cloud-fan commented on a change in pull request #25239: [SPARK-28495][SQL]
AssignableCast: A new type coercion following store assignment rules of ANSI SQL
URL: https://github.com/apache/spark/pull/25239#discussion_r306708242
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
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@@ -1407,3 +1440,12 @@ case class UpCast(child: Expression, dataType:
DataType, walkedTypePath: Seq[Str
extends UnaryExpression with Unevaluable {
override lazy val resolved = false
}
+
+/**
+ * Cast the child expression to the target data type, but will throw error if
the cast violates
+ * the store assignment rules of ANSI SQL, e.g. string -> int, array -> string.
+ */
+case class AssignableCast(child: Expression, dataType: DataType,
walkedTypePath: Seq[String] = Nil)
Review comment:
BTW I'm not sure if we need `walkedTypePath`. `Upcast` needs it because it
needs to record the field path in a class. I think for `AssignableCast` we only
need to record the column name.
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