[GitHub] [flink] klion26 commented on a change in pull request #12078: [FLINK-17610][state]Align the behavior of result of internal map state to re…

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klion26 commented on a change in pull request #12078:
URL: https://github.com/apache/flink/pull/12078#discussion_r427116721



##########
File path: flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBMapState.java
##########
@@ -227,6 +220,7 @@ public void migrateSerializedValue(
 		}
 	}
 
+	@Nonnull

Review comment:
       As the [code stye](https://flink.apache.org/contributing/code-style-and-quality-common.html#nullability-of-the-mutable-parts) said , we can get rid of the annotation.
   ```
   Note: This means that @Nonnull annotations are usually not necessary, but can be used in certain cases to override a previous annotation, or to point non-nullability out in a context where one would expect a nullable value.
   ```

##########
File path: flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendTestBase.java
##########
@@ -2875,7 +2875,8 @@ public void testMapStateDefaultValue() throws Exception {
 				VoidNamespaceSerializer.INSTANCE, kvId);
 
 		backend.setCurrentKey(1);
-		assertNull(state.entries());
+		assertNotNull(state.entries());

Review comment:
       maybe we need to verify the result of `entries` is what we want.

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/heap/HeapMapState.java
##########
@@ -140,25 +141,25 @@ public boolean contains(UK userKey) {
 	@Override
 	public Iterable<Map.Entry<UK, UV>> entries() {
 		Map<UK, UV> userMap = stateTable.get(currentNamespace);
-		return userMap == null ? null : userMap.entrySet();
+		return userMap == null ? Collections.emptyList() : userMap.entrySet();

Review comment:
       Do we need to return `Collections.emptySet` here to align with the `userMap.entrySet()`?




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