 +714,17 @@ object TypeCoercion {
// try to find the first one we can implicitly cast.
case (_, TypeCollection(types)) => types.flatMap(implicitCast(e,
_)).headOption.orNull
+ case (ArrayType(_, nullable), ArrayType(internalType: DataType,
expectedNullable))
+ if (expectedNullable || nullable == expectedNullable) =>
--- End diff --
This might work:
```scala
def implicitCast(e: Expression, expectedType: AbstractDataType):
Option[Expression] = {
implicitCast(e.dataType, expectedType).collect {
case dt if dt != e.dataType => Cast(e, dt)
}
}
private def implicitCast(inType: DataType, expectedType: AbstractDataType):
Option[DataType] = {
// 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: DataType = (inType, expectedType) match {
// If the expected type is already a parent of the input type, no need
to cast.
case _ if expectedType.acceptsType(inType) => inType
// Cast null type (usually from null literals) into target types
case (NullType, target) => target.defaultConcreteType
// If the function accepts any numeric type and the input is a string,
we follow the hive
// convention and cast that input into a double
case (StringType, NumericType) => NumericType.defaultConcreteType
// Implicit cast among numeric types. When we reach here, input type is
not acceptable.
// If input is a numeric type but not decimal, and we expect a decimal
type,
// cast the input to decimal.
case (d: NumericType, DecimalType) => DecimalType.forType(d)
// For any other numeric types, implicitly cast to each other, e.g.
long -> int, int -> long
case (_: NumericType, target: NumericType) => target
// Implicit cast between date time types
case (DateType, TimestampType) => TimestampType
case (TimestampType, DateType) => DateType
// Implicit cast from/to string
case (StringType, DecimalType) => DecimalType.SYSTEM_DEFAULT
case (StringType, target: NumericType) => target
case (StringType, DateType) => DateType
case (StringType, TimestampType) => TimestampType
case (StringType, BinaryType) => BinaryType
// Cast any atomic type to string.
case (any: AtomicType, StringType) if any != StringType => StringType
// When we reach here, input type is not acceptable for any types in
this type collection,
// try to find the first one we can implicitly cast.
case (_, TypeCollection(types)) =>
types.flatMap(implicitCast(inType, _)).headOption.orNull
case (ArrayType(dt1, n1), ArrayType(dt2: DataType, n2)) if n2 || !n1 =>
implicitCast(dt1, dt2).map(ArrayType(_, n2)).orNull
case _ => null
}
Option(ret)
}
```
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