liuyongvs commented on code in PR #3189:
URL: https://github.com/apache/calcite/pull/3189#discussion_r1187344362


##########
core/src/main/java/org/apache/calcite/sql/fun/SqlCastFunction.java:
##########
@@ -122,8 +128,50 @@ static SqlReturnTypeInference returnTypeInference(boolean 
safe) {
   /** Derives the type of "CAST(expression AS targetType)". */
   public static RelDataType deriveType(RelDataTypeFactory typeFactory,
       RelDataType expressionType, RelDataType targetType, boolean safe) {
-    return typeFactory.createTypeWithNullability(targetType,
-        expressionType.isNullable() || safe);
+    return createTypeWithNullabilityFromExpr(typeFactory, expressionType, 
targetType, safe);
+  }
+
+  public static RelDataType 
createTypeWithNullabilityFromExpr(RelDataTypeFactory typeFactory,
+      RelDataType expressionType, RelDataType targetType, boolean safe) {
+    boolean isn = expressionType.isNullable() || safe;
+
+    if (isCollection(expressionType)) {
+      RelDataType expressionElementType = expressionType.getComponentType();
+      RelDataType targetElementType = targetType.getComponentType();
+      RelDataType newElementType =
+          createTypeWithNullabilityFromExpr(typeFactory, 
expressionElementType, targetElementType, false);

Review Comment:
   it should not. because the try_cast/safe_cast(different vendors, flink/spark 
former, mssql latter) will return null when it can not cast to targettype 
instead of throw exception like cast.
   
   it only changes the outer nullable



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