[GitHub] [spark] LuciferYang commented on a diff in pull request #40790: [SPARK-43116][SQL] Fix Cast.forceNullable

["LuciferYang (via GitHub)" <gi...@apache.org>]

LuciferYang commented on code in PR #40790:
URL: https://github.com/apache/spark/pull/40790#discussion_r1173364511


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala:
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@@ -396,6 +396,22 @@ object Cast extends QueryErrorsBase {
 
     case (_, to: DecimalType) if !canNullSafeCastToDecimal(from, to) => true
     case (_: FractionalType, _: IntegralType) => true  // NaN, infinity
+
+    case (_: ArrayType, _: ArrayType) => false
+    case (_: MapType, _: MapType) => false
+    case (_: StructType, _: StructType) => false
+    case (_: ArrayType | _: MapType | _: StructType, _) => true
+
+    case (DateType | TimestampType, TimestampNTZType) => false
+    case (_, TimestampNTZType) => true
+    case (TimestampNTZType, DateType | TimestampType) => false
+    case (TimestampNTZType, _) => true
+
+    case (_: IntegralType | _: DecimalType, _: AnsiIntervalType) => false
+    case (_, _: AnsiIntervalType) => true
+    case (_: AnsiIntervalType, _: IntegralType | _: DecimalType) => false
+    case (_: AnsiIntervalType, _) => true
+

Review Comment:
   > Hm. It is a little hard to add a test for this, as the nullable cases encountered by different type conversions are different. Any better idea for this?
   
   friendly ping @wangyum , any better suggestion?



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