kennknowles commented on code in PR #37530:
URL: https://github.com/apache/beam/pull/37530#discussion_r3289021107
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnSignatures.java:
##########
@@ -2327,12 +2331,58 @@ private static Map<String,
DoFnSignature.StateDeclaration> analyzeStateDeclarati
(TypeDescriptor<? extends State>)
TypeDescriptor.of(fnClazz).resolveType(unresolvedStateType);
+ // Warn if ValueState contains a collection type that could benefit from
specialized state
+ warnIfValueStateContainsCollection(fnClazz, id, stateType);
+
declarations.put(id, DoFnSignature.StateDeclaration.create(id, field,
stateType));
}
return ImmutableMap.copyOf(declarations);
}
+ /**
+ * Warns if a ValueState is declared with a collection type (Map, List, Set)
that could benefit
+ * from using specialized state types (MapState, BagState, SetState) for
better performance.
+ */
+ private static void warnIfValueStateContainsCollection(
+ Class<?> fnClazz, String stateId, TypeDescriptor<? extends State>
stateType) {
+ if (!stateType.isSubtypeOf(TypeDescriptor.of(ValueState.class))) {
+ return;
+ }
+
+ // Use TypeDescriptor.resolveType() to extract ValueState's type parameter
+ // This preserves generic type information better than raw Type
manipulation
+ TypeDescriptor<?> valueTypeDescriptor =
+ stateType.resolveType(ValueState.class.getTypeParameters()[0]);
+
+ // Skip if the type has unresolved parameters (e.g., TypeVariable,
WildcardType)
+ if (valueTypeDescriptor.hasUnresolvedParameters()) {
Review Comment:
I'm not sure this is desirable. For example if the type is
`ValueState<Set<T>>` I still think we can suggest using `SetState`.
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