[GitHub] [iceberg] rdblue commented on a diff in pull request #7517: API, Flink: StructProjection returns null projection object for null nested struct value

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

rdblue commented on code in PR #7517:
URL: https://github.com/apache/iceberg/pull/7517#discussion_r1189229609


##########
api/src/main/java/org/apache/iceberg/util/StructProjection.java:
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@@ -189,16 +189,12 @@ public int size() {
 
   @Override
   public <T> T get(int pos, Class<T> javaClass) {
-    if (struct == null) {
-      // Return a null struct when projecting a nested required field from an optional struct.
-      // See more details in issue #2738.
-      return null;
-    }
-
     int structPos = positionMap[pos];
-
     if (nestedProjections[pos] != null) {
-      return javaClass.cast(nestedProjections[pos].wrap(struct.get(structPos, StructLike.class)));
+      StructLike nestedStruct = struct.get(structPos, StructLike.class);

Review Comment:
   I agree with this change. The only issue is what happens when struct is null. That could still happen if `wrap` is never called.
   
   I think I would favor the original null check (rather than the precondition) and the new behavior to return null instead of a `StructProjection` that wraps null. That way if somehow a null slips in, we at least just produce null. That seems to fit the intent as well, which is to return `null` when there is no value.



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